title: A new Wolf-Rayet star in Cygnus

abstract:
  We report the discovery of a new Wolf-Rayet star in the direction of Cygnus.
The star is strongly reddened but quite bright in the infrared, with J = 9.22,
H = 8.08 and K = 7.09 (2MASS). On the basis of its H + K spectrum, we have
classified WR 142a a WC8 star. We have estimated its properties using as a
reference those of other WC8 stars in the solar neighbourhood as well as those
of WR 135, whose near-infrared spectrum is remarkably similar. We thus obtain a
foreground reddening of A(V) = 8.1 mag, M(J) = -4.3, log(L/Lo) = 5.0 - 5.2, R =
0.8 Ro, T = 125,000 K, M = 7.9 - 9.7 Mo, and a mass loss of (1.4 - 2.3)e-05
Mo/yr. The derived distance modulus, DM = 11.2 +/- 0.7 mag, places it in a
region occupied by several OB associations in the Cygnus arm, and particularly
in the outskirts of both Cygnus OB2 and Cygnus OB9. The position in the sky
alone does not allow us to unambiguously assign the star to either association,
but based on the much richer massive star content of Cygnus OB2 membership in
this latter association appears to be more likely.


title: Origin of non-keplerian motions of masers in NGC 1068

abstract:
  We demonstrate that the ``sub-keplerian'' rotation curve of maser spots in
NGC 1068 can be explained by the gravitational attraction of the disc orbiting
the central black hole. Possible parameters matching observations are: black
hole mass of 12 million solar masses, disc outer edge > 1.3 pc, aspect ratio in
the range 0.003 to 0.3, surface density varying approximately as 1/R, and disc
mass of about 9.4 million solar masses. The physical conditions required for
the excitation of masers are fulfilled, and the outer disc would stand in a
gravitationally marginally stable state.


title:
What does the Unexpected Detection of Water Vapor in Arcturus'
  Atmosphere Tell us?

abstract:
  In this talk I presented and discussed our unexpected detection of water
vapor in the disk-averaged spectrum of the K2IIIp red giant Arcturus [for
details, see Ryde et al. (2002)]. Arcturus, or alpha Bootes is, with its
effective temperature of 4300 K, the hottest star yet to show water vapor
features. We argue that the water vapor is photospheric and that its detection
provides us with new insights into the outer parts of the photosphere. We are
not able to model the vater vapor with a standard, one-component, 1D,
radiative-equilibrium, LTE model photosphere, which probably means we are
lacking essential physics in such models. However, we are able to model several
OH lines of different excitation and the water-vapor lines satisfactorily after
lowering the temperature structure of the very outer parts of the photosphere
at log tau_500=-3.8 and beyond compared to a flux-constant, hydrostatic,
standard marcs model photosphere. Our new semi-empirical model is consistently
calculated from the given temperature structure. I will discuss some possible
reasons for a temperature decrease in the outer-most parts of the photosphere
and the assumed break-down of the assumptions made in classical
model-atmosphere codes. In order to understand the outer photospheres of these
objects properly, we will, most likely, need 3D hydrodynamical models of red
giants also taking into account full non-LTE and including time-dependent
effects of, for example, acoustic wave heating sensitive to thermal
instabilities.


title:
Tracing the Mass during Low-Mass Star Formation, IV: Observations and
  Modeling of the Submillimeter Continuum Emission from Class I Protostars

abstract:
  We present results from the observations and modeling of seventeen Class I
cores with the Submillimetre Common Users Bolometer Array (SCUBA) on the James
Clerk Maxwell Telescope (JCMT). By modeling the transfer of radiation through
the envelope for nine cores, we find, for a power law distribution
n(r)=n_f(r/r_f)^-p, the average and standard deviation p=1.6 +/- 0.4 and a
median of p=1.8. However, the inclusion of a disk or other point-like component
can cause the derived p to be shallower by as much as 0.5. In addition, we test
the Shu collapse model for our sources and discuss the application of simpler
analyses that derive a density power law distribution directly from the slope
of the intensity radial profile. The total mass of the envelope in our sample
has a range from 0.04 to 5.0 M_sun, but these masses disagree with the virial
masses derived from molecular line observations. Finally, we discuss the nature
of these sources in light of various evolutionary indicators and find that
T_bol and L_obs/L_smm are often inconsistent in distinguishing Class 0 from
Class I cores.


title: A SCUBA galaxy in the Protocluster around 53W002 at z=2.4

abstract:
  We analyse an 850-um SCUBA map of the environment of the z=2.39 radio galaxy
53W002, which has been shown to reside in an over-density of Ly-alpha detected
galaxies. We identify four luminous submillimeter (submm) sources within a 2.3'
(1.2Mpc at z=2.39) diameter area around the radio galaxy (which itself is a
weak submm source). We employ a 1.4-GHz map to accurately locate the
counterpart of one of these sources, SMMJ17142+5016, and identify this source
with a narrow-line AGN with an extended Ly-alpha halo at z=2.390 which is
member of the structure around 53W002. Hence SMMJ17142+5016 is the first
spectroscopically-confirmed, submm-selected companion to a high-redshift radio
galaxy. We discuss the OHS JHK spectrum of this galaxy and in addition present
five new constraints on its spectral energy distribution longward of 1um, using
these to estimate its bolometric luminosity as ~8x10^12 Lo, or a star formation
rate of ~1000Mo/yr if young stars provide the bulk of the luminosity. This
result provides direct support for the statistical detection of over-densities
of SCUBA galaxies around high-redshift radio galaxies and confirms theoretical
predictions that SCUBA galaxies, as the progenitors of massive ellipticals,
should be strongly clustered in the highest density regions of the distant
Universe.


title:
Supersymmetric dark matter in M31: can one see neutralino annihilation
  with CELESTE?

abstract:
  It is widely believed that dark matter exists within galaxies and clusters of
galaxies. Under the assumption that this dark matter is composed of the
lightest, stable supersymmetric particle, assumed to be the neutralino, the
feasibility of its indirect detection via observations of a diffuse gamma-ray
signal due to neutralino annihilations within M31 is examined. To this end,
first the dark matter halo of the close spiral galaxy M31 is modeled from
observations, then the resultant gamma-ray flux is estimated within
supersymmetric model configurations. We conclude that under favorable
conditions such as the rapid accretion of neutralinos on the central black hole
in M31 and/or the presence of many clumps inside its halo with $r^{-3/2}$ inner
profiles, a neutralino annihilation gamma-ray signal is marginally detectable
by the ongoing collaboration CELESTE.


title: Continuum Equations for Stellar Dynamics

abstract:
  The description of a stellar system as a continuous fluid represents a
convenient first approximation to stellar dynamics, and its derivation from the
kinetic theory is standard. The challenge lies in providing adequate closure
approximations for the higher-order moments of the phase-space density function
that appear in the fluid dynamical equations. Such closure approximations may
be found using representations of the phase-space density as embodied in the
kinetic theory. In the classic approach of Chapman and Enskog, one is led to
the Navier-Stokes equations, which are known to be inaccurate when the mean
free paths of particles are long, as they are in many stellar systems. To
improve on the fluid description, we derive here a modified closure relation
using a Fokker-Planck collision operator. To illustrate the nature of our
approximation, we apply it to the study of gravitational instability. The
instability proceeds in a qualitative manner as given by the Navier-Stokes
equations but, in our description, the damped modes are considerably closer to
marginality, especially at small scales.


title: The Type la Supernova 2001V in NGC 3987

abstract:
  CCD photometry of the type Ia SN 2001V occured in the edge-on spiral galaxy
NGC 3987 is presented. The observations made through Johnson-Cousins BVRI
filters were collected from Feb. 24 (t = -8 days, with respect to B-maximum),
up to May 5 (t = +62 days). The light curves are analyzed with the revised
Multi-Colour Light Curve Shape (MLCS) method by fitting template vectors to the
observed light curves simultaneously. The reddening of SN 2001V is estimated to
be E(B-V)=0.05 mag, while the galactic component is E(B-V) = 0.02 mag,
suggesting that part of the reddening may be due to the ISM in the host galaxy.
The Delta parameter in MLCS converged to -0.47 mag, indicating that this SN was
overluminous relative to the majority of Type Ia SNe. The inferred distance to
its host galaxy, NGC 3987, is 74.5 \pm 5 Mpc, which is in good agreement with
recently determined kinematic distances, based on radial velocity corrected for
Virgo-infall and Hubble constant H_0 = 65 km/s/Mpc.


title: Confirmation of Two Cyclotron Lines in Vela X-1

abstract:
  We present pulse phase-resolved X-ray spectra of the high mass X-ray binary
Vela X-1 using the Rossi X-ray Timing Explorer. We observed Vela X-1 in 1998
and 2000 with a total observation time of ~90 ksec. We find an absorption
feature at 23.3 +1.3 -0.6 kev in the main pulse, that we interpret as the
fundamental cyclotron resonant scattering feature (CRSF). The feature is
deepest in the rise of the main pulse where it has a width of 7.6 +4.4 -2.2 kev
and an optical depth of 0.33 +0.06 -0.13. This CRSF is also clearly detected in
the secondary pulse, but it is far less significant or undetected during the
pulse minima. We conclude that the well known CRSF at 50.9 +0.6 -0.7 kev, which
is clearly visible even in phase-averaged spectra, is the first harmonic and
not the fundamental. Thus we infer a magnetic field strength of B=2.6 x 10^12
G.


title: The Infrared Spectrum of R Doradus

abstract:
  Here, we present our modelling (Ryde & Eriksson, 2002 A&A 386, 874) of the
2.6-3.7 micron spectrum of the red semiregular variable R Doradus observed with
the Short-Wavelength Spectrometer on board the Infrared Space Observatory. We
will also present the entire spectrum of R Dor up to 5 microns based on our
model photosphere in order to show which molecules are important for the
emergent spectrum.


title:
Spectral Response of the Pulsationally-Induced Shocks in the Atmosphere
  of BW Vulpeculae

abstract:
  The star BW Vul excites an extremely strong radial pulsation that grows in
its envelope and is responsible for visible shock features in the continuum
flux and spectral line profiles emerging in the atmosphere At two phases
separated by 0.8 cycles. Material propelled upwards in the atmosphere from the
shock returns to the lower photosphere where it creates a second shock just
before the start of the next cycle. We have obtained three nights of echelle
data for this star over about 5 pulsation cycles (P = 0.201 days) in order to
evaluate the effects of on a number of important lines in the spectrum,
including the HeI 5875A and 6678A lines. These data were supplemented by
archival high-dispersion IUE (UV) data from 1994. A comparison of profiles of
the two HeI lines during the peak of the infall activity suggests that
differences in the development of the blue wing at this time are due to heating
and short-lived formations of an optically thin layer above the atmospheric
region compressed by the infall. This discovery and the well-known decreases in
equivalent widths of the CII 6578-83A doublet at the two shock phases, suggests
that shock flattens the temperature gradient and produces heating in heating
the upper atmosphere. Except for absorptions in the blue wings of the UV
resonance lines, we find no evidence for sequential shock delays arriving at
various regions of line formation of the photosphere (a "Van Hoof effect").
Phase lags cited by some former observers may be false indicators arising from
varying degrees of desaturation of multiple lines, such as for the red HeI
lines. In addition, an apparent lag in the equivalent width curve of lines
arising from less excited atomic levels could instead be caused by post-shock
cooling, followed by a rebound shock.


title:
X-Ray Evidence for Flare Density Variations and Continual Chromospheric
  Evaporation in Proxima Centauri

abstract:
  Using the XMM-Newton X-ray observatory to monitor the nearest star to the
Sun, Proxima Centauri, we recorded the weakest X-ray flares on a magnetically
active star ever observed. Correlated X-ray and optical variability provide
strong support for coronal energy and mass supply by a nearly continuous
sequence of rapid explosive energy releases. Variable emission line fluxes were
observed in the He-like triplets of OVII and NeIX during a giant flare. They
give direct X-ray evidence for density variations, implying densities between
2x10^{10} - 4x10^{11} cm^{-3} and providing estimates of the mass and the
volume of the line-emitting plasma. We discuss the data in the context of the
chromospheric evaporation scenario.


title:
The chemical composition of White Dwarfs as a test of convective
  efficiency during core He-burning

abstract:
  Pulsating white dwarfs provide constraints to the evolution of progenitor
stars. We revise He-burning stellar models, with particular attention to core
convection and to its connection with the nuclear reactions powering energy
generation and chemical evolution Theoretical results are compared to the
available measurements for the variable white dwarf GD 358, which indicate a
rather large abundance of central oxygen. We show that the attempt to constrain
the relevant nuclear reaction rate by means of the white dwarf composition is
faced with a large degree of uncertainty related to evaluating the efficiency
of convection-induced mixing.By combining the uncertainty of the convection
theory with the error on the relevant reaction rate we derive that the present
theoretical prediction for the central oxygen mass fraction in white dwarfs
varies between 0.3 and 0.9. Unlike previous claims, we find that models taking
into account semiconvection and a moderate C12(alpha,gamma)O16 reaction rate
are able to account for a high central oxygen abundance. The rate of the
C12(alpha,gamma)O16 used in these models agrees with the one recently obtained
in laboratory experiments (Kunz et al. 2002). On the other hand, when
semiconvection is inhibited, as in the case of classical models (bare
Schwarzschild criterion) or in models with mechanical overshoot, an extremely
high rate of the C12(\alpha,\gamma)O16 reaction is needed to account for a
large oxygen production. Finally, we show that the apparent discrepancy between
our result and those reported in previous studies depends on the method used to
avoid the convective runaways (the so called breathing pulses), which are
usually encountered in modeling late stage of core He-burning phase.


title: Spectral Features and Masses in the PeV Region

abstract:
  An analysis is made of the masses and spectral features for cosmic rays in
the PeV region, insofar as they have a bearing on the problem of the
interaction of cosmic ray particles. In our Single Source Model we identified
two 'peaks' seen in a summary of the world's data on primary spectra, and
claimed that they are probably due to oxygen and iron nuclei from a local,
recent supernova. In the present work we examine other possible mass
assignments. We conclude that of the other possibilities only Helium and Oxygen
(instead of O and Fe) has much chance of success; the original suggestion is
still preferred, however. Concerning our location with respect to the SNR
shell, the analysis suggests that we are close to it - probably just inside.


title:
Galaxy Star-Formation as a Function of Environment in the Early Data
  Release of the Sloan Digital Sky Survey

abstract:
  (Abridged) We present in this paper a detailed analysis of the effect of
environment on the star-formation activity of galaxies within the EDR of the
SDSS. We have used the Halpha emission line to derive the star-formation rate
(SFR) for each galaxy within a volume-limited sample of 8598 galaxies with 0.05
< z < 0.095 and M(r)<= -20.45. We find that the SFR of galaxies is strongly
correlated with the local (projected) galaxy density and thus we present here
the density-SFR relation that is analogous to the density-morphology relation.
The effect of density on the SFR of galaxies is seen in three ways. First, the
overall distribution of SFRs is shifted to lower values in dense environments
compared with the field population. Second, the effect is most noticeable for
the strongly star-forming galaxies in the 75th percentile of the SFR
distribution. Third, there is a ``break'' (or characteristic density) in the
density-SFR relation at a local galaxy density of 1h-2 Mpc-2. To understand
this break further, we have studied the SFR of galaxies as a function of
clustercentric radius from 17 clusters and groups objectively selected from the
SDSS EDR data. The distribution of SFRs of cluster galaxies begins to change,
compared with the field population, at a clustercentric radius of 3-4 virial
radii, which is consistent with the characteristic break in density that we
observe in the density-SFR relation. Our tests suggest that the
density-morphology relation alone is unlikely to explain the density-SFR
relation we observe. Taken all together, these works demonstrate that the
decrease in SFR of galaxies in dense environments is a universal phenomenon
over a wide range in density (from 0.08 to 10h-2 Mpc-2) and redshift (out to z
= 0.5).


title: Detection of Optical Synchrotron Emission from the Radio Jet of 3C279

abstract:
  We report the detection of optical and ultraviolet emission from the
kiloparsec scale jet of the well-known quasar 3C~279. A bright knot, discovered
in archival V and U band {\it Hubble Space Telescope} Faint Object Camera
images, is coincident with a peak in the radio jet $\sim0.6\arcsec$ from the
nucleus. The detection was also confirmed in Wide Field Planetary Camera-2
images. Archival Very Large Array and MERLIN radio data are also analyzed which
help to show that the high-energy optical/UV continuum, and spectrum, are
consistent with a synchrotron origin from the same population of relativistic
electrons responsible for the radio emission.


title: Orbital migration and the brown dwarf desert

abstract:
  The orbital elements of extreme mass ratio binaries will be modified by
interactions with surrounding circumstellar disks. For brown dwarf companions
to Solar-type stars the resulting orbital migration is sufficient to drive
short period systems to merger, creating a brown dwarf desert at small
separations. We highlight the similarities and the differences between the
migration of brown dwarfs and massive extrasolar planets, and discuss how
observations can test a migration model for the brown dwarf desert.


title:
The Physical Conditions of Intermediate Redshift MgII Absorbing Clouds
  from Voigt Profile Analysis

abstract:
  [Slightly Abridged] We present a detailed statistical analysis of the column
densities, N, and Doppler parameters, b, of MgII absorbing clouds at redshifts
0.4<z<1.2. We use the HIRES/Keck data and Voigt profile (VP) fitting results
presented by Churchill & Vogt (Paper I). The sample is comprised of 175 clouds
from 23 systems along 18 quasar lines of sight. In order to understand whether
inferred conditions could be "false", we performed extensive simulations of our
VP analyses. In brief, we find: (1) N(FeII) and N(MgII) are correlated at the
9-sigma level. There is a 5-sigma anti-correlation between N(MgI)/N(MgII) and
N(MgII). (2) Power-law fits to the distributions of N(MgII), N(FeII), and
N(MgI) yielded power-law slopes of -1.6, -1.7, and -2.0. (3) The modes of the
Doppler parameter distributions were <b>~5 km/s for MgII and FeII and <b>~7
km/s for MgI. The clouds are consistent with being thermally broadened, with
temperatures in the 30-40,000K range. (4) A two-component Gaussian model to the
velocity two-point correlation function yielded velocity dispersions of 54 km/s
and 166 km/s. The narrow component has roughly twice the amplitude of the
broader component. The width and amplitude of the broader component decreases
as equivalent width increases. (5) From photoionization models we find that the
column density ratios are most consistent with photoionization by the
extragalactic background, as opposed to stars. Based upon N(MgI)/N(MgII), it
appears that at least two-phase ionization models are required to explain the
data.


title:
COLA II - Radio and Spectroscopic Diagnostics of Nuclear Activity in
  Galaxies

abstract:
  We present optical spectroscopic observations of 93 galaxies taken from the
infra-red selected COLA (Compact Objects in Low Power AGN) sample. The sample
spans the range of far-IR luminosities from normal galaxies to LIRGs. Of the
galaxies observed, 78 (84%) exhibit emission lines. Using a theoretically-based
optical emission-line scheme we classify 15% of the emission-line galaxies as
Seyferts, 77% as starbursts, and the rest are either borderline AGN/starburst
or show ambiguous characteristics. We find little evidence for an increase in
the fraction of AGN in the sample as a function of far-IR luminosity but our
sample covers only a small range in infrared luminosity and thus a weak trend
may be masked. As a whole the Seyfert galaxies exhibit a small, but
significant, radio excess on the radio-FIR correlation compared to the galaxies
classified as starbursts. Compact (<0.05'') radio cores are detected in 55% of
the Seyfert galaxies, and these galaxies exhibit a significantly larger radio
excess than the Seyfert galaxies in which cores were not detected. Our results
indicate that there may be two distinct populations of Seyferts,
``radio-excess'' Seyferts, which exhibit extended radio structures and compact
radio cores, and ``radio-quiet'' Seyferts, in which the majority of the radio
emission can be attributed to star-formation in the host galaxy. No significant
difference is seen between the IR and optical spectroscopic properties of
Seyferts with and without radio cores. (Abridged)


title: A warped accretion disc in PX And ?

abstract:
  We have undertaken a photometric study of the SW Sex star, PX And. We clearly
identify a negative superhump signal which might be regarded as the signature
of a nodal precessing disc, possibly warped. PX And is also observed to possess
highly variable eclipse depth and we discuss two possible explanations.


title: Multi-frequency Analysis of the two CSS quasars 3C 43 & 3C 298

abstract:
  We present and discuss observations made with MERLIN and VLBI at 1.7 and 5
GHz of the two CSS quasars 3C 43 and 3C 298. They show quite different
morphologies, the former being a very distorted triple radio source, the latter
a small FRII type object. Relativistic effects and structural distortions are
discussed. Source ages are evaluated to be of the order of ~10^5 years,
therefore 3C 43 and 3C 298 can be considered fairly ''young'' radio sources.
Some inference is also derived on the properties of the medium surrounding the
radio emitting regions in these sub-galactic objects, whose density could be as
low as 10^-3 cm^-3.


title: Understanding dwarf galaxies as galactic building blocks

abstract:
  This is a summary of a general discussion held during the third
EuroConference on galaxy evolution. Various observational features of the
stellar populations in present--day dwarf galaxies were presented to introduce
the discussion on the possibility that these systems be the main building
blocks of spiral and elliptical galaxies. Many people in the audience turned
out to think that the inconsistencies among the observed properties of large
and dwarf galaxies are too many to believe that the former are built up only by
means of successive accretions of the latter. However, theorists of
hierarchical galaxy formation suggested that present--day dwarfs are not
representative of the galactic building blocks, which may be completely
invisible nowadays. Some of them suggested that, contrary to what is usually
assumed in hierarchical modelling, the actual building blocks were still fully
gaseous systems when their major mergers occurred. If this is the case, then
most of the inconsistencies can be overcome, and the scenario of hierarchical
galaxy formation becomes not too different from that of a slow gas accretion.


title: The Y^2 Stellar Evolutionary Tracks

abstract:
  We present a database of the latest stellar models of the $Y^2$ (Yonsei-Yale)
collaboration. This database contains the stellar evolutionary tracks from the
pre-main-sequence birthline to the helium core flash that were used to
construct the $Y^2$ isochrones. We also provide a simple interpolation routine
that generates stellar tracks for given sets of parameters (metallicity, mass,
and $\alpha$-enhancement).


title: Uncertainties of Synthetic Integrated Colors as Age Indicators

abstract:
  We investigate the uncertainties in the synthetic integrated colors of simple
stellar populations. Three types of uncertainties are from the stellar models,
the population synthesis techniques, and from the spectral libraries. Despite
some skepticism, synthetic colors appear to be reliable age indicators when
used for select age ranges. Rest-frame optical colors are good age indicators
at ages 2 -- 7Gyr. At ages sufficiently large to produce hot HB stars, the
UV-to-optical colors provide an alternative means for measuring ages. This UV
technique may break the age-metallicity degeneracy because it separates old
populations from young ones even in the lack of metallicity information. One
can use such techniques on extragalactic globular clusters and perhaps even for
high redshift galaxies that are passively evolving to study galaxy evolution
history.


title: Ultra Fast Self-Compton Cooling

abstract:
  We investigate the synchrotron self-Compton process in a planar shell taking
the shock structure into account. We find that the energy density of the seed
photons could deviate from the one-zone estimate by order of unity depending on
the shock velocity and the electron cooling time. We also find that as the
electron cooling becomes faster, the seed photons are increased more, so that
the inverse Compton cooling becomes more efficient. This ``ultra'' fast cooling
may work in such as gamma-ray bursts, blazars and microquasars.


title: Gas models for inflation and quintessence

abstract:
  Specific internal self-interactions in gaseous cosmic fluids are shown to
give rise to effective negative pressures which may violate the strong energy
condition. On this basis we discuss the transition from an initial de Sitter
phase to a subsequent Friedmann-Lema\^{\i}tre-Robertson-Walker period as a
non-equilibrium configuration of an ultrarelativistic gas. An accelerated
expansion of the present universe is obtained as the consequence of a negative
internal friction force which is self-consistently exerted on the
non-relativistic cold dark matter (CDM) type microscopic constituents of the
cosmic gas.


title:
Classical, non-linear, internal dynamics of large, isolated,
  vibrationally excited molecules

abstract:
  This work reports numerical experiments intended to clarify the internal
equilibration process in large molecules, following vibrational excitation. A
model of amorphous and oxygenated hydrocarbon macromolecule (about 500
atoms)--simulating interstellar dust-- is built up by means of a chemical
simulation code. Its structure is optimized, and its normal modes determined.
About 4.5 eV of potential energy is then deposited locally by perturbing one of
the C-H peripheral bonds, thus simulating the capture of a free H atom by a
dangling C bond. The ensuing relaxation of the system is followed for up to 300
ps, using a molecular mechanics code. When steady state is reached, spectra and
time correlation functions of kinetic energy and bond length fluctuations
indicate that most normal modes have been activated, but the motion remains
quasi-periodic or regular. By contrast, when the molecule is violently excited
or embedded in a thermal bath (modelled by Langevin dynamics), the same markers
clearly depict chaotic motions. Thus it appears that even such a large system
of oscillators is unable to provide the equivalent of a thermal bath to any one
of these, unless there are strong resonances between some of them. In general,
therefore, an energy of a few eV's deposited in an isolated molecule will not
be immediately thermalized. This conclusion is of consequence for the
interpretation of astronomical UIB spectra.
  Key Words:IS dust--UIBs--Excitation, relaxation processes.


title: Dynamics of relativistic reconnection

abstract:
  The dynamics of the steady-state Sweet--Parker-type reconnection is analyzed
in relativistic regime when energy density in the inflowing region is dominated
by magnetic field. The structure of reconnection layer (its thickness, inflow
and outflow velocities) depends on the ratio of two large dimensionless
parameters of the problem - magnetization parameter $\sigma \gg 1$ (the ratio
of the magnetic to particle energy-densities in the inflowing region) and the
Lundquist number $S$. The inflow velocity may be relativistic (for $ S<
\sigma$) or non-relativistic (for $ S > \sigma$), while the outflowing plasma
is moving always relativisticly. For extremely magnetized plasmas with $\sigma
\geq S^2$, the inflow four-velocity becomes of the order of the \Alfven
four-velocity.


title: Nature of fault planes in solid neutron star matter

abstract:
  The properties of tectonic earthquake sources are compared with those deduced
here for fault planes in solid neutron-star matter. The conclusion that
neutron-star matter cannot exhibit brittle fracture at any temperature or
magnetic field is significant for current theories of pulsar glitches, and of
the anomalous X-ray pulsars and soft-gamma repeaters.


title: The microlensing signatures of starspots

abstract:
  Point lens microlensing events with impact parameter close to the source
stellar radius allow the observer to study the surface brightness profile of
the lensed source. We have examined the effect of photospheric star spots on
multicolour microlensing lightcurves and investigated the detectability of such
spots in different wavebands as a function of spot temperature, position,
radius and lens trajectories. We include the effect of limb darkening and spot
projection as a function of position on the stellar disc. In particular we
apply the updated, state-of-the-art NEXTGEN stellar atmosphere models of
Hauschildt et al which predict very strong limb darkening and which are likely
to be applicable to the source stars considered here. Our results indicate that
star spots generally give a clear signature for transit events. Moreover, this
signature is strongly suppressed by limb darkening for spots close to the limb,
although the spots may still be clearly detected for favourable lens
trajectories. It is also clear that intensive temporal sampling throughout the
duration of the transit is necessary in order for such events to be effective
as a tool for imaging stellar photospheres. Nonetheless, with sufficiently well
sampled light curves of good photometric precision, microlensing can indeed
place useful constraints on the presence or otherwise of photospheric
starspots.


title: Model-independent dark energy differentiation with the ISW effect

abstract:
  We study the integrated Sachs-Wolfe (ISW) effect using a model-independent
parameterization of the dark energy equation of state. Cosmic variance severely
restricts the class of models distinguishable from Lambda-CDM. In particular if
the present value of the equation of state satisfies w_Q^o <-0.8, the only
distinguishable models are those with a rapidly varying equation of state,
characterized by a late transition occurring at redshifts z<3. Due to the
degeneracy with other cosmological parameters, models with a slowly varying
behavior cannot be differentiated from each other or from a cosmological
constant using even cosmic variance-limited CMB measurements. This may place a
fundamental limit on our understanding of the origin of the presently observed
acceleration.


title:
Time-resolved, multi-color photometry and spectroscopy of Virgo 4 (OU
  Vir): a high orbital inclination, short orbital period dwarf nova

abstract:
  We present multi-color photometry and time resolved spectroscopy of OU Vir.
The analysis of the quiescent light curve shows that OU Vir is characterized by
i) strong cycle-to-cycle brightness variations, and ii) hot spot modulated
light curve with grazing eclipse of the impact region. Colors are derived both
in- and out- of eclipse. The time-resolved spectroscopy allows us to produce
the radial velocity curve from the H$\alpha$ accretion disk emission line which
possibly reveals only weak evidence for hot spot line emission. The hot spot is
believed to be a turbulent optically thick region, producing mostly continuum
emission.


title: Gravitational Radiation from Gamma-Ray Burst Progenitors

abstract:
  We study gravitational radiation from various proposed gamma-ray burst (GRB)
progenitor models, in particular compact mergers and massive stellar collapses.
These models have in common a high angular rotation rate, and the final stage
involves a rotating black hole and accretion disk system. We consider the
in-spiral, merger and ringing phases, and for massive collapses we consider the
possible effects of asymmetric collapse and break-up, as well bar-mode
instabilities in the disks. We calculate the strain and frequency of the
gravitational waves expected from various progenitors, at distances based on
occurrence rate estimates. Based on simplifying assumptions, we give estimates
of the probability of detection of gravitational waves by the advanced LIGO
system from the different GRB scenarios.


title: The Mechanism of Core-Collapse Supernova Explosions: A Status Report

abstract:
  We review the status of the current quest to understand the mechanism of
core-collapse supernovae, if neutrino-driven. In the process, we discuss the
spherical explosion paradigm and its problems, some results from our new suite
of collapse calculations performed using a recently-developed 1D implicit,
multi-group, Feautrier/tangent-ray, Boltzmann solver coupled to explicit
predictor/corrector hydrodynamics, the basic energetics of supernova
explosions, and the promise of multi-D radiation/hydro simulations to explain
why the cores of massive stars explode.


title: The shear power spectrum from the COMBO-17 survey

abstract:
  We perform a cosmic shear analysis of the COMBO-17 survey -- a unique dataset
with shear quality R-band imaging and accurate photometric redshift estimates
(dz=0.05) for ~90% of galaxies to R=24.0. We undertake a full maximum
likelihood analysis to measure the weak lensing power spectra, Cl^kk, Cl^bb &
Cl^kb from l=400 to l=10^4. We find a strong measurement of the convergence
power over five fields. The b-field has a much lower significance, indicating
our data is free of major systematics, while the cross-correlation of k & b is
consistent with zero. We have also calculated the shear correlation functions
and variance over a range of scales between 0.5 and 20 arcmin. In addition, we
have used our results to measure cosmological parameters, constraining the
normalisation of the matter power spectrum to be sigma_8=(0.72 \pm
0.09)(Omega_m/0.3)^-0.49, where the errors quoted are 1-sigma due to the
intrinsic dispersion in galaxy ellipticities, cosmic and sampling variance. We
have significantly reduced the usual additional uncertainty in the median
redshift (z_m) of the survey by estimating z_m directly from the data. To
demonstrate the power of accurate redshift information, we have also measured
parameters from a shear analysis of only those galaxies with accurate
redshifts. In this case, we have eliminated the uncertainty in the redshift
distribution of sources and we show that the uncertainty in the resulting
parameter constraints are reduced by more than a factor of 2 compared to the
typical uncertainties found in cosmic shear surveys to date. Finally, we
combine our parameter measurements with constraints from the 2dFGRS and from
the CMB. With these additional constraints, we measure sigma_8=0.73 +0.05/-0.03
and Omega_m=0.27 +/- 0.02.


title:
Implications of Variability Patterns observed in TeV Blazars on the
  Structure of the Inner Jet

abstract:
  The recent long look X-ray observations of TeV blazars have revealed many
important new features concerning their time variability. In this paper, we
suggest a physical interpretation for those features based on the framework of
the internal and external shock scenarios. We present a simplified model
applicable to TeV blazars, and investigate through simulations how each of the
model parameters would affect to the observed light curve or spectrum. In
particular, we show that the internal shock scenario naturally leads to all the
observed variability properties including the structure function, but for it to
be applicable, the fractional fluctuation of the initial bulk Lorentz factors
must be small, with sigma_gamma / gamma_average < 0.01. This implies very low
dynamical efficiency of the internal shock scenario. We also suggest that
several observational quantities -- such as the characteristic time scale, the
relative amplitude of flares as compared to the steady (``offset'') component,
and the slope of the structure function -- can be used to probe the inner jet.
The results are applied to the TeV blazar Mrk421, and this, within the context
of the model, leads to the determination of several physical parameters: the
ejection of a shell with average thickness of ~1E13 cm occurs on average every
10 minutes, and the shells collide ~1E17 cm away from the central source.


title: The Galaxy Luminosity Function and Luminosity Density at Redshift z=0.1

abstract:
  Using a catalog of 147,986 galaxy redshifts and fluxes from the Sloan Digital
Sky Survey (SDSS) we measure the galaxy luminosity density at z=0.1 in five
optical bandpasses corresponding to the SDSS bandpasses shifted to match their
restframe shape at z=0.1. We denote the bands {0.1}{u}, {0.1}{g}, {0.1}{r},
{0.1}{i}, {0.1}{z}, with \lambda_{eff} = [3216, 4240, 5595, 6792, 8111]
Angstroms respectively. We use a maximum likelihood method which allows for a
general form for the shape of the luminosity function, simple luminosity and
number evolution, incorporates flux uncertainties, and accounts for the flux
limits of the survey. We find luminosity densities at z=0.1 in absolute AB
magnitudes in a Mpc^3 of [-14.10 \pm 0.15, -15.18 \pm 0.03, -15.90 \pm 0.03,
-16.24 \pm 0.03, -16.56 \pm 0.02] in [{0.1}{u}, {0.1}{g}, {0.1}{r}, {0.1}{i},
{0.1}{z}], respectively, using \Omega_0 =0.3, \Omega_\Lambda=0.7, and h=1, and
using Petrosian magnitudes. Similar results are obtained using Sersic model
magnitudes, suggesting that flux from outside the Petrosian apertures is not a
major correction. In the {0.1}{r} band, the best fit Schechter function to our
results has \phi_\ast = (1.49 \pm 0.04) \times 10^{-2} h^3 Mpc^{-3}, M_\ast -
5\log_{10} h = -20.44 \pm 0.01, and \alpha = -1.05\pm 0.01. In solar
luminosities, the luminosity density in {0.1}{r} is (1.84 \pm 0.04) h 10^8
L_{{0.1}{r},\odot} Mpc^{-3}. Our results are consistent with other estimates of
the luminosity density, from the Two-degree Field Galaxy Redshift Survey and
the Millenium Galaxy Catalog. They represent a substantial change (\sim 0.5
mag) from earlier SDSS luminosity density results based on commissioning data,
almost entirely because of the inclusion of evolution in the luminosity
function model.


title: Theoretical Spectra and Atmospheres of Extrasolar Giant Planets

abstract:
  We present a comprehensive theory of the spectra and atmospheres of
irradiated extrasolar giant planets. We explore the dependences on stellar
type, orbital distance, cloud characteristics, planet mass, and surface
gravity. Phase-averaged spectra for specific known extrasolar giant planets
that span a wide range of the relevant parameters are calculated, plotted, and
discussed. The connection between atmospheric composition and emergent spectrum
is explored in detail. Furthermore, we calculate the effect of stellar
insolation on brown dwarfs. We review a variety of representative observational
techniques and programs for their potential for direct detection, in light of
our theoretical expectations, and we calculate planet-to-star flux ratios as a
function of wavelength. Our results suggest which spectral features are most
diagnostic of giant planet atmospheres and reveal the best bands in which to
image planets of whatever physical or orbital characteristics.


title: Probing Dark Energy with SNAP

abstract:
  The distance-redshift relation observed for supernovae has led to the
discovery that the expansion of the universe is accelerating. A next generation
experiment, the Supernova/Acceleration Probe (SNAP), can investigate the nature
of the dark energy responsible, determining its energy density contribution and
equation of state. In addition, indications of time variation in the equation
of state could provide critical clues to the underlying fundamental physics; we
show how SNAP can achieve 3 sigma detection of such time variation in some
cases.


title: Diffusive Nuclear Burning on Neutron Star Envelopes

abstract:
  We calculate the rate of hydrogen burning for neutron stars (NSs) with
hydrogen atmospheres and an underlying reservoir of nuclei capable of proton
capture. This burning occurs in the exponentially suppressed diffusive tail of
H that extends to the hotter depths of the envelope where protons are rapidly
captured. This process, which we call diffusive nuclear burning (DNB), can
change the H abundance at the NS photosphere on timescales as short as
$10^{2-4}$ years. In the absence of diffusion, the hydrogen at the photosphere
(where $T\approx 10^6 {\rm K}$ and $\rho\sim 0.1 {\rm g cm^{-2}}$) would last
for far longer than a Hubble time. Our work impacts the understanding of the
evolution of surface abundances of isolated NSs, which is important to their
thermal spectrum and their effective temperature-core temperature relation. In
this paper, we calculate the rate of H burning when the overall consumption
rate is controlled by the nuclear timescales, rather than diffusion timescales.
The immediate application is for H burning on millisecond radio pulsars and in
quiescence for the accreting NS Cen X-4. We will apply this work to young radio
pulsars and magnetars once we have incorporated the effects of strong
$B>10^{12} {\rm G}$ magnetic fields.


title:
Possible in situ Tests of the Evolution of Elemental and Isotopic
  Abundances in the Solar Convection Zone

abstract:
  Helioseismology has shown that the chemical composition of the Sun has
changed over its lifetime. The surface abundance of helium and heavy elements
is believed to have decreased by up to 10% relative to their initial values.
However, this reduction is too small to be tested by direct observations of the
photospheric chemical composition. Here, we compare the predicted variations in
the solar photospheric composition with precise measurements of abundances in
meteorites and the solar wind composition. Although elemental composition
ratios can vary by roughly a percent (e. g. for Ca/Mg and Ca/Fe) over the Sun's
lifetime, their measurements are rife with uncertainties related to
uncertainties in the interpretation of meteoritic measurements, photospheric
determinations, and the complex fractionation processes occurring between the
upper photosphere and lower chromosphere and the corona. On the other hand,
isotopic ratios can be measured much more accurately and are not expected to be
affected as much by extrasolar processes, although more work is required to
quantify their effect. As the isotopic ratios evolve in the Sun proportionally
to the mass ratios of the isotopes, light elements yield the highest variations
in isotopic ratios. They are predicted to reach as high as 0.6% for
$^{18}$O/$^{16}$O and are only slightly lower in the cases of
$^{26}$Mg/$^{24}$Mg and $^{30}$Si/$^{28}$Si. Such a value should be well within
the sensitivity of new missions such as Genesis.


title:
An Unidentified Variable Gamma-Ray Source near the Galactic Plane
  Detected by COMPTEL

abstract:
  We report the detection of an unidentified gamma-ray source near the Galactic
plane by the COMPTEL experiment aboard the Compton Gamma-Ray Observatory. The
source is detected at a significance level of ~ 7.2 sigma in the energy range
1-3 MeV and at ~ 4.6 sigma in the lower 0.75-1 MeV band in the time period
March to July 1995. At energies above 3 MeV are only marginal hints or upper
limits obtained. The MeV spectrum has a soft shape. Strong flux variability is
found within one year at energies below 3 MeV. Possible counterparts of
galactic and extragalactic nature are discussed.


title:
An analysis of the emission line spectra of AG Pegasi between phases
  7.34 and 9.44

abstract:
  The UV and optical spectra from the HST FOS and from the FAST spectrograph at
the Whipple Observatory at different phases are analysed, leading to new
results about the configuration of AG Peg. Consistent modelling by the code
SUMA, which accounts for the coupled effect of photoionisation from the hot
star and the shock, shows the important role of at least three nebulae: 1) the
nebula between the stars, downstream of the shock created by collision of the
winds, which propagates in reverse towards the WD, 2) the nebula downstream of
the shock expanding in the outskirts of the giant atmosphere, and 3) the shock
propagating outwards the binary system, that is not reached by the hot source
radiation. The relative contribution of the three nebulae to the final spectra
at different phases are calculated for all the lines. It is found that the
contribution to the different lines changes with the viewing angle of the
system. The relatively low preshock density and magnetic field adopted in the
modelling of the expanding shocks reveal that they are merging with the ISM,
thus explaining the slow decline of AG Peg.


title:
On a mechanism for enhancing magnetic activity in tidally interacting
  binaries

abstract:
  We suggest a mechanism for enhancing magnetic activity in tidally interacting
binaries. We suppose that the deviation of the primary star from spherical
symmetry due to the tidal influence of the companion leads to stellar pulsation
in its fundamental mode. It is shown that stellar radial pulsation amplifies
torsional Alfv{\'e}n waves in a dipole-like magnetic field, buried in the
interior, according to the recently proposed swing wave-wave interaction
(Zaqarashvili 2001). Then amplified Alfv{\'e}n waves lead to the onset of
large-scale torsional oscillations, and magnetic flux tubes arising towards the
surface owing to magnetic buoyancy diffuse into the atmosphere producing
enhanced chromospheric and coronal emission.


title:
Evolutionary Synthesis Modelling of Young Star Clusters in Merging
  Galaxies

abstract:
  The observational properties of globular cluster systems (GCSs) are vital
tools to investigate the violent star formation histories of their host
galaxies. This violence is thought to have been triggered by galaxy
interactions or mergers. The most basic properties of a GCS are its luminosity
function (number of clusters per luminosity bin) and color distributions. A
large number of observed GCS show bimodal color distributions, which can be
translated into a bimodality in either metallicity and/or age. An additional
uncertainty comes into play when one considers extinction. These effects can be
disentangled either by obtaining spectroscopic data for the clusters or by
imaging observations in at least four passbands. This allows us then to
discriminate between various formation scenarios of GCSs, e.g. the merger
scenario by Ashman & Zepf, and the multi-phase collapse model by Forbes et.
al.. Young and metal-rich star cluster populations are seen to form in
interacting and merging galaxies. We analyse multiwavelength broad-band
observations of these young cluster systems provided by the ASTROVIRTEL
project.


title:
Large-Scale, Decelerating, Relativistic X-ray Jets from the Microquasar
  XTE J1550-654

abstract:
  We have discovered at x-ray and radio wavelengths large-scale moving jets
from the microquasar XTE J1550-654. Plasma ejected from near the black hole
traveled at relativistic velocities for at least four years. We present direct
evidence for gradual deceleration in a relativistic jet. The broadband spectrum
of the jets is consistent with synchrotron emission from high energy (up to 10
TeV) particles accelerated in shock waves formed within the relativistic ejecta
or by the interaction of the jets with the interstellar medium. XTE J1550-654
offers a unique opportunity to study the dynamical evolution of relativistic
jets on time scales inaccessible for active galactic nuclei jets, with
implications for our understanding of relativistic jets from Galactic x-ray
binaries and active galactic nuclei.


title: On the origin of nitrogen

abstract:
  The problem of the origin of nitrogen is considered within the framework of
an empirical approach. The oxygen abundances and nitrogen to oxygen abundances
ratios are derived in HII regions of a number of spiral galaxies through the
recently suggested P-method using more than six hundred published spectra. The
N/O - O/H diagram for HII regions in irregular and spiral galaxies is
constructed. It is found that the N/O values in HII regions of spiral galaxies
of early morphological types are higher than those in HII regions with the same
metallicity in spiral galaxies of late morphological types. This suggests a
long-time-delayed contribution to the nitrogen production. The N/O ratio of a
galaxy can then be used as an indicator of the time that has elapsed since the
bulk of star formation occurred, or in other words of the nominal "age" of the
galaxy as suggested by Edmunds and Pagel more than twenty years ago. The
scatter in N/O values at a given O/H can be naturally explained by differences
in star formation histories in galaxies. While low-metallicity dwarf galaxies
with low N/O do not contain an appreciable amount of old stars, low-metallicity
dwarf galaxies with an appreciable fraction of old stars have high N/O.
Consideration of planetary nebulae in the Small Magellanic Cloud and in the
Milky Way Galaxy suggests that the contribution of low-mass stars to the
nitrogen production is significant, confirming the conclusion that there is a
long-time-delayed contribution to the nitrogen production.


title:
A radio catalog of Galactic HII regions for applications from decimeter
  to millimeter wavelengths

abstract:
  By collecting the information from 24 previously published lists and
catalogs, we produce a comprehensive catalog (Master Catalog) of 1442 Galactic
HII regions. For each object, we quote the original fluxes and diameters as
well as the available information on radio line velocities, line widths and
line temperatures and the errors on these quantitities. References to the
original works are also reported. By exploiting all these data we produce a
Synthetic Catalog of fluxes and diameters (with corresponding errors) at 2.7
GHz. This choice is motivated by the extensive, although not complete,
information available at this frequency, widely spread among many different
catalogs, and by its relevance for both detailed studies on Galactic HII
regions and the extrapolation up to millimetric wavelengths. The catalog can be
used for detailed studies of Galactic HII regions and, by extrapolation, for
investigations of HII regions up to millimetric wavelengths. In particular, we
discuss the study of the effects of microwave emission from HII regions on the
new generation of Cosmic Microwave Background (CMB) experiments. We present
simulations of the detection of HII regions in the high resolution CMB survey,
and briefly analize some of the typical applications of our catalog to the
evaluation of CMB anisotropy experiments such as calibration, beam
reconstruction and straylight effects. The Master Catalog and the Synthetic
Catalog are available via ftp at: cdsarc.u-strasbg.fr. This work is related to
Planck-LFI activities.


title: The 2MASS Tully-Fisher Relation and Local Peculiar Velocities

abstract:
  This study assesses the utility of applying the Tully-Fisher (TF) relation
using photometric data from the 2MASS project. This is achieved by performing a
preliminary analysis using 2MASS extended source data with the SCI sample of
Giovanelli et al. (1997). Distances and peculiar velocities are measured for 11
clusters out to approx. 75/h Mpc. Statistics are found to be limited by the 47%
coverage of the current 2MASS second incremental release. However, the 2MASS J,
H and K-band photometry produce results in good agreement with those derived
from the SCI I-band data. These results are also generally in reasonable
agreement with Giovanelli et al.s' (1997, 1998) own analysis. Comparison of the
results obtained with two different 2MASS magnitudes suggests they are not
overly sensitive to the type of magnitude used. It is concluded that the 2MASS
TF is a useful tool for distance and peculiar velocity work, especially with
the improved coverage that will be provided by the full 2MASS release.
  A general discussion of the Tully-Fisher relation and previous work,
particularly in the near-infra-red, is also presented.


title: Observations of the neutral gas and dust in the radio galaxy 3C305

abstract:
  We present MERLIN and Hubble Space Telescope (HST) observations of the
central region of the nearby radio galaxy 3C305 and use them to study the gas
and dust in this object. The MERLIN observations are of neutral hydrogen (HI)
absorption against the strong non-thermal 20cm continuum seen towards the
central 4kpc of 3C305. Our 0.2-arcsec (160 pc) resolution observations show
that the HI absorption is highly localised against the south-western
radio-emission with column densities 1.9x10^21/cm2. The absorption is broad and
red-shifted by 130 km/s relative to the systemic velocity. The HST images in
430nm, 702nm, [OIII] 500.7nm, [FeII] 1.64um and K-band polarization are
presented. Evidence is seen for coincidence of the [FeII] emission with the
knot at the end of the radio jet, suggesting the presence of shocks. We compare
the optical and radio images in order to investigate the relationship between
the dust and neutral gas. An unresolved (0.07-arcsec) nucleus is detected in H
and K and its properties are consistent with a quasar reddened by A(V)>4. We
propose that the absorption arises in a region of neutral gas and dust whose
structure is complex but is broadly consistent with an inclined disc
encircling, but not covering, the active galactic nucleus. A comparison of the
neutral gas observations and previous emission-line observations suggests that
both the neutral and ionised gas are undergoing galactic rotation towards the
observer in the north-east and away from the observer in the south-west. We
propose that the outflow giving rise to the radio emission has a component
towards the observer in the north-east and away from the observer in the
south-west.


title: SIMBOL-X, an X-ray telescope for the 0.5-70 keV range

abstract:
  SIMBOL-X is a high energy "mini" satellite class mission that is proposed by
a European collaboration for a launch in 2009. SIMBOL-X is making use of a
classical X-ray mirror, of ~600 cm2 maximum effective area, with a 30 m focal
length in order to cover energies up to several tens of keV. This focal length
will be achieved through the use of two spacecrafts in a formation flying
configuration. This will give to SIMBOL-X unprecedented spatial resolution (20
arcsec HEW) and sensitivity in the hard X-ray range. By its coverage, from 0.5
to 70 keV, and sensitivity, SIMBOL-X will be an excellent instrument for the
study of high energy processes in a large number of sources, both compact and
extended.


title:
Simultaneous Optical and X-ray Observations of Flares and Rotational
  Modulation on the RS CVn Binary HR 1099 (V711 Tau) from the MUSICOS 1998
  Campaign

abstract:
  We present simultaneous and continuous observations of the H$\alpha$,
H$\beta$, He {\sc i} D$_{3}$, Na {\sc i} D$_{1}$,D$_{2}$ doublet and the Ca
{\sc ii} H & K lines for the RS CVn system HR 1099. The spectroscopic
observations were obtained during the MUSICOS 1998 campaign involving several
observatories and instruments, both echelle and long-slit spectrographs. During
this campaign, HR 1099 was observed almost continuously for more than 8 orbits
of $2\fd8$. Two large optical flares were observed, both showing an increase in
the emission of H$\alpha$, Ca {\sc ii} H & K, H$\beta$ and He {\sc i} D$_{3}$
and a strong filling-in of the Na {\sc i} D$_{1}$,D$_{2}$ doublet.
{Contemporary photometric observations were carried out with the robotic
telescopes APT-80 of Catania and Phoenix-25 of Fairborn Observatories. Maps of
the distribution of the spotted regions on the photosphere of the binary
components were derived using the Maximum Entropy and Tikhonov photometric
regularization criteria}. Rotational modulation was observed in H$\alpha$ and
He {\sc i} D$_{3}$ in anti-correlation with the photometric light curves. Both
flares occurred at the same binary phase (0.85), suggesting that these events
took place in the same active region. Simultaneous X-ray observations,
performed by ASM on board RXTE, show several flare-like events, some of which
correlate well with the observed optical flares. Rotational modulation in the
X-ray light curve has been detected with minimum flux when the less active G5 V
star was in front. A possible periodicity in the X-ray flare-like events was
also found.


title: Scientific goals of the UKIRT Infrared Deep Sky Survey

abstract:
  UKIDSS is the next generation near-infrared sky survey. The survey will
commence in early 2004, and over 7 years will collect 100 times as many photons
as 2MASS. UKIDSS will use the UKIRT Wide Field Camera to survey 7500 square
degrees of the northern sky, extending over both high and low Galactic
latitudes, in JHK to K=18.5 (over three magnitudes deeper than 2MASS). UKIDSS
will be the true near-infrared counterpart to the Sloan survey, and will
produce as well a panoramic clear atlas of the Galactic plane. In fact UKIDSS
is made up of five surveys and includes two deep extra-Galactic elements, one
covering 35 square degrees to K=21, and the other reaching K=23 over 0.77
square degrees. This paper provides the details of the five UKIDSS surveys and
describes the main science goals.


title: AGN fueling: the observational point of view

abstract:
  Observations at multiple wavelengths are reviewed to search for evidence for
fueling mechanisms in galaxies, both for nuclear starbursts and AGN activity.
Although it is undisputed that dynamical perturbations such as bars or tidal
interactions accumulate gas in the central regions and sometimes trigger
nuclear starbursts, the evidence remains scarce that these are necessary to
fuel AGNs. Interpretations in terms of time-scales, feed-back, and black hole
evolution are discussed. It is suggested that the AGN phase corresponds to the
early-type phases of galaxies.


title:
Color, spectral and morphological transformations of galaxies in
  clusters

abstract:
  In this review I focus on the galactic properties in clusters at $z>0.1-02$.
The most salient results regarding the evolution in galaxy colors, spectral
features and morphologies are discussed.


title: CLASS B0445+123: a new two-image gravitational lens system

abstract:
  A new two-image gravitational lens system has been discovered as a result of
the Cosmic Lens All-Sky Survey (CLASS). Radio observations with the VLA, MERLIN
and the VLBA at increasingly higher resolutions all show two components with a
flux density ratio of ~7:1 and a separation of 1.34". Both components are
compact and have the same spectral index. Followup observations made with the
VLA at 8.4 GHz show evidence of a feature to the south-east of the brighter
component and a corresponding extension of the weaker component to the
north-west. Optical observations with the WHT show ~1.7" extended emission
aligned in approximately the same direction as the separation between the radio
components with an R-band magnitude of 21.8 +/- 0.4.


title: Tidal dwarfs in the M81 group: the second generation?

abstract:
  We derive quantitative star formation histories of the four suspected tidal
dwarf galaxies in the M81 group, HolmbergIX, BK3N, Arp-loop (A0952+69), and
Garland, using Hubble Space Telescope/Wide Field Planetary Camera2 images in
F606W and F814W obtained as part of a Snapshot survey of dwarf galaxies in the
Local Universe. We consider the spatial distribution and ages of resolved
stellar populations in these dwarf irregular galaxies. We use synthetic
color-magnitude diagrams to derive the ages of the major star formation
episodes, star formation rates, and approximate metallicity ranges. All the
galaxies show evidence of continuous star formation between about 20 and 200
Myr ago with star formation rates in the range 7.5*10^(-3)- 7.6*10^(-4)
M(sun)/yr. The metallicity of the detected stars spans a wide range, and have
lower than solar abundance. A possible scenario is that all four dwarf galaxies
were formed from material in the metal-poor outer part of the giant spiral
galaxy M81 after the tidal interaction between M81, M82, and NGC3077 about 200
Myr ago. While we do not directly detect pronounced old stellar populations,
the photometric limits of our data are such that the presence of such a
population is not entirely ruled out.


title: Did SN 1989B Exhibit a Light Echo?

abstract:
  The late light curves of SN 1989B exhibited an emission excess relative to
other type Ia supernovae. We investigate whether this emission excess suggests
light echo emission from this supernova, or rather intense background galaxy
contamination at the location of the supernova. We conclude that stellar
emission can better explain the late spectra, and that the emission excess is
likely due to background contamination.


title: Comment on "Chandra Reveals The X-ray Glint in the Cat's Eye"

abstract:
  Chu et al (2001; ApJ, 533, L69) report that they find the diffuse X-ray
emission from the Cat's Eye Nebula, NGC 6543, to be inconsistent with nebular
abundances but consistent with abundances expected for the stellar wind
although the location of the emission and the temperature they derive for the
X-ray emitting region of NGC 6543 require that a significant fraction of the
X-ray emitting material be nebular. A recent, refined, determination by
Bernard-Salus et al (personal communication) of nebular abundances in NGC 6543
incorporating infrared, optical, and ultraviolet observations provides a
resolution of this apparent anomaly.


title: The ROTSE-III Robotic Telescope System

abstract:
  The observation of a prompt optical flash from GRB990123 convincingly
demonstrated the value of autonomous robotic telescope systems. Pursuing a
program of rapid follow-up observations of gamma-ray bursts, the Robotic
Optical Transient Search Experiment (ROTSE) has developed a next-generation
instrument, ROTSE-III, that will continue the search for fast optical
transients. The entire system was designed as an economical robotic facility to
be installed at remote sites throughout the world. There are seven major system
components: optics, optical tube assembly, CCD camera, telescope mount,
enclosure, environmental sensing & protection and data acquisition. Each is
described in turn in the hope that the techniques developed here will be useful
in similar contexts elsewhere.


title:
Vertical scaleheights in a gravitationally coupled, three-component
  Galactic disk

abstract:
  The vertical scaleheight of the atomic hydrogen gas shows a remarkably flat
distribution with the galactocentric radius in the inner Galaxy. This has been
a long-standing puzzle (Oort 1962) because the gas scaleheight should increase
with radius when treated as responding to the gravitational potential of the
exponential stellar disk. We argue that the gravitational force of the
molecular and atomic hydrogen gas should also be brought into the picture to
explain this. We treat the stars, the HI and H_2 gas as three gravitationally
coupled components in the Galactic disk, and find the response of each
component to the joint potential and thus obtain their vertical distribution in
a self-consistent fashion. The effect of the joint potential is different for
the three components because of their different velocity dispersions. We show
that this approach cohesively and naturally explains the observed scaleheight
distribution of all the three components, namely, the HI and H_2 gas and the
stars, in the region studied (2-12 kpc). This includes the constant scaleheight
for the HI seen in the inner Galaxy. The effect of H_2 dominates in the
molecular ring region of 4-8.5 kpc, while that due to HI is dominant in the
outer Galaxy.


title:
Nitrogen Abundances in DLA Systems: The Combined Effects of SNII and
  SNIa in a Hierarchical Clustering Scenario

abstract:
  The combined enrichment of Supernovae II and I in a hierarchical clustering
scenario could produce regions with low N content respect to $\alpha$-elements
consistent with observed values measured in Damped Ly-$\alpha$ (DLAs). We have
studied the formation of DLAs in a hierarchical clustering scenario under the
hypothesis that the building blocks of current field galaxies could be part of
the structures mapped by DLAs. In our models the effects of the non-linear
evolution of the structure (which produces bursty star formation histories, gas
infall, etc.) and the contributions of SNIa and SNII are found to be
responsible of producing these N regions with respect to the $\alpha$-elements.
Although SNIa are not main production sites for Si or O, because of the
particular timing Consistently, we found the simulated low nitrogen DLAs to
have sub-solar [Fe/H]. We show that low nitrogen DLAs have experienced
important star formation activity in the past with higher efficiency than
normal DLAs. Our chemical model suggests that SNIa play a relevant role in the
determination of the abundance pattern of DLA and, that the observed low
nitrogen DLA frequency could be explained taking into account the time-delay of
$\approx $ 0.5 Gyr introduced by these supernova to release metals.


title:
Long-term Properties of Accretion Disks in X-ray Binaries: I. the
  variable third period in SMC X-1

abstract:
  Long term X-ray monitoring data from the RXTE ASM and CGRO BATSE reveal that
the third (superorbital) period in SMC X-1 is not constant, but varies between
40-60 days. A dynamic power spectrum analysis indicates that the third period
has been present continuously throughout the five years of ASM observations.
This period changed smoothly from 60 days to 45 days and then returned to its
former value, on a timescale of approximately 1600 days. During the nearly 4
years of overlap between the CGRO & RXTE missions, the simultaneous BATSE hard
X-ray data confirm and extend this variation in SMC X-1. Our discovery of such
an instability in the superorbital period of SMC X-1 is interpreted in the
context of recent theoretical studies of warped, precessing accretion disks. We
find that the behaviour of SMC X-1 is consistent with a radiation-driven
warping model.


title: The Environmental Dependence of Star Formation in the Nearby Universe

abstract:
  We have investigated how the incidence of star-forming galaxies varies with
the environment using a volume-limited sample of nearby galaxy spectra
extracted from the 2dF Galaxy Redshift Survey. The environment is characterized
by the local number density of galaxies, corrected for sample incompleteness
and border effects. Using the equivalent widths of [O II]$\lambda$3727 and
H$\delta$ we discriminate the star-forming galaxies in two classes, starbursts
and ordinary star-forming galaxies, and evaluate their properties as a function
of the local density. We show that the fraction of ordinary star-forming
galaxies decreases regularly with increasing density, indicating that star
formation is sensitive to the environment for all range of densities present in
the sample. The fraction of starbursts is approximately independent of the
density and, consequently, the fraction of starbursts relative to star-forming
galaxies increases with local density. This suggests that a mechanism that acts
everywhere, like tidal interactions, is the responsible for triggering
starbursts. We also show that while the mean EW(H$\alpha$) of ordinary
star-forming galaxies is progressively reduced as density increases, for
starbursts it suffers a strong decrease at densities corresponding to scales of
$\rho^{-1/3} \sim 2.5 ~h^{-1}$ Mpc. A visual inspection of starburst images in
the {\it Digital Sky Survey} reveals that this corresponds to a change in the
morphology of starburst galaxies, from mainly apparently normal spirals and
galaxies with apparently compact morphologies at low densities, to tidally
distorted spirals at high densities.


title: Chandra Detection of X-ray Absorption from Local Warm/Hot Gas

abstract:
  Recently, with the Chandra X-ray Telescope we have detected several local
X-ray absorption lines along lines-of-sight towards distant quasars. These
absorption lines are produced by warm/hot gas located in local intergalactic
space and/or in our Galaxy. I will present our observations and discuss the
origin of the X-ray absorption and its implications in probing the warm/hot
component of local baryons.


title: The Formation of Nuclear Rings in Barred Spiral Galaxies

abstract:
  Although nuclear rings of gas and star formation are common in barred spiral
galaxies, current theories of why and how they form do not provide the level of
detail needed to quantify the effect that these rings can have on the fueling
of active galactic nuclei and on the evolution of their host galaxy. In this
paper we use detailed modeling to show that existence of nuclear rings is
directly related to the existence of the orbit family whose major axis is
perpendicular to the major axis of the bar (x_2). We explore a large range of
barred galaxy potentials and for each potential we use a two-dimensional
hydrodynamic simulation to determine whether and at what radius a nuclear ring
forms. We compare the results of the hydrodynamic simulations to numerical
integrations of periodic orbits in a barred potential and show that the rings
only form when a minimum amount of x_2 orbits exists. Because the rings migrate
inwards with time as they accumulate gas, the radius at which a nuclear ring is
seen does not give direct information on the shape of the rotation curve. We
also show that the common assumption that nuclear rings are related to an inner
Lindblad resonance is incorrect. In fact, we show that there is no RESONANCE at
the inner Lindblad resonance in barred galaxies. We also compare the
predictions of this theory to HST observations and show that it correctly
predicts the observed gas and star formation morphology of nuclear rings.


title:
Abundances in Stars from the Red Giant Branch Tip to Near the Main
  Sequence Turn Off in M5

abstract:
  We present the iron abundance and abundance ratios for 18 elements with
respect to Fe in a sample of stars with a wide range in luminosity from
luminous giants to stars near the turnoff in the globular cluster M5. The
analyzed spectra, obtained with HIRES at the Keck Observatory, are of high
dispersion (R=35,000). We find that the neutron capture, the iron peak and the
alpha-element abundance ratios show no trend with Teff, and low scatter around
the mean between the top of the RGB and near the main sequence turnoff To
within the precision of the measurements (~0.1 dex), gravitationally induced
heavy element diffusion does not appear to be present among the stars near the
main sequence turnoff studied here. Our work and other recent studies suggest
that heavy element diffusion is inhibited in the surface layers of metal poor
stars. Differences in the Na abundance from star to star which extend to the
main sequence turnoff are detected in our sample in M5. The anti-correlation
between O and Na abundances, observed in other metal poor globular clusters, is
not detected in our sample, but it may be hidden among stars with only upper
limits for their O abundances. Overall the abundance ratios of M5 appear very
similar to those of M71, with the possible exception of the neutron capture
element Ba, where we argue that the apparent difference may be due to
difficulties in the analysis. As in M71, the alpha-elements Mg, Ca, Si and Ti
are overabundant relative to Fe. The results of our abundance analysis of 25
stars in M5 provide further evidence of abundance variations among specific
light elements at unexpectedly low luminosities, which cannot be explained by
our current understanding of stellar evolution.


title:
Constraints on Star Formation from the Close Packing of Protostars in
  Clusters

abstract:
  The mm-wave continuum sources (MCS) in Ophiuchus have mutual collision rates
less than their collapse rates by a factor of 10 to 100, suggesting most will
form stars without further interactions. However, this ratio of rates would
have exceeded unity in the past if the MCS were 2.5 times larger than they are
now. Such a high previous ratio was not likely, suggesting that the MCS grew
from smaller sizes at a constant high density, possible behind turbulent
shocks. Proximity constraints are even more important in massive clusters,
where massive stars with the same or greater space density are more strongly
interacting than the Ophiuchus MCS. As a result, the density contrast for MCS
must be larger in massive clusters than it is in Ophiuchus, or significant
coalescence will occur in the protostellar phase, possible forming a massive
black hole. A proportionality to the second power of the Mach number allows the
MCS cores to collapse independently. These results suggest that stars in dense
clusters generally form on a dynamical time by the continuous collection and
rapid collapse of turbulence-shocked gas. Implications of proximity constraints
on the initial stellar mass function are also discussed.


title: The effect of bandpass uncertainties on component separation

abstract:
  Multi-frequency measurements of the microwave sky can be decomposed into maps
of distinct physical components such as the cosmic microwave background (CMB)
and the Sunyaev-Zel'dovich (SZ) effect. Each of the multi--frequency
measurements is a convolution of the spectrum on the sky with the bandpass of
the instrument. Here we analytically calculate the contamination of the
component maps that can result from errors in our knowledge of the bandpass
shape. We find, for example, that for Planck an unknown 10% ramp across each
band results in a CMB map dT = dT_{CMB} - 4.3e-3 dT_{SZ} plus the usual
statistical noise. The variance of this contaminant is more than a factor of
100 below the noise variance at all angular scales and even further below the
CMB signal variance. This contamination might lead to an error in the velocity
of rich clusters inferred from the kinetic SZ effect, however the error is
negligible, O(50 km/s), if the bandpass is known to 10%. Bandpass errors might
be important for future missions measuring the CMB-SZ correlation.


title: Obscured AGN from the ELAIS Deep X-ray Survey

abstract:
  The sources discovered in deep hard X-ray surveys with 2-8 keV fluxes of
10^-14 erg cm^-2 s^-1 make up the bulk of the X-ray background at these
energies. We present here detailed multi-wavelength observations of three such
sources from the ELAIS Deep X-ray Survey. The observations include sensitive
near-infrared spectroscopy with the Subaru Telescope and X-ray spectral
information from the Chandra X-ray Observatory. The sources observed all have
optical-to-near-IR colours redder than an unobscured quasar and comprise a
reddened quasar, a radio galaxy and an optically-obscured AGN. The reddened
quasar is at a redshift z=2.61 and shows a very large X-ray absorbing column of
N_H approx 3.10^23 cm^-2. This contrasts with the relatively small amount of
dust reddening, implying a gas-to-dust ratio along the line-of-sight a hundred
times greater than that of the Milky Way. The radio galaxy at z=1.57 shows only
narrow emission lines, but has a surprisingly soft X-ray spectrum. The softness
of this spectrum either indicates an unusually low gas-to-dust ratio for the
absorbing medium or X-ray emission related to the young radio source. The host
galaxy is extremely red (R-K=6.4) and its optical/near-IR spectrum is best fit
by a strongly reddened (A_V~2) starburst. The third X-ray source discussed is
also extremely red (R-K=6.1) and lies in a close grouping of three other R-K>6
galaxies. No emission or absorption lines were detected from this object, but
its redshift (and that of one of the nearby galaxies) are constrained by
SED-fitting to be just greater than z=1. The extremely red colours of these two
galaxies can be accounted for by old stellar populations. These observations
illustrate the diverse properties of hard X-ray selected AGN.


title:
TeV gamma rays and cosmic rays from the nucleus of M87, a mis-aligned BL
  Lac object

abstract:
  The unresolved nuclear region of M87 emits strong non-thermal emission from
radio to X-rays. Assuming this emission to originate in the pc scale jet
aligned at $\theta \sim 30^\circ$ to the line of sight, we interpret this
emission in the context of the Synchrotron Proton Blazar (SPB) model. We find
the observed nuclear jet emission to be consistent with M87 being a mis-aligned
BL Lac Object and predict gamma-ray emission extending up to at least 100 GeV
at a level easily detectable by GLAST and MAGIC, and possibly by VERITAS
depending on whether it is high-frequency or low-frequency peaked. Predicted
neutrino emission is below the sensitivity of existing and planned neutrino
telescopes. Ultra-high energy neutrons produced in pion photoproduction
interactions decay into protons after escaping from the host galaxy. Because
energetic protons are deflected by the intergalactic magnetic field, the
protons from the decay of neutrons emitted in all directions, including along
the jet axis where the Doppler factor and hence emitted neutron energies are
higher, can contribute to the observed ultra-high energy cosmic rays. We
consider the propagation of these cosmic ray protons to Earth and conclude that
M87 could account for the observed flux if the extragalactic magnetic field
topology were favourable.


title: X-ray properties of 4U 1543-624

abstract:
  4U 1543-624 is a relatively bright persistent low-mass X-ray binary. Analysis
of archival data from ASCA, SAX and RXTE is presented. The X-ray continuum be
can modeled with the standard low-mass X-ray binary spectrum, an isothermal
blackbody and a Comptonized component. Variations in the luminosity and flux
ratio of the continuum components are seen. An increase in luminosity is
accompanied by a decrease in the blackbody luminosity and a hardening of the
spectrum. Most low-mass X-ray binaries have softer spectra and higher blackbody
luminosities in high luminosity states. The Fe K-alpha line is seen only in the
high luminosity spectra. A narrow feature near 0.7 keV, previously detected in
the ASCA data, is also seen in the SAX data. A qualitative model of the system
is presented. The X-ray observations can be explained by a low inclination
system (face-on disk) containing a slowly (P >> ms) rotating neutron star. A
slowly rotating neutron star would imply either that the system is a young
low-mass X-ray binary, or that the accretion rate is unusually low. The
empirical relation between optical and X-ray luminosity and orbital period
suggests a relatively short period.


title: Modes of disc accretion onto black holes

abstract:
  I review our current theoretical understanding of the different possible
rotating modes of accretion onto a black hole. I discuss both thick adiabatic
flows and radiatively efficient thin disc solutions. I present a new
self-consistent unified analytical description of two-phase thin disc--corona
systems in which magneto-rotational instability is responsible for angular
momentum transport in the disc and for the corona generation. Finally, I
briefly discuss the role of magnetic fields in bridging the gap between
accretion discs theory and jet production mechanisms


title:
A Spectrophotometric Method to Determine the Inclination of Class I
  Objects

abstract:
  A new method which enables us to estimate the inclination of Class I young
stellar objects is proposed. Since Class I objects are not spherically
symmetric, it is likely that the observed feature is sensitive to the
inclination of the system. Thus, we construct a protostar model by carefully
treating two-dimensional (2D) radiative transfer and radiative equilibrium. We
show from the present 2D numerical simulations that the emergent luminosity
L_SED,which is the frequency integration of spectral energy distribution (SED),
depends strongly on the inclination of the system i, whereas the peak flux is
insensitive to i. Based on this result, we introduce a novel indicator f_L,
which is the ratio of L_SED to the peak flux, as a good measure for the
inclination. By using f_L, we can determine the inclination regardless of the
other physical parameters. The inclination would be determined by f_L within
the accuracy of +- 5 degree, if the opening angle of bipolar outflows is
specified by any other procedure. Since this spectrophotometric method is
easier than a geometrical method or a full SED fitting method, this method
could be a powerful tool to investigate the feature of protostars statistically
with observational data which will be provided by future missions, such as
SIRTF, ASTRO-F, and ALMA.


title: Cosmological Parameters and Black Holes

abstract:
  This work is related to different questions within cosmology. The principal
idea herein is to develop cosmological knowledge making use of the analyses of
observational data in order to find the values of the matter density Omega_m
and vacuum energy density Omega_Lambda.
  Data fitting is carried out using two statistical methods, chi^2 and maximum
likelihood. The data analysis exhibits that a low density and flat Universe is
strongly favoured.
  Applying the Omega_m value found for clusters of galaxies, we demonstrate
that clusters have very little room for baryonic dark matter. An upper limit to
the small but non-negligible sum of baryonic dark matter and galaxy mass can be
estimated, requiring the use of special statistics.
  A Toroidal Black Hole (TBH) study, in contrast to the Spherical Black Hole
(SBH), shows that the TBH can be used as an important tool in explaining AGN
phenomena.


title:
Development of an atmospheric Cherenkov imaging camera for the
  CANGAROO-III experiment

abstract:
  A Cherenkov imaging camera for the CANGAROO-III experiment has been developed
for observations of gamma-ray induced air-showers at energies from 10$^{11}$ to
10$^{14}$ eV. The camera consists of 427 pixels, arranged in a hexagonal shape
at 0.17$^\circ$ intervals, each of which is a 3/4-inch diameter photomultiplier
module with a Winston-cone--shaped light guide. The camera was designed to have
a large dynamic range of signal linearity, a wider field of view, and an
improvement in photon collection efficiency compared with the CANGAROO-II
camera. The camera, and a number of the calibration experiments made to test
its performance, are described in detail in this paper.


title: New Mass Estimators for Tracer Populations

abstract:
  We introduce the tracer mass estimator. This is a new and simple way to
estimate the enclosed mass from the projected positions and line of sight
velocities of a tracer population (such as globular clusters, halo stars and
planetary nebulae). Like the projected mass estimator, it works by averaging
(projected distance) x (radial velocity squared)/ G over the sample. However,
it applies to the commonest case of all, when the tracer population does not
follow the overall dark matter density. The method is verified against
simulated datasets drawn from Monte Carlo realisations of exact solutions of
the collisionless Boltzmann equation and applied to the recent M31 globular
cluster data set of Perrett et al. (2002), as well as to M31's satellite
galaxies.


title: On the Study of the Substructure of N-body Systems

abstract:
  Statistical properties of nonlinear systems revealed in an unexpected way
already in Fermi-Pasta-Ulam paper, are responsible for the appearance of
substructures. We represent a method within S-tree diagram formalism for
investigation of the substructures of N-body gravitating systems in a defined
time interval. This approach enables one to consider the link between
substructures of the system and its relative instability and is efficient for
the study of the substructures in clusters of galaxies.


title: Dark energy effects in the Cosmic Microwave Background Radiation

abstract:
  Understanding the nature of the dark energy is one of the most important task
in cosmology. In principle several cosmological observations can be used to
discriminate amid a static cosmological constant contribution and a dynamical
quintessence component. In view of the upcoming high resolution CMB
experiments, using a model independent approach we study the dark energy
imprint in the CMB anisotropy power spectrum and the degeneracy with other
cosmological parameters.


title:
Observational clues for a role of circumstellar accretion in PMS X-ray
  activity

abstract:
  We revisit the published analyses of ROSAT X-ray observations of the star
forming regions NGC 2264 and Chamaeleon I (~3 and ~5 Myr old respectively) in
the light of newly published optical data. At odds with previous results on
Chamaeleon I members, we find that low mass stars in both regions have
near-saturated emission levels. Similarly to what previously found in the Orion
Nebula Cluster, Weak Line T-Tauri Stars in NGC 2264 and in the Chamaeleon I
cloud have higher X-ray activity levels respect to Classical T Tauri Stars,
arguing in favor of a role of the disk and/or accretion in determining X-ray
emission.


title: Upper limit on the mass of RX J1856.5--3754 as a possible quark star

abstract:
  Recent deep Chandra LETG+HRC-S observations suggest the possibility that RX
J1856.5--3754 is a compact star whose radiation radius is 3.8--8.2 km. In this
paper, we systematically calculate the mass-radius relations of quark stars
within the bag model. Assuming that RX J1856.5--3754 is a pure quark star, we
derive an upper limit on its mass for various sets of the bag-model parameters.


title:
A census of metals at high and low redshifts and the connection between
  submillimetre sources and spheroid formation

abstract:
  Deep surveys in many wavebands have shown that the rate at which stars were
forming was at least a factor of 10 higher at z > 1 than today. Heavy elements
(metals) are produced by stars, and the star formation history deduced by these
surveys implies that a significant fraction of metals in the universe today
should already exist at z~2-3. However, only 10% of the total metals expected
to exist at this epoch have so far been accounted for (in DLAs and the Lyman
forest). In this paper, we use the results of submillimetre surveys of the
local and high redshift universe to show that there was much more dust in
galaxies in the past. We find that a large proportion of the missing metals are
traced by this dust, bringing the metals implied from the star formation
history and observations into agreement. We also show that the observed
distribution of dust masses at high redshift can be reproduced remarkably well
by a simple model for the evolution of dust in spheroids, suggesting that the
descendants of the dusty galaxies found in the deep submm surveys are the
relatively dust-free spiral bulges and ellipticals in the universe today.


title: The Three-Point Correlation Function for Spin-2 Fields

abstract:
  The three-point correlation function (3PCF) of the spin-2 fields, the cosmic
shear and cosmic microwave background polarization fields, is a statistical
measure of non-Gaussian signals. At each vertex of a triangle, the shear field
has two independent components. The resulting eight possible 3PCFs were
recently investigated by Schneider & Lombardi (2002) and Zaldarriaga &
Scoccimarro (2002). Using rotation and parity transformations they addressed
the question: how many non-zero components for the shear 3PCF exist? We address
this question using an analytical model and measurements from ray-tracing
simulations. We show that all the eight 3PCFs are generally non-zero and have
comparable amplitude. These eight 3PCFs can be used to improve the
signal-to-noise from survey data and their configuration dependence can be used
to separate the contribution from E and B-modes. We estimate the
signal-to-noise for measuring the shear 3PCF from weak lensing surveys using
simulated maps that include the noise due to intrinsic ellipticities. A deep
lensing survey with area exceeding 10 square degrees would allow for the
detection of the shear 3PCFs, but a survey area of order 100 square degrees is
needed for accurate measurements.


title:
The Unified Model & Evolution of Active Galaxies: Implications from a
  Spectropolarimetric Study

abstract:
  We extend the analysis presented in Tran (2001) of a spectropolarimetric
survey of the CfA and 12micron samples of Seyfert 2 galaxies (S2s). We confirm
that S2s with hidden broad line regions (HBLRs) tend to have hotter
circumnuclear dust temperatures, show mid-IR spectra more characteristic of S1
galaxies, and are intrinsically more luminous than non-HBLR S2s. The level of
obscuration and circumnuclear star formation, however, appear to be similar
between HBLR and non-HBLR S2 galaxies, based on an examination of various
observational indicators. HBLR S2s, on average, share many similar large-scale,
presumably isotropic, characteristics with Seyfert 1 galaxies (S1s), as would
be expected if the unified model is correct, while non-HBLR S2s generally do
not. The active nuclear engines of non-HBLR S2s then, appear to be truly weaker
than HBLR S2s, which in turn, are fully consistent with being S1s viewed from
another direction. There is also evidence that the fraction of detected HBLR
increases with radio power of the AGN. Thus, not all Seyfert 2 galaxies may be
intrinsically similar in nature, and we speculate that evolutionary processes
may be at work.


title:
Iron abundances and heating of the ICM in hydrodynamical simulations of
  galaxy clusters

abstract:
  Results from a large set of hydrodynamical SPH simulations of galaxy clusters
in a flat LCDM cosmology are used to investigate the metal enrichment and
heating of the ICM. The physical modeling of the gas includes radiative
cooling, star formation, energy feedback and metal enrichment that follow from
the explosions of SNe of type II and Ia. The metallicity dependence of the
cooling function is also taken into account. For a fiducial set of model
prescriptions the results indicate radial iron profiles in broad agreement with
observations; global iron abundances are also consistent with data. It is found
that the iron distribution in the ICM is critically dependent on the shape of
the metal deposition profile. For low temperatu re clusters simulations yield
iron abundances below the allowed observational range, unless it is introduced
a minimum diffusion length of metals in the ICM. The simulated
emission-weighted radial temperature profiles are in good agreement with data
for cooling flow clusters, but at very small distances from the cluster centres
($\sim 2%$ of the virial radii) the temperatures are a factor $\sim$ two higher
than the measured spectral values. The luminosity-temperature relation is in
excellent agreement with the data, cool clusters ($T_X\sim 1keV$) have a core
excess entropy of $\sim 200 keVcm^2$ and their X-ray properties are unaffected
by the amount of feedback energy that has heated the ICM. The fraction of hot
gas $f_g$ at the virial radius increases with $T_X$ and the distribution
obtained from the simulated cluster sample is consistent with the observational
ranges.


title: The Evolution of Stars and Gas in starburst Galaxies

abstract:
  In systems undergoing starbursts the evolution of the young stellar
population is expected to drive changes in the emission line properties. This
evolution is usually studied theoretically, with a combination of evolutionary
synthesis models for the spectral energy distribution of starbursts and
photoionization calculations. In this paper we present a more empirical
approach to this issue. We apply empirical population synthesis techniques to
samples of Starburst and HII galaxies in order to measure their evolutionary
state and correlate the results with their emission line properties. A couple
of useful tools are introduced which greatly facilitate the interpretation of
the synthesis: (1) an evolutionary diagram, whose axis are the strengths of the
young, intermediate age and old components of the stellar population mix, and
(2) the mean age of stars associated with the starburst, $\ov{t}_{SB}$. These
tools are tested with grids of theoretical galaxy spectra and found to work
very well even when only a small number of observed properties (absorption line
equivalent widths and continuum colors) is used in the synthesis.
  Starburst nuclei and HII galaxies are found to lie on a well defined sequence
in the evolutionary diagram. Using the empirically defined mean starburst age
in conjunction with emission line data we have verified that the equivalent
widths of H$\beta$ and [OIII] decrease for increasing $\ov{t}_{SB}$. The same
evolutionary trend was identified for line ratios indicative of the gas
excitation, although no clear trend was identified for metal rich systems. All
these results are in excellent agreement with long known, but little tested,
theoretical expectations.


title:
An Intermediate Redshift Supernova Search at ESO: Reduction Tools and
  Efficiency Tests

abstract:
  We present the reduction and archiving tools developed for our search for
supernovae at intermediate redshifts at ESO as well as the efficiency tests
performed. The data reduction recipes developed for the SN candidates selection
are described. All the variable sources detected are stored using a MySQL
database which enables the identification of previously detected variable
sources during past observational runs. Finally, experiments performed with
artificial stars have shown that seeing plays a crucial role for the limiting
magnitude of detection. Crucial is also the detection threshold used by
Sextractor.


title:
Testing gravity in Large Extra Dimensions using Bose-Einstein
  Condensates

abstract:
  Recent conjectures that there are mesoscopically ``large'' extra dimensions,
through which gravity propagates have interesting implications for much of
physics. The scenario implies gross departures from Newton's law of gravity at
small length scales. Testing departures from Coulomb's law on sub-millimetre
scales is hard. It is now possible to routinely create Bose-Einstein
condensates with de Broglie wavelengths of order a $\mu m$ and total size of
order $10 \mu m$. BEC condensates move coherently under gravitational
acceleration, and I propose that the transverse fringe shift due to the
acceleration of pair of interfering BECs passing a dense linear mass may be
measurable, and provide direct evidence for anomalous gravitational
acceleration. Ideally such experiments are best carried out in free fall to
maximise the time spent by a BEC in the non-Newtonian regime.


title: The Role of Helium Stars in the Formation of Double Neutron Stars

abstract:
  We have calculated the evolution of 60 model binary systems consisting of
helium stars in the mass range of M_He= 2.5-6Msun with a 1.4Msun neutron star
companion to investigate the formation of double neutron star systems.Orbital
periods ranging from 0.09 to 2 days are considered, corresponding to Roche lobe
overflow starting from the helium main sequence to after the ignition of carbon
burning in the core. We have also examined the evolution into a common envelope
phase via secular instability, delayed dynamical instability, and the
consequence of matter filling the neutron star's Roche lobe. The survival of
some close He-star neutron-star binaries through the last mass transfer episode
(either dynamically stable or unstable mass transfer phase) leads to the
formation of extremely short-period double neutron star systems (with
P<~0.1days). In addition, we find that systems throughout the entire calculated
mass range can evolve into a common envelope phase, depending on the orbital
period at the onset of mass transfer. The critical orbital period below which
common envelope evolution occurs generally increases with M_He. In addition, a
common envelope phase may occur during a short time for systems characterized
by orbital periods of 0.1-0.5 days at low He-star masses (~ 2.6-3.3Msun).
  The existence of a short-period population of double neutron stars increases
the predicted detection rate of inspiral events by ground-based
gravitational-wave detectors and impacts their merger location in host galaxies
and their possible role as gamma-ray burst progenitors. We use a set of
population synthesis calculations and investigate the implications of the
mass-transfer results for the orbital properties of DNS populations.


title: First Light and the Reionization of the Universe

abstract:
  The development of primordial inhomogeneities into the non-linear regime and
the formation of the first bound objects mark the transition from a simple
cooling universe -- described by just a few parameters -- to a very messy hot
one -- the realm of radiative, hydrodynamic and star formation processes. In
popular cold dark matter cosmological scenarios, stars and quasars may have
first appeared in significant numbers around a redshift of 10 or so, as the gas
within subgalactic halos cooled rapidly due to atomic processes and fragmented.
This early generation of sources generated the ultraviolet radiation and
kinetic energy that ended the cosmic ``dark ages'' and reheated and reionized
most of the hydrogen in the cosmos by a redshift of 6. The detailed thermal
history of the intergalactic medium -- the main repository of baryons at high
redshift -- during and soon after these crucial formative stages depends on the
power-spectrum of density fluctuations on small scales and on a complex network
of poorly understood `feedback' mechanisms, and is one of the missing link in
galaxy formation and evolution studies.