title: Lensing of ultra-high energy cosmic rays in turbulent magnetic fields

abstract:
  We consider the propagation of ultra high energy cosmic rays through
turbulent magnetic fields and study the transition between the regimes of
single and multiple images of point-like sources. The transition occurs at
energies around $E_c\simeq Z~41 {\rm EeV}(B_{rms}/5 \mu{\rm G}) (L/ 2 {\rm
kpc})^{3/2}\sqrt{50 {\rm pc}/L_c}$, where $L$ is the distance traversed by the
CR's with electric charge $Ze$ in the turbulent magnetic field of root mean
square strength $B_{rms}$ and coherence length $L_c$. We find that above $2
E_c$ only sources located in a fraction of a few % of the sky can reach large
amplifications of its principal image or start developing multiple images. New
images appear in pairs with huge magnifications, and they remain amplified over
a significant range of energies. At decreasing energies the fraction of the sky
in which sources can develop multiple images increases, reaching about 50% for
$E>E_c/2$. The magnification peaks become however increasingly narrower and for
$E<E_c/3$ their integrated effect becomes less noticeable. If a uniform
magnetic field component is also present it would further narrow down the
peaks, shrinking the energy range in which they can be relevant. Below $E\simeq
E_c/10$ some kind of scintillation regime is reached, where many demagnified
images of a source are present but with overall total magnification of order
unity. We also search for lensing signatures in the AGASA data studying
two-dimensional correlations in angle and energy and find some interesting
hints.


title:
Spectral Energy Distributions and Age Estimates of 78 Star Clusters in
  M33

abstract:
  In this third paper of our series, we present CCD spectrophotometry of 78
star clusters that were detected by Chandar, Bianchi, & Ford in the nearby
spiral galaxy M33. CCD images of M33 were obtained as a part of the BATC Color
Survey of the sky in 13 intermediate-band filters from 3800 to 10000{\AA}. By
aperture photometry, we obtain the spectral energy distributions of these 78
star clusters. As Chandar, Bianchi, & Ford did, we estimate the ages of our
sample clusters by comparing the photometry of each object with theoretical
stellar population synthesis models for different values of metallicity. We
find that the sample clusters formed continuously in M33 from $\sim
3\times10^6$ -- $10^{10}$ years. This conclusion is consistent with Chandar,
Bianchi, & Ford. The results also show that, there are two peaks in cluster
formation, at $\sim 8\times10^6$ and $\sim 10^9$ years in these clusters.


title: Long Term Operation of LISA and Galactic Close White Dwarf Binaries

abstract:
  The binary confusion noise spectrum at LISA band depends strongly on
observational period and abundance of Galactic close white dwarf binaries
(CWDBs). We have investigated how the number of the resolved Galactic CWDBs
varies with operation period of LISA, and found that the resolved number would
typically grows by a factor of 5 when the operation period increases from 1yr
to 10yr. We have also made a similar estimation for number of CWDBs whose chirp
signal can be measured in matched filtering analysis.


title: Thermal Featureless Spectrum: Evidence for Bare Strange Stars

abstract:
  Motivated by trying to understand the absence of spectral lines in the
thermal components of the X-ray compact sources observed recently by Chandra or
XMM, we propose that these sources could be simply bare strange stars. The
formation, cooling, and thermal photon radiation of bare strange stars have
been investigated. It is suggested that thermal featureless spectrum could be a
new probe for identifying strange stars.


title:
Predictions for Fourier-resolved X-ray spectroscopy from the model of
  magnetic flare avalanches above an accretion disc with hot ionized skin

abstract:
  The magnetic flare avalanches model of Poutanen & Fabian for X-ray
variability of accreting black holes is combined with computations of vertical
structure of illuminated accretion discs in hydrostatic equilibrium. The latter
predict the existence of a hot ionized skin, due to the thermal instability of
X-ray illuminated plasma. The presence of such ionized skin, with properties
dependent on disc radius, introduces a dependence of the emitted X-ray spectrum
on the position on the disc. If the position is related to the time scale of
the flares, the X-ray energy spectra (both the primary continuum and the
reprocessed component) gain an additional dependence on Fourier frequency,
beside that resulting from spectral evolution during a flare. We compute the
Fourier frequency resolved spectra in this model and demonstrate that the
presence of the hot skin introduces trends opposite to those observed in black
hole binaries. Furthermore, the flare profile is strongly constrained, if the
Fourier frequency dependence due to spectral evolution is to agree with
observations.


title:
Low power BL Lacertae objects and the blazar sequence: Clues on the
  particle acceleration process

abstract:
  The spectral properties of blazars seem to follow a phenomenological sequence
according to the source luminosity. By inferring the source physical parameters
through (necessarily) modeling the blazar spectra, we have previously proposed
that the sequence arises because the particles responsible for most of the
emission suffer increasing radiative losses as the luminosity increases. Here
we extend those results by considering the widest possible range of blazar
spectral properties. We find a new important ingredient for shaping the spectra
of the lowest power objects, namely the role of a finite timescale for the
injection of relativistic particles. Only high energy particles radiatively
cool in such timescale leading to a break in the particle distribution:
particles with this break energy are those emitting most of the power, and this
gives raise to a link between blazar spectra and total energy density inside
the source, which controls the cooling timescale. The emerging picture requires
two phases for the particle acceleration: a first pre-heating phase in which
particles reach a characteristic energy as the result of balancing heating and
radiative cooling, and a more rapid acceleration phase which further accelerate
these particles to form a power law distribution. While in agreement with
standard shock theory, this scenario also agrees with the idea that the
luminosity of blazars is produced through internal shocks, which naturally lead
to shocks lasting for a finite time.


title:
Deuterium fractionation on interstellar grains studied with modified
  rate equations and a Monte Carlo approach

abstract:
  The formation of singly and doubly deuterated isotopomers of formaldehyde and
of singly, doubly, and multiply deuterated isotopomers of methanol on
interstellar grain surfaces has been studied with a semi-empirical modified
rate approach and a Monte Carlo method in the temperature range 10-20 K.
Agreement between the results of the two methods is satisfactory for all major
and many minor species throughout this range. If gas-phase fractionation can
produce a high abundance of atomic deuterium, which then accretes onto grain
surfaces, diffusive surface chemistry can produce large abundances of
deuterated species, especially at low temperatures and high gas densities.
Warming temperatures will then permit these surface species to evaporate into
the gas, where they will remain abundant for a considerable period. We
calculate that the doubly deuterated molecules CHD2OH and CH2DOD are
particularly abundant and should be searched for in the gas phase of
protostellar sources. For example, at 10 K and high density, these species can
achieve up to 10-20% of the abundance of methanol.


title:
Rapid rotation of ultra-Li-depleted halo stars and their association
  with blue stragglers

abstract:
  Observations of eighteen halo main-sequence-turnoff stars, four of which are
extremely deficient in Li, show that three of the Li-poor ones have substantial
line broadening. We attribute this to stellar rotation. Despite the great ages
of halo stars, for G202-65, BD+51:1817 and Wolf 550 we infer vsini = 8.3 +/-
0.4, 7.6 +/- 0.3, and 5.5 +/- 0.6 km/s respectively. The stated errors are
3sigma. For CD-31:19466 we derive a 3sigma upper limit vsini < 2.2 km/s. The
three rotating stars are known spectroscopic binaries. We explain the high
rotation velocities in terms of mass and angular momentum transfer onto the
surface of the turnoff star from an initially more-massive donor. Estimates of
the specific angular momentum of accreted material indicate that quite small
transfer masses could have been involved, though the unknown subsequent
spin-down of the accretor prevents us from assigning definitive values for each
star. The accretor is now seen as an ultra-Li-deficient star whose origin makes
it a low-mass counterpart of field blue stragglers. The Li could have been
destroyed before or during the mass-transfer episode. Such objects must be
avoided in studies of the primordial Li abundance and in investigations into
the way normal single stars process their initial Li.


title:
Limits to the muon flux from WIMP annihilation in the center of the
  Earth with the AMANDA detector

abstract:
  A search for nearly vertical up-going muon-neutrinos from neutralino
annihilations in the center of the Earth has been performed with the AMANDA-B10
neutrino detector. The data sample collected in 130.1 days of live-time in
1997, ~10^9 events, has been analyzed for this search. No excess over the
expected atmospheric neutrino background is oberved. An upper limit at 90%
confidence level on the annihilation rate of neutralinos in the center of the
Earth is obtained as a function of the neutralino mass in the range 100
GeV-5000 GeV, as well as the corresponding muon flux limit.


title:
Photometric standard stars in the BVI system in a wide field centered on
  the spiral galaxy NGC 300

abstract:
  Based on 13 nights of observations of four fields in NGC 300, we have set up
an extensive sequence of stars with accurate BVI photometry covering a
relatively large (25 x 25 arcmin) region centered on this galaxy. This sequence
of standard stars is very useful for calibrating the photometry of variable
stars and other objects in NGC 300 and other galaxies obtained from wide field
mosaic images. Our standard star list contains B, V and I measurements for 390
stars. The accuracy of the zero points in the V filter and B-V color is better
than 0.02 mag, and about 0.03 mag for the V-I color. We found very good
agreement between our measurements and those previously obtained by Walker for
26 stars near NGC 300.


title: Status of the EPIC/MOS calibration

abstract:
  The XMM-Newton observatory has the largest collecting area flown so far for
an X-ray imaging system, resulting in a very high sensitivity over a broad
spectral range. In order to exploit fully these performances, a very accurate
calibration of the XMM-Newton instruments is required, and has led to an
extensive ground and flight calibration program. We report here on the current
status of the EPIC/MOS cameras calibrations, highlighting areas for which a
reasonably good accuracy has been achieved, and noting points where further
work is needed.


title: Chandra detects inverse Compton emission from the radio galaxy 3C 219

abstract:
  We report the results from a {\it Chandra} observation of the powerful nearby
(z=0.1744) radio galaxy 3C 219. We find evidence for non--thermal X-ray
emission from the radio lobes which fits fairly well with a combination of IC
scattering of CMB and of nuclear photons. The comparison between radio
synchrotron and IC fluxes yields a magnetic field strength significantly lower
($\sim 3$) than that calculated under minimum energy conditions; the majority
of the energetics is then associated to the relativistic particles.


title: Is it e or is it c? Experimental Tests of Varying Alpha

abstract:
  Is the recent evidence for a time-varying fine structure 'constant' $\alpha$
to be interpreted as a varying $e$, $c$, $\hbar$, or a combination thereof? We
consider the simplest varying electric charge and varying speed of light
theories (VSL) and prove that for the same type of dark matter they predict
opposite senses of variation in $\alpha$ over cosmological times. We also show
that unlike varying $e$ theories, VSL theories do not predict violations of the
weak equivalence principle (WEP). Varying $e$ theories which explain
astronomical inferences of varying $\alpha$ predict WEP violations only an
order of magnitude smaller than existing E\"otv\"os experiment limits but could
be decisively tested by STEP. We finally exhibit a set of atomic-clock and
related experiments for which {\it all} (hyperbolic) varying $\alpha$ theories
predict non-null results. They provide independent tests of the recent
astronomical evidence.


title:
Evidence for Spin and Energy Extraction in a Galactic Black Hole
  Candidate: The XMM-Newton/EPIC-pn Spectrum of XTE J1650-500

abstract:
  We observed the Galactic black hole candidate XTE J1650-500 early in its
Fall, 2001 outburst with the XMM-Newton European Photon Imaging pn Camera
(EPIC-pn). The observed spectrum is consistent with the source having been in
the "very high" state. We find a broad, skewed Fe K-alpha emission line which
suggests that the primary in this system may be a Kerr black hole, and which
indicates a steep emissivity profile that is hard to explain in terms of a
standard accretion disk model. These results are quantitatively and
qualitatively similar to those from an XMM-Newton observation of the Seyfert
galaxy MCG--6-30-15. The steep emissivity in MCG--6-30-15 may be explained by
the extraction and dissipation of rotational energy from a black hole with
nearly- maximal angular momentum or material in the plunging region via
magnetic connections to the inner accretion disk. If this process is at work in
both sources, an exotic but fundamental general relativistic prediction may be
confirmed across a factor of 10^6 in black hole mass. We discuss these results
in terms of the accretion flow geometry in stellar-mass black holes, and the
variety of enigmatic phenomena often observed in the very high state.


title:
Degeneracies and scaling relations in general power-law models for
  gravitational lenses

abstract:
  The time delay in gravitational lenses can be used to derive the Hubble
constant in a relatively simple way. The results of this method are less
dependent on astrophysical assumptions than in many other methods. The most
important uncertainty is related to the mass model used. We discuss a family of
models with a separable radial power-law and an arbitrary angular dependence
for the potential psi = r^beta * F(theta). Isothermal potentials are a special
case of these models with beta=1. An additional external shear is used to take
into account perturbations from other galaxies. Using a simple linear formalism
for quadruple lenses, we can derive H0 as a function of the observables and the
shear. If the latter is fixed, the result depends on the assumed power-law
exponent according to H0 proportional to (2-beta)/beta. The effect of external
shear is quantified by introducing a `critical shear' gamma_c as a measure for
the amount of shear that changes the result significantly. The analysis shows,
that in the general case H0 and gamma_c do not depend on the position of the
lens galaxy. We discuss these results and compare with numerical models for a
number of real lens systems.


title:
High Angular Resolution and Extrasolar Planets: Beyond Basic
  Instrumental Performances

abstract:
  I review the characteristics of planetary systems accessible to imaging. I
show that, beyond the basic angular resolution and dynamics performances of an
optical ``architecture'', other performances such as photometric precision,
spectral range or timing are necessary to access some physical characteristics
of the planets.


title:
Four Years Monitoring of Blazar PKS 2155-304 with BeppoSAX: Probing the
  Dynamics of the Jet

abstract:
  PKS 2155--304 is one of the brightest blazars in the X-ray band. It was
repeatedly monitored with BeppoSax during three long campaigns of about 2 days
each in November of 1996, 1997 and 1999. The source underwent different states
of intensity and was clearly variable with successive flares detected. This
paper presents temporal and spectral analysis to study the X-ray variability
trends for a blazar. The rich phenomenology is interpreted in the context of a
model where relativistic electrons are accelerated through internal shocks
taking place in the jets. The most important parameter turns out to be the
initial time interval between the two shells ejected from the central engine to
produce the flare, which may determine the structure of the shock and in turn
the physical quantities of the emitting region to reproduce the observed trends
of the X-ray variability (abridged).


title:
Adaptive Spatial Binning of 2D Spectra and Images Using Voronoi
  Tessellations

abstract:
  We present new techniques to perform adaptive spatial binning of
two-dimensional (2D) data to reach a chosen constant signal-to-noise ratio per
bin. These methods are required particularly for the proper analysis of
Integral Field Spectrograph (IFS) observations, but can also be used for
standard photometric imagery. Various schemes are tested and compared using
data obtained with the panoramic IFS SAURON.


title:
A Laboratory Plasma Experiment for Studying Magnetic Dynamics of
  Accretion Discs and Jets

abstract:
  This work describes a laboratory plasma experiment and initial results which
should give insight into the magnetic dynamics of accretion discs and jets. A
high-speed multiple-frame CCD camera reveals images of the formation and
helical instability of a collimated plasma, similar to MHD models of disc jets,
and also plasma detachment associated with spheromak formation, which may have
relevance to disc winds and flares. The plasmas are produced by a planar
magnetized coaxial gun. The resulting magnetic topology is dependent on the
details of magnetic helicity injection, namely the force-free state eigenvalue
alpha_gun imposed by the coaxial gun.


title:
Variable Stars in Leo A: RR Lyraes, Short-period Cepheids, and
  Implications on Stellar Content

abstract:
  We present the results of a search for short-period variable stars in Leo A.
We have found 92 candidate variables, including eight candidate RR Lyrae stars.
  From the RR Lyraes, we measure a distance modulus of (m-M)_0 = 24.51 +/-
0.12, or 0.80 +/- 0.04 Mpc. This discovery of RR Lyraes confirms, for the first
time, the presence of an ancient (> ~11 Gyr) population in Leo A accounting for
at least 0.1% of the galaxy's V luminosity. We have also discovered a halo of
old (> ~2 Gyr) stars surrounding Leo A, with a scale length roughly 50% larger
than that of the dominant young population.
  We also report the discovery of a large population of Cepheids in Leo A. The
median absolute magnitude of our Cepheid sample is M_V = -1.1, fainter than 96%
of SMC and 99% of LMC Cepheids. Their periods are also unusual, with three
Cepheids that are deduced to be pulsating in the fundamental mode having
periods of under 1 day. Upon examination, these characteristics of the Leo A
Cepheid population appear to be a natural extension of the classical Cepheid
period-luminosity relations to low metallicity, rather than being indicative of
a large population of ``anomalous'' Cepheids. We demonstrate that the periods
and luminosities are consistent with the expected values of low-metallicity
blue helium-burning stars (BHeBs), which populate the instability strip at
lower luminosities than do higher-metallicity BHeBs.


title: The Mass of the Central Black Hole in the Seyfert Galaxy NGC 3783

abstract:
  Improved analysis of ultraviolet and optical monitoring data on the Seyfert 1
galaxy NGC 3783 provides evidence for the existence of a supermassive,
(8.7+/-1.1)x10^6 M_sun, black hole in this galaxy. By using recalibrated
spectra from the International Ultraviolet Explorer satellite and ground-based
optical data, as well as refined techniques of reverberation mapping analysis,
we have reduced the statistical uncertainties in the response of the emission
lines to variations in the ionizing continuum. The different time lags in the
emission line responses indicate a stratification in the ionization structure
of the broad-line region and are consistent with the virial relationship
suggested by the analysis of similar active galaxies.


title:
Optical spectroscopy of metal-rich HII regions and circumnuclear hot
  spots in M83 and NGC 3351

abstract:
  We present optical spectroscopy of a sample of metal-rich extragalactic HII
regions in the spiral galaxies M83, NGC 3351 and NGC 6384, including a number
of circumnuclear HII regions (hot spots). Different age estimators (equivalent
width of the Hbeta emission line W(Hb), Balmer line absorption profiles, UV
spectra) provide consistently young ages (4-6 Myr) for the hot spots. We have
detected the W-R bump feature at 4650 A in five of the objects, and in fewer
cases possibly the WC features at 5696 A and 5808 A. Six additional objects
showing W-R features are drawn from our previous work on extragalactic HII
regions. From the measured luminosity of the W-R blue bump we estimate a small
number of WN stars (from 1-2 to about 30). By assuming instantaneous bursts of
star formation the ages derived from W(Hb) (3-6 Myr) and the strength of the
W-R bump are in agreement with the predictions of evolutionary stellar
population models, provided we account for stochastic effects on the IMF. From
a comparison with published photoionization models based on synthetic cluster
spectral energy distributions we find some evidence for an overestimation of
the number of He ionizing photons in the model fluxes. In general, however, the
massive star diagnostics are in agreement with the predictions of recent
evolutionary models calculated with a Salpeter IMF and a high mass limit. We
find no compelling evidence for a depletion of massive stars (M > 40-50 solar
masses) in the IMF of metal-rich clusters, contrary to our previous conclusions
based on older evolutionary models.


title:
Resonance line-profile calculations based on hydrodynamical models of
  cataclysmic variable winds

abstract:
  We present synthetic line profiles as predicted by the models of 2-D line-
driven disk winds due to Proga, Stone & Drew. We compare the model line
profiles with HST observations of the cataclysmic variable IX Vel. The model
wind consists of a slow outflow that is bounded on the polar side by a fast
stream. We find that these two components of the wind produce distinct spectral
features. The fast stream produces profiles which show features consistent with
observations. These include the appearance of the P-Cygni shape for a range of
inclinations, the location of the maximum depth of the absorption component at
velocities less than the terminal velocity, and the transition from absorption
to emission with increasing inclination. However the model profiles have too
little absorption or emission equivalent width. This quantitative difference
between our models and observations is not a surprise because the line-driven
wind models predict a mass loss rate that is lower than the rate required by
the observations. We note that the model profiles exhibit a double-humped
structure near the line center which is not echoed in observations. We identify
this structure with a non-negligible redshifted absorption which is formed in
the slow component of the wind where the rotational velocity dominates over
expansion velocity. We conclude that the next generation of disk wind models,
developed for application to CVs, needs to yield stronger wind driving out to
larger disk radii than do the present models.


title: Nova Sco and coalescing low mass black hole binaries as LIGO sources

abstract:
  Double neutron star binaries, analogous to the well known Hulse--Taylor
pulsar PSR 1913+16, are guaranteed-to-exist sources of high frequency
gravitational radiation detectable by LIGO. There is considerable uncertainty
in the estimated rate of coalescence of such systems, with conservative
estimates of ~1 per million years per galaxy, and optimistic theoretical
estimates one or more magnitude larger. Formation rates of low-mass black
hole-neutron star binaries may be higher than those of NS-NS binaries, and may
dominate the detectable LIGO signal rate.
  We estimate the enhanced coalescence rate for BH-BH binaries due to weak
asymmetric kicks during the formation of low mass black holes like Nova Sco,
and find they may contribute significantly to the LIGO signal rate, possibly
dominating the phase I detectable signals if the range of BH masses for which
there is significant kick is broad enough. For a standard Salpeter IMF,
assuming mild natal kicks, we project that the R6 merger rate of BH-BH systems
is ~0.5, smaller than that of NS-NS systems. However, the higher chirp mass of
these systems produces a signal nearly four times greater, on average, with a
commensurate increase in search volume.
  The BH-BH coalescence channel considered here also predicts that a
substantial fraction of BH-BH systems should have at least one component with
near-maximal spin (a/M ~ 1).The waveforms produced by the coalescence of such a
system should produce a clear spin signature, so this hypothesis could be
directly tested by LIGO.


title: The 2dF BL Lac Survey

abstract:
  We have optically identified a sample of 56 featureless continuum objects
without significant proper motion from the 2dF QSO Redshift Survey (2QZ). The
steep number--magnitude relation of the sample, $n(\bj) \propto 10^{0.7\bj}$,
is similar to that derived for QSOs in the 2QZ and inconsistent with any
population of Galactic objects. Follow up high resolution, high
signal-to-noise, spectroscopy of five randomly selected objects confirms the
featureless nature of these sources. Assuming the objects in the sample to be
largely featureless AGN, and using the QSO evolution model derived for the 2QZ,
we predict the median redshift of the sample to be $z=1.1$. This model also
reproduces the observed number-magnitude relation of the sample using a
renormalisation of the QSO luminosity function, $\Phi^* = \Phi^*_{\rm \sc
qso}/66 \simeq 1.65 \times 10^{-8} $mag$^{-1}$Mpc$^{-3}$. Only $\sim$20 per
cent of the objects have a radio flux density of $S_{1.4}>3 $mJy, and further
VLA observations at 8.4 GHz place a $5\sigma$ limit of $S_{8.4} < 0.2$mJy on
the bulk of the sample. We postulate that these objects could form a population
of radio-weak AGN with weak or absent emission lines, whose optical spectra are
indistinguishable from those of BL Lac objects.


title:
Efficient acceleration and radiation in Poynting flux powered GRB
  outflows

abstract:
  We investigate the effects of magnetic energy release by local magnetic
dissipation processes in Poynting flux-powered GRBs. For typical GRB parameters
(energy and baryon loading) the dissipation takes place mainly outside the
photosphere, producing non-thermal radiation. This process converts the total
burst energy into prompt radiation at an efficiency of 10-50%. At the same time
the dissipation has the effect of accelerating the flow to a large Lorentz
factor. For higher baryon loading, the dissipation takes place mostly inside
the photosphere, the efficiency of conversion of magnetic energy into radiation
is lower, and an X-ray flash results instead of a GRB. We demonstrate these
effects with numerical one-dimensional steady relativistic MHD calculations.


title: Lorentz Invariance Violation and the QED Formation Length

abstract:
  It was recently suggested that possible small volations of Lorentz invariance
could explain the existence of UHECR beyond the GZK cutoff and the observations
of multi-TeV gamma-rays from Mkn 501. Our analysis of Lorentz-violating
kinematics shows that in addition to the modified threshold conditions solving
cosmic ray puzzles we should expect a strong suppression of electromagnetic
processes like bremsstrahlung and pair creation. This leads to drastic effects
in electron-photon cascade development in the atmosphere and in detectors.


title:
The power-law behaviours of angular spectra of polarized Galactic
  synchrotron

abstract:
  We study the angular power spectra of polarized Galactic synchrotron in the
range 10<l<800, at several frequencies between 0.4 and 2.7 GHz and at several
Galactic latitudes up to near the North Galactic Pole. Electric- and
magnetic-parity polarization spectra are found to have slopes around alpha
_{E,B} = 1.4 - 1.5 in the Parkes and Effelsberg Galactic-Plane surveys, but
strong local fluctuations of alpha_{E,B} are found at | b | ~ 10 degree from
the 1.4 GHz Effelsberg survey. The C_{PIl} spectrum, which is insensitive to
the polarization direction, is somewhat steeper, being alpha_{PI} = 1.6 - 1.8
for the same surveys. The low-resolution multifrequency survey of Brouw and
Spoelstra (1976) shows some flattening of the spectra below 1 GHz, more intense
for C_{E,Bl} than for C_{PIl}. In no case we find evidence for really steep
spectra. The extrapolation to the cosmological window shows that at 90 GHz the
detection of E-mode harmonics in the cosmic background radiation should not be
disturbed by synchrotron, even around l~10 for a reionization optical depth tau
_{ri}>~0.05.


title:
A comparison of stellar populations in galaxy populations across a wide
  range of Hubble types

abstract:
  We present line-strengths and kinematics from the central regions of 32
galaxies with Hubble types ranging from E to Sbc. Spectral indices, based on
the Lick system, are measured in the optical and near infra-red (NIR). The 24
indices measured, in conjunction with models of the effects of varying
abundance ratios, permit the breaking of age/metallicity degeneracy and allow
estimation of enhancements in specific light elements (particularly C and Mg).
The large range of Hubble types observed allows direct comparison of
line-strengths in the centres of early-type galaxies (E and S0) with those in
spiral bulges, free from systematic differences that have plagued comparisons
of results from different studies. Our sample includes field and Virgo cluster
galaxies. For early-type galaxies our data are consistent with previously
reported trends of Mg2 and Mgb with velocity dispersion. In spiral bulges we
find trends in all indices with velocity dispersion. We estimate
luminosity-weighted ages, metallicities and heavy element abundance
ratios(enhancements) from optical indices. These show that bulges are less
enhanced in light (alpha-capture) elements and have lower average age than
early-type galaxies. Trends involving age and metallicity also differ sharply
between early and late types. An anti-correlation exists between age and
metallicity in early types, while, in bulges, metallicity is correlated with
velocity dispersion. We consider the implications of these findings for models
of the formation of these galaxies. We find that primordial collapse models of
galaxy formation are ruled out by our observations, while several predictions
of hierarchical clustering (merger) models are confirmed.


title: The stellar mass to light ratio in the isolated spiral NGC 4414

abstract:
  We present high resolution CO(1-0) interferometric observations and deep HST
B-V-I images of the flocculent isolated Sc type spiral NGC 4414. The goal is to
determine the stellar mass-to-light (M/L) ratio in a galactic disk. The stars
are seen without a dust screen, the central gas mass is very low (undetected),
and we show that the dark matter is negligible in the central regions. We have
developed an axisymmetric analytical gravitational potential model to account
for the central light (mass) profile, the dynamics of the molecular gas in the
highly obscured molecular ring, and the stellar light profile outside the
highly obscured region. The contribution of dark matter is constrained by the
extremely extended HI rotation curve and is small, possibly negligible, at
distances less than 5 -- 7 kpc from the center. Furthermore, the M/L ratios we
derive are low, about 1.5 in I band and 0.5 in K' band. The B and V band M/L
ratios vary greatly due to absorption by dust, reaching 4 in the molecular ring
and decreasing to about 1.6 -- 1.8 at larger radii. This unequivocally shows
that models, like most maximum disk models, assuming constant M/L ratios in an
optical waveband, simply are not appropriate. We illustrate this by making mock
maximum disk models with a constant V band M/L ratio. The key is having the
central light distribution unobscured such that it can be used to trace the
mass. A primitive attempt to determine the intrinsic M/L ratio yields values
close to unity in the B,V, and I bands and slightly below 0.5 in K'.


title: The BeppoSAX view of bright Compton-thin Seyfert 2 galaxies

abstract:
  We present the analysis of 31 observations of 20 bright Compton thin Seyfert
2s, in the 0.1-200 keV band, performed with the BeppoSAX satellite. The sample
consists of all Seyfert 2s in the BeppoSAX public archive, with a 2-10 keV flux
higher than 5x10^(-12) erg/cm^2/s. The good statistics available and the broad
energy band permit a detailed study of the main continuum components of these
sources, i.e. the primary power-law, the reflected component, the soft emission
and the high-energy cut-off. The main results of our analysis are: (1) the
3-200 keV intrinsic power-law has a mean photon index Gamma=1.79+-0.01, with a
dispersion of sigma=0.23. (2) The high-energy exponential cut-off at E~100-300
keV is not an ubiquitous property of Seyfert galaxies: in ~30% of the objects
the continuum power-law does not drop up to energies of 300 keV or more. (3) A
reflected component is present in almost all the sources (17 out of 21). The
small variations of this component with respect to the intrinsic continuum, in
objects with multiple observations, suggests that the reflector is not the
accretion disk, but must be located much farther from the nucleus. (4) The
range of ratios between the reflected and intrinsic components suggests that
the circumnuclear medium is not homogeneous, and a significant fraction of the
solid angle is covered by a gas thicker than that along the line of sight. (5)
The iron Kalpha line is present is all but one the sources. The equivalent
width is in the typical range of Seyfert 1s (EW=100-300 eV) in sources with low
absorption (N_H < 3x10^23 cm^(-2)), and increases in more absorbed objects, as
expected according to unified models. (6) The energy resolution of BeppoSAX is
in general too low to measure the iron line width. However, in 6 cases we
measured a significant line broadening.


title:
The abundance and clustering of dark haloes in the standard Lambda CDM
  cosmogony

abstract:
  Much evidence suggests that we live in a flat Cold Dark Matter universe with
a cosmological constant. Accurate analytic formulae are now available for many
properties of the dark halo population in such a Universe. Assuming current
``concordance'' values for the cosmological parameters, we plot halo abundance
against redshift as a function of halo mass, of halo temperature, of the
fraction of cosmic matter in haloes, of halo clustering strength, and of the
clustering strength of the z=0 descendants of high redshift haloes. These plots
are useful for understanding how nonlinear structure grows in the model. They
demonstrate a number of properties which may seem surprising, for example: 10^9
solar mass haloes are as abundant at z=20 as L_* galaxies are today; 10^6K
haloes are equally abundant at z=8 and at z=0; 10% of all matter is currently
in haloes hotter than 1 keV, while more than half is in haloes too cool to trap
photo-ionized gas; 1% of all matter at z=15 is in haloes hot enough to ionise
hydrogen; haloes of given mass or temperature are more clustered at higher
redshift; haloes with the abundance of present-day L_* galaxies are equally
clustered at all z<20; the metals produced by star-formation at z>10 are more
clustered at z=0 than are L_* galaxies.


title: Near Infrared observations of Soft X-ray selected AGN

abstract:
  We report the results of near infrared observations of 19 soft X-ray selected
AGN. The goal of the observations was to search for strong, narrow
Paschen-alpha or Brackett-gamma emission lines, as a sign of nuclear
starbursts. We found Pa-alpha emission in the spectra of 11 sources and
Br-gamma in at least five. Strong NIR emission has been found in two sources,
CBS 126 and Mkn 766, both objects with strong [OIII]5007 emission, weak FeII
emission and wavelength dependent degree of polarization in the optical.
Classical Narrow Line Seyfert 1 galaxies do not show exceptionally strong NIR
emission lines. We present the results of our study and discuss how our
findings fit into an evolutionary scheme of AGN.


title: Photometric study of eclipsing binary RV Tri

abstract:
  We present new photometric observations of RV Tri.
  A complete light curve was obtained in the R and V filters.
  These light curves were processed by the Wilson-Devinney (WD) code and the
FOTEL to get solution of this eclipsing binary system. We discuss
characteristics of the system and compare our model with a previous
calculation. Our observations of primary minima and the comparison with those
predicted on the base of the GCVS catalogue indicates that there are
significant differences. We discuss these differences in the context of period
change.


title: 3-D General Relativistic MHD Simulations of Generating Jets

abstract:
  We have performed a first fully 3-D GRMHD simulation with Schwarzschild black
hole with a free falling corona. The initial simulation results show that a jet
is created as in previous axisymmetric simulations. However, the time to
generate the jet is longer than in the 2-D simulations. We expect that due to
the additional azimuthal dimension the dynamics of jet formation can be
modified.


title:
High resolution spectroscopy of metal rich giants in omega Cen: first
  indication of SNe Ia enrichment

abstract:
  We have obtained high-resolution, high S/N spectra for six red giants in
omega Cen: three belonging to the recently discovered, metal-rich Red Giant
Branch (RGB-a, Pancino et al. 2000) and three to the metal intermediate
population (RGB-MInt). Accurate Iron, Copper and alpha-elements (Ca and Si)
abundances have been derived and discussed. In particular, we have obtained the
first direct abundance determination based on high-resolution spectroscopy for
the RGB-a population, <[Fe/H]>=-0.60+/-0.15. Although this value is lower than
previous estimates based on Calcium triplet measurements, we confirm that this
population is the most metal rich in omega Cen. In addition, we have found a
significant difference in the alpha-elements enhancement of the two
populations. The three RGB-MInt stars have the expected overabundance, typical
of halo and globular clusters stars: <[alpha/Fe]>=+0.29+/-0.01. The three RGB-a
stars show, instead, a significantly lower alpha-enhancement:
<[alpha/Fe]>=+0.10+/-0.04. We have also detected an increasing trend of [Cu/Fe]
with metallicity, similar to the one observed for field stars by Sneden et al.
(1991). The observational facts presented in this letter, if confirmed by
larger samples of giants, are the first indication that supernovae type Ia
ejecta have contaminated the medium from which the metal rich RGB-a stars have
formed. The implications for current scenarios on the formation and evolution
of omega Cen are briefly discussed.


title:
XMM-Newton observations of the neutron star X-ray transient KS 1731-260
  in quiescence

abstract:
  We report on XMM-Newton observations performed on 2001 September 13-14 of the
neutron star X-ray transient KS 1731-260 in quiescence. The source was detected
at an unabsorbed 0.5-10 keV flux of only 4 - 8 x 10^{-14} erg/s, depending on
the model used to fit the data, which for a distance of 7 kpc implies a 0.5-10
keV X-ray luminosity of approximately 2 - 5 x 10^{32} erg/s. The September 2001
quiescent flux of KS 1731-260 is lower than that observed during the Chandra
observation in March 2001. In the cooling neutron star model for the quiescent
X-ray emission of neutron star X-ray transients, this decrease in the quiescent
flux implies that the crust of the neutron star in KS 1731-260 cooled down
rapidly between the two epochs, indicating that the crust has a high
conductivity. Furthermore, enhanced cooling in the neutron star core is also
favored by our results.


title: An adaptive filter for the PLANCK Compact Source Catalogue construction

abstract:
  We develop a linear algorithm for extracting extragalactic point sources for
the Compact Source Catalogue of the upcoming PLANCK mission. This algorithm is
based on a simple top-hat filter in the harmonic domain with an adaptive
filtering range which does not require a priori knowledge of the CMB power
spectrum and the experiment parameters such as the beam size and shape nor
pixel noise level.


title:
Constraining the difference in convective blueshift between the
  components of alpha Cen with precise radial velocities

abstract:
  New radial velocities of alpha Cen A & B obtained in the framework the
Anglo-Australian Planet Search programme as well as in the CORALIE programme
are added to those by Endl et al. (2001) to improve the precision of the
orbital parameters. The resulting masses are 1.105+/-0.0070 MSun and
0.934+/-0.0061 MSun for A and B respectively. The factors limiting how
accurately these masses can be derived from a combined visual-spectroscopic
solution are investigated. The total effect of the convective blueshift and the
gravitational redshift is also investigated and estimated to differ by 215+/-8
m/s between the components. This suggests that the difference in convective
blueshift between the components is much smaller than predicted from current
hydrodynamical model atmosphere calculations.


title: Imaging of z~2 QSO host galaxies with the Hubble Space Telescope

abstract:
  We report on deep imaging in 2 filters with the PC2 camera of HST, of five
QSOs at redshift ~2, with a range of optical and radio luminosity. The
observations included a suite of PSF observations which were used to construct
new PSF models, described elsewhere by Dumont et al. The new PSF models were
used to remove the QSO nucleus from the images. We find that the host galaxies
have resolved flux of order 10% of the QSO nuclei, and are generally luminous
and blue, indicating active star-formation. While most have clearly irregular
morphologies, the bulk of the flux can be modelled approximately by an r**1/4
law. However, all host galaxies also have an additional approximately
exponential luminosity profile beyond a radius about 0.8 arcsec, as also seen
in ground-based data with larger telescopes. The QSOs all have a number of
nearby faint blue companions which may be young galaxies at the QSO redshift.
We discuss implications for evolution of the host galaxies, their spheroidal
populations, and central black holes.


title: 3D Hydrodynamic Simulations of Relativistic Extragalactic Jets

abstract:
  We describe a new numerical 3D relativistic hydrodynamical code, the results
of validation tests, and a comparison with earlier, 2D studies. The 3D code has
been used to study the deflection and precession of relativistic flows. We find
that even quite fast jets (gamma~10) can be significantly influenced by
impinging on an oblique density gradient, exhibiting a rotation of the Mach
disk in the jet's head. The flow is bent via a potentially strong, oblique
internal shock that arises due to asymmetric perturbation of the flow by its
cocoon. In extreme cases this cocoon can form a marginally relativistic flow
orthogonal to the jet, leading to large scale dynamics quite unlike that
normally associated with astrophysical jets. Exploration of a gamma=5 flow
subject to a large amplitude precession (semi-angle 11.25dg) shows that it
retains its integrity, with modest reduction in Lorentz factor and momentum
flux, for almost 50 jet-radii, but thereafter, the collimated flow is
disrupted. The flow is approximately ballistic, with velocity vectors not
aligned with the local jet `wall'. We consider simple estimators of the flow
emissivity in each case and conclude that a) while the oblique internal shocks
which mediate a small change in the direction of the deflected flows have
little impact on the global dynamics, significantly enhanced flow emission (by
a factor of 2-3) may be associated with such regions; and b) the convolution of
rest frame emissivity and Doppler boost in the case of the precessed jet
invariably leads to a core-jet-like structure, but that intensity fluctuations
in the jet cannot be uniquely associated with either change in internal
conditions or Doppler boost alone, but in general are a combination of both
factors.


title: How to Construct a GRB Engine?

abstract:
  According to the fireball model GRBs are produced when a relativistic flow is
dissipated by shocks. The questions how does a GRB's "inner engine" accelerates
and collimated the relativistic flow is today the most interesting (and most
difficult) open question concerning GRBs. We summarize, here, the known
constrains on the "inner engines". These constrains arise mostly from the
temporal structure seen in the light curves of GRBs. We discuss the well-known
NO GO theorem: An explosive source cannot produce a variable GRB. We show that
various attempts to find a way around this theorem are rules out by new
observational data: similarity between pulse width and pulse intervals and a
correlation between a pulse and the preceding interval. We show that a simple
toy model explains these features in terms of the internal shocks model. We
discuss the implications of these findings to GRBs' inner engines.


title: GRBs Light Curves - Another Clue on the Inner Engine

abstract:
  The nature of the `inner engine' that accelerate and collimate the
relativistic flow at the cores of GRBs is the most interesting current puzzle
concerning GRBs. Numerical simulations have shown that the internal shocks'
light curve reflects the activity of this inner engine. Using a simple analytic
toy model we clarify the relations between the observed $ \gamma $-rays light
curve and the inner engine's activity and the dependence of the light curves on
the inner engine's parameters. This simple model also explains the observed
similarity between the observed distributions of pulses widths and the
intervals between pulses and the correlation between the width of a pulse and
the length of the preceding interval. Our analysis suggests that the
variability in the wind's Lorentz factors arises due to a modulation of the
mass injected into a constant energy flow.


title: Dust Emission from Active Galactic Nuclei

abstract:
  Unified schemes of active galactic nuclei (AGN) require an obscuring dusty
torus around the central source, giving rise to Seyfert 1 line spectrum for
pole-on viewing and Seyfert 2 characteristics in edge-on sources. Although the
observed IR is in broad agreement with this scheme, the behavior of the 10
micron silicate feature and the width of the far-IR emission peak remained
serious problems in all previous modeling efforts. We show that these problems
find a natural explanation if the dust is contained in about 5-10 clouds along
radial rays through the torus. The spectral energy distributions (SED) of both
type 1 and type 2 sources are properly reproduced from different viewpoints of
the same object if the visual optical depth of each cloud is larger than about
60 and the clouds' mean free path increases roughly in proportion to radial
distance.


title:
X-ray Synchrotron Spectral Hardenings from Compton and Synchrotron
  Losses in Extended Chandra Jets

abstract:
  Chandra observations of knots and hot spots in spatially resolved X-ray jets
of radio galaxies show that the X-ray fluxes often lie above an extrapolation
from the radio-to-optical continuum fluxes. We show that combined synchrotron
and Compton losses on a single power-law electron injection function can
produce a hardening in the electron spectrum at electron Lorentz factors \gamma
\~ 2e8/[\Gamma(1+z)] due to KN energy losses on the cosmic microwave background
radiation. Here \Gamma is the bulk Lorentz factor of the outflow, and z is the
source redshift. This produces a flattening in the spectrum at frequencies >~
8e16 \delta B_{\mu G}/[\Gamma^2(1+z)^3] Hz, where B_{\mu G} is the magnetic
field in the comoving plasma frame in units of micro-Gauss and \delta is the
Doppler factor. A single population of synchrotron-emitting electrons may
therefore produce the radio-to-X-ray continuum in some radio galaxy knots, such
as those in 3C 273.


title: The Galactic Distribution of Asymptotic Giant Branch Stars

abstract:
  We study the Galactic distribution of ~10,000 Asymptotic Giant Branch (AGB)
stars selected by IRAS colors and variability index. The distance to each star
is estimated by assuming a narrow luminosity function and a model-derived
bolometric correction. The characteristic AGB star luminosity, L_AGB, is
determined from the condition that the highest number density must coincide
with the Galactic bulge. Assuming a bulge distance of 8 kpc, we determine L_AGB
\~ 3,500 Lo, in close agreement with values obtained for nearby AGB stars using
the HIPPARCOS data. We find that there are no statistically significant
differences in the Galactic distribution of AGB stars with different IRAS
colors, implying a universal density distribution. The direct determination of
this distribution shows that it is separable in the radial, R, and vertical, z,
directions. Perpendicular to the Galactic plane, the number density of AGB
stars is well described by an exponential function with a vertical scale height
of 300 pc. In the radial direction the number density of AGB stars is constant
up to R ~ 5 kpc, and then it decreases exponentially with a scale length of
\~1.6 kpc. This fall-off extends to at least 12 kpc, where the sample becomes
too small. The overall normalization implies that there are about 200,000 AGB
stars in the Galaxy. We estimate the [25]-[12] color distribution of AGB stars
for an unbiased volume-limited sample. By using a model-dependent
transformation between the color and mass-loss rate, Mdot, we constrain the
time dependence of Mdot. The results suggest that for 10^-6 Mo/yr < Mdot <
10^-5 Mo/yr the mass-loss rate increases exponentially with time. We find only
marginal evidence that the mass-loss rate increases with stellar mass.


title:
Optical and Radio Properties of Extragalactic Sources Observed by the
  FIRST and SDSS Surveys

abstract:
  We discuss the optical and radio properties of 30,000 FIRST sources
positionally associated with an SDSS source in 1230 deg$^2$ of sky. The
majority (83%) of the FIRST sources identified with an SDSS source brighter
than r=21 are optically resolved. We estimate an upper limit of 5% for the
fraction of quasars with broad-band optical colors indistinguishable from those
of stars. The distribution of quasars in the radio flux -- optical flux plane
supports the existence of the "quasar radio-dichotomy"; 8% of all quasars with
i<18.5 are radio-loud and this fraction seems independent of redshift and
optical luminosity. The radio-loud quasars have a redder median color by 0.08
mag, and a 3 times larger fraction of objects with red colors. FIRST galaxies
represent 5% of all SDSS galaxies with r<17.5, and 1% for r<20, and are
dominated by red galaxies. Magnitude and redshift limited samples show that
radio galaxies have a different optical luminosity distribution than non-radio
galaxies selected by the same criteria; when galaxies are further separated by
their colors, this result remains valid for both blue and red galaxies. The
distributions of radio-to-optical flux ratio are similar for blue and red
galaxies in redshift-limited samples; this similarity implies that the
difference in their luminosity functions, and resulting selection effects, are
the dominant cause for the preponderance of red radio galaxies in flux-limited
samples. We confirm that the AGN-to-starburst galaxy number ratio increases
with radio flux, and find that radio emission from AGNs is more concentrated
than radio emission from starburst galaxies (abridged).


title: Geometrically Thin Disk Accreting Into a Black Hole

abstract:
  A numerical model of a steady state, thin accretion disk with a constant
effective speed of sound is presented. We demonstrate that `zero torque' inner
boundary condition is a reasonable approximation provided that the disk
thickness, including the thickness of the torquing magnetic fields, is small
everywhere. It is likely that this conclusion is correct also for non-steady
disks, as long as the total thickness at the sonic point, H_c, is much smaller
than the radius there, r_c ~ r_{ms}. The very existence of thin disks is not
proved or disproved in this work, but such disks are believed to exist for
moderate accretion rates.
  Within our model there is a small torque at r_{ms}, which may increase disk
luminosity by several percent. An important result of our analysis is that the
physically acceptable steady state solutions in our toy model exist only for
\alpha < 0.14 (100 v_s/c)^{1/3}.
  A significant torque may be applied to a thin disk if there is a large scale
magnetic field, like in a modified Blandford-Znajek mechanism.


title:
On the Direct Detectability of the Cosmic Dark Ages: 21-cm Emission from
  Minihalos

abstract:
  In the standard Cold Dark Matter (CDM) theory of structure formation,
virialized minihalos (with T_vir}<10^4 K) form in abundance at high redshift
(z>6), during the cosmic ``dark ages.'' The hydrogen in these minihalos, the
first nonlinear baryonic structures to form in the universe, is mostly neutral
and sufficiently hot and dense to emit strongly at the 21-cm line. We calculate
the emission from individual minihalos and the radiation background contributed
by their combined effect. Minihalos create a ``21-cm forest'' of emission
lines. We predict that the angular fluctuations in this 21-cm background should
be detectable with the planned LOFAR and SKA radio arrays, thus providing a
direct probe of structure formation during the ``dark ages.'' Such a detection
will serve to confirm the basic CDM paradigm while constraining the shape of
the power-spectrum of primordial density fluctuations down to much smaller
scales than have previously been constrained, the onset and duration of the
reionization epoch, and the conditions which led to the first stars and
quasars. We present results here for the currently-favored, flat $\Lambda$CDM
model, for different tilts of the primordial power spectrum.


title: Second Order Corrections to Weak Lensing by Large-Scale Structure

abstract:
  We calculate corrections to the power spectrum predictions of weak lensing by
large scale structure due to higher order effects in the gravitational
potential. Using a perturbative approach to third order in transverse
displacements, we calculate a second order correction to the angular power
spectra of E and B mode shear and convergence resulting from dropping the
so-called Born approximation, where one integrates along the unperturbed photon
path. We also consider a correction to the power spectra from the coupling
between lenses at different redshifts. Both effects generate B-mode shear and
the latter also causes a net rotation of the background galaxy images. We show
all these corrections are at least two orders of magnitude below the
convergence or E-mode power and hence relevant only to future ultra high
precision measurements. These analytical calculations are consistent with
previous numerical estimates and validate the use of current large scale
structure weak lensing predictions for cosmological studies and future use of
B-modes as a monitor of systematic effects.


title: The Circum-Galactic Environment of Bright IRAS Galaxies

abstract:
  This paper studies systematically, for the first time, the circumgalactic
environment of bright IRAS galaxies as defined by Soifer et al. (1989). While
the role of gravitational interaction for luminous and ultraluminous IRAS
galaxies has been well established by various studies, the situation is by far
more obscure in the IR luminosity range of the bright IRAS sample, 10^{10}Lsol
< Lfir < 10^{11} Lsol. To easily identify nearby companion galaxies, the bright
IRAS sample was restricted to 87 objects with redshift range 0.008 < z < 0.018
and galactic latitude > 30^{o}. A control sample, selected from the Center for
Astrophysics redshift survey catalogue, includes 90 objects matching the Bright
IRAS sample for distribution of isophotal diameter, redshift, and morphological
type. From a search of nearby companion galaxies within 250 Kpc on the
second-generation Digitized Sky Survey (DSS-II), we found that the
circumgalactic environment of the Bright IRAS galaxies contains more large
companions than the galaxies in the optically selected control sample, and is
similar to that of Seyfert 2 galaxies. We found a weak correlation over a wide
range of far IR luminosity (10^9 Lsol < Lfir < 10^{12.5}Lsol) between projected
separation and Lfir, which confirms a very close relationship between star
formation rate of a galaxy and the strength of gravitational perturbations. We
also find that the far IR colors depend on whether a source is isolated or
interacting. Finally, we discuss the intrinsic difference and evolution
expectations for the bright IRAS galaxies and the control sample, as well as
the relationship between starbursting and active galaxies.


title:
Deep Near-Infrared Imaginmg of Galaxies at z > 2 with Subaru: Color and
  Magnitude Distribution in HDF-N and the 53W002 Field

abstract:
  We present the results of the deep NIR imaging observations using the Subaru
telescope. At the Hubble Deep Field North, we obtained the new and deepest
K'-band image (10 hours) to study the rest-frame optical morphology of galaxies
at z > 3 and the stellar mass distribution of galaxies at 2 < z < 4.5. We also
study the rest-frame optical properties of the 'building blocks' in the field
of 53W002 and overall color distribution there. We then combined these data to
compare the color and magnitude distribution in these two fields. The opt-NIR
color-magnitude distributions in the two fields looks very similar and we
report the conspicuous color change below K_AB =22 and discuss the cause of the
feature.


title:
ASCA View of the Supernova Remnant Gamma Cygni (G78.2+2.1):
  Bremsstrahlung X-ray Spectrum from Loss-flattened Electron Distribution

abstract:
  We perform X-ray studies of the shell-type supernova remnant (SNR)
gamma-Cygni associated with the brightest EGRET unidentified source 3EG
J2020+4017. In addition to the thermal emissions with characteristic
temperature of kT = 0.5-0.9 keV, we found an extremely hard X-ray component
from several clumps localized in the northern part of the remnant. This
component is described by a power-law with a photon index of 0.8-1.5. Both the
absolute flux and the spectral shape of the nonthermal X-rays cannot be
explained by the synchrotron or inverse-Compton mechanisms. We argue that the
unusually hard X-ray spectrum can be naturally interpreted in terms of
nonthermal bremsstrahlung from Coulomb-loss-flattened electron distribution in
dense environs with the gas density about 10 to 100 cm^-3 . For given spectrum
of the electron population, the ratio of the bremsstrahlung X- and gamma-ray
fluxes depends on the position of the ``Coulomb break'' in the electron
spectrum. The bulk of gamma-rays detected by EGRET would come from the
radio-bright and X-ray dim cloud at southeast, where very dense gas and strong
magnetic field would illuminate the cloud in the radio and gamma-ray bands, but
suppress the bremsstrahlung X-ray emission due to the shift of the ``Coulomb
break'' in the electron spectrum towards higher energies.


title: On the Mass-Period Correlation of the Extrasolar Planets

abstract:
  We report on a possible correlation between the masses and periods of the
extrasolar planets, manifested as a paucity of massive planets with short
orbital periods. Monte-Carlo simulations show the effect is significant, and is
not solely due to an observational selection effect. We also show the effect is
stronger than the one already implied by published models that assumed
independent power-law distributions for the masses and periods of the
extrasolar planets. Planets found in binary stellar systems may have an
opposite correlation. The difference is highly significant despite the small
number of planets in binary systems. We discuss the paucity of short-period
massive planets in terms of some theories for the close-in giant planets.
Almost all models can account for the deficit of massive planets with short
periods, in particular the model that assumes migration driven by a planet-disk
interaction, if the planet masses do not scale with their disk masses.


title:
The peculiar small-scale X-ray morphology of NGC 5846 observed with
  Chandra

abstract:
  The excellent quality of the Chandra observation of NGC 5846 reveals a
complex X-ray morphology of the central regions of this galaxy. An intriguing
morphological similarity between the X-ray and the optical line emission,
discovered before using ROSAT HRI images (Trinchieri, Noris & Di Serego
Alighieri 1997), is confirmed here in unprecedented detail. Complex spectral
characteristics are associated with the morphological peculiarities, indicating
a possibly turbulent gas in this object. A population of ~ 40 individual
sources is also observed, with Lx in the range ~ 3 x 10**{38}- 2 x 10**{39}
erg/sec, with an X-ray luminosity function that is steeper in the
high-luminosity end than in other early-type galaxies.


title: MHD Shock Conditions for Accreting Plasma onto Kerr Black Holes - I

abstract:
  We extend the work by Appl and Camenzind (1988) for special relativistic
magnetohydrodynamic (MHD) jets, to fully general relativistic studies of the
standing shock formation for accreting MHD plasma in a rotating, stationary and
axisymmetric black hole magnetosphere. All the postshock physical quantities
are expressed in terms of the relativistic compression ratio, which can be
obtained in terms of preshock quantities. Then, the downstream state of a
shocked plasma is determined by the upstream state of the accreting plasma. In
this paper sample solutions are presented for slow magnetosonic shocks for
accreting flows in the equatorial plane. We find that some properties of the
slow magnetosonic shock for the rotating magnetosphere can behave like a fast
magnetosonic shock. In fact, it is confirmed that in the limit of weak gravity
for the upstream non-rotating accretion plasma where the magnetic field lines
are leading and rotating, our results are very similar to the fast magnetosonic
shock solution by Appl and Camenzind (1988). However, we find that the
situation becomes far more complicated due to the effects of strong gravity and
rotation, such as the frame dragging-effects. We show the tendency that the
large spin of the black hole makes the slow magnetosonic shock strong for the
accretion solutions with the same energy-flux.


title: A full orbit XMM-Newton observation of PKS 2155-304

abstract:
  XMM observed the BL Lac PKS 2155-304 for a full orbit (about 150 ksec) on
2000 November 19-21. Preliminary results on the temporal and spectral analysis
of data from the EPIC PN camera and Optical Monitor are presented. The
variability amplitude depends systematically on energy, however the slopes of
the structure functions of the light-curves in different bands do not appear to
be significantly different. No evidence of time lags is found by cross
correlating the light-curves in different bands.


title:
Ultraviolet Properties of Primeval Galaxies: Theoretical Models from
  Stellar Population Synthesis

abstract:
  The ultraviolet luminosity evolution of star-forming galaxies is explored
from the theoretical point of view, especially focusing on the theory of UV
energetics in simple and composite stellar populations and its relationship to
the star formation rate and other main evolutionary parameters.
  Galaxy emission below 3000 Angstroms directly correlates with actual star
formation, not depending on the total mass of the system. A straightforward
calibration is obtained, in this sense, from the theoretical models at 1600,
2000 and 2800 Angstroms, and a full comparison is carried out with IUE data and
other balloon-borne observations for local galaxies.
  The claimed role of late-type systems as prevailing contributors to the
cosmic UV background is reinforced by our results; at 2000 Angstroms Im
irregulars are found in fact nearly four orders of magnitude brighter than
ellipticals, per unit luminous mass.
  The role of dust absorption in the observation of high-redshift galaxies is
assessed, comparing model output and observed spectral energy distribution of
local galaxy samples. Similar to what we observe in our own galaxy, a quick
evolution in the dust environment might be envisaged in primeval galaxies, with
an increasing fraction of luminous matter that would escape the regions of
harder and "clumpy" dust absorption on a timescale of some 10^7 yr, comparable
with the lifetime of stars of 5-10 solar masses.


title:
Low and high frequency variability as a function of spectral properties
  in the bright X-ray binary GX 5-1

abstract:
  We report on a detailed analysis of data obtained over nearly four years with
the Rossi X-ray Timing Explorer of the Z source GX 5-1. From a spectral
analysis using a hardness-intensity diagram it was found that the source traced
out the typical Z-shaped pattern. The study of the power spectral properties
showed that when the source moved on the Horizontal Branch towards the Normal
Branch the fractional rms amplitudes and timescales of all variability
decreased, while their FWHMs increased. The frequency separation of the two kHz
QPO peaks decreased from 344+-12 Hz to 232+-13 Hz. At low frequencies, besides
the horizontal branch oscillation (HBO) and its second harmonic, two additional
broad Lorentzian components were needed to obtain acceptable fits. These broad
Lorentzians have Q-values of ~1-2 and have frequencies 0.5 and 1.5 times the
HBO frequency. When interpreted as being related to the HBO, they seem to favor
disc models for the HBO over the magnetic beat-frequency model. We compare the
timing properties and colour-colour diagrams (CDs) of GX 5-1 with those of the
back hole candidate XTE J1550-564 and the atoll source 4U 1608-52. The CDs are
strikingly similar when a colour scheme is used that is commonly employed in
back hole studies. However, this may be a degeneracy as the CDs turn out to be
more complicated when colours common in neutron star studies are employed.
Apart from some remarkable similarities between the CD of XTE J1550-564 and
that of 4U 1608-52, several differences can be seen between these CDs and that
of GX 5-1. Conclusions on spectral states or properties based solely on the use
of CDs using the ``black hole scheme'' should be regarded with caution.


title: Gamma-Ray Astronomy of Cosmic Rays

abstract:
  Many of the basic problems in the astrophysics of charged Cosmic Rays remain
on principle unresolved by in situ observations in the Solar System due to the
chaotic nature of the propagation of these particles in Interstellar space.
This concerns the existence and the nature of localized individual particle
sources as well as the transport in the Galaxy and establishes the need for
astronomical observations of secondary gamma-rays. The only exception may be
the highest energy particles at energies around $10^{20}$ eV which possibly
reach us on straight line orbits from their production sites. Recently such
gamma-ray observations, both in space and on the ground, have made great
progress even though the instrumental sensitivities are still low. It is argued
that two basic questions, regarding first of all the Supernova Remnant source
hypothesis and secondly the contributions to the diffuse gamma-ray background,
have come close to an empirical resolution. Apart from motivations deriving
from extragalactic astronomy this expectation is at the root of the
construction of a new generation of high-sensitivity gamma-ray instruments. As
a representative example the H.E.S.S. array of atmospheric Cherenkov telescopes
is described.


title:
Low resolution spectroscopy of ISOGAL sources: Search for early-type
  stars with infrared excess

abstract:
  An analysis of low resolution spectra and infared data of 29 ISOGAL-DENIS
sources with mid-IR excess is presented. Eight ISOGAL sources from our sample
with 7-15 micron excess are found to be B and A-type stars, some of them with
emission lines. Two ISOGAL sources, J175614.4-240831 (B3-4IIIe) and
J173845.3-312403 (B7III), show a bump between 5000 and 6000 Angstroem which
maybe attributed to extended red emission (ERE). Some of the B,A and F-type
giants with a large infrared excess might be in the post-AGB phase. For about
50% of the sources in this preliminary study, a nearby second (or even
multiple) component was found. Such sources, in particular two B-stars, are not
discussed when the probability of the optical spectrum being associated with
the ISOGAL source is low. These results confirm that the DENIS-ISOGAL
I-J/K-[15] diagram is the most suitable diagram to distinguish between early
(AB) and late spectral types (KM). It provides the most useful tool to
systematically search for nearby early-type stars with an infrared excess among
the background of distant AGB stars in ISOGAL fields of the Galactic disk.


title:
Restrictions to the galaxy evolutionary models from the Hawaiian Deep
  Fields SSA13 and SSA22

abstract:
  Quantitative structural analysis of the galaxies present in the Hawaiian Deep
Fields SSA13 and SSA22 is reported. The structural parameters of the galaxies
have been obtained automatically by fitting a two-component model (Sersic
r^{1/n} bulge and exponential disc) to the surface brightness of the galaxies.
The galaxies were classified on the basis of the bulge-to-total luminosity
ratio (B/T). The magnitude selection criteria and the reliability of our method
have been checked by using Monte Carlo simulations. A complete sample of
objects up to redshift 0.8 has been achieved. Spheroidal objects (E/S0)
represent ~33% and spirals ~41% of the total number of galaxies, while mergers
and unclassified objects represent ~26%. We have computed the comoving space
density of the different kinds of objects. In an Einstein-de Sitter universe a
decrease in the comoving density of E/S0 galaxies is observed as redshift
increases (a ~30% less at z=0.8), while for spiral galaxies a relatively quiet
evolution is reported. The framework of hierarchical clustering evolution
models of galaxies seems to be the most appropriate to explain our results.


title: Cosmological Magnetic Fields from Primordial Helical Seeds

abstract:
  Most early Universe scenarios predict negligible magnetic fields on
cosmological scales if they are unprocessed during subsequent expansion of the
Universe. We present a new numerical treatment of the evolution of primordial
fields and apply it to weakly helical seeds as they occur in certain early
Universe scenarios. We find that initial helicities not much larger than the
baryon to photon number can lead to fields of about 10^{-13} Gauss with
coherence scales slightly below a kilo-parsec today.


title: Introduction to Cosmic Rays

abstract:
  Energetic particles, traditionally called Cosmic Rays, were discovered nearly
a hundred years ago, and their origin is still uncertain. Their main
constituents are the normal nuclei as in the standard cosmic abundances of
matter, with some enhancements for the heavier elements; there are also
electrons, positrons and anti-protons, but no anti-nuclei. Today we also have
information on isotopic abundances, which show some anomalies, as compared with
the interstellar medium. The known spectrum extends over energies from a few
hundred MeV to 3*10^{20} eV and shows few clear spectral signatures: There is a
small spectral break near 5*10^{15} eV, the "knee", where the spectrum turns
down; there is another spectral break near 3*10^{18} eV, the "ankle", where the
spectrum turns up again. Up to the ankle the cosmic rays are usually
interpreted as originating from Galactic supernova explosions; however, we do
not know what the origin of the knee is. The particles beyond the ankle have to
be extragalactic, it is usually assumed, because the Larmor radii in the
Galactic magnetic field are too large; this argument could be overcome if those
particles were very heavy nuclei as Fe, an idea which appears to be
inconsistent, however, with the airshower data immediately above the energy of
the ankle. Due to interaction with the cosmic microwave background there is a
strong cut-off expected near 5*10^{19} eV, which is, however, not seen; The
high energy cosmic rays beyond this "GZK-cutoff" (after its discoverers
Greisen, Zatsepin and Kuzmin) are the challenge to interpret. We will describe
the various approaches to understand the origin and physics of cosmic rays
(abridged).


title:
Numerical simulations of stellar SiO maser variability. Investigation of
  the effect of shocks

abstract:
  A stellar hydrodynamic pulsation model has been combined with a SiO maser
model in an attempt to calculate the temporal variability of SiO maser emission
in the circumstellar envelope (CE) of a model AGB star. This study investigates
whether the variations in local physical conditions brought about by shocks are
the predominant contributing factor to SiO maser variability because, in this
work, the radiative part of the pump is constant. We find that some aspects of
the variability are not consistent with a pump provided by shock-enhanced
collisions alone. In these simulations, gas parcels of relatively enhanced SiO
abundance are distributed in a model CE by a Monte Carlo method, at a single
epoch of the stellar cycle. From this epoch on, Lagrangian motions of
individual parcels are calculated according to the velocity fields encountered
in the model CE during the stellar pulsation cycle. The potentially masing gas
parcels therefore experience different densities and temperatures, and have
varying line-of-sight velocity gradients throughout the stellar cycle, which
may or may not be suitable to produce maser emission. At each epoch (separated
by 16.6 days), emission lines from the parcels are combined to produce
synthetic spectra and VLBI-type images. We report here the results for v=1,
J=1-0 (43-GHz) and J=2-1 (86-GHz) masers.


title: The Evolution of type 1 AGN in the IR (15mu). The view from ELAIS-S1

abstract:
  We present the 15 micron luminosity function of type 1 AGN (QSO + Seyfert 1).
Our sample of 21 high-redshift sources is selected from the Preliminary
Analysis catalogue in the S1 field of the European Large Area ISO Survey
(ELAIS). To study the cosmological evolution of the AGN1 luminosity function,
our sample has been combined with a local sample of 41 sources observed by
IRAS. We find that the luminosity function of AGN1 at 15 micron is fairly well
represented by a double-power-law-function. There is evidence for significant
cosmological evolution consistent with a pure luminosity evolution (PLE) model
L(z) (1+z)^k, with k=3.0-3.3. The value of k depends on the existence or not of
an evolution cut-off at redshift ~2, and on the adopted cosmology. From the
luminosity function and its evolution we estimate a contribution of AGN1 to the
Cosmic Infrared Background (CIRB) of nuI_nu ~ 6 x 10^{-11}W m^{-2} sr^{-1} at
15 micron. This corresponds to ~2-3% of the total observed CIRB at this
wavelength. Under the usual assumptions of unified models for AGN, the expected
contribution of the whole AGN population to the CIRB at 15 micron is 10-15%.


title: X-rays from the jet in 3C 273: clues from the radio-optical spectra

abstract:
  Using new deep VLA and HST observations of the large-scale jet in 3C273
matched to 0.3" resolution, we have detected excess near-ultraviolet emission
(300 nm) above a synchrotron cutoff spectrum accounting for the emission from
radio through optical (3.6 cm - 620 nm). This necessitates a two-component
model for the emission. The radio-optical-X-ray spectral energy distributions
suggest a common origin for the UV excess and the X-rays from the jet.


title:
The Chemical Composition and Age of the Metal-Poor Halo Star BD
  +17^\circ 3248

abstract:
  We have combined new high-resolution spectra obtained with the Hubble Space
Telescope (HST) and ground-based facilities to make a comprehensive new
abundance analysis of the metal-poor, halo star BD +17^\circ 3248. We have
detected the third r-process peak elements osmium, platinum, and (for the first
time in a metal-poor star) gold, elements whose abundances can only be reliably
determined using HST. Our observations illustrate a pattern seen in other
similar halo stars with the abundances of the heavier neutron-capture elements,
including the third r-process peak elements, consistent with a scaled solar
system r-process distribution. The abundances of the lighter neutron-capture
elements, including germanium and silver, fall below that same scaled solar
r-process curve, a result similar to that seen in the ultra-metal-poor star CS
22892--052. A single site with two regimes or sets of conditions, or perhaps
two different sites for the lighter and heavier neutron-capture elements, might
explain the abundance pattern seen in this star. In addition we have derived a
reliable abundance for the radioactive element thorium. We tentatively identify
U II at 3859 A in the spectrum of BD +17^\circ 3248, which makes this the
second detection of uranium in a very metal-poor halo star. Our combined
observations cover the widest range in proton number (from germanium to
uranium) thus far of neutron-capture elements in metal-poor Galactic halo
stars. Employing the thorium and uranium abundances in comparison with each
other and with several stable elements, we determine an average
cosmochronological age for BD +17^\circ 3248 of 13.8 +/- 4 Gyr, consistent with
that found for other similar metal-poor halo stars.


title: The sources of the X-ray background

abstract:
  Deep X-ray surveys have shown that the cosmic X-ray background (XRB) is
largely due to the accretion onto supermassive black holes, integrated over
cosmic time. The ROSAT, Chandra and XMM-Newton satellites have resolved more
than 80% of the 0.1-10 keV X-ray background into discrete sources. Optical
spectroscopic identifications are about 90% and 60% complete for the deepest
ROSAT and Chandra/ XMM-Newton surveys, respectively, and show that the sources
producing the bulk of the X-ray background are a mixture of obscured (type-2)
and unobscured (type-1) AGNs, as predicted by the XRB population synthesis
models, following the unified AGN scenarios. The characteristic hard spectrum
of the XRB can be explained if most of the AGN are heavily absorbed, and in
particular a class of highly luminous type-2 AGN, so called QSO-2s exist. The
deep Chandra and XMM-Newton surveys have recently detected several examples of
QSO-2s. The space density of the X-ray selected AGN, as determined from ROSAT
surveys does not seem to decline as rapidly as that of optically selected QSO,
however, the statistics of the high-redshift samples is still rather poor. The
new Chandra and XMM-Newton surveys at significantly fainter fluxes are starting
to provide additional constraints here, but the preliminary observed redshift
distribution peaks at much lower redshifts (z=0.5-0.7) than the predictions
based on the ROSAT luminosity function.


title:
Chandra view of the dynamically young cluster of galaxies A1367 II.
  point sources

abstract:
  A 40 ks \emph{Chandra} ACIS-S observation of the dynamically young cluster
A1367 yields new insights on X-ray emission from cluster member galaxies. We
detect 59 point-like sources in the ACIS field, of which 8 are identified with
known cluster member galaxies. Thus, in total 10 member galaxies are detected
in X-rays when three galaxies discussed in paper I (Sun & Murray 2002; NGC 3860
is discussed in both papers) are included. The superior spatial resolution and
good spectroscopy capability of \chandra allow us to constrain the emission
nature of these galaxies. Central nuclei, thermal halos and stellar components
are revealed in their spectra. Two new low luminosity nuclei (LLAGN) are found,
including an absorbed one (NGC 3861). Besides these two for sure, two new
candidates of LLAGN are also found. This discovery makes the LLAGN/AGN content
in this part of A1367 very high ($\gsim$ 12%). Thermal halos with temperatures
around 0.5 - 0.8 keV are revealed in the spectra of NGC 3842 and NGC 3837,
which suggests that Galactic coronae can survive in clusters and heat
conduction must be suppressed. The X-ray spectrum of NGC 3862 (3C 264)
resembles a BL Lac object with a photon index of $\sim$ 2.5. We also present an
analysis of other point sources in the field and discuss the apparent source
excess ($\sim$ 2.5 $\sigma$) in the central field.


title:
The continuum variability of MCG--6-30-15: A detailed analysis of the
  long 1999 ASCA observation

abstract:
  We report on an analysis in the 3--10 keV X-ray band of the long 1999 ASCA
observation of MCG--6-30-15. The time-averaged broad iron K line is
well-described by disk emission near a Schwarzschild black hole, confirming the
results of earlier analyses on the ASCA 1994 and 1997 data. The time-resolved
iron-line profile is remarkably stable over a factor of three change in source
flux, and the line and continuum fluxes are uncorrelated. Detailed fits to the
variable iron-line profile suggest that the active region (parametrized by the
best-fit inner and outer radii of the accretion disk) responsible for iron line
emission actually narrows with increasing flux to a region around 4--5 r_g. In
contrast to the iron line, the power-law continuum exhibits significant
variability during the 1999 observation. Time-resolved spectral analysis
reveals a new feature in the well-known photon index (Gamma) vs. flux
correlation: Gamma appears to approach a limiting value of Gamma ~ 2.1 at high
flux. Two models are proposed to explain both the new feature in the Gamma vs.
flux correlation and the uncorrelated iron-line flux: a phenomenological two
power-law model, and the recently proposed ``thundercloud'' model of Merloni &
Fabian (2001). Both models are capable of reproducing the data well, but
because they are poorly constrained by the observed Gamma vs. flux relation,
they cannot at present be tested meaningfully by the data. The various
implications and the physical interpretation of these models are discussed.


title:
Far-Infrared photometry of a statistical sampleof late-type Virgo
  Cluster galaxies

abstract:
  We present deep diffraction-limited far-infrared (FIR) strip maps of a sample
of 63 galaxies later than S0 and brighter than B_T 16.8, selected from the
Virgo Cluster Catalogue of Binggeli, Sandage & Tammann. The ISOPHOT instrument
on board the Infrared Space Observatory was used to achieve sensitivities
typically an order of magnitude deeper than IRAS in the 60 and 100 micron bands
and to reach the confusion limit at 170 microns. The averaged 3 sigma upper
limits for integrated flux densities of point sources at 60, 100 and 170
microns are 43, 33 and 58 mJy, respectively. 54 galaxies (85.7 percent) are
detected at least at one wavelength, and 40 galaxies (63.5 percent) are
detected at all three wavelengths. The highest detection rate (85.7 percent) is
in the 170 micron band. In many cases the galaxies are resolved, allowing the
scale length of the infrared disks to be derived from the oversampled
brightness profiles in addition to the spatially integrated emission. The data
presented should provide the basis for a variety of statistical investigations
of the FIR spectral energy distributions of gas rich galaxies in the local
universe spanning a broad range in star-formation activity and morphological
types, including dwarf systems and galaxies with rather quiescent star
formation activity.


title:
Separation of Gravitational-Wave and Cosmic-Shear Contributions to
  Cosmic Microwave Background Polarization

abstract:
  Inflationary gravitational waves (GW) contribute to the curl component in the
polarization of the CMB. Cosmic shear--gravitational lensing of the CMB--
converts a fraction of the dominant gradient polarization to the curl
component. Higher-order correlations can be used to map the cosmic shear and
subtract this contribution to the curl. Arcminute resolution will be required
to pursue GW amplitudes smaller than those accessible by Planck. The finite
cutoff in CMB power at small scales leads to a minimum detectable GW amplitude
corresponding to an inflation energy near 10^15 GeV.


title: Multi-wavelength Study of IRAS 19254-7245 - The Superantennae

abstract:
  We present observations in the optical, near-infrared and millimetre bands of
the Ultraluminous Infrared galaxy IRAS 19254-7245, also known as "The
Superantennae". This galaxy is an interacting system with a double nucleus and
long tails extending for about 350 kpc. We studied in detail the southern
component of the system which is optically classified as a Sy2 galaxy. We have
developed a method to determine the parameters of the emission lines in a
spectrum in the case of multiple components and severe blending. Our data allow
us to build a picture of the environment around the nucleus of the galaxy with
unprecedented detail. The optical lines show a complex dynamical structure that
is not observable in the near-infrared. In addition we find typical features of
AGN such as the coronal lines of [FeVII]5721 and [SiVI]1.96. We also detect
strong emission from [FeII]1.64 and $H_2$.


title:
On the evolution of aspherical perturbations in the universe: an
  analytical model

abstract:
  I study the role of shear fields by using an analytical approximate solution
for the equations of motion of homogeneous ellipsoids embedded in a homogeneous
background. The equations of motion of a homogeneous ellipsoid (Icke 1973;
White & Silk 1979 (hereafter WS)) are modified in order to take account of the
tidal field as done in Watanabe 1993 and then are integrated analytically,
similarly to what done in WS. The comparison of the analytical solution with
numerical simulations shows that it is a good approximation to the numerical
one. This solution is used to study the evolution of the configuration ofthe
ellipsoids, to calculate the evolution of the density contrast and that of the
axial peculiar velocity of the ellipsoids for several values of the amplitude
of the external tidal field, and compared again with numerical simulations. In
order to calculate the evolution of the density contrast at turn-around and
collapse velocity at the epoch of collapse, as a function of the ratio of the
initial value of the semi-axes, I use the previously obtained approximate
solution to modify the analytical model proposed by Barrow & Silk (1981) for
the ellipsoids evolution in the non-linear regime. The density contrast at
turn-around and the collapse velocity are found to be reduced with respect to
that found by means of the spherical model. The reduction increases with
increasing strength of the external tidal field and with increasing initial
asymmetry of the ellipsoids. These last calculations are also compared with
numerical solutions and they are again in good agreement with the numerical
ones.


title: The luminosity function of the Virgo Cluster from M_B=-22 to M_B=-11

abstract:
  We measure the galaxy luminosity function (LF) for the Virgo Cluster between
blue magnitudes M_B = -22 and M_B = -11 from wide-field CCD imaging data. The
LF is only gradually rising for -22 < M_B < -16. Between M_B = -16 and M_B =
-14 it rises steeply, with a logarithmic slope alpha ~ -1.6. Fainter than M_B =
-14, the LF flattens again. This LF is shallower (although turning up at
brighter absolute magnitudes) than the R-band LF recently measured by Phillipps
et al. (1998), who found alpha ~ -2.2 fainter than M_R = -13. It is similar,
however, to the LF determined from the Virgo Cluster Catalog by Sandage et al.
(1985). A few faint galaxies are found which Sandage, et al. missed because
their surface-brightness threshold for detection was too high, but these do not
dominate the luminosity function at any magnitude. Most of the faint galaxies
we find are dwarf elliptical, alternatively called dwarf spheroidal, galaxies.
The most important potential source of systematic error is that we may have
rejected some high surface-brightness galaxies from the cluster sample because
we think that they are background galaxies. This is quite different from what
has conventionally been regarded as the most serious source of systematic error
in this kind of study: that we are missing many LOW surface-brightness galaxies
because they are never visible above the sky.


title: Detection of superhumps in XTE J1118+480 approaching quiescence

abstract:
  We present the results of our monitoring of the halo black-hole soft X-ray
transient (SXT) XTE J1118+480 during its decline to quiescence. The system has
decayed 0.5 mags from December 2000 to its present near quiescent level at
R=18.65 (June 2001). The ellipsoidal lightcurve is distorted by an additional
modulation that we interpret as a superhump of P_sh=0.17049(1) d i.e. 0.3%
longer than the orbital period. This implies a disc precession period P_prec=
52 d. After correcting the average phase-folded light curve for veiling, the
amplitude difference between the minima suggests that the binary inclination
angle lies in the range i=71-82 deg. However, we urge caution in the
interpretation of these values because of residual systematic contamination of
the ellipsoidal lightcurve by the complex form of the superhump modulation. The
orbital--mean H-alpha profiles exhibit clear velocity variations with ~500 km/s
amplitude. We interpret this as the first spectroscopic evidence of an
eccentric precessing disc.


title:
A Multifrequency Analysis of the Polarized Diffuse Galactic Radio
  Emission at Degree Scales

abstract:
  The polarized diffuse Galactic radio emission, mainly synchrotron emission,
is expected to be one of the most relevant source of astrophysical
contamination at low and moderate multipoles in cosmic microwave background
polarization anisotropy experiments at frequencies lower then 50 to 100 GHz. We
present here preliminary results based on a recent analysis of the Leiden
surveys covering about 50% of the sky at low as well as at middle and high
Galactic latitudes. By implementing specific interpolation methods to deal with
these data, which show a large variation of the sampling across the sky, we
produce maps of the polarized diffuse Galactic synchrotron component at
frequencies between 408 and 1411 MHz with pixel sizes larger or equal to about
0.92 degrees. We derive the angular power spectrum of this component for the
whole covered region and for three patches in the sky significantly oversampled
with respect to the average and at different Galactic latitudes. We find
multipole spectral indices typically ranging between about -3 and about -1,
according to the considered frequency and sky region. At frequencies higher or
equal to 610 MHz, the frequency spectral indices observed in the considered sky
regions are about -3.5, compatible with an intrinsic frequency spectral index
of about -5.8 and a depolarization due to Faraday rotation with a rotation
measure RM of about 15 radians per square meter. This implies that the observed
angular power spectrum of the polarized signal is about 85% or 20% of the
intrinsic one at 1411 MHz or 820 MHz respectively.


title:
Effects of boundary conditions on the dynamics of the solar convection
  zone

abstract:
  Recent analyses of the helioseismic data have produced evidence for a variety
of interesting dynamical behaviour associated with torsional oscillations. What
is not so far clear is whether these oscillations extend all the way to the
bottom of the convection zone and, if so, whether the oscillatory behaviour at
the top and the bottom of the convection zone is different. Attempts have been
made to understand such modes of behaviour within the framework of nonlinear
dynamo models which include the nonlinear action of the Lorentz force of the
dynamo generated magnetic field on the solar angular velocity. One aspect of
these models that remains uncertain is the nature of the boundary conditions on
the magnetic field. Here by employing a range of physically plausible boundary
conditions, we show that for near-critical and moderately supercritical dynamo
regimes, the oscillations extend all the way down to the bottom of the
convection zone. Thus, such penetration is an extremely robust feature of the
models considered. We also find parameter ranges for which the supercritical
models show spatiotemporal fragmentation for a range of choices of boundary
conditions. Given their observational importance, we also make a comparative
study of the amplitude of torsional oscillations as a function of the boundary
conditions.


title:
Dwarf Nova Oscillations and Quasi-Periodic Oscillations in Cataclysmic
  Variables: I. Observations of VW Hyi

abstract:
  From archived and recent high speed photometry of VW Hyi we find Dwarf Nova
Oscillations (DNOs) occasionally present throughout outburst, evolving from
14.06 s period at maximum to > 40 s near the end of outburst. A relatively slow
increase of period is followed by rapid increase and subsequent decrease.
  Quasi-periodic Oscillations (QPOs) are seen at periods of hundreds of
seconds. For the first time, an evolution of QPO period is seen, steadily
increasing during the final decline of an outburst. The occasional presence of
two DNOs, separated in frequency by the QPO frequency, suggests reprocessing of
the rotating DNO beam by a `wall' rotating progradely in the disc at the QPO
period.


title:
The Origin of X-ray Emission from a Galactic Center Molecular Cloud: Low
  Energy Cosmic Ray Electrons

abstract:
  The Galactic center region near l$\approx0.2^0$ hosts a mixture of nonthermal
linear filaments and thermal radio continuum features associated with the radio
Arc. Chandra observations of this region reveal an X-ray filament and diffuse
emission with an extent of roughly 60$''\times2''$ and 5$'\times3'$,
respectively. The X-ray filament lies at the edge of the nonthermal radio
filaments and a dense molecular shell G0.13-0.13 that has an unusually high
kinetic temperature $\ge$70K. These observations demonstrate that the
G0.13--0.13 molecular cloud and the nonthermal radio filaments of the Arc are
interacting. The diffuse X-ray emission is correlated with the molecular shell
and is fitted either by two-temperature (1 and 10 keV) thermal emission or by
power-law and 1 keV thermal gas. Fluorescent 6.4 keV line emission is also
detected throughout the molecular shell. This cloud coincides within the error
circle of a steady unidentified EGRET source 3EGJ1746--2851. We argue that
low-energy cosmic ray electrons (LECRe) produce the power-law continuum by
bremsstrahlung and 6.4 keV line emission from the filament and the diffuse
cloud with the implication on the origin of the Galactic ridge X-ray emission.
The strong 6.4 keV Fe-line emission seen from other Galactic center clouds
could be produced in a similar fashion rather than via fluorescent emission
induced by a transient hard X-ray source in the Galactic center. In addition,
heating by ionization induced by LECRe are also responsible for the high
temperature of G0.13-0.13. The gamma-ray source is a result of brehmsstrahlung
by the high-energy tail of the electron energy distribution.


title:
The effect of Planck scale space time fluctuations on Lorentz invariance
  at extreme speeds

abstract:
  The starting point of this work is the axiomatic existence of a smallest
measurable interval, viz. the Planck time $t_P$, set by quantum fluctuations in
the vacuum metric tensor. By the Relativity Principle, the same limit must then
apply to the accuracy of all clocks which register time of events in their own
frames. Further, it implies that the ordinary meaning of distance also ceases
in the same manner beyond a scale l_P = c t_P. We demonstrate that quantum
space-time, if real, may be made manifest by observing very energetic
collisions, defined as interactions which occurred with the center-of-mass
frame $\Sigma'$ (of the participating bodies) moving at a high speed $v$
relative to our laboratory frame $\Sigma$. In such situations, the initial
conditions of the interaction are determined from direct measurements of the
ultra-energetic particles or photons by instruments aboard $\Sigma$: they
gather a raw dataset ${\cal S}$ which are subject to the limiting uncertainties
\~ (t_P, l_P). Yet a meaningful (i.e. experimentally verified) version of the
interaction is one where the interaction is viewed from frame $\Sigma'$. Since
no instruments aboard $\Sigma'$ have taken any data, the way we proceeded is by
a Lorentz transformation of ${\cal S}$ from $\Sigma$ to $\Sigma'$. Beware
however that the resulting ${\cal S'}$ no longer consists of raw data, i.e.
Lorentz distortions of probability distributions render the uncertainties
non-Planckian - in fact, it will be shown that as v -> c they are >> (t_P,
l_P), and are no longer negligible. Examples will given to indicate how a
proper interpretation of the most current high energy cosmic and gamma-ray data
necessitates incorporation of the said effect.

categories: astro-ph gr-qc hep-ex hep-ph hep-th math-ph math.MP