title:
Some remarks on the angular momenta of galaxies, their clusters and
  superclusters

abstract:
  We discuss the relation between angular momenta and masses of galaxy
structures base on the Li model of the universe with global rotation. In our
previous paper (God{\l}owski et al 2002) it was shown that the model predicts
the presence of a minimum in this relation. In the present paper we discuss
observational evidence allowing us to verify this relation. We find null
angular momentum J=0 for the masses corresponding to mass of galaxy grups and
non-vanishing angular momenta for other galactic structures. We check these
theoretical predictions analysing Tully's galaxy grups. The existing data
comparing alignment in different galactic structure are consistent with
obtained theoretical relation $J(M)$ if we interpret the groving alignment as
the galactic increasing angular momenta in the galactic structure.


title: Can AB Dor C be a Tight Binary Brown Dwarf?

abstract:
  AB Dor C, a low-mass companion to the young star AB Dor A has recently been
imaged. Direct detection and astrometric observations have been used to solve
the AB Dor C orbit and obtain a dynamical mass estimate. Near-infrared
magnitudes and effective temperatures from models have then been compared with
observed values. Models and observations disagree at more than the 2 sigma
level. This result prompts Close et al. 2005 to claim that models are
overestimating young low-mass object luminosities by roughly a factor of two.
This claim is based on the hypothesis that the detected source, AB Dor C, is a
single object. Another possible interpretation of the data that was not
considered is that AB Dor C is an unresolved binary brown dwarf. Considering
that 21 brown dwarfs companions have been found to date around stars and that
three of them are confirmed or potential brown dwarf binaries (Gl569Ba & Bb,
GL564B & C and Indi Ba & Bb), this suggests that brown dwarf binaries may
constitute a significant fraction (14% +/- 8%) of the brown dwarf population
around stars. For these reasons, the possibility that AB Dor C is an unresolved
binary brown dwarf deserves attention.


title: Quintessence models of Dark Energy with non-minimal coupling

abstract:
  We explore quintessence models of dark energy which exhibit non-minimal
coupling between the dark matter and the dark energy components of the cosmic
fluid. The kind of coupling chosen is inspired in scalar-tensor theories of
gravity. We impose a suitable dynamics of the expansion allowing to derive
exact Friedmann-Robertson-Walker solutions once the coupling function is given
as input. Coupling functions that lead to self-interaction potentials of the
single and double exponential types are the target of the present
investigation. The stability and existence of the solutions is discussed in
some detail. The models are tested against the observational evidence.


title:
The Magnetic Properties of an L Dwarf Derived from Simultaneous Radio,
  X-ray, and H-alpha Observations

abstract:
  We present the first simultaneous, multi-wavelength observations of an L
dwarf, the L3.5 candidate brown dwarf 2MASS J00361617+1821104, conducted with
the Very Large Array, the Chandra X-ray Observatory, and the Kitt Peak 4-m
telescope. We detect strongly variable and periodic radio emission (P=3 hr)
with a fraction of about 60% circular polarization. No X-ray emission is
detected to a limit of L_X/L_{bol}<2e-5, several hundred times below the
saturation level observed in early M dwarfs. Similarly, we do not detect
H-alpha emission to a limit of L_{H-alpha}/L_{bol}<2e-7, the deepest for any L
dwarf observed to date. The ratio of radio to X-ray luminosity is at least four
orders of magnitude in excess of that observed in a wide range of active stars
(including M dwarfs) providing the first direct confirmation that late-M and L
dwarfs violate the radio/X-ray correlation. The radio emission is due to
gyrosynchrotron radiation in a large-scale magnetic field of about 175 G, which
is maintained on timescales longer than three years. The detected 3-hour period
may be due to (i) the orbital motion of a companion at a separation of about
five stellar radii, similar to the configuration of RS CVn systems, (ii) an
equatorial rotation velocity of about 37 km/s and an anchored, long-lived
magnetic field, or (iii) periodic release of magnetic stresses in the form of
weak flares. In the case of orbital motion, the magnetic activity may be
induced by the companion, possibly explaining the unusual pattern of activity
and the long-lived signal. We conclude that fully convective stars can maintain
a large-scale and stable magnetic field, but the lack of X-ray and H-alpha
emission indicates that the atmospheric conditions are markedly different than
in early-type stars and even M dwarfs. [abridged]


title: Spitzer Imaging of i'-drop Galaxies: Old Stars at z~6

abstract:
  We present new evidence for mature stellar populations with ages >100Myr in
massive galaxies (M_stellar>10^10M_sun) seen at a time when the Universe was
less than 1Gyr old. We analyse the prominent detections of two z~6 star-forming
galaxies (SBM03#1 & #3) made at wavelengths corresponding to the rest-frame
optical using the IRAC camera onboard the Spitzer Space Telescope. We had
previously identified these galaxies in HST/ACS GOODS images of Chandra Deep
Field South through the "i-drop" Lyman break technique, and subsequently
confirmed spectroscopically with the Keck telescope. The new Spitzer photometry
reveals significant Balmer/4000Ang discontinuities, indicative of dominant
stellar populations with ages >100Myr. Fitting a range of population synthesis
models (for normal initial mass functions) to the HST/Spitzer photometry yields
ages of 250-650Myr and implied formation redshifts z~7.5-13.5 in
presently-accepted world models. Remarkably, our sources have best-fit stellar
masses of 1.3-3.8x10^10M_sun (95% confidence) assuming a Salpeter initial mass
function. This indicates that at least some galaxies with stellar masses >20%
of those of a present-day L* galaxy had already assembled within the first Gyr
after the Big Bang. We also deduce that the past average star formation rate
must be comparable to the current observed rate (SFR_UV~5-30M_sun/yr),
suggesting that there may have been more vigorous episodes of star formation in
such systems at higher redshifts. Although a small sample, limited primarily by
Spitzer's detection efficiency, our result lends support to the hypothesis
advocated in our earlier analyses of the Ultra Deep Field and GOODS HST/ACS
data. The presence of established systems at z~6 suggests long-lived sources at
earlier epochs (z>7) played a key role in reionizing the Universe.


title: The Halo of the Milky Way

abstract:
  We show that the star counts in the spheroid of the Milky Way are not
symmetric about the l=0, l=180 deg. plane. The minimum counts are found towards
l=155 deg. The Galactic longitude of maximum star counts depends on the
magnitude and color selection of the halo stars. We interpret this as evidence
that the spheroid population is triaxial with a major axis oriented 65 deg from
the line of sight from the Sun to the Galactic center, and approximately
perpendicular to the Galactic bar. Large local star concentrations from tidal
debris and possible tidal debris are also observed. A full understanding of the
Galactic spheroid population awaits position information and three dimensional
space velocities for a representative set of stars in every substructure.
Tangential velocities for many stars will be provided by current and planned
astrometry missions, but no planned mission will measure stars faint enough to
unravel the more distant parts of the spheroid, which contain the majority of
the spatial substructure. This paper uses data from the Sloan Digital Sky
Survey (SDSS) public data release DR3.


title:
Measurement of Spectral Breaks in Pulsar Wind Nebulae with
  Millimeter-wave Interferometry

abstract:
  We have observed pulsar wind nebulae in the three supernova remnants
G11.2-0.3, G16.7+0.1, and G29.7-0.3 at 89 GHz with the
Berkeley-Illinois-Maryland Association Array, measuring total flux densities of
two of them for comparison with archival data at other frequencies . In
G16.7+0.1, we find a break in the spectrum of the PWN at ~26 GHz. In G29.7-0.3,
our data suggest a break in the integrated spectrum of the central nebula at
~55 GHz, lower than previously estimated. However, we have found spatial
structure in the spectrum of this nebula. The emission to the north of pulsar
J1846-0258 has a broken spectrum, with break frequency ~< 100 GHz, consistent
with a conventional pulsar-powered nebula. The emission to the south of the
pulsar has a near-power-law spectrum from radio to X-rays: this component may
be unrelated to the PWN, or may be evidence of asymmetries and/or time
evolution in the pulsar's energy output. We present 89 GHz images of each
remnant.


title: Toward an understanding of the periastron puzzle of PSR B1259-63

abstract:
  Efforts are made to understand the timing behaviors (e.g., the jumps of the
projected pulsar semimajor axis in the periastron passages) observed via
13-year timing for PSR B1259-63. In the first, planet-like objects are
suggested to orbit around the Be star, which may gravitationally perturb the
(probably low mass) pulsar when it passes through periastron. Second, an
accretion disk should exist outside the pulsar's light cylinder, which creates
a spindown torque on the pulsar due to the propeller effect. The observed
negative braking index and the discrepant timing residuals close to periastron
could be relevant to the existence of the disk with varying accretion rates.
Third, a speculation is presented that the accretion rate may increase on a
long timescale in order to explain the negative braking index.


title:
Hydrodynamical stability of thin accretion discs: transient growth of
  global axisymmetric perturbations

abstract:
  The purpose of this paper is to explore how accretion discs manifest the
phenomenon of transient growth on a global scale. We investigate analytically
the time response of a thin accretion disc to particular axisymmetric
perturbations. To facilitate an analytical treatment we replace the energy
equation with a general polytropic assumption. The asymptotic expansion of
Klu\'zniak & Kita (2000), which extended the method of Regev (1983) to a full
steady polytropic disc (with $n=3/2$), is further developed and implemented for
both the steady (for any polytropic index) and time-dependent problems. The
spatial form and temporal behaviour of selected dynamical disturbances are
studied in detail. We identify the perturbation space which leads to transient
growth and provide analytical solutions which manifest this expected transient
growth behaviour. Three terms (physical causes) responsible for the appearance
of transient growth are identified. Two depend explicitly on the viscosity
while the third one is relevant also for inviscid discs. The main conclusion we
draw is that the phenomenon of transient growth exists in discs on a global
scale.


title: Mass Limit on Nemesis

abstract:
  We assume that if the sun has a companion, it has a period of 27 Myr
corresponding to the periodicity seen in cometary impacts on earth. Based on
this assumption, it is seen that the inner Lagrengian point of the interaction
between the Sun and its companion is in the Oort cloud. From this we calculate
the mass -- distance relation for the companion. We then compute the expected
apparent magnitude (visible and J band) for the companion using the models of
Burrows (1993). We then compare this with the catalogue completeness of optical
and infrared catalogues to show that the sun cannot have a companion of mass
greater than 44 M_jup (0.042 M_sun)


title: Soft gamma repeaters and starforming galaxies

abstract:
  We propose that the best sites to search for SGRs outside the Local group are
galaxies with active star formation. Different possibilities to observe SGR
activity from these sites are discussed. In particular we searched for giant
flares from M82, M83, NGC 253, and NGC 4945 in the BATSE data. We present a
list of potential candidates, however, in our opinion no good candidates alike
giant SGR flares were found. Still, hyperflares similar to the one of 27
December 2004 can be observed from larger distances. From the BATSE data we
select 5 candidates coincident with the galaxies Arp 299 and NGC 3256 which
have very high rate of starformation, and propose that they can be examples of
hyperflares; but this result has low statistical significance.


title:
Pulsations, Boundary Layers, and Period Bounce in the Cataclysmic
  Variable RE J1255+266

abstract:
  We report time-series photometry of the quiescent optical counterpart of the
EUV transient RE J1255+266. The star appears as a DA white dwarf with bright
emission lines and a complex spectrum of periodic signals in its light curve. A
signal at 0.0829 d is likely to be the orbital period of the underlying
cataclysmic binary (probably a dwarf nova). Characteristic periods of 1344,
1236, and 668 s are seen, and a host of weaker signals. We interpret these
noncommensurate signals as (nonradial) pulsation periods of the white dwarf.
The donor star is unseen at all wavelengths, and the accretion rate is very
low. We estimate a distance of 180+-50 pc, and M_v=14.6+-1.3 for the accretion
light. The binary probably represents a very late stage of evolution, with the
donor star whittled down to M_2<0.05 M_sol. Such binaries stubbornly resist
discovery due to their faintness and reluctance to erupt, but are probably a
very common type of cataclysmic variable. If the signal at 0.0829 d is indeed
the orbital period, then the binary is an excellent candidate as a "period
bouncer". Plausible colleagues in this club include four dwarf novae and the
(so far) noneruptive stars GD 552 and 1RXS J105010.3-140431 (hereafter RX
1050).
  The 1994 EUV eruption implies a soft X-ray/EUV luminosity of 10^(34-35)
erg/s, greater than that of any other dwarf nova. We attribute that to a
favorable blend of properties: a high-mass white dwarf; a very transparent line
of sight (the "Local Chimney"); and a low binary inclination. The first
maximizes the expected temperature and luminosity of boundary-layer emission;
the other two increase the likelihood that soft X-rays can survive their
perilous passage through an accretion-disk wind and the interstellar medium.


title:
An expanding radio nebula produced by a giant flare from the magnetar
  SGR 1806-20

abstract:
  Soft gamma repeaters (SGRs) are "magnetars", a small class of slowly spinning
neutron stars with extreme surface magnetic fields, ~10^15 gauss. On 2004
December 27, a giant flare was detected from the magnetar SGR 1806-20, the
third such event ever recorded. This burst of energy was detected by a variety
of instruments and even caused an ionospheric disturbance in the Earth's upper
atmosphere recorded around the globe. Here we report the detection of a fading
radio afterglow produced by this outburst, with a luminosity 500 times larger
than the only other detection of a similar source. From day 6 to day 19 after
the flare from SGR 1806-20, a resolved, linearly polarized, radio nebula was
seen, expanding at approximately a quarter the speed of light. To create this
nebula, at least 4x10^43 ergs of energy must have been emitted by the giant
flare in the form of magnetic fields and relativistic particles. The
combination of spatially resolved structure and rapid time evolution allows a
study in unprecedented detail of a nearby analog to supernovae and gamma-ray
bursts.


title:
A simple test for the existence of two accretion modes in Active
  Galactic Nuclei

abstract:
  By analogy to the different accretion states observed in black-hole X-ray
binaries (BHXBs), it appears plausible that accretion disks in active galactic
nuclei (AGN) undergo a state transition between a radiatively efficient and
inefficient accretion flow. If the radiative efficiency changes at some
critical accretion rate, there will be a change in the distribution of black
hole masses and bolometric luminosities at the corresponding transition
luminosity. To test this prediction, I consider the joint distribution of AGN
black hole masses and bolometric luminosities for a sample taken from the
literature. The small number of objects with low Eddington-scaled accretion
rates mdot < 0.01 and black hole masses Mbh < 10^9 Msun constitutes tentative
evidence for the existence of such a transition in AGN. Selection effects, in
particular those associated with flux-limited samples, systematically exclude
objects in particular regions of the black hole mass-luminosity plane.
Therefore, they require particular attention in the analysis of distributions
of black hole mass, bolometric luminosity, and derived quantities like the
accretion rate. I suggest further observational tests of the BHXB-AGN
unification scheme which are based on the jet domination of the energy output
of BHXBs in the hard state, and on the possible equivalence of BHXB in the very
high (or "steep power-law") state showing ejections and efficiently accreting
quasars and radio galaxies with powerful radio jets.


title: Supernova search at intermediate z. I. Spectroscopic analysis

abstract:
  We study 8 supernovae discovered as part of the International Time Programme
(ITP) project ``Omega and Lambda from Supernovae and the Physics of Supernova
Explosions'' at the European Northern Observatory (ENO). The goal of the
project is to increase the sample of intermediate redshift (0.1<z<0.4) SNe Ia
for testing properties of SNe Ia along z and for enlarging the sample in the
Hubble diagram up to large z.


title:
A microlensing measurement of the size of the broad emission line region
  in the lensed QSO 2237+0305

abstract:
  We present spatially resolved spectroscopic images of the gravitationally
lensed QSO 2237+0305 taken with the GMOS Integral Field Unit (IFU) on the
Gemini North telescope. These observations have the best spatial resolution of
any IFU observations of this object to date and include the redshifted CIII]
and MgII QSO broad lines. Unlike Mediavilla et al. 1998, we find no evidence
for an arc of resolved broad line emission in either the CIII] or MgII lines.
  We calculate the image flux ratios of both the integrated emission lines and
the surrounding continua. The flux ratios of the CIII] and MgII emission lines
are consistent with each other but differ substantially from their
corresponding continuum flux ratios and the radio/mid-IR flux ratios previously
published. We argue that the broad emission line region must be microlensed and
the CIII] and MgII emission regions must be approximately the same size and
co-located along the line-of-sight. Assuming a simple model for the broad
emission line region and the continuum region, we show the size of the CIII] /
MgII broad line region is ~0.06 h_{70}^{1/2} pc and the continuum region is <=
0.02 h_{70}^{1/2} pc.


title: Supernova search at intermediate z. II. Host galaxy morphology

abstract:
  We discuss the host galaxy morphology of the 8 SNe discovered as a part of
the International Time Programme (ITP) project ``Omega and Lambda from
Supernovae, and the Physics of Supernovae Explosions'' at the European Northern
Observatory (ENO). Identification of the SN host galaxy types was done
exploiting both imaging and spectroscopy. A peculiar SNIa at z= 0.033 is found
in a spiral galaxy, as most other SNeIa with z between 0.1 and 0.4. A complete
account of these studies will be given elsewhere.


title:
Supernova search at intermediate z. III. Expansion velocities of the
  ejecta

abstract:
  We discuss the expansion velocities of different elements in the ejecta of
the intermediate-z SNe Ia discovered as a part of the International Time
Programme (ITP) project ``Omega and Lambda from Supernovae and the Physics of
  Supernova Explosions'' at the European Northern Observatory (ENO). The
expansion velocities measured for each normal SNIa are found to be within the
typical velocity dispersion for their epoch. Meanwhile, the subluminous SN
2002lk SiII expansion velocity is significantly higher than that of SN 1991bg
shortly after maximum. The observed phase was younger in SN2002lk than in the
local subluminous SNIa SN1991bg.


title: The Nova Stella and its Observers

abstract: Views on mechanics and cosmology by the observers of the supernova of 1572


title:
The OH 1612 MHz maser pump rates of stellar, interstellar and post-AGB
  OH masers

abstract:
  (Pseudo) radiative pumprate of OH 1612 MHz masers is defined for a sample of
44 OH/IR sources (infrared sources with OH 1612 MHz maser), irrespective of the
real maser pumping mechanisms. The correlation between the (pseudo) maser
pumprates and the evolutionary status of the maser sources reveals that the
radiative pumprates of stellar OH masers are nearly fixed, which agrees with
the theoretical prediction for radiatively pumped OH maser. The (pseudo)
radiative pumprates of interstellar OH masers are not only very small but also
varying broadly over two orders of magnitude, which is argued to be the
manifestation of varying number of quiet absorbing OH cloudlets and/or various
OH maser pumping mechanisms and/or competitive gain between mainline and 1612
MHz OH masers and/or anisotropy of the maser emission. The radiative pumprates
of post-AGB OH masers very possibly decrease with increasing IRAS C32 color
indices and distribute in an interim region between the stellar and
interstellar OH masers in the pumprate-color diagram.


title: Radio-quiet objects in the 2QZ survey

abstract:
  Co-addition of blank-field FIRST data at the location of over 8000 QSOs in
the 2QZ survey has yielded statistical detections of radio quiet QSOs with
median flux levels of 20-40microJy. We show that the total radio flux of
radio-quiet QSOs in the 2QZ is consistent with a smooth extrapolation of the
2QZ radio-loud QSO number-flux distribution based on the slope of the relation
flattening near the FIRST flux limit. However, we are unable to distinguish a
smooth extrapolation of the luminosity function to faint levels from a bimodal
luminosity function with a break close to or below the FIRST radio detection
limit. We also demonstrate that the redshift dependence of the median
radio-to-optical spectral index for these radio quiet QSOs is consistent with
that obtained for individual radio-loud 2QZ QSOs detected by FIRST.


title:
H-alpha imaging of the Local Volume galaxies I. The NGC 6946 galaxy
  group

abstract:
  We present new H-alpha imaging of all known dwarf irregular companions to NGC
6946: UGC 11583, KK 251, KK 252, KKR 55, KKR 56, Cepheus 1, KKR 59, and KKR 60.
The galaxies span a range of blue absolute magnitudes of [-13.6, -17.6],
relative gas content of [0.1, 2.5] M_sun/L_sun, current star formation activity
of [0.2, 5.2]10^-2 M_sun yr^-1, and timescale to exhaust the current gas supply
of [6, 86] Gyr.


title: Evolution of the ISM and Galactic Activity

abstract:
  We study the effects of time-dependent mass injection and heating on the
evolution of the interstellar medium (ISM) in elliptical galaxies. As the large
and luminous ellipticals have supermassive black holes at their cores, which
were probably much less massive in the young universe, feeding these black
holes is essential. We examine steady state solutions and describe the impact
of the initial starburst on the evolution of the ISM and consequences for
galactic activity, based on results from Starburst99.


title:
High Orbital Eccentricities of Extrasolar Planets Induced by the Kozai
  Mechanism

abstract:
  One of the most remarkable properties of extrasolar planets is their high
orbital eccentricities. Observations have shown that at least 20% of these
planets, including some with particularly high eccentricities, are orbiting a
component of a wide binary star system. The presence of a distant binary
companion can cause significant secular perturbations to the orbit of a planet.
In particular, at high relative inclinations, a planet can undergo a
large-amplitude eccentricity oscillation. This so-called "Kozai mechanism" is
effective at a very long range, and its amplitude is purely dependent on the
relative orbital inclination. In this paper, we address the following simple
question: assuming that every host star with a detected giant planet also has a
(possibly unseen, e.g., substellar) distant companion, with reasonable
distributions of orbital parameters and masses, how well could secular
perturbations reproduce the observed eccentricity distribution of planets? Our
calculations show that the Kozai mechanism consistently produces an excess of
planets with very high (e >0.6) and very low (e < 0.1) eccentricities. The
paucity of near-circular orbits in the observed sample cannot be explained
solely by the Kozai mechanism, because, even with high enough inclinations, the
Kozai mechanism often fails to produce significant eccentricity perturbations
when there are other competing sources of orbital perturbations on secular
timescales, such as general relativity. On the other hand, the Kozai mechanism
can produce many highly eccentric orbits. Indeed the overproduction of high
eccentricities observed in our models could be combined with plausible
circularizing mechanisms (e.g., friction from residual gas) to create more
intermediate eccentricities (e=0.1-0.6).


title:
Dichroic Masers due to Radiation Anisotropy and the Influence of the
  Hanle Effect on the Circumstellar SiO Polarization

abstract:
  The theory of the generation and transfer of polarized radiation, mainly
developed for interpreting solar spectropolarimetric observations, allows to
reconsider, in a more rigorous and elegant way, a physical mechanism that has
been suggested some years ago to interpret the high degree of polarization
often observed in astronomical masers. This mechanism, for which the name of
'dichroic maser' is proposed, can operate when a low density molecular cloud is
illuminated by an anisotropic source of radiation (like for instance a nearby
star). Here we investigate completely unsaturated masers and show that
selective stimulated emission processes are capable of producing highly
polarized maser radiation in a non-magnetic environment. The polarization of
the maser radiation is linear and is directed tangentially to a ring
equidistant to the central star. We show that the Hanle effect due to the
presence of a magnetic field can produce a rotation (from the tangential
direction) of the polarization by more that 45 degrees for some selected
combinations of the strength, inclination and azimuth of the magnetic field
vector. However, these very same conditions produce a drastic inhibition of the
maser effect. The rotations of about 90 degrees observed in SiO masers in the
evolved stars TX Cam by Kemball & Diamond (1997) and IRC+10011 by Desmurs et al
(2000) may then be explainedby a local modification of the anisotropy of the
radiation field, being transformed from mainly radial to mainly tangential.


title:
Uncertainties of Cosmic Ray Spectra and Detectability of Antiproton
  mSUGRA Contributions With PAMELA

abstract:
  We studied the variation of $e^+$ and $\bar p$ top of the atmosphere spectra
due to the parameters uncertainties of the Milky Way geometry, propagation
models and cross sections. We used the B/C data and Galprop code for the
propagation analysis. We also derived the uncertainty bands for subFe/Fe ratio,
H and He. Finally, we considered a neutralino induced component in the
antiproton flux in the mSUGRA framework. PAMELA expectations for positrons and
antiprotons are calculated. We studied in details the possibility of
disentanglement of an eventual signal component in the antiproton spectra in a
clumpy halo scenario: minimal values of clumpiness factors necessary to
disentangle the signal from the background without violating the quality of the
antiproton data fit are found. There are also given examples of total spectra
in comparison with existing experimental data and an example of PAMELA
prediction for the total spectra. The main result of this work is that for the
diffusion and convection background model PAMELA will be able to disentangle an
eventual supersymmetric signal even for small clumpiness factors.


title: The Near-Infrared Extinction Law in Regions of High Av

abstract:
  We present a spectroscopic study of the shape of the dust-extinction law
between 1.0 and 2.2um towards a set of nine ultracompact HII regions with Av >
15 mag. We find some evidence that the reddening curve may tend to flatten at
higher extinctions, but just over half of the sample has extinction consistent
with or close to the average for the interstellar medium. There is no evidence
of extinction curves significantly steeper than the standard law, even where
water ice is present. Comparing the results to the predictions of a simple
extinction model, we suggest that a standard extinction law implies a robust
upper limit to the grain-size distribution at around 0.1 - 0.3um. Flatter
curves are most likely due to changes in this upper limit, although the effects
of flattening due to unresolved clumpy extinction cannot be ruled out.


title: Six detached white-dwarf close binaries

abstract:
  We determine the orbits of four double degenerate systems (DDs), composed of
two white dwarfs, and of two white dwarf -- M dwarf binaries. The four DDs,
WD1022+050, WD1428+373, WD1824+040, and WD2032+188, show orbital periods of
1.157155(5) d, 1.15674(2) d, 6.26602(6) d and 5.0846(3) d respectively. These
periods combined with estimates for the masses of the brighter component, based
on their effective temperatures, allow us to constrain the masses of the unseen
companions. We estimate that the upper limit for the contribution of the unseen
companions to the total luminosity in the four DDs ranges between 10 and 20 per
cent. In the case of the two white dwarf - M dwarf binaries, WD1042-690 and
WD2009+622, we calculate the orbital parameters by fitting simultaneously the
absorption line from the white dwarf and the emission core from the M-dwarf.
Their orbital periods are 0.337083(1) d and 0.741226(2) d respectively. We find
signatures of irradiation on the inner face of WD2009+622's companion. We
calculate the masses of both components from the gravitational redshift and the
mass-radius relationship for white dwarfs and find masses of 0.75 -- 0.78 Msun
and 0.61 -- 0.64 Msun for WD1042-690 and WD2009+622 respectively. This
indicates that the stars probably reached the asymptotic giant branch in their
evolution before entering a common envelope phase. These two white dwarf - M
dwarf binaries will become cataclysmic variables, although not within a Hubble
time, with orbital periods below the period gap.


title:
The luminosity function of Ly-alpha emitters at 2.3 < z < 4.6 from
  integral-field spectroscopy

abstract:
  We have used VIsible MultiObject Spectrograph Integral-Field Unit (VIMOS-IFU)
observations centred on a radio galaxy at z=2.9 to search for Ly-alpha emitters
within a comoving volume of ~ 10^4 Mpc^3. We find 14 Ly-alpha emitters with
flux > 1.4 x 10^-20 Wm^-2, yielding a comoving space density of 0.0018 +/-
0.0006 Mpc^-3. We fit a Schechter luminosity function which agrees well with
previous studies both at similar redshift (z ~ 3.4) and higher redshift (z ~
5.7). We therefore find no evidence for evolution in the properties of Ly-alpha
emitters between 3 < z < 6, although our sample is small. By summing the
star-formation rates of the individual Ly-alpha emitters we find a total cosmic
star-formation rate density of rho_SFR = 6.7 +/- 0.5 x 10^-3 M_solar yr^-1
Mpc^-3. Integrating over the luminosity function for the combined Ly-alpha
surveys at z ~ 3.4 and accounting for the difference in obscuration between the
Ly-alpha line and the UV-continuum yields an estimate of rho_SFR ~ 2.2 x 10^-2
M_solar yr^-1 Mpc^-3, in line with previous multi-colour and narrow-band
surveys of high-redshift star-forming galaxies.
  The detection of high-redshift emission-line galaxies in our volumetric
search shows that the unique capabilities of wide-field integral-field
spectroscopy are well suited in searching for high-redshift galaxies in a
relatively unbiased manner.


title: Infall and SiO emission in V838 Mon

abstract:
  We present moderate and high resolution infrared spectroscopy of the peculiar
eruptive variable V838 Mon, which underwent a series of remarkable outbursts in
early 2002. During the period covered by our observations, 2002 December-2003
December, the near-infrared spectrum continued to show many of the
characteristics of a very cool supergiant. However, throughout this period the
spectrum also revealed strong and variable SiO first overtone emission, and
Paschen Beta emission. The 2003 December spectrum contained a series of Ti I
lines with inverse P Cygni profiles. This is clear evidence that some material
is falling inward towards the star.


title:
Aperture Photometry of Saturated Star Images from Digitised Photographic
  Plates

abstract:
  Saturated stellar images on digitised photographic plates are many times
greater in area than the `seeing disk' seen in unsaturated CCD images. Indeed
the flux profile of a bright star can be traced out for several degrees from
the star's centre. The radius of the saturated stellar image can often be
directly related to the magnitude of the star, a fact well known and exploited
in iris photometry. In this work we compare the radial flux profile of stars in
the approximate range B ~9 to ~13 mag, obtained from scans of plates from the
Bamberg Sky Patrol archive, with a profile of the form measured by King. We
show that simple aperture photometry of saturated stellar images, obtained from
photo-positives of scanned photographic plates, yield data that are in
agreement with simulations using a (saturated) synthetic stellar radius
profile. Raw plate magnitudes from this aperture photometry can be easily and
satisfactorily transformed to standard magnitudes, as demonstrated in a recent
study carried out by the current authors.


title:
Complementary constraints on non-standard cosmological models from CMB
  and BBN

abstract:
  We study metric-affine gravity (MAG) inspired cosmological models. Those
models were statistically estimated using the SNIa data. We also use the cosmic
microwave background observations and the big-bang nucleosynthesis analysis to
constrain the density parameter $\Omega_{\psi,0}$ which is related to the
non-Riemannian structure of the underlying spacetime. We argue that while the
models are statistically admissible from the SNIa analysis, complementary
stricter limits obtained from the CMB and BBN indicate that the models with
density parameters with a $a^{-6}$ scaling behaviour are virtually ruled out.
If we assume the validity of the particular MAG based cosmological model
throughout all stages of the Universe, the parameter estimates from the CMB and
BBN put a stronger limit, in comparison to the SNIa data, on the presence of
non-Riemannian structures at low redshifts.


title: An Analysis of Optical Pick-up in SCUBA Data

abstract:
  The Sub-millimetre Common User Bolometer Array (SCUBA) at the JCMT employs a
chopping and nodding observation technique to remove variations in the
atmospheric signal and improve the long term stability of the instrument. In
order to understand systematic effects in SCUBA data, we have analysed
single-nod time streams from across SCUBA's lifetime, and present an analysis
of an ubiquitous optical pick-up signal connected to the pointing of the
secondary mirror. This pick-up is usually removed to a high level by
subtracting data from two nod positions and is therefore not obviously present
in most reduced SCUBA data. However, if the nod cancellation is not perfect
this pick-up can swamp astronomical signals. We discuss various methods which
have been suggested to account for this type of imperfect cancellation, and
also examine the impact of this pick-up on observations with future bolometric
cameras at the JCMT.


title: Dynamics of dense star-gas systems: BHs and their precursors

abstract:
  This thesis embraces several aspects of theoretical stellar dynamics in
clusters, both analytically and numerically. We try to elucidate the phenomena
currently observed in all types of galaxies, including AGNs and quasars, some
of the most powerful objects in the universe. The interactions between the
stellar system and the central black hole give rise to a lot of interesting
phenomena. The scheme we employ enables a study of clean-cut aspects without
any noise that particle methods suffer from. We study the most important
physical processes that are readily available in the evolution of a spherical
cluster, like self-gravity, two-body relaxation etc, the interaction with a
central black hole and the role of a mass spectrum. Not only embark we upon
this subject, but we set about an analysis on super-massive stars. How these
stars could power the quasar activity by star accretion and energy flows is one
of the questions that arises. We undertake other questions, such as the
uncertain evolution of such an object and its interaction with the surrounding
stellar system. This is of crucial importance in astrophysics, for these
objects could be regarded as super-massive black holes progenitors.


title:
Study of molecular layers in the atmosphere of the supergiant star mu
  Cep by interferometry in the K band

abstract:
  Infrared interferometry of supergiant and Mira stars has recently been
reinterpreted as revealing the presence of deep molecular layers. Empirical
models for a photosphere surrounded by a simple molecular layer or envelope
have led to a consistent interpretation of previously inconsistent data. The
stellar photospheres are found to be smaller than previously understood, and
the molecular layer is much higher and denser than predicted by hydrostatic
equilibrium. However, the analysis was based on spatial observations with
medium-band optical filters, which mixed the visibilities of different spatial
structures. This paper reports spatial interferometry with narrow spectral
bands, isolating near-continuum and strong molecular features, obtained for the
supergiant mu Cep. The measurements confirm strong variation of apparent
diameter across the K-band. A layer model shows that a stellar photosphere of
angular diameter 14.11+/-0.60 mas is surrounded by a molecular layer of
diameter 18.56+/-0.26 mas, with an optical thickness varying from nearly zero
at 2.15 microns to >1 at 2.39 microns. Although mu Cep and alpha Ori have a
similar spectral type, interferometry shows that they differ in their radiative
properties. Comparison with previous broad-band measurements shows the
importance of narrow spectral bands. The molecular layer or envelope appears to
be a common feature of cool supergiants.


title: GEMS: The Size Evolution of Disk Galaxies

abstract:
  We combine HST imaging from the GEMS survey with photometric redshifts from
COMBO-17 to explore the evolution of disk-dominated galaxies since z<1.1. The
sample is comprised of all GEMS galaxies with Sersic indices n<2.5, derived
from fits to the galaxy images. We account fully for selection effects through
careful analysis of image simulations; we are limited by the depth of the
redshift and HST data to the study of galaxies with absolute magnitudes
M(V)<-20, or equivalently stellar masses log(M)>10. We find strong evolution in
the magnitude-size scaling relation for galaxies with M(V)<-20, corresponding
to a brightening of 1 mag per sqarcsec in rest-frame V-band by z=1. Yet, disks
at a given absolute magnitude are bluer and have lower stellar mass-to-light
ratios at z=1 than at the present day. As a result, our findings indicate weak
or no evolution in the relation between stellar mass and effective disk size
for galaxies with log(M)>10 over the same time interval. This is strongly
inconsistent with the most naive theoretical expectation, in which disk size
scales in proportion to the halo virial radius, which would predict that disks
are a factor of two denser at fixed mass at z=1. The lack of evolution in the
stellar mass-size relation is consistent with an ``inside-out'' growth of
galaxy disks on average (galaxies increasing in size as they grow more
massive), although we cannot rule out more complex evolutionary scenarios.


title:
A XMM-Newton View of the Soft Gamma-ray Repeater SGR 1806--20: Long Term
  Variability in the pre-Super Giant Flare Epoch

abstract:
  The low energy (<10 keV) X-ray emission of the Soft Gamma-ray Repeater
SGR1806-20 has been studied by means of four XMM-Newton observations carried
out in the last two years, the latter performed in response to a strong
sequence of hard X-ray bursts observed on 2004 October 5. The source was caught
in different states of activity: over the 2003-2004 period the 2-10 keV flux
doubled with respect to the historical level observed previously. The long term
raise in luminosity was accompanied by a gradual hardening of the spectrum,
with the power law photon index decreasing from 2.2 to 1.5, and by a growth of
the bursting activity. The pulse period measurements obtained in the four
observations are consistent with an average spin-down rate of 5.5x10e-10 s/s,
higher than the values observed in the previous years. The long-term behavior
of SGR1806-20 exhibits the correlation between spectral hardness and spin-down
rate previously found only by comparing the properties of different sources
(both SGRs and Anomalous X-ray Pulsars). The best quality spectrum (obtained on
6 September 2004) cannot be fitted by a single power law, but it requires an
additional blackbody component (kT=0.79 keV, R_BB = 1.9 (d/15 kpc)^2 km),
similar to the spectra observed in other SGRs and in Anomalous X-ray Pulsars.
No spectral lines were found in the persistent emission, with equivalent width
upper limits in the range 30-110 eV. Marginal evidence for an absorption
feature at 4.2 keV is present in the cumulative spectrum of 69 bursts detected
in September-October 2004.


title:
Upper limit on the photon fraction in highest-energy cosmic rays from
  AGASA data

abstract:
  A new method to derive an upper limit on photon primaries from small data
sets of air showers is developed which accounts for shower properties varying
with the primary energy and arrival direction. Applying this method to the
highest-energy showers recorded by the AGASA experiment, an upper limit on the
photon fraction of 51% (67%) at a confidence level of 90% (95%) for primary
energies above 1.25 * 10^20 eV is set. This new limit on the photon fraction
above the GZK cutoff energy constrains the Z-burst model of the origin of
highest-energy cosmic rays.


title: Reionization History from Coupled CMB/21cm Line Data

abstract:
  We study CMB secondary anisotropies produced by inhomogeneous reionization by
means of cosmological simulations coupled with the radiative transfer code
CRASH. The reionization history is consistent with the WMAP Thomson optical
depth determination. We find that the signal arising from this process
dominates over the primary CMB component for l > 4000 and reaches a maximum
amplitude of l(l+1)C_l/2\pi ~ 1.6 x 10^{-13} on arcmin scale, i.e. l as large
as several thousands. We then cross-correlate secondary CMB anisotropy maps
with neutral hydrogen 21cm line emission fluctuations obtained from the same
simulations. The two signals are highly anti-correlated on angular scales
corresponding to the typical size of HII regions (including overlapping) at the
21cm map redshift. We show how the CMB/21cm cross-correlation can be used to:
(a) study the nature of the reionization sources, (b) reconstruct the cosmic
reionization history, (c) infer the mean cosmic ionization level at any
redshift. We discuss the feasibility of the proposed experiment with
forthcoming facilities.


title: Intracluster stars in the Virgo cluster core

abstract:
  We have investigated the properties of the diffuse light in the Virgo cluster
core region, based on the detection of intracluster planetary nebulae (PNe) in
four fields. We eliminate the bias from misclassified faint continuum objects,
using improved Monte Carlo simulations, and the contaminations by high redshift
Ly$\alpha$ galaxies, using the Ly$\alpha$ luminosity function in blank fields.
Recent spectroscopic observations confirm that our photometric PN samples are
well-understood. We find that the diffuse stellar population in the Virgo core
region is inhomogeneous on scales of 30'-90': there exist significant
field-to-field variations in the number density of PNe and the inferred amount
of intracluster light, with some empty fields, some fields dominated by
extended Virgo galaxy halos, and some fields dominated by the true intracluster
component. There is no clear trend with distance from M87. The mean surface
luminosity density, its rms variation, and the mean surface brightness of
diffuse light in our 4 fields are $\Sigma_B = 2.7 x 10^{6}$ L$_{B\odot}$
arcmin$^{-2}$, ${rms} = 2.1 \times 10^{6}$ L$_{B\odot}$ arcmin$^{-2}$, and
$\bar{\mu}_{B}=29.0$ mag arcsec$^{-2}$ respectively. Our results indicate that
the Virgo cluster is a dynamically young environment, and that the intracluster
component is associated at least partially with local physical processes like
galaxy interactions or harassment. We also argue, based on kinematic evidence,
that the so-called 'over-luminous' PNe in the halo of M84 are dynamically
associated with this galaxy, and must thus be brighter than and part of a
different stellar population from the normal PN population in elliptical
galaxies.


title:
The line-of-sight velocity distributions of intracluster planetary
  nebulae in the Virgo cluster core

abstract:
  Radial velocities of 40 intracluster planetary nebulae (ICPNe) in the Virgo
cluster were obtained with the new multi-fiber FLAMES spectrograph on UT2 at
VLT. For the first time, the lambda 4959 AA line of the [OIII] doublet is seen
in a large fraction (50%) of ICPNe spectra, and a large fraction of the
photometric candidates with m(5007) <\= 27.2 is spectroscopically confirmed.
ICPNe with the velocity dispersion of the Virgo cluster are found in our CORE
field 1 deg from M87. These may have originated from tidal mass loss of smaller
galaxies in the M87 subcluster halo. In a field 0.25 deg from M87, we see an
extended stellar halo of M87 in approximate dynamical equilibrium, but with few
ICPNe. Finally, in a field near M84/M86, the ICPNe velocities are highly
correlated with the galaxy velocities, showing that any well-mixed intracluster
population is yet to form. Overall, the measured velocity distributions confirm
the non-uniform dynamical structure and on-going assembly of the Virgo
cluster.(Based on data collected with the FLAMES spectrograph at the UT2 of the
VLT at Cerro Paranal, Chile, operated by ESO, during observing run
71.B-0147(A))


title:
The role of General Relativity in the evolution of Low Mass X-ray
  Binaries

abstract:
  We study the evolution of Low Mass X-ray Binaries (LMXBs) and of millisecond
binary radio pulsars (MSPs), with numerical simulations that keep into account
the evolution of the companion, of the binary system and of the neutron star.
According to general relativity, when energy is released, the system loses
gravitational mass. Moreover, the neutron star can collapse to a black hole if
its mass exceeds a critical limit, that depends on the equation of state. These
facts have some interesting consequences: 1) In a MSP the mass-energy is lost
with a specific angular momentum that is smaller than the one of the system,
resulting in a positive contribution to the orbital period derivative. If this
contribution is dominant and can be measured, we can extract information about
the moment of inertia of the neutron star, since the energy loss rate depends
on it. Such a measurement can therefore help to put constraints on the equation
of state of ultradense matter. 2) In LMXBs below the bifurcation period (\sim
18 h), the neutron star survives the period gap only if its mass is smaller
than the maximum non-rotating mass when the companion becomes fully convective
and accretion pauses. Therefore short period (P < 2h) millisecond X-ray pulsar
like SAX J1808.4-3658 can be formed only if either a large part of the
accreting matter has been ejected from the system, or the equation of state of
ultradense matter is very stiff. 3) In Low Mass X-ray binaries above the
bifurcation period, the mass-energy loss lowers the mass transfer rate. As side
effect, the inner core of the companion star becomes 1% bigger than in a system
with a non-collapsed primary. Due to this difference, the final orbital period
of the system becomes 20% larger than what is obtained if the mass-energy loss
effect is not taken into account.


title:
Broad-band spectra of Cyg X-1 and correlations between spectral
  characteristics

abstract:
  We present the results of spectral analysis of 42 simultaneous broad-band
Ginga--OSSE and RXTE--OSSE observations of Cyg X-1 carried out in 1991 and
1996--1999. The hardest spectra in our sample in the energy range from 3 to
\~1000 keV can be well described by thermal Comptonization model with
reflection from the cold disc, while the rest of the spectra are more complex
and require an additional component below 10 keV. We consider a number of
physically realistic models to describe the shape of the E<10 keV excess. The
additional soft component can result from thermal Comptonization by electrons
with a low Compton parameter, or can be a part of a nonthermal, power-law like
emission extending above 1 MeV. We study correlations between parameters
obtained from the spectral fits with different models. We confirm a general
correlation between the photon index $\Gamma$ and the amplitude of reflection
R. We find that simple phenomenological models (like power-law plus Compton
reflection) applied to the narrow band (3--20 keV) data overestimated the
values of R and $\Gamma$, although the simple models did rank correctly the
spectra according to R and $\Gamma$. The dynamic corona model provides a
satisfactory description of the observed correlation, while the hot inner disc
models have problems in reproducing it quantitatively. We do not find
significant correlation between the electron temperature and other spectral
parameters, while the optical depth of the hot medium seems to decrease when
the spectrum becomes softer. It is also shown that spectral parameters are well
correlated with the timing characteristics of the source.


title: Gamma-ray burst spectra from continuously accelerated electrons

abstract:
  We discuss here constraints on the particle acceleration models from the
observed gamma-ray bursts spectra. The standard synchrotron shock model assumes
that some fraction of available energy is given instantaneously to the
electrons which are injected at high Lorentz factor. The emitted spectrum in
that case corresponds to the spectrum of cooling electrons, F_\nu ~ \nu^{-1/2},
is much too soft to account for the majority of the observed spectral slopes.
We show that continuous heating of electrons over the life-time of a source is
needed to produce hard observed spectra. In this model, a prominent peak
develops in the electron distribution at energy which is a strong function of
Thomson optical depth \tau_T of heated electrons (pairs). At \tau_T>1, a
typical electron Lorentz factor \gamma ~ 1-2 and quasi-thermal Comptonization
operates. It produces spectrum peaking at a too high energy. Optical depths
below 10^{-4} would be difficult to imagine in any physical scenario. At \tau_T
=10^{-4}-10^{-2}, \gamma ~ 30-100 and synchrotron self-Compton radiation is the
main emission mechanism. The synchrotron peak should be observed at 10--100 eV,
while the self-absorbed low-energy tail with F_\nu ~ \nu^2 can produce the
prompt optical emission (like in the case of GRB 990123). The first Compton
scattering radiation by nearly monoenergetic electrons peaks in the BATSE
energy band and can be as hard as F_\nu ~ \nu^1 reproducing the hardness of
most of the observed GRB spectra. The second Compton peak should be observed in
the high-energy gamma-ray band, possibly being responsible for the 10-100 MeV
emission detected in GRB 941017. A significant electron-positron pair
production reduces the available energy per particle, moving spectral peaks to
lower energies as the burst progresses.


title: Lensed CMB power spectra from all-sky correlation functions

abstract:
  Weak lensing of the CMB changes the unlensed temperature anisotropy and
polarization power spectra. Accounting for the lensing effect will be crucial
to obtain accurate parameter constraints from sensitive CMB observations.
Methods for computing the lensed power spectra using a low-order perturbative
expansion are not good enough for percent-level accuracy. Non-perturbative
flat-sky methods are more accurate, but curvature effects change the spectra at
the 0.3-1% level. We describe a new, accurate and fast, full-sky
correlation-function method for computing the lensing effect on CMB power
spectra to better than 0.1% at l<2500 (within the approximation that the
lensing potential is linear and Gaussian). We also discuss the effect of
non-linear evolution of the gravitational potential on the lensed power
spectra. Our fast numerical code is publicly available.


title:
Synthesis of H-alpha absorption in old stellar systems: Formation of the
  cluster red sequence by "Downsizing"

abstract:
  We compute population synthesis models for the variation of H-alpha
absorption indices (HaA and HaF), as a function of age and metallicity in old
stellar systems. The models are based on the STELIB spectral library, and
defined at resolution of 3 Angstrom FWHM. The indices are found to be highly
sensitive to age variation, with only moderate response to metallicity. For
galaxies uncontaminated by nebular emission, our HaA index is more powerful in
breaking the age/metallicity degeneracy than H-beta or H-gamma_F. Using a
sample of red cluster galaxies carefully selected to exclude objects with
emission, we find a steep decline of HaA with velocity dispersion (slope -0.75
+/- 0.07 Angstrom/dex). The slope can be translated to constraints on age and
metallicity scaling relations, incorporating measurement and model errors. If
the HaA-sigma slope is due only to age, we obtain Age proportional to
sigma^{0.95 +/- 0.12}. Because HaA depends quite weakly on [Fe/H], a
metallicity interpretation would require Fe/H proportional to sigma^1.2 or
steeper. The HaA-sigma slope is consistent with the combined age and
metallicity scaling relations reported by Nelan et al. from classical Lick
indices. The relations obtained by Thomas et al. significantly under-predict
the observed slope. The discrepancy could arise from differences in the sample
compositions.We discuss in detail the effects of emission contamination on the
results, and conclude that these are unlikely to yield the observed behaviour
in the Ha-sigma relations. The steep age--mass relation supports a "downsizing"
formation scenario: fainter red-sequence galaxies became quiescent at lower
redshifts, z < 0.5. This picture accords with recent observations of truncated
red sequences in clusters at z ~ 0.7.


title:
A safety net for fast migrators: Interactions between gap-opening and
  sub-gap-opening bodies in a protoplanetary disk

abstract:
  Young planets interact with their parent gas disks through tidal torques. An
imbalance between inner and outer torques causes bodies of mass $\ga 0.1$ Earth
masses to lose angular momentum and migrate inward rapidly relative to the
disk; this is known as ``Type I'' migration. However, protoplanets that grow to
gas giant mass, O($10^2) M_\oplus$, open a gap in the disk and are subsequently
constrained to migrate more slowly, locked into the disk's viscous evolution in
what is called "Type II" migration. In a young planetary system, both Type I
and Type II bodies likely coexist; if so, differential migration ought to
result in close encounters when the former originate on orbits exterior to the
latter. We investigate the resulting dynamics, using two different numerical
approaches: an N-body code with dissipative forces added to simulate the effect
of the gas disk, and a hybrid code which combines an N-body component with a
1-dimensional viscous disk model, treating planet-disk interactions in a more
self-consistent manner. In both cases, we find that sub-gap-opening bodies have
a high likelihood of being resonantly captured when they encounter a
gap-opening body. A giant planet thus tends to act as a barrier in a
protoplanetary disk, collecting smaller protoplanets outside of its orbit. Such
behavior has two important implications for giant planet formation: First, for
captured protoplanets it mitigates the problem of the migration timescale
becoming shorter than the growth timescale. Secondly, it suggests one path to
forming systems with multiple giant planets: Once the first has formed, it
traps/accretes the future solid core of the second in an exterior mean-motion
resonance, and so on. The most critical step in giant planet formation may thus
be the formation of the very first one.


title:
Discovery of a Radio Source following the 27 December 2004 Giant Flare
  from SGR 1806-20

abstract:
  Over a decade ago it was established that the remarkable high energy
transients, known as soft gamma-ray repeaters (SGRs), are a Galactic population
and originate from neutron stars with intense (<~ 10^15 G) magnetic fields
("magnetars"). On 27 December 2004 a giant flare (fluence >~ 0.3 erg/cm^2) was
detected from SGR 1806-20. Here we report the discovery of a fading radio
counterpart. We began a monitoring program from 0.2GHz to 250GHz and obtained a
high resolution 21-cm radio spectrum which traces the intervening interstellar
neutral Hydrogen clouds. Analysis of the spectrum yields the first direct
distance measurement of SGR 1806-20. The source is located at a distance
greater than 6.4 kpc and we argue that it is nearer than 9.8 kpc. If true, our
distance estimate lowers the total energy of the explosion and relaxes the
demands on theoretical models. The energetics and the rapid decay of the radio
source are not compatible with the afterglow model that is usually invoked for
gamma-ray bursts. Instead we suggest that the rapidly decaying radio emission
arises from the debris ejected during the explosion.


title:
PROMPT: Panchromatic Robotic Optical Monitoring and Polarimetry
  Telescopes

abstract:
  Funded by $1.2M in grants and donations, we are now building PROMPT at CTIO.
When completed in late 2005, PROMPT will consist of six 0.41-meter diameter
Ritchey-Chretien telescopes on rapidly slewing mounts that respond to GRB
alerts within seconds, when the afterglow is potentially extremely bright. Each
mirror and camera coating is being optimized for a different wavelength range
and function, including a NIR imager, two red-optimized imagers, a
blue-optimized imager, an UV-optimized imager, and an optical polarimeter.
PROMPT will be able to identify high-redshift events by dropout and distinguish
these events from the similar signatures of extinction. In this way, PROMPT
will act as a distance-finder scope for spectroscopic follow up on the larger
4.1-meter diameter SOAR telescope, which is also located at CTIO. When not
chasing GRBs, PROMPT serves broader educational objectives across the state of
North Carolina. Enclosure construction and the first two telescopes are now
complete and functioning: PROMPT observed Swift's first GRB in December 2004.
We upgrade from two to four telescope in February 2005 and from four to six
telescopes in mid-2005.


title:
The effect of long range gravitational perturbations on the first
  acoustic peak of the cosmic microwave background

abstract:
  In the standard cosmological model, the temperature anisotropy of the cosmic
microwave background is interpreted as variation in the gravitational potential
at the point of emission, due to the emitter being embedded in a region ${\cal
C}$ of over- or under-density spanning the length (or size) scale $\lambda$ on
which the anisotropy is measured. If the Universe is inhomogeneous, however,
similar density contrasts of size $\lambda$ are also located everywhere
surrounding ${\cal C}$. Since they are superposition states of many independent
Fourier modes with no preferred direction, such primordial clumps and voids
should not be configured according to some prescribed spatial pattern. Rather,
they can randomly trade spaces with each other while preserving the
Harrison-Zeldovich character of the matter spectrum. The outcome is an {\it
extra} perturbation of the potential when averaged over length $\lambda$ at the
emitter, and consequently an additional anisotropy on the same scale, which has
apparently been overlooked. Unlike the conventional application of the
Sachs-Wolfe effect to the WMAP observations, this extra effect is {\it not}
scale independent over the $P(k) \sim k$ part of the matter spectrum, but
increases towards smaller lengths, as $\sqrt{k}$. The consequence is a
substantial revision of the currently advertised values of the key cosmological
parameters, {\it unless} one postulates a more rapid decrease in the
gravitational force with distance than that given by the inverse-square law.


title: Radiation spectra and polarization in magnetar bursts

abstract:
  We present Monte Carlo simulations of radiative transfer in magnetar
atmospheres. We include the effects of vacuum polarization, electron and proton
scattering, and free-free absorption. Simulations are performed for the
atmosphere model with the magnetic field perpendicular and also tilted with
respect to the neutron star surface, and we show that the average spectrum does
not strongly depend on the orientation of the magnetic field. We investigate
the region of the parameter space where the vacuum absorption-like feature
appears in the spectrum and we analyze the shape of the proton cyclotron line.
Our results indicate that the existence of the vacuum polarization feature
should be a general attribute of soft gamma-ray repeaters burst spectra,
provided that the energy release takes place at the sufficiently dense region,
and the atmosphere scaleheight is large enough. We discuss the existence of
such a feature in recent observational data on these sources.


title:
Spectroscopic Identification of a Proto-Cluster at z=2.300:
  Environmental Dependence of Galaxy Properties at High Redshift

abstract:
  We have discovered a highly significant over-density of galaxies at
z=2.300+/-0.015 in the course of a redshift survey designed to select
star-forming galaxies in the redshift range z=2.3+/-0.4 in the field of the
bright z=2.72 QSO HS1700+643. The structure has a redshift-space galaxy
over-density of delta_g,z ~= 7 and an estimated matter over-density in real
space of delta_m ~= 1.8, indicating that it will virialize by z~0 with a mass
scale of ~= 1.4x10^15 M_sun, that of a rich galaxy cluster. Detailed modeling
of the spectral energy distribution -- from the rest-far-UV to the rest-near-IR
-- of the 72 spectroscopically confirmed galaxies in this field for which we
have obtained K_s and Spitzer/IRAC photometry, allows for a first direct
comparison of galaxy properties as a function of large-scale environment at
high redshift. We find that galaxies in the proto-cluster environment have mean
stellar masses and inferred ages that are ~2 times larger (at z=2.30) than
identically UV-selected galaxies outside of the structure, and show that this
is consistent with simple theoretical expectations for the acceleration of
structure formation in a region that is over-dense on large scales by the
observed amount. The proto-cluster environment contains a significant number of
galaxies that already appear old, with large stellar masses (>10^11 M_sun), by
z=2.3.


title: Variability of Fe II Emission Features in the Seyfert 1 Galaxy NGC 5548

abstract:
  We study the low-contrast Fe II emission blends in the ultraviolet
(1250--2200A) and optical (4000--6000A) spectra of the Seyfert 1 galaxy NGC
5548 and show that these features vary in flux and that these variations are
correlated with those of the optical continuum. The amplitude of variability of
the optical Fe II emission is 50% - 75% that of Hbeta and the ultraviolet Fe II
emission varies with an even larger amplitude than Hbeta. However, accurate
measurement of the flux in these blends proves to be very difficult even using
excellent Fe II templates to fit the spectra. We are able to constrain only
weakly the optical Fe II emission-line response timescale to a value less than
several weeks; this upper limit exceeds all the reliably measured emission-line
lags in this source so it is not particularly meaningful. Nevertheless, the
fact that the optical Fe II and continuum flux variations are correlated
indicates that line fluorescence in a photoionized plasma, rather than
collisional excitation, is responsible for the Fe II emission. The iron
emission templates are available upon request.


title: Fluorine Abundances in the Orion Nebula Cluster

abstract:
  This study uses cool dwarfs as sources with which to probe fluorine
abundances via HF. This molecule is detected for the first time in young K-M
dwarf members of an OB association. Fluorine, oxygen, and carbon abundances
were derived from the HF(1--0) R9 line along with samples of OH and CO
vibration-rotation lines present in high-resolution infrared spectra observed
with the Phoenix spectrograph on the Gemini South Telescope. The fluorine and
oxygen results obtained for these targets, still in the pre-main-sequence stage
of evolution, agree well with the general trend defined for the Milky Way disk;
the latter being deduced from observations of more evolved giant stars. In
addition, the carbon and oxygen abundances obtained for the studied stars
overlap results from previous studies of the more massive OB stars and FG dwarf
members of the Orion Nebula Cluster. We conclude from this agreement that the
fluorine abundances derived for the Orion K-M dwarfs (when there is no
conspicuous evidence of disks) can be considered a good representation of the
current fluorine abundance value for the Milky Way disk.


title: The SuperCDMS Experiment

abstract:
  WIMP-nucleon cross sections in the range 10^{-46} - 10^{-44} cm^2 may be
probed by a ton-scale experiment with low energy thresholds and excellent
discrimination of backgrounds. Because CDMS ZIP detectors are the most proven
means of achieving such good discrimination, we intend to scale CDMS up to a
ton detector mass. Development of this experiment, dubbed "SuperCDMS," is
discussed. Improved analysis and optimization of the charge collection and
athermal phonon sensors should improve surface-background rejection by over two
orders of magnitude. Siting the SuperCDMS experiment deep enough to remove the
fast neutron background, and reducing radioactive beta contamination near or on
the detectors, should sufficiently reduce these otherwise troubling
backgrounds. The primary challenge is making the experiment easy enough to
build. We discuss methods of improving the detector manufacturability, removing
the need for large-scale cryogenic detector testing, and allowing simplified
infrastructure by using more sophisticated readout.


title:
Finite Source Effects in Strong Lensing: Implications for the
  Substructure Mass Scale

abstract:
  Flux ratio `anomalies' in quadruply-imaged gravitational lenses can be
explained with galactic substructure of the sort predicted by CDM, but the
strength and uniqueness of that hypothesis needs to be further assessed. A good
way to do that is to use the physical scale associated with the size of the
source quasar, and its dependence on wavelength. We develop an analytic toy
model to study finite source effects in substructure lensing and identify
general principles. We find that image positions and magnifications are
basically independent of source size until the source is large enough to
intersect a substructure caustic. Even sources that are much larger than the
substructure Einstein radius can be perturbed at a detectable level. A
tremendous amount could be learned by comparing image positions and
magnifications at wavelengths that correspond to different source sizes.
  In a separate analysis, we carefully study four observed radio lenses to
determine which of the images are anomalous. In B0712+472, if the flux ratio
anomaly is real it is probably in image C. In B1422+231, the anomaly is in
image A. Interestingly, B2045+265 and B1555+375 both appear to have two
anomalous images. It remains to be seen whether CDM predicts enough
substructure to explain multiple anomalies in multiple lenses. When we join our
modeling results and substructure theory, we obtain lower bounds on the masses
of the substructures responsible for the observed anomalies. The mass bounds
are broadly consistent with expectations for CDM. Perhaps more importantly, we
outline various systematic effects in the mass bounds; poor knowledge of
whether the substructure lies within the main lens galaxy or elsewhere along
the line of sight appears to be the dominant systematic. [Abridged]


title:
Spatial Correlation of Massive Black Hole Mergers: Probing the Formation
  Mechanism and Reionization

abstract:
  We consider the spatial clustering of massive black hole (MBH) mergers, and
discuss possible ways to use gravitational wave observations in the LISA and
DECIGO/BBO range for obtaining cosmological and cosmogonical information.
Constraints on large scale structure (LSS) and merger histories may be possible
by detections of an alignment of the GW polarization direction with principal
axes of the LSS. Constraints on the merger physics and the reionization epoch
may be obtained by GW measurements of MBH correlation lengths, in the case when
the MBH angular momentum loss occurs through gas drag. Such measurements would
provide information about the LSS and the reionization epoch, additional to and
independent of any obtained from electromagnetic signals, as well as about the
astrophysics of MBH mergers.


title:
Characterizing a new class of variability in GRS 1915+105 with
  simultaneous INTEGRAL/RXTE observations

abstract:
  We report on the analysis of 100 ks INTEGRAL observations of the Galactic
microquasar GRS 1915+105. We focus on INTEGRAL Revolution number 48 when the
source was found to exhibit a new type of variability as preliminarily reported
in Hannikainen et al. (2003). The variability pattern, which we name $\xi$, is
characterized by a pulsing behaviour, consisting of a main pulse and a shorter,
softer, and smaller amplitude precursor pulse, on a timescale of 5 minutes in
the JEM-X 3-35 keV lightcurve. We also present simultaneous RXTE data. From a
study of the individual RXTE/PCA pulse profiles we find that the rising phase
is shorter and harder than the declining phase, which is opposite to what has
been observed in other otherwise similar variability classes in this source.
The position in the colour-colour diagram throughout the revolution corresponds
to State A (Belloni et al. 2000) but not to any previously known variability
class. We separated the INTEGRAL data into two subsets covering the maxima and
minima of the pulses and fitted the resulting two broadband spectra with a
hybrid thermal--non-thermal Comptonization model. The fits show the source to
be in a soft state characterized by a strong disc component below ~6 keV and
Comptonization by both thermal and non-thermal electrons at higher energies.


title: Cosmology from decaying dark energy, primordial at the Planck scale

abstract:
  The consideration of dark energy's quanta, required also by thermodynamics,
introduces its chemical potential into the cosmological equations. Isolating
its main contribution, we obtain solutions with dark energy decaying to matter
or radiation. When dominant, their energy densities tend asymptotically to a
constant ratio, explaining today's dark energy-dark matter coincidence, and in
agreement with supernova redshift data, and a universe-age constraint. This
also connects the Planck's and today's scales through time. This decay may be
manifested in the highest-energy cosmic rays, recently detected.


title:
Red variables in the OGLE-II data base -- III. Constraints on the
  three-dimensional structures of the LMC and SMC

abstract:
  We present an analysis of the 3-D structure of the Magellanic Clouds, using
period-luminosity (P-L) relations of pulsating red giants in the OGLE-II
sample. By interpreting deviations from the mean P-L relations as distance
modulus variations, we examine the three-dimensional distributions of the
sample. The results for the Large Magellanic Cloud, based solely on stars below
the tip of the Red Giant Branch, confirm previous results on the inclined and
possibly warped bar of the LMC. The depth variation across the OGLE-II field is
about 2.4 kpc, interpreted as the distance range of a thin but inclined
structure. The inclination angle is about 29 deg. A comparison with OGLE-II red
clump distances revealed intriguing differences that seem to be connected to
the red clump reddening correction. A spatially variable red clump population
in the LMC can explain the deviations, which may have a broader impact on our
understanding of the LMC formation history. For the Small Magellanic Cloud, we
find a complex structure showing patchy distribution scattered within 3.2 kpc
of the mean. However, the larger range of the overall depth on every
line-of-sight is likely to smooth out significantly the real variations.


title: Evidence for Planet-Planet Scattering in Upsilon Andromedae

abstract:
  Doppler spectroscopy has detected 136 planets around nearby stars. A major
puzzle is why their orbits are highly eccentric, while all planets in our Solar
System are on nearly circular orbits, as expected if they formed by accretion
processes in a protostellar disk. Several mechanisms have been proposed to
generate large eccentricities after planet formation, but so far there has been
little observational evidence to support any particular one. Here we report
that the current orbital configuration of the three giant planets around
Upsilon Andromedae (ups And) provides evidence for a close dynamical
interaction with another planet, now lost from the system. The planets started
on nearly circular orbits, but chaotic evolution caused the outer planet (ups
And d) to be perturbed suddenly into a higher-eccentricity orbit. The coupled
evolution of the system then causes slow periodic variations in the
eccentricity of the middle planet (ups And c). Indeed, we show that ups And c
periodically returns to a very nearly circular state every 9000 years. Our
analysis shows that strong planet-planet scattering, one of several mechanisms
previously discussed for increasing orbital eccentricities, must have operated
in this system.


title:
Squared visibility estimator. Calibrating biases to reach very high
  dynamic range

abstract:
  In the near infrared where detectors are limited by read-out noise, most
interferometers have been operated in wide band in order to benefit from larger
photon rates. We analyze in this paper the biases caused by instrumental and
turbulent effects to $V^2$ estimators for both narrow and wide band cases.
Visibilities are estimated from samples of the interferogram using two
different estimators, $V^{2}_1$ which is the classical sum of the squared
modulus of Fourier components and a new estimator $V^{2}_2$ for which complex
Fourier components are summed prior to taking the square. We present an
approach for systematically evaluating the performance and limits of each
estimator, and to optimizing observing parameters for each. We include the
effects of spectral bandwidth, chromatic dispersion, scan length, and
differential piston. We also establish the expression of the Signal-to-Noise
Ratio of the two estimators with respect to detector and photon noise. The
$V^{2}_1$ estimator is insensitive to dispersion and is always more sensitive
than the $V^{2}_2$ estimator. However, the latter allows to reach better
accuracies when detection is differential piston noise limited. Biases and
noise directly impact the dynamic range of reconstructed images. Very high
dynamic ranges are required for direct exoplanet detection by interferometric
techniques thus requiring estimators to be bias-free or biases to be accurately
calibrated. We discuss which estimator and which conditions are optimum for
astronomical applications especially when high accuracy visibilities are
required. We show that there is no theoretical limit to measuring visibilities
with accuracies as good as $10^{-5}$ which is important in the prospect of
detecting faint exoplanets with interferometers.


title: Self-enrichment in globular clusters. I. An analytic approach

abstract:
  By means of analytical calculations, we explore the self-enrichment scenario
for Globular Cluster formation. According to this scenario, an initial burst of
star formation occurs inside the core radius of the initial gaseous
distribution. The outward-propagating shock wave sweeps up a shell in which
gravitational instabilities may arise, leading to the formation of a second,
metal-enriched, population of stars. We find a minimum mass of the
proto-globular cluster of the order of 10^6 solar masses. We also find that the
observed spread in the Magnitude-Metallicity relation can be explained assuming
cluster-to-cluster variations of some parameters like the thermalization
efficiency, the mixing efficiency and the Initial Mass Function, as well as
variations of the external pressure.


title:
Panoramic Views of Cluster-Scale Assemblies Explored by Subaru
  Wide-Field Imaging

abstract:
  We have started PISCES project; a panoramic imaging and spectroscopic survey
of distant clusters on Subaru. It exploits the unique wide-field imaging
capability of Suprime-Cam, which provides a 34'x27' field of view corresponding
to a physical area of 16x13Mpc^2 at z~1. We plan to target 15 clusters in total
at 0.4<z<1.3. In this paper, we report on our first results concerning the
inner structures and large-scale structures of two distant clusters at z=0.55
and 0.83 together with the earlier results on a z=0.41 cluster. The photometric
redshift technique has been applied to multi-color data in order to efficiently
remove most of the foreground/background galaxies so as to isolate the cluster
member candidates. We have found large-scale filamentary structures around the
clusters, extending out to >5Mpc from the cores, as well as complex inner
structures. The galaxy distributions in the inner regions of the clusters look
similar to the X-ray intensity maps, suggesting that most of the optical
structures trace physically bound systems. We also compared the structures of
the three clusters with those of model clusters in a numerical simulation
(N-body + semi-analytic model) by parameterising the shapes of the iso-density
contours of galaxies, and found a broad agreement. Our results provide good
evidence that cluster-scale assembly takes place along filaments during
hierarchical clustering, while the structures found here need to be confirmed
spectroscopically in the near future.


title:
Cluster AgeS Experiment (CASE): Detection of a dwarf nova in the
  globular cluster M55

abstract:
  We report the detection of a dwarf nova (DN) in the core region of the
globular cluster M55. Six outbursts were observed during 8 observing seasons
spanning the period 1997-2004. The variable has an X-ray counterpart detected
on images taken with the ROSAT telescope. Although we cannot offer proof of
cluster membership, one can see that both the position on the H-R diagram and
the X-ray flux are consistent with a bright DN at the cluster distance.
According to our outburst statistics, no more than one similar DN could remain
undetected in our field of view, centred at the cluster core.


title: A near-infrared survey for new low-mass members in Alpha Per

abstract:
  We present a near-infrared (K'-band) survey of 0.7 square degree area in the
Alpha Persei open cluster (age = 90 Myr, distance = 182 pc) carried out with
the Omega-Prime camera on the Calar Alto 3.5-m telescope. Combining optical
data (Rc and Ic) obtained with the KPNO/MOSA detector and presented in Stauffer
et al. (1999) with the K' observations, a sample of new candidate members has
been extracted from the optical-infrared colour-magnitude diagram. The location
of these candidates in the colour-colour diagram suggests that two-thirds of
them are actually reddened background giants. About 20 new candidate members
with masses between 0.3 and 0.04 Msun are added to the 400 known Alpha Per
cluster members. If they are indeed Alpha Per members, four of the new
candidates would be brown dwarfs. We discuss the advantages and drawbacks of
the near-infrared survey as compared to the optical selection method. We also
describe the outcome of optical spectroscopy obtained with the Twin
spectrograph on the Calar Alto 3.5-m telescope for about 30 candidates,
including selected members from the optical sample presented in Barrado y
Navascues et al. (2002) and from our joint optical/infrared catalogue. These
results argue in favour of the optical selection method for this particular
cluster.


title:
On the origin of the radial mass density profile of the Galactic halo
  Globular Cluster System

abstract:
  We investigate what may be the origin of the presently observed spatial
distribution of the mass of the Galactic Old Halo globular cluster system. We
propose its radial mass density profile to be a relic of the distribution of
the cold baryonic material in the protoGalaxy. Assuming that this one arises
from the profile of the whole protoGalaxy minus the contribution of the dark
matter (and a small contribution of the hot gas by which the protoglobular
clouds were bound), we show that the mass distributions around the Galactic
centre of this cold gas and of the Old Halo agree satisfactorily. In order to
demonstrate our hypothesis even more conclusively, we simulate the evolution
with time, up to an age of 15 Gyr, of a putative globular cluster system whose
initial mass distribution in the Galactic halo follows the profile of the cold
protogalactic gas. We show that beyond a galactocentric distance of order 2 to
3 kpc, the initial shape of such a mass density profile is preserved in spite
of the complete destruction of some globular clusters and the partial
evaporation of some others. This result is almost independent of the choice of
the initial mass function for the globular clusters, which is still
ill-determined. The shape of these evolved cluster system mass density profiles
also agree with the presently observed profile of the Old Halo globular cluster
system, thus strengthening our hypothesis. Our result might suggest that the
flattening shown by the Old Halo mass density profile at short distance from
the Galactic centre is, at least partly, of primordial origin.


title: Radio Recombination Lines from the Starburst Galaxy NGC 3256

abstract:
  We have detected the radio recombination lines H91-alpha and H92-alpha with
rest frequencies of 8.6 GHz and 8.3 GHz from the starburst nucleus NGC 3256 at
an angular resolution of 16.4" x 9.6" using the Australia Telescope Compact
Array and at an angular resolution of 12.0" x 2.9" using the VLA. The line was
detected at ~ 1 mJy/beam peak with a width of 160 km/s with the ATCA and at ~
0.5 mJy/beam peak with a width of 114 km/s with the VLA. Modelling the line
emitting region as a collection of HII regions, we derive constraints on the
required number of HII regions, their temperature, density, and distribution.
We find that a collection of 10 to 300 HII regions with temperatures of 5000 K,
densities of 1000 cm^-3 to 5000 cm^-3 and diameters of 15 pc produced good
matches to the line and continuum emmission. The Lyman continuum production
rate required to maintain the ionization is 2 x 10^52 s^-1 to 6 x 10^53 s^-1,
which requires 600 to 17000 O5 stars to be produced in the starburst.


title: High Energy Neutrinos from the TeV Blazar 1ES 1959+650

abstract:
  The AMANDA neutrino telescope has recently reported the detection of
high-energy neutrinos spatially and temporally coincident with the flaring of
the TeV blazar 1ES 1959+650. At present, the statistical significance of this
observation cannot be reliably assessed, however. In this letter, we
investigate whether circumstances exist where the source can produce the flux
implied by the coincident events. We show that if the TeV gamma-ray emission
observed from 1ES 1959+650 or other nearby TeV blazars is the result of
accelerated protons interacting with nucleons, it is reasonable that AMANDA
could detect several events during a flaring period. Such rates require that
the spectral index of the source be rather high (for instance $\sim2.8$ for 1ES
1959+650) and that the Lorentz factor of the jet be fairly small ($\Gamma \sim
1$).


title:
Upper limit on the gas density in the Beta-Pictoris system: On the
  effect of gas drag on the dust dynamics

abstract:
  We investigate in this paper the effect of gas drag on the dynamics of the
dust particles in the edge-on Beta-Pictoris disc in order to derive an upper
limit on the mass of gas in this system. Our study is motivated by the large
uncertainties on the amount of gas in the Beta-Pictoris disc currently found in
the literature. The dust particles are assumed to originate from a colliding
annulus of planetesimals peaked around 100AU from the central star as proposed
by Augereau et al.(2001). We consider the various gas densities that have been
inferred from independent observing techniques and we discuss their impact on
the dust dynamics and on the disc profile in scattered light along the
midplane. We show that the observed scattered light profile of the disc cannot
be properly reproduced if hydrogen gas number density at 117AU exceeds 10**4
cm**-3. This corresponds to an upper limit on the total gas mass of about 0.4
Mearth assuming the gas density profile inferred by Brandeker et al.(2004) and
thus to a gas to dust mass ratio smaller than 1. Our approach therefore
provides an independent diagnostic for a gas depletion in the Beta-Pictoris
system relative to the dust disc. Such an approach could also be used to
constrain the gas content of recently identified systems like the edge-on disc
around AUmic.


title: Proper motion measurements as indicators of binarity in open clusters

abstract:
  We analyze 9 open clusters with ages in the range 70 Myr to 3.2 Gyr using
UCAC2 proper motion data and 2MASS photometry. For each cluster we consider the
projected velocity distributions in the core and off-core regions separately.
In the projected velocity distribution of all sample clusters we find a
well-defined low-velocity peak, as well as an excess in the number of stars at
larger velocities. The low-velocity peak is accounted for by the random motion
of the single stars, while the high-velocity excess can be attributed to the
large velocity changes produced by a significant fraction of unresolved
binaries in a cluster. We derive kinematic parameters of the single-star
distribution, in particular the projected velocity dispersion. The relatively
large velocity dispersions derived in this work may reflect the non-virialized
state of the clusters. Based on the relative number of high-velocity (binary)
and single stars, we inferred for the sample clusters unresolved binary
fractions in the range $15%-54%$, for both core and off-core regions. The
present results suggest that care must be taken when applying proper-motion
filters to sort out members, especially binaries in a star cluster. This paper
shows that proper motions turn out to be a useful tool for identifying
high-velocity stars as unresolved binary cluster members, and as a consequence,
map and quantify the binary component in colour-magnitude diagrams.


title:
Testing the fireball/blastwave model by monitoring afterglows from soft
  gamma repeaters

abstract:
  The popular fireball/blastwave model of classical gamma-ray bursts is applied
to soft gamma-ray bursts. It is found that X-ray afterglows from strong events
may be above their quiescent levels for 40 -- 400 seconds. Optical afterglows
may also be detectable. By monitoring the three repeaters, we will have an
ideal way to check the fireball/blastwave model.


title:
Spatial dependence of 2MASS luminosity and mass functions in the old
  open cluster NGC 188

abstract:
  Luminosity and mass functions in the old open cluster NGC 188 are analysed by
means of J and H 2MASS photometry. Within the uncertainties, the observed
projected radial density profile of NGC 188 departs from the two-parameter King
model in two inner regions, which reflects the non-virialized dynamical state
and possibly, some degree of non-sphericity in the spatial shape of this old
open cluster. Fits with two and three-parameter King models to the radial
distribution of stars resulted in a core radius of 1.3 pc and a tidal radius of
21 pc. The present 2MASS analysis resulted in significant slope variations with
distance in the mass function $\phi(m)\propto m^{-(1+\chi)}$, being flat in the
central parts ($\chi=0.6\pm0.7$) and steep in the cluster outskirts
($\chi=7.2\pm0.6$). The overall mass function has a slope $\chi=1.9\pm0.7$,
slightly steeper than a standard Salpeter mass function. Solar metallicity
Padova isochrone fits to the near-infrared colour-magnitude diagram of NGC 188
resulted in an age of $7.0\pm1.0$ Gyr. The best fit, obtained with the 7.1 Gyr
isochrone, produced a distance modulus $\mM=11.1\pm0.1$, $\ebv=0.0$, and a
distance to the Sun $\ds=1.66\pm0.08$ kpc. The observed stellar mass (in the
range $0.98 \ms - 1.08 \ms$) in NGC 188 is $\mobs=380\pm12 \ms$. A simple
extrapolation of the observed overall mass function to stars with $0.08 \ms$
resulted in a total present mass of $\mtot\sim(1.8\pm0.7)\times10^4 \ms$. On
the other hand, for a more realistic initial mass function which flattens in
the low-mass range, the total mass in NGC 188 drops to
$\mtot\sim(3.8\pm1.6)\times10^3 \ms$.


title:
Diagnostics of irradiated gas in galaxy nuclei. I: A Far-ultraviolet and
  X-ray dominated region code

abstract:
  We present a far-ultraviolet (PDR) and an X-ray dominated region (XDR) code.
We include and discuss thermal and chemical processes that pertain to
irradiated gas. An elaborate chemical network is used and a careful treatment
of PAHs and H2 formation, destruction and excitation is included. For both
codes we calculate four depth-dependent models for different densities and
radiation fields, relevant to conditions in starburst galaxies and active
galactic nuclei. A detailed comparison between PDR and XDR physics is made for
total gas column densities between ~10^20 and ~10^25 cm^-2. We show cumulative
line intensities for a number of fine-structure lines (e.g., [CII], [OI], [CI],
[SiII], [FeII]), as well as cumulative column densities and column density
ratios for a number of species (e.g., CO/H2, CO/C, HCO+/HCN, HNC/HCN). The
comparison between the results for the PDRs and XDRs shows that column density
ratios are almost constant up to N_H=10^22 cm^-2 for XDRs, unlike those in
PDRs. For example, CO/C in PDRs changes over four orders of magnitude from the
edge to N_H=10^22 cm^-2. The CO/C and CO/H2 ratios are lower in XDRs at low
column densities and rise at N_H > 10^23 cm^-2. At most column densities N_H >
10^21.5 cm^-2, HNC/HCN ratios are lower in XDRs too, but they show a more
moderate increase at higher N_H.


title: On the kinematics of the neutron star low mass X-ray binary Cen X-4

abstract:
  We present the first determination of the proper motion of the neutron star
low mass X-ray binary {Cen X-4} measured from relative astrometry of the
secondary star using optical images at different epochs. We determine the
Galactic space velocity components of the system and find them to be
significantly different from the mean values that characterize the kinematics
of stars belonging to the halo, and the thin and the thick disc of the Galaxy.
The high metallicity of the secondary star of the system rules out a halo
origin and indicates that the system probably originated in the Galactic disc.
A statistical analysis of the galactocentric motion revealed that this binary
moves in a highly eccentric ($e\simeq 0.85\pm0.1$) orbit with an inclination of
$\simeq 110^\circ$ to the Galactic plane. The large Galactic space velocity
components strongly support that a high natal kick as a result of a supernova
explosion could have propelled the system into such an orbit from a birth place
in the Galactic disc. The high Li abundance in the secondary, comparable to
that of stars in star forming regions and young stellar clusters like the
Pleiades, may suggest a relatively recent formation of the system. Following
the orbit backwards in time, we found that the system could have been in the
inner regions of the Galactic disc $\sim$100--200 Myr ago. The neutron star
might have formed at that moment. However, we cannot rule out the possibility
that the system formed at a much earlier time if a Li production mechanism
exists in this LMXB.


title: Non-thermal radio emission from O-type stars. I. HD 168112

abstract:
  We present a radio lightcurve of the O5.5 III(f+) star HD 168112, based on
archive data from the Very Large Array (VLA) and the Australia Telescope
Compact Array (ATCA). The fluxes show considerable variability and a negative
spectral index, thereby confirming that HD 168112 is a non-thermal radio
emitter. The non-thermal radio emission is believed to be due to synchrotron
radiation from relativistic electrons that have been Fermi accelerated in
shocks. For HD 168112, it is not known whether these shocks are due to a
wind-wind collision in a binary system or to the intrinsic instability of the
stellar wind driving mechanism. Assuming HD 168112 to be a single star, our
synchrotron model shows that the velocity jump of the shocks should be very
high, or there should be a very large number of shocks in the wind. Neither of
these is compatible with time-dependent hydrodynamical calculations of O star
winds. If, on the other hand, we assume that HD 168112 is a binary, the high
velocity jump is easily explained by ascribing it to the wind-wind collision.
By further assuming the star to be an eccentric binary, we can explain the
observed radio variability by the colliding-wind region moving in and out of
the region where free-free absorption is important. The radio data presented
here show that the binary has a period between one and two years. By combining
the radio data with X-ray data, we find that the most likely period is about
1.4 yr.


title: Observations of cooling neutron stars

abstract:
  Observations of cooling neutron stars allow to measure photospheric radii and
to constrain the equation of state of nuclear matter at high densities. In this
paper we concentrate on neutron stars, which show thermal (photospheric) X-ray
emission and have measured distances. After a short summary of the radio
pulsars falling into this category we review the observational data of the 7
radio quiet isolated neutron stars discovered by ROSAT which have been studied
in detail by Chandra, XMM-Newton and optical observations. Their spectra show
blackbody temperatures between 0.5 and 1 million Kelvin and an optical excess
of a factor of 5-10 over the extrapolation of the X-ray spectrum. Four of these
sources show periodicities between 3.45 and 11.37 s, indicating slow rotation.
The pulsed fractions are small, between 6 and 18 %. The magnetic fields derived
from spin down and/or possible proton cyclotron lines are of the order
10$^{13}-10^{14}$ G. We then discuss RX J1856.5-3754 in detail and suggest that
the remarkable absence of any line features in its X-ray spectrum is due to
effects of strong magnetic fields ($\sim 10^{13}$ G). Assuming blackbody
emission to fit the optical and X-ray spectrum we derive a conservative lower
limit of the ``apparent'' neutron star radius of 16.5 km $\times$ (d/117 pc).
This corresponds to the radius for the ``true'' radius of 14 km for a 1.4
M$_{\odot}$ neutron star, indicating a stiff equation of state at high
densities. A comparison of the result with mass-radius relations shows that in
this case a quark star or a neutron star with a quark matter core can be ruled
out with high confidence.


title: Cooling and Clusters: When Is Heating Needed?

abstract:
  There are (at least) two unsolved problems concerning the current state of
the thermal gas in clusters of galaxies. The first is identifying the source of
the heating which offsets cooling in the centers of clusters with short cooling
times (the ``cooling flow'' problem). The second is understanding the mechanism
which boosts the entropy in cluster and group gas. Since both of these problems
involve an unknown source of heating it is tempting to identify them with the
same process, particular since AGN heating is observed to be operating at some
level in a sample of well-observed ``cooling flow'' clusters. Here we show,
using numerical simulations of cluster formation, that much of the gas ending
up in clusters cools at high redshift and so the heating is also needed at
high-redshift, well before the cluster forms. This indicates that the same
process operating to solve the cooling flow problem may not also resolve the
cluster entropy problem.


title: Mixed Morphology Pairs as a Breeding Ground for Active Nuclei

abstract:
  Mixed morphology pairs offer a simplification of the interaction equation
that involves a gas-rich fast rotator paired with a gas-poor slow rotator. In
past low resolution IRAS studies it was assumed that the bulk of the far
infrared emission originated in the spiral component. However our ISO studies
revealed a surprising number of early-type components with significant IR
emission some of which turned out to show active nuclei. This motivated us to
look at the current statistics of active nuclei in mixed pairs using the
FIR-radio continuum correlation as a diagnostic. We find a clear excess of
early-type components with radio continuum emission and an active nucleus. We
suggest that they arise more often in mixed pairs via cross fueling of gas from
the spiral companion. This fuel is more efficiently channeled into the nucleus
of the slow rotating receptor. In a sample of 112 mixed-morphology pairs from
the Karachentsev catalog we find that about 25-30% of detected mixed pairs show
a displacement from the radio-FIR relation defined by normal star forming
galaxies. The latter objects show excess radio continuum emission while others
extend the relation to unusually high radio and FIR flux levels. Many of the
outliers/extreme emitters involve an early-type component with an active
nucleus. The paired E/S0 galaxies in the sample exhibit a significant excess
detection fraction and a marginal excess luminosity distribution compared to
isolated unpaired E/S0 galaxies.