title: Brown Dwarfs and the TW Hya Association

abstract:
  I report the results of a survey for low-mass (0.030 <~ M <~ 0.013 M_solar)
brown dwarfs in the direction of the TW Hya association using 2MASS. Two late-M
dwarfs show signs of low surface gravity and are strong candidates to be young,
very-low-mass (M ~ 0.025 M_solar) brown dwarfs related to the TW Hya
association. 2MASSW J1207334-393254 is particularly notable for its strong H
alpha emission. The number of detected brown dwarfs is consistent with the
substellar mass function in richer star formation environments. Newly
identified late-M and L dwarfs in the field are also discussed. Unusual objects
include an L dwarf with strong H alpha emission, a possible wide M8/M9 triple
system, and a possible L dwarf companion to an LHS star.


title: Spectrophotometric Observations of Blue Compact Dwarf Galaxies: Mrk 370

abstract:
  We present results from a detailed spectrophotometric analysis of the blue
compact dwarf galaxy (BCD) Mrk 370, based on deep UBVRI broad-band and Halpha
narrow-band observations, and long-slit and two-dimensional spectroscopy of its
brightest knots. The spectroscopic data are used to derive the internal
extinction, and to compute metallicities, electronic density and temperature in
the knots. By subtracting the contribution of the underlying older stellar
population, modeled by an exponential function, removing the contribution from
emission lines, and correcting for extinction, we can measure the true colors
of the young star-forming knots. We show that the colors obtained this way
differ significantly from those derived without the above corrections, and lead
to different estimates of the ages and star-forming history of the knots. Using
predictions of evolutionary synthesis models, we estimate the ages of both the
starburst regions and the underlying stellar component. We found that we can
reproduce the colors of all the knots with an instantaneous burst of star
formation and the Salpeter initial mass function with an upper mass limit of
100 solar masses. The resulting ages range between 3 and 6 Myrs. The colors of
the low surface brightness component are consistent with ages larger than 5
Gyr. The kinematic results suggest ordered motion around the major axis of the
galaxy.


title:
Dark and luminous matter in the NGC 3992 group of galaxies, II. The
  dwarf companions UGC 6923, UGC 6940, UGC 6969, and the Tully-Fisher relation

abstract:
  Detailed neutral hydrogen observations have been obtained of the large barred
spiral galaxy NGC 3992 and its three small companion spiral galaxies, UGC 6923,
UGC 6940, and UGC 6969. Contrary to the large galaxy, for the companions the HI
distribution ends quite abruptly at the optical edges. Velocity fields have
been constructed from which rotation curves have been derived. Assuming a
reasonable M/L ratio, a decomposition of these rotation curves generates nearly
equal dark matter halos. When comparing the position-velocity diagrams of the
two brightest galaxies, UGC 6923 and UGC 6969, it is obvious that the rotation
curve of the latter has a shape closer to solid body than the former, yet the
same maximum rotational level is reached. This is likely generated by the equal
dark matter halos in combination with UGC 6923 being a factor five more
luminous than UGC 6969 and so its luminous matter gives a higher contribution
to the rotation in the inner regions. An NFW-CDMLambda dark halo is consistent
with the observed rotation curve of UGC 6923 but not consistent with the
rotation curve of UGC 6969. If the NGC 3992 group is part of the Ursa Major
cluster, then the I-band M/L ratio of NGC 3992 has to be at least 1.35 times as
large as that of the average spiral galaxy in the cluster. On the other hand,
equal M/L ratios can be achieved when the NGC 3992 group is placed more than 3
Mpc behind the cluster. Both possibilities can explain why NGC 3992 appears to
be 0.43 magnitudes too faint for its rotation.


title:
The extreme ultraviolet excess emission in five clusters of galaxies
  revisited

abstract:
  Evidence for excess extreme ultraviolet (EUV) emission over a tail of X-ray
gas bremsstrahlung emission has been building up recently, but in some cases
remains controversial, mostly due to the moderate quality of the EUV data. In
order to improve the signal to noise ratio in the EUV, we have performed the
wavelet analysis and image reconstructions for five clusters of galaxies
observed both at EUV and X-ray energies with the EUVE and ROSAT satellites
respectively. The profiles of the EUV and X-ray reconstructed images all differ
at a very large confidence level and an EUV excess over a thermal
bremsstrahlung tail is detected in all five clusters (Abell 1795, Abell 2199,
Abell 4059, Coma and Virgo) up to large radii. These results, coupled with
recent XMM-Newton observations, suggest that the EUV excess is probably non
thermal in origin.


title:
Terrestrial origin of SNC meteorites and 30 Myr extinctions' shower
  source

abstract:
  Strong strengthening of material under high confining pressure and jet nature
of outflow from impact craters permit to show meteoroid impacts of >=10E6 Mt
TNT equivalent are capable of ejecting rocks up to ~1 km in size from the Earth
into space. That permits one to propose the terrestrial origin of some NEA's
and SNC meteorites. It is shown the isotopic anomalies of nitrogen, argon and
xenon can be related with terrestrial mantle samples. The same applies to the
oxygen isotope shifts if one recalls the known manifestations of the kinetic
effects of isotopic fractionation.


title: Coronal heating distribution due to low-frequency wave-driven turbulence

abstract:
  The heating of the lower solar corona is examined using numerical simulations
and theoretical models of magnetohydrodynamic turbulence in open magnetic
regions. A turbulent energy cascade to small length scales perpendicular to the
mean magnetic field can be sustained by driving with low-frequency Alfven waves
reflected from mean density and magnetic field gradients. This mechanism
deposits energy efficiently in the lower corona, and we show that the spatial
distribution of the heating is determined by the mean density through the
Alfven speed profile. This provides a robust heating mechanism that can explain
observed high coronal temperatures and accounts for the significant heating
(per unit volume) distribution below two solar radius needed in models of the
origin of the solar wind. The obtained heating per unit mass on the other hand
is much more extended indicating that the heating on a per particle basis
persists throughout all the lower coronal region considered here.


title: The Stellar Content of Obscured Galactic Giant H II Regions IV.: NGC3576

abstract:
  We present deep, high angular resolution near-infrared images of the obscured
Galactic Giant H II region NGC3576. Our images reach objects to ~3M_sun. We
collected high signal-to-noise K-band spectra of eight of the brightest
objects, some of which are affected by excess emission and some which follow a
normal interstellar reddening law. None of them displayed photospheric features
typical of massive OB type stars. This indicates that they are still enshrouded
in their natal cocoons. The K-band brightest source (NGC3576 #48) shows CO 2.3
micron bandhead emission, and three others have the same CO feature in
absorption. Three sources display spatially unresolved H_2 emission, suggesting
dense shocked regions close to the stars. We conclude that the remarkable
object NGC3576 #48 is an early-B/late-O star surrounded by a thick
circumstellar disk. A number of other relatively bright cluster members also
display excess emission in the K-band, indicative of reprocessing disks around
massive stars (YSOs). Such emission appears common in other Galactic Giant H II
regions we have surveyed. The IMF slope of the cluster, Gamma = -1.51, is
consistent with Salpeter's distribution and similar to what has been observed
in the Magellanic Cloud clusters and in the periphery of our Galaxy.


title: Fourier Techniques for Very Long Astrophysical Time Series Analysis

abstract:
  In this paper, we present an assortment of both standard and advanced Fourier
techniques that are useful in the analysis of astrophysical time series of very
long duration -- where the observation time is much greater than the time
resolution of the individual data points. We begin by reviewing the operational
characteristics of Fourier transforms (FTs) of time series data, including
power spectral statistics, discussing some of the differences between analyses
of binned data, sampled data, and event data, and briefly discuss algorithms
for calculating discrete Fourier transforms (DFTs) of very long time series. We
then discuss the response of DFTs to periodic signals, and present techniques
to recover Fourier amplitude "lost" during simple traditional analyses if the
periodicities change frequency during the observation. These techniques include
Fourier interpolation which allows us to correct the response for signals that
occur between Fourier frequency bins. We then present techniques for estimating
additional signal properties such as the signal's centroid and duration in
time, the first and second derivatives of the frequency, the pulsed fraction,
and an overall estimate of the significance of a detection. Finally, we present
a recipe for a basic but thorough Fourier analysis of a time series for
well-behaved pulsations.


title: Gamma-ray bursts in normal and extreme star-forming galaxies

abstract:
  We discuss how gamma-ray burst (GRB) optical afterglows and multiwavelength
observations of their host galaxies can be used to obtain information about the
relative amounts of star formation happening in optical and submillimetre
galaxies. That such an analysis will be possible follows from the
currently-favoured idea that GRBs are closely linked with high-mass star
formation. Studying GRB host galaxies offers a method of finding low-luminosity
submillimetre galaxies, which cannot be identified either in optical Lyman
break surveys, because so much of their star formation is hidden by dust, or in
submillimetre surveys, because their submillimetre fluxes are close to or below
the confusion limit. Much of the star formation in the Universe could have
occurred in such objects, so searching for them is an important exercise. From
current observations, GRB host galaxies appear to be neither optically-luminous
Class-2 SCUBA galaxies like SMM J02399$-$0136 or SMM J14011+0252, nor galaxies
containing dense molecular cores like local ultraluminous infrared galaxies
(ULIGs), but rather some intermediate kind of galaxy. The host galaxy of GRB
980703 is a prototype of this kind of galaxy.


title: CV evolution: AM Her binaries and the period gap

abstract:
  AM Her variables -- synchronised magnetic cataclysmic variables (CVs) --
exhibit a different period distribution from other CVs across the period gap.
We show that non-AM Her systems may infiltrate the longer-period end of the
period gap if they are metal-deficient, but that the position and width of the
gap in orbital period is otherwise insensitive to other binary parameters
(excepting the normalisation of the braking rate). In AM Her binaries, magnetic
braking is reduced as the wind from the secondary star may be trapped within
the magnetosphere of the white dwarf primary. This reduced braking fills the
period gap from its short-period end as the dipole magnetic moment of the white
dwarf increases. The consistency of these models with the observed distribution
of CVs, both AM Her and non-AM Her type, provides compelling evidence
supporting magnetic braking as the agent of angular momentum loss among
long-period CVs, and its disruption as the explanation of the 2 - 3 hour period
gap among nonmagnetic CVs.


title: Polarization statistics of extra-solar systems

abstract:
  We have analysed the optical polarimetric properties of nearby
intermediate-late type MS stars and examined in some detail the pecularities
displayed by those known to have planets. We find that: i) the polarization
degree is not strictly correlated with the presence of planets; ii) there is a
lack of high eccentricity planets at high optical linear polarization levels;
iii) no clear correlation is seen between metallicity and polarization amongst
extra-solar systems; iv) the contribution to the polarization by the
interstellar medium seems to become effective only after ~70 pc.


title: IW And is a Z Cam-Type Dwarf Nova

abstract:
  IW And was discovered as a unique blue variable, which spends 72% of time in
"inactive" state, and was only occasionally observed in bright or faint states.
Although the past spectroscopy confirmed that the object is a cataclysmic
variable (CV), the object has been regarded as significantly different from the
known subclasses of CVs. We observed IW And on 55 nights between 2001 December
6 and 2002 March 25. These observations clearly indicate that the object is a Z
Cam-type dwarf nova. The duty cycle of standstill in IW And is exceptionally
high among Z Cam stars. IW And is apparently the first object to fill the gap
between classical Z Cam stars and novalike (NL) stars.


title: Recurrent Nova IM Normae

abstract:
  We detected the second historical outburst of the 1920 nova IM Nor. Accurate
astrometry of the outbursting object revealed the true quiescent counterpart
having a magnitude of R=17.0 mag and B=18.0 mag. We show that the quiescent
counterpart shows a noticeable variation. From the comparison of light curves
and spectroscopic signatures, we propose that IM Nor and CI Aql comprise a new
class of recurrent novae bearing some characteristics similar to those of
classical novae. We interpret that the noticeable quiescent variation can be a
result of either high orbital inclination, which may be also responsible for
the low quiescent brightness, or the presence of high/low states. If the second
possibility is confirmed by future observations, IM Nor becomes the first
recurrent nova showing state changes in quiescence. Such state changes may
provide a missing link between recurrent novae and supersoft X-ray sources.


title:
CMB Comptonization by Energetic Nonthermal Electrons in Clusters of
  Galaxies

abstract:
  Use of the Sunyaev-Zeldovich effect as a precise cosmological probe
necessitates a realistic assessment of all possible contributions to
Comptonization of the cosmic microwave background in clusters of galaxies. We
have calculated the additional intensity change due to various possible
populations of energetic electrons that have been proposed in order to account
for measurements of intracluster radio, nonthermal X-ray and (possibly also)
EUV emission. Our properly normalized estimates of (the highly model dependent
value of) the predicted intensity change due to these electrons is well below
$\sim 6%$ and $\sim 35%$ of the usual Sunyaev-Zeldovich effect due to electrons
in the hot gas in Coma and A2199, respectively. These levels constitute high
upper limits since they are based on energetic electron populations whose
energy densities are {\it comparable} to those of the thermal gas. The main
impact of nonthermal Comptonization is a shift of the crossover frequency
(where the thermal effect vanishes) to higher values. Such a shift would have
important consequences for our ability to measure cluster peculiar velocities
from the kinematic component of the Sunyaev-Zeldovich effect.


title: Magnetic Activity of the Cool Companion in Symbiotic Systems

abstract:
  I argue that cool giant companions in most symbiotic binary systems possess
magnetic activity on a much higher level than isolated, or in wide binary
systems, cool giants. Based on the behavior of main sequence stars, I assume
that magnetic activity and X-ray luminosity increase with rotation velocity. I
then show that the cool companions in symbiotic systems are likely to rotate
much faster than isolated, or in wide binary systems, cool giants. The magnetic
activity of the cool giant may be observed as a global axisymmetrical mass loss
geometry from the cool giant (before the hot companion influences the outflow),
a stochastic mass loss process, i.e., variation of mass loss rate with time and
location on the giant's surface, and in relatively strong X-ray emission. The
variation in the mass loss process from the cool giant may cause variation in
the properties of jets blown by the hot compact companion. I conclude that
symbiotic systems should be high-priority X-ray targets.


title: A Cosmological Tale of Two Varying Constants

abstract:
  We formulate a simple extension of general relativity which incorporates
space-time variations in the Newtonian gravitation 'constant', $G$, and the
fine structure 'constant', $\alpha $, which generalises Brans-Dicke theory and
our theory of varying $\alpha .$ We determine the behaviour of Friedmann
universes in this theory. In the radiation and dust-dominated eras $\alpha G$
approaches a constant value and the rate of variation of $\alpha $ is equal to
the magnitude of the rate of variation in $G$. The expansion dynamics of the
universe are dominated by the variation of $G$ but the variation of $G$ has
significant effects upon the time variation of $\alpha .$ Time variations in
$\alpha $ are extinguished by the domination of the expansion by spatial
curvature or quintessence fields, as in the case with no $G$ variation.


title: Gamma-ray bursts, supernova kicks, and gravitational radiation

abstract:
  We suggest that the collapsing core of a massive rotating star may fragment
to produce two or more compact objects. Their coalescence under gravitational
radiation gives the resulting black hole or neutron star a significant kick
velocity, which may explain those observed in pulsars. A gamma-ray burst can
result only when this kick is small. Thus only a small fraction of
core-collapse supernovae produce gamma-ray bursts. The burst may be delayed
significantly (hours - days) after the supernova, as suggested by recent
observations. If this picture is correct, core-collapse supernovae should be
significant sources of gravitational radiation with a chirp signal similar to a
coalescing binary.


title: The nature of ultra-luminous X-ray sources in NGC4565

abstract:
  We report the optical identifications of two X-ray luminous point sources in
the spiral galaxy NGC4565 based on archive data of Chandra and the Hubble Space
Telescope. The central X-ray point source, RXJ1236.3+2559, is found to be the
nucleus of NGC4565 with an X-ray luminosity of Lx= 4.3 10^{39} erg. We show
that its multi-waveband properties are consistent with it being a
low-luminosity active galactic nucleus. A faint optical counterpart with B=25.1
and I=24.0 was identified for the off-nucleus X-ray point source,
RXJ1236.2+2558. Its extinction corrected B magnitude is estimated to be 24.5.
The X-ray to optical flux ratio (fx/fB) is about 540. From the optical and
X-ray properties we argue that RXJ1236.2+2558 is an ultra-luminous X-ray
compact source with Lx=6.5 10^{39} erg. The source is probably located in a
faint globular cluster at the outer edge of NGC4565's bulge.


title:
Evidence for a connection between the gamma-ray and the highest energy
  cosmic-ray emissions by BL Lacertae objects

abstract:
  A set of potentially gamma-ray--loud BL Lac objects is selected by
intersecting the EGRET and BL Lac catalogs. Of the resulting 14 objects, eight
are found to correlate with arrival directions of ultra--high-energy cosmic
rays (UHECRs), with significance of the order of 5 sigma. This suggests that
gamma-ray emission can be used as a distinctive feature of those BL Lac objects
that are capable of producing UHECR.


title:
High-resolution X-ray imaging and spectroscopy of the core of NGC 4945
  with XMM-Newton and Chandra

abstract:
  We utilize the complimentary capabilities of XMM-Newton and Chandra, to
conduct a detailed imaging and spectral study of the nearby galaxy NGC 4945
focussing on its nucleus and immediate surroundings (within ~1 kpc of the
nucleus). A complex morphology is revealed including a predominantly hard, but
partially resolved, nuclear source plus a spectrally soft, conically shaped
X-ray "plume", which extends 30" (500 pc) to the northwest. In NGC 4945 our
direct view of the active galactic nucleus (AGN) is blocked below ~10 keV by
extremely heavy line-of-sight absorption and the observed X-ray spectrum is
dominated by multi-temperature thermal emission associated with the nuclear
starburst and the X-ray plume. Nevertheless the signature of the AGN is present
in the form of a neutral Compton reflection component and a 6.4 keV fluorescent
iron Ka line. We conjecture that the site of the continuum reprocessing is the
far wall of a highly inclined molecular torus, a geometry which is consistent
with the presence of H2O megamaser emission in this source. The soft spectrum
(~0.6 keV) and limb-brightened appearance of the X-ray plume suggest an
interpretation in terms of a mass-loaded superwind emanating from the nuclear
starburst.


title: The X-ray fast-time variability of Sco X-2 (GX 349+2) with RXTE

abstract:
  Sco X-2 (GX 349+2) is a low-mass X-ray binary and Z source. We have analysed
156 ks of Rossi X-ray Timing Explorer data, obtained in 1998 January, on this
source. We investigated the fast-time variability as a function of position on
the Z track. During these observations, Sco X-2 traced out the most extensive Z
track ever reported from this object, making this the most comprehensive study
thus far. We found the broad peaked flaring branch noise that is typical of Sco
X-2, with a centroid frequency in the range 3.3--5.8 Hz. We also discovered low
frequency noise, and a new peaked noise feature, with centroid frequencies in
the range 5.4--7.6 Hz and 11--54 Hz, respectively. We discuss the phenomenology
of these features, their relationship with the power spectral components found
in other low-mass X-ray binaries, and the implications for current models. In
particular, the low frequency noise we observed was strongest at intermediate
energies, in contrast to the low frequency noise seen in other Z sources. We
also detected very low frequency noise, and have calculated complex cross
spectra between intensity and hardness. We found that the very low frequency
noise is not entirely due to motion along the Z track.


title:
Emission-Line Eclipse Mapping of Velocity Fields in Dwarf-Nova Accretion
  Disk

abstract:
  We propose a new method, emission-line eclipse mapping, to map the velocity
fields of an accretion disk in position space. Quiescent dwarf novae usually
exhibit double-peaked emission line profiles because of disk rotation. Since a
part of the disk having a different line-of-sight velocity is successively
obscured by a companion in eclipsing systems, they show time-varying line
profiles. We calculate time changes of the emission line profiles, assuming
Keplerian rotation fields (v_\phi\propto r^(-1/2) with r being the distance
from the disk center) and the emissivity distribution of j \propto r^(-3/2).
We, then, apply the usual eclipse mapping technique to the light curves at each
of 12-24 wavelengths across the line center to map the region with the same
line-of-sight velocity. The reconstructed images typically exhibit a `two-eye'
pattern for high line-of-sight velocities and we can recover the relation,
v_\phi \propto d^(-1/2), on the assumption of the axisymmetric disk, where d is
the separation between the two `eyes'. We will be able to probe the Keplerian
rotation law, the most fundamental assumption adopted in many disk models, by
high-speed spectroscopic observations with 8-m class telescopes.


title: Physics Results from the AMANDA-B10 Neutrino Telescope

abstract:
  The data from the first year of operation of the 10-string, AMANDA-B10,
high-energy neutrino detector array at the South Pole have been analyzed and
searched for evidence of neutrinos from cosmic sources. Differently optimized
selection criteria have been used and limits on the flux of high-energy
neutrinos from a variety of objects have been derived


title: Optical and Radio monitoring of S5 1803+74

abstract:
  The optical (BVRI) and radio (8.4 GHz) light curves of S5 1803+784 on a time
span of nearly 6 years are presented and discussed. The optical light curve
showed an overall variation greater than 3 mag, and the largest changes occured
in three strong flares. No periodicity was found in the light curve on time
scales up to a year. The variability in the radio band is very different, and
shows moderate oscillations around an average constant flux density rather than
relevant flares, with a maximum amplitude of $\sim$30%, without a simultaneous
correspondence between optical and radio luminosity. The optical spectral
energy distribution was always well fitted by a power law. The spectral index
shows small variations and there is indication of a positive correlation with
the source luminosity. Possible explanations of the source behaviour are
discussed in the framework of current models.


title: Galaxy Formation: CDM, Feedback and the Hubble Sequence

abstract:
  TreeSPH simulations of galaxy formation in a LCDM cosmology, with star
formation, energetic stellar feedback and a meta-galactic UV field have been
performed, resulting in realistic disk, S0 and E galaxies at z=0. The disk
galaxies are deficient in angular momentum by only about a factor of two
compared to observations for runs where fairly strong star-bursts in early,
proto-galactic clouds lead to "blow-away" of the remaining gas. The surface
density profiles of the stellar disks are approximately exponential and those
of the bulges range from exponential to r^(1/4). B/D ratios and integrated B-V
colours are consistent with observations. The observed I-band TF relation can
be matched with M/L_I ~ 0.8, in fair agreement with recent determinations. The
(E/S0)s have approximately r^(1/4) profiles, non disk-like kinematics and are
flattened due to non-isotropic stellar velocity distributions. We predict hot
halo gas to cool out and accrete onto the Galactic disk at 0.5-1 Msun/yr at
z=0, consistent with upper limits from FUSE observations of O VI. We analyzed
two Milky Way-sized galaxies and find accretion rates, and X-ray halo
luminosities, 6-7 times larger at z=1 than at z=0. The gas infall declines
nearly exponentially with time, supporting the approximation often used in
chemical evolution models. The infall time-scales are comparable to what is
used to solve the "G-dwarf problem". One disk forms "inside-out", the other
"outside-in". For both, the mean stellar ages in the outskirts agree with
findings for the disk of M31. The amount of hot gas in disk galaxy haloes is
consistent with observational upper limits, as are dispersion measures to
pulsars in the globular cluster M53 and the LMC, which were "inserted" in the
disk galaxy haloes.


title: Interstellar Scintillation of PSR J0437-4715 on Two Scales

abstract:
  We sought to determine the scale of scintillation in the interstellar plasma
of PSR J0437-4715. We used the Very Long Baseline Array to obtain scintillation
amplitude and phase data, from dynamic spectra at 327 MHz. We observe two
scales of scintillation of pulsar PSR J0437-4715, differing by more than an
order of magnitude in scintillation bandwidth. The wider-bandwidth scale of
scintillation that we observe indicates less scattering for this pulsar than
for other nearby pulsars, except for PSR B0950+08.


title: Power Spectra of X-ray Binaries

abstract:
  The interpretation of Fourier spectra in the time domain is critically
examined. Power density spectra defined and calculated in the time domain are
compared with Fourier spectra in the frequency domain for three different types
of variability: periodic signals, Markov processes and random shots. The power
density spectra for a sample of neutron stars and black hole binaries are
analyzed in both the time and the frequency domains. For broadband noise, the
two kinds of power spectrum in accreting neutron stars are usually consistent
with each other, but the time domain power spectra for black hole candidates
are significantly higher than corresponding Fourier spectra in the high
frequency range (10--1000 Hz). Comparing the two kinds of power density spectra
may help to probe the intrinsic nature of timing phenomena in compact objects.


title:
The Effects of Burst Activity on Soft Gamma Repeater Pulse Properties
  and Persistent Emission

abstract:
  Soft Gamma Repeaters (SGRs) undergo changes in their pulse properties and
persistent emission during episodes of intense burst activity. SGR 1900+14 has
undergone large flux increases following recent burst activity. Both SGR
1900+14 and SGR 1806-20 have shown significant changes in their pulse profile
and spin-down rates during the last several years. The pulse profile changes
are linked with the burst activity whereas the torque variations are not
directly correlated with the bursts. Here, we review the observed dynamics of
the pulsed and persistent emission of SGR 1900+14 and SGR 1806-20 during burst
active episodes and discuss what implications these results have for the burst
emission mechanism, the magnetic field dynamics of magnetars, the nature of the
torque variability, and SGRs in general.


title:
The enrichment history of the intergalactic medium: O VI in Ly-alpha
  forest systems at redshift z ~ 2

abstract:
  A search for O VI at redshifts corresponding to Ly-alpha lines in the z_em ~
2.4 QSOs HE1122-1648 and HE2217-2818 reveals that a substantial fraction of
those with H I column densities log N(HI) > 14 (cm^{-2}) are highly ionized and
show some heavy element enrichment. If these two sight lines are typical, then
the O VI systems contain a cosmologically significant fraction of the baryons
and the metals in the universe. For most systems the temperatures derived from
the line widths are too low for collisional ionization to be responsible for
the O VI lines. Photoionization models with a substantial hard ultraviolet flux
can reproduce the observations for densities that are in good agreement with a
model assuming local, hydrostatic equilibrium and heavy element abundances in
the range ~ 10^{-3} - 10^{-2} solar. Photoionization by a UV flux much softer
than that predicted by Haardt & Madau (1996) for a background dominated by
quasars can be ruled out. Finally, we find one system with a very low H I
column density for which both photoionization and collisional ionization models
yield a metallicity close to solar and a density that is inconsistent with
gravitational confinement, unless the gas fraction is negligible.


title:
The Central Starburst and Ionization Mechanism in the LINER/H II Region
  Transition Nucleus in NGC 4569

abstract:
  We present a comprehensive study to determine if the LINER/H II region
transition spectrum in NGC 4569 can be generated solely by photoionization by
the nuclear starburst. A review of the multiwavelength data from the literature
reveals no additional sources that contribute to the ionization. We find that
the young starburst dominating the UV emission is distinct from the nuclear
population of A supergiants identified in the optical spectrum by Keel (1996).
Spectral synthesis analysis provides constraints on the physical nature of the
starburst, revealing a 5-6 Myr, approximately instantaneous starburst with
subsolar metallicity. These results are used to model the spectral energy
distribution of the ionizing continuum. Luminosity constraints place limits on
the steepness of the extinction curve for the young starburst. The Savage &
Mathis (1979) curve satisfies all luminosity constraints and the derived
reddening is similar to the emission line reddening. These results imply
extreme conditions in the nuclear starburst, with ~5x10^4 O and B stars
compacted in the inner 9" x 13" region of the nucleus. Using photoionization
analysis and employing all observational constraints on the emission line gas,
we find very specific conditions are required if the spectrum is generated
solely by stellar photoionization. At least two spatially distinct components
are required - a compact region with strong O III emission and an extended, low
density component emitting most of the S II flux. A high density component is
also needed to generate the O I flux. Additionally, a limited contribution from
Wolf-Rayet stars to the ionizing SED is necessary, consistent with the results
of Barth & Shields (2000). We present a physical interpretation for the
multi-component emission line gas.


title: Spatially Resolved Observations of the Galactic Center Source, IRS 21

abstract:
  We present diffraction-limited 2-25 micron images obtained with the W. M.
Keck 10-m telescopes that spatially resolve the cool source, IRS 21, one of a
small group of enigmatic objects in the central parsec of our Galaxy that have
eluded classification. Modeled as a Gaussian, the azimuthally-averaged
intensity profile of IRS 21 has a half-width half-maximum (HWHM) size of
650+/-80 AU at 2.2 microns and an average HWHM size of 1600+/-200 AU at
mid-infrared wavelengths. These large apparent sizes imply an extended
distribution of dust. The mid-infrared color map indicates that IRS 21 is a
self-luminous source rather than an externally heated dust clump as originally
suggested. The spectral energy distribution has distinct near- and mid-infrared
components. A simple radiative transfer code, which simultaneously fits the
near- and mid- infrared photometry and intensity profiles, supports a model in
which the near-infrared radiation is scattered and extincted light from an
embedded central source, while the mid-infrared emission is from thermally
re-radiating silicate dust. We argue that IRS 21 (and by analogy the other
luminous sources along the Northern Arm) is a massive star experiencing rapid
mass loss and plowing through the Northern Arm, thereby generating a bow shock,
which is spatially resolved in our observations.


title:
The Numerical Simulation of Radiative Shocks I: The elimination of
  numerical shock instabilities using a localized oscillation filter

abstract:
  We address a numerical instability that arises in the directionally split
computation of hydrodynamic flows when shock fronts are parallel to a grid
plane. Transverse oscillations in pressure, density and temperature are
produced that are exacerbated by thermal instability when cooling is present,
forming post--shock `stripes'. These are orthogonal to the classic post--shock
'ringing' fluctuations. The resulting post--shock `striping' substantially
modifies the flow. We discuss three different methods to resolve this problem.
These include (1) a method based on artificial viscosity; (2) grid--jittering
and (3) a new localized oscillation filter that acts on specific grid cells in
the shock front. These methods are tested using a radiative wall shock problem
with an embedded shear layer. The artificial viscosity method is unsatisfactory
since, while it does reduce post--shock ringing, it does not eliminate the
stripes and the excessive shock broadening renders the calculation of cooling
inaccurate, resulting in an incorrect shock location. Grid--jittering
effectively counteracts striping. However, elsewhere on the grid, the shear
layer is unphysically diffused and this is highlighted in an extreme case. The
oscillation filter method removes stripes and permits other high velocity
gradient regions of the flow to evolve in a physically acceptable manner. It
also has the advantage of only acting on a small fraction of the cells in a two
or three dimensional simulation and does not significantly impair performance.


title: Birkhoff's Theorem and the Void Matter Density

abstract:
  According to the discussion on Birkhoff's theorem by Peebles (1993), a void
with a negative perturbation \delta may evolve as a separate homogeneous
universe with a local expansion parameter H_V\simeq H_0(1-\delta/3). This
slightly low density ``universe'' will diverge from the mean, producing a void
of ever lower density. As a result, the contents of voids will ``fall'' outward
at a velocity equal to the difference between the local, and the mean expansion
parameters times the radius of the void. Observational constraints on the
outfall velocity can be placed as a result of the fortuitous event that void,
and non-void hydrogen LyA absorbers have distinct characteristics -- both in
their equivalent width distributions and their Doppler parameter distributions
-- which are clearly distinguished when cloud environments are measured in
terms of the sum of the tidal fields of surrounding galaxies acting on the
cloud (Manning 2002). These constraints dictate that the radial outfall
velocity from an average void of radius ~ 15 h_{75}^{-1} Mpc must be less than
\~100 km/s. The implications of this are probed with a ``negative'' top-hat
simulation, using a 1-D Lagrangian code, to determine the relationship between
the mass deficit in voids and the local expansion parameter in a flat lambda
cosmology. The outfall velocity constraint shows that the void matter density
must be greater than 75% of the mean matter density. I argue that this implies
that \Omega_m >~ 0.86$. Thus the total amount of matter in voids is of order
twice the total mass in the filamentary structures.


title: WIMP Stars as Dark Matter in the Universe

abstract:
  It is suggested that Dark Matter in the Universe is made of stars and black
holes of WIMP matter.


title:
Constraints on the Star Formation Rate from Supernova Relic Neutrino
  Observations

abstract:
  We discuss the implication of the observation of supernova relic neutrinos on
the study of the star formation rate (SFR) in galaxies. The limit recently
obtained at Super-Kamiokande (SK) is already marginally significant: The SFR we
derived $\psi(t_0)<0.040M_{\odot}$yr$^{-1}$Mpc$^{-3}$(at a 90% CL) is about
twice the SFR estimated from radio observations, and five times the rate from
H$\alpha$ allowing for uncertainties in the model supernova neutrino flux.


title: ASTRO-F/FIS Observing Simulation: Detection Limits for Point Sources

abstract:
  We describe the observing simulation software FISVI (FIS Virtual Instrument),
which was developed for the Far-Infrared Surveyor (FIS) that will be on the
Japanese infrared astronomy mission ASTRO-F. The FISVI has two purposes: one is
to check the specifications and performances of the ASTRO-F/FIS as a whole; the
other is to prepare input data sets for the data analysis softwares prior to
launch. In the FISVI, special care was taken by introducing the "Compiled PSF
(Point Spread Function)" to optimise inevitable, but time-consuming,
convolution processes. With the Compiled PSF, we reduce the computation time by
an order of magnitude. The photon and readout noises are included in the
simulations. We estimate the detection limits for point sources from the
simulation of virtual patches of the sky mostly consisting of distant galaxies.
We studied the importance of source confusion for simple power-law models for
N(>S), the number of sources brighter than S. We found that source confusion
plays a dominant role in the detection limits only for models with rapid
luminosity evolution for the galaxy counts, the evolution of which is suggested
by recent observations.


title: Scaling up Tides in Numerical Models of Galaxy- and Halo-Formation

abstract:
  The purpose of this article is to show that when dynamically cold,
dissipationless self-gravitating systems collapse, their evolution is a strong
function of the symmetry in the initial distribution. We explore with a set of
pressure-less homogeneous fluids the time-evolution of ellipsoidal
distributions and map the depth of potential achieved during relaxation as
function of initial ellipsoid axis ratios. We then perform a series of $N$-body
numerical simulations and contrast their evolution with the fluid solutions. We
verify an analytic relation between collapse factor ${\cal C}$ and particle
number $N$ in spherical symmetry, such that ${\cal C} \propto N^{1/3}$. We
sought a similar relation for axisymmetric configurations, and found an
empirical scaling relation such that ${\cal C} \propto N^{1/6}$ in these cases.
We then show that when mass distributions do not respect spherical- or
axial-symmetry, the ensuing gravitational collapse deepens with increasing
particle number $N$ but only slowly: 86% of triaxial configurations may
collapse by a factor of no more than 40 as $N\to\infty$. For $N\approx 10^5$
and larger, violent relaxation develops fully under the Lin-Mestel-Shu
instability such that numerical $N$-body solutions now resolve the different
initial morphologies adequately.


title: Multi-object spectroscopy of low redshift EIS clusters. I

abstract:
  We report the results of the first multi-object spectroscopic observations at
the Danish 1.54m telescope at La Silla, Chile. Observations of five cluster
candidates from the ESO Imaging Survey Cluster Candidate Catalog are described.
  From these observations we confirm the reality of the five clusters with
measured redshifts of 0.11<=z<=0.35. We estimate velocity dispersions in the
range 294-621km/s indicating rather poor clusters. This, and the measured
cluster redshifts are consistent with the results of the matched filter
procedure applied to produce the Cluster Candidate Catalog.


title:
Spin-down of Relativistic Stars with Phase Transitions and PSR
  J0537-6910

abstract:
  Using a highly accurate numerical code, we study the spin down of rotating
relativistic stars, undergoing a quark deconfinement phase transition. Such
phase transitions have been suggested to yield an observable signal in the
braking index of spinning-down pulsars, which is based on a ``backbending''
behaviour of the moment of inertia. We focus on a particular equation of state
that has been used before to study this behaviour, and find that for the
population of normal pulsars the moment of inertia does not exhibit a
backbending behaviour. In contrast, for supramassive millisecond pulsars a very
strong backbending behaviour is found. Essentially, once a quark core appears
in a spinning-down supramassive millisecond pulsar, the star spins up and
continues to do so until it reaches the instability to collapse. This strong
spin-up behaviour makes it easier to distinguish a phase transition in such
pulsars: a negative first time-derivative of the rotational period suffices and
one does not have to measure the braking index. In the spin-up era, the usually
adopted spin-down power law fails to describe the evolution of the angular
velocity. We adopt a general-relativistic spin-down power law and derive the
equations that describe the angular velocity and braking index evolution in
rapidly rotating pulsars.


title: Chemical Processes in Cometary Comae

abstract:
  Recent developments in the chemical modelling of cometary comae are
described. We discuss the cyanide chemistry and present new HCN observations of
the recent comet C/2002 C1 (Ikeya-Zhang). The connection between interstellar
and cometary organic molecules is discussed from the perspective of recent
theories of interstellar gas-grain chemistry.


title: V39: an unusual object in the field of IC 1613

abstract:
  The variable star V39 in the field of IC 1613 is discussed in the light of
the available photometric and new spectroscopic data. It has strong emission
Balmer lines, and the observed characteristics could be explained by a W Vir
pulsating star with a period of 14.341 d, located at more than 115 kpc, that is
in the very outer halo of our Galaxy. It should have an apparent companion, a
long period (1118d) red variable, belonging to IC 1613. The main uncertainty in
this interpretation is an emission feature at 668.4 nm, which we tentatively
identified as a He I line.


title: Dynamical Confirmation of SDSS Weak Lensing Scaling Laws

abstract:
  Galaxy masses can be estimated by a variety of methods; each applicable in
different circumstances, and each suffering from different systematic
uncertainties. Confirmation of results obtained by one technique with analysis
by another is particularly important. Recent SDSS weak lensing measurements of
the projected-mass correlation function reveal a linear relation between galaxy
luminosities and the depth of their dark matter halos (measured on 260 \hinv
kpc scales). In this work we use an entirely independent dynamical method to
confirm these results. We begin by assembling a sample of 618 relatively
isolated host galaxies, surrounded by a total of 1225 substantially fainter
satellites. We observe the mean dynamical effect of these hosts on the motions
of their satellites by assembling velocity difference histograms. Dividing the
sample by host properties, we find significant variations in satellite velocity
dispersion with host luminosity. We quantify these variations using a simple
dynamical model, measuring \mtsd a dynamical mass within 260 \hinv kpc. The
appropriateness of this mass reconstruction is checked by conducting a similar
analysis within an N-body simulation. Comparison between the dynamical and
lensing mass-to-light scalings shows reasonable agreement, providing some
quantitative confirmation for the lensing results.


title: Tables of the partition functions for iron, Fe I -- Fe X

abstract:
  We present extensive tables of the Atomic Partition Function for iron ions,
Fe I -- Fe X, and discuss details of the computational method. Partition
functions are given in wide range of temperatures, 10^3 K < T < 10^6 K, and
lowering of ionization energy (0.001 eV < LIE < 5.0 eV). Our APF take into
account all energy levels predicted by quantum mechanics, including
autoionization levels. The tables can be applied for the computations of model
stellar atmospheres and theoretical spectra over all existing spectral and
luminosity classes.


title: High-resolution X-ray spectroscopy of Procyon by Chandra and XMM-Newton

abstract:
  We report the analysis of the high-resolution soft X-ray spectrum of the
nearby F-type star Procyon in the wavelength range from 5 to 175 Angstrom
obtained with the Low Energy Transmission Grating Spectrometer (LETGS) on board
Chandra and with the Reflection Grating Spectrometers (RGS) and the EPIC-MOS
CCD spectrometers on board XMM-Newton. Line fluxes have been measured
separately for the RGS and LETGS. Spectra have been fitted globally to obtain
self-consistent temperatures, emission measures, and abundances. The total
volume emission measure is ~4.1 x 10e50/cm3 with a peak between 1 and 3 MK. No
indications for a dominant hot component (T > 4 MK) were found. We present
additional evidence for the lack of a solar-type FIP-effect, confirming earlier
EUVE results.


title:
Hydrogen column density evaluations toward Capella: consequences on the
  interstellar deuterium abundance

abstract:
  The deuterium abundance evaluation in the direction of Capella has for a long
time been used as a reference for the local interstellar medium (ISM) within
our Galaxy. We show here that broad and weak HI components could be present on
the Capella line of sight, leading to a large new additional systematic
uncertainty on the N(HI) evaluation.
  The D/H ratio toward Capella is found to be equal to 1.67 (+/-0.3)x10^-5 with
almost identical chi^2 for all the fits (this range includes only the
systematic error; the 2 sigma statistical one is almost negligible in
comparison). It is concluded that D/H evaluations over HI column densities
below 10^19 cm^-2 (even perhaps below 10^20 cm^-2 if demonstrated by additional
observations) may present larger uncertainties than previously anticipated. It
is mentionned that the D/O ratio might be a better tracer for DI variations in
the ISM as recently measured by the Far Ultraviolet Spectroscopic Explorer
(FUSE).


title: Dim Matter in the Disks of Low Surface Brightness Galaxies

abstract:
  An attempt is made to set constraints on the otherwise ambiguous
decomposition of the rotation curves of low surface brightness galaxies into
contributions due to the various components of the galaxies. For this purpose
galaxies are selected which show clear spiral structure. Arguments of density
wave theory of galactic spiral arms are then used to estimate the masses of the
galactic disks. These estimates seem to indicate that the disks of low surface
brightness galaxies might be much more massive than currently thought. This
unexpected result contradicts stellar population synthesis models. This would
also mean that low surface brightness galaxies are not dominated by dark matter
in their inner parts.


title:
Search for sub-electronvolt solar axions using coherent conversion of
  axions into photons in magnetic field and gas helium

abstract:
  A search for solar axions has been performed using an axion helioscope which
is equipped with a 2.3m-long 4T superconducting magnet, PIN-photodiode X-ray
detectors, and a telescope mount mechanism to track the sun. In addition, a gas
container to hold dispersion-matching gas has been developed and a mass region
up to m_a=0.27eV was newly explored. From the absence of any evidence, analysis
sets a limit on axion-photon coupling constant to be
$g_{a\gamma\gamma}<6.8-10.9\times10^{-10}GeV^{-1}$ for the axion mass of
0.05<m_a<0.27eV at 95% confidence level, which is more stringent than the limit
inferred from the solar-age consideration. This result gives currently the most
stringent observational limit on the existence of solar axions in this mass
region.


title:
Evidence for Shock Acceleration and Intergalactic Magnetic Fields in a
  Large-Scale Filament of Galaxies ZwCl 2341.1+0000

abstract:
  We report the discovery of large-scale diffuse radio emission from what
appears to be a large-scale filamentary network of galaxies in the region of
cluster ZwCl 2341.1+0000, and stretching over an area of at least $6
h^{-1}_{50}$ Mpc in diameter. Multicolour CCD observations yield photometric
redshifts indicating that a significant fraction of the optical galaxies in
this region is at a redshift of z=0.3. This is supported by spectroscopic
measurements of 4 galaxies in the SDSS survey at a mean z=0.27. We present VLA
images at 20 cm (NVSS) and 90 cm wavelengths, showing the detailed radio
structure of the filaments. Comparison with the VLA high resolution FIRST radio
survey shows that the diffuse emission is not due to known individual point
sources. The diffuse radio-emission has a spectral index $\alpha \lesssim
-0.5$, and is most likely synchrotron emission from relativistic charged
particles in an inter-galactic magnetic field. Furthermore, this optical/radio
structure is detected in X-rays by the ROSAT all-sky survey. It has a 0.1--2.4
keV luminosity of about $10^{44}$ erg s$^{-1}$ and shows an extended highly
non-relaxed morphology. These observations suggest that ZwCl 2341.1+0000 is
possibly a proto-cluster of galaxies in which we are witnessing the process of
structure formation. We show (both analytically and by numerical simulations)
that the energetics of accretion shocks generated in forming large-scale
structures are sufficient to produce enough high energy cosmic-ray (CR)
electrons required to explain the observed radio emission, provided a magnetic
field of strength of about 1 micro Gauss is present there.Thus it is the first
evidence of cosmic-ray particle acceleration and magnetic fields occuring on a
super-cluster scale. (Abridged)


title:
On Be Star Candidates and Possible Blue Pre-Main Sequence Objects in the
  Small Magellanic Cloud

abstract:
  Recently the OGLE experiment has provided accurate light curves and colours
for about 2 millions stars in the Small Magellanic Cloud. We have examined this
database for its content of Be stars, applying some selection criteria, and we
have found a sample of $\sim$ 1000 candidates. Some of these stars show
beautiful light curves with amazing variations never observed in any Galactic
variable. We find outbursts in 13% of the sample (Type-1 stars), high and low
states in 15%, periodic variations in 7%, and the usual variations seen in
Galactic Be stars in 65% of the cases. The Galactic counterparts of Type-1
objects could be the outbursting Be stars found by Hubert & Floquet (1998)
after the analysis of Hipparcos photometry. We discuss the possibility that
Type-1 stars could correspond to Be stars with accreting white dwarf companions
or alternatively, blue pre-main sequence stars surrounded by thermally unstable
accretion disks. We provide coordinates and basic photometric information for
these stars and some examples of light curves.


title:
A two-dimensional Kolmogorov-Smirnov test for crowded field source
  detection: ROSAT sources in NGC 6397

abstract:
  We present a two-dimensional version of the classical one-dimensional
Kolmogorov-Smirnov (K-S) test, extending an earlier idea due to Peacock (1983)
and an implementation proposed by Fasano & Franceschini (1987). The
two-dimensional K-S test is used to optimise the goodness of fit in an
iterative source-detection scheme for astronomical images. The method is
applied to a ROSAT/HRI x-ray image of the post core-collapse globular cluster
NGC 6397 to determine the most probable source distribution in the cluster
core. Comparisons to other widely-used source detection methods, and to a
Chandra image of the same field, show that our iteration scheme is superior in
measuring statistics-limited sources in severely crowded fields.


title:
In Dust We Trust: An Overview of Observations and Theories of
  Interstellar Dust

abstract:
  The past century of interstellar dust has brought us from first ignoring it
to finding that it is an important component of the interstellar medium and
plays an important role in the evolution of galaxies, the formation of stars
and planetary systems, and possibly, the origins of life. Current observational
results in our galaxy provide a complex physical and chemical evolutionary
picture of interstellar dust starting with the formation of small refractory
particles in stellar atmospheres to their modification in diffuse and molecular
clouds and ultimately to their contribution to star forming regions. In this
review, a brief history of the studies of interstellar dust is presented. Our
current understanding of the physical and chemical properties of interstellar
dust are summarized, based on observational evidences from interstellar
extinction, absorption, scattering, polarization, emission (luminescence,
infrared vibrational emission, and microwave rotational emission), interstellar
depletions, and theoretical modelling. Some unsolved outstanding problems are
listed.


title:
Mid-Infrared Spectropolarimetric Constraints on the Core-Mantle
  Interstellar Dust Model

abstract:
  In the framework of the silicate core-carbonaceous organic mantle
interstellar dust model, the bulk of the visual/near-IR extinction and the
entire polarization are from nonspherical and aligned core-mantle grains. The
3.4 micron C-H and 9.7 micron Si-O absorption features, respectively arising
from the hydrocarbon mantle and the amorphous silicate core, are expected to be
polarized to a modestly different degree. Spectropolarimetric observations
toward the same lines of sight both in the 3.4 micron region and in the 9.7
micron region would be of great value to test the core-mantle dust model. The
fact that the 3.4 micron feature is not polarized along the line of sight
toward the Galactic center source IRS 7 is not yet sufficient to reject the
core-mantle model due to the lack of spectropolarimetric observation of this
region in the 9.7 micron region.


title:
Modelling the Astronomical Silicate Features: I. On the Spectrum
  Subtraction Method

abstract:
  The {\it assumption of additive absorptivity} by different components in
compound particles is a widely used method applied in the literature to the
analysis of the chemical and structural properties of astronomical
(circumstellar, interstellar, protostellar, and cometary) silicates as well as
other materials. The errors intrinsic in this additivity assumption, which, in
application to astronomical spectra, amounts in some case to {\it spectrum
subtraction} have not always been adequately considered in previous works on
silicate mineralogy. The failings in the ``{\it spectrum subtraction method''}
(intrinsically the same as the additive absorptivity assumption) are discussed
here in terms of silicate core-ice mantle grains with various shapes. It is
shown that these assumptions result in substantial errors for spherical grains.
For spheroidal grains, the errors are less significant and the spectrum
subtraction method can be used to remove the ice mantle effects. It is
demonstrated that there is no significant improvement by considering a
distribution of spheroidal shapes. It is further shown that the presence of
additional organic mantles substantially modifies the silicate mineralogy
interpretation.


title: Molecular Hydrogen Outflows in W51

abstract:
  We present the results of a deep search for the molecular hydrogen shock
fronts associated with young stellar outflows in the giant molecular cloud and
massive star forming region W51. A total of 14 outflows were identified, and a
few of these were studied in detail with high-resolution imaging and
spectroscopy.


title: Molecular Gas and Star Formation in Lynds 870

abstract:
  We present molecular line and submillimeter dust continuum observations of
the Lynds 870 cloud in the vicinity of IRAS 20231+3440.
  Two submillimeter cores, SMM1 and SMM2, are identified mapping the 870 micron
dust continuum and ammonia emission. The total molecular mass is ~70-110 solar
mass. The northern core is warmer and denser than the southern one. Molecular
outflows are discovered in both cores. In the northern one a significant amount
of low velocity (1.3-2.8 km/s) outflowing gas is found, that is hidden in the
relatively broad CO lines but that is revealed by the narrower HCO+ spectra.
While IRAS 20231+3440 is most likely the exciting star of the northern outflow,
the driving source of the southern outflow is not detected by infrared surveys
and must be deeply embedded in the cloud core. Large scale (~0.2 pc) infall
motion is indicated by blue asymmetric profiles observed in the HCO+ J = 3-2
spectra. Red K_s band YSO candidates revealed by the 2MASS survey indicate
ongoing star formation throughout the cloud. The calculated masses and the
measured degree of turbulence are also reminiscent of clouds forming groups of
stars. The excitation of the molecular lines, molecular abundances, and outflow
properties are discussed. It is concluded that IRAS 20231+3440 is a ClassI
object, while the southern core most likely contains a Class0 source.


title: Measuring Neutron Star Radii with Gravitational Wave Detectors

abstract:
  Coalescing binary neutron stars (NS) are expected to be an important source
of gravitational waves (GW) detectable by laser interferometers. We present
here a simple method for determining the compactness ratio M/R of NS based on
the observed deviation of the GW energy spectrum from point-mass behavior at
the end of an inspiral event. Our method is based on the properties of
quasi-equilibrium binary NS sequences and does not require the computation of
the full GW signal h(t). Combined with the measurement of the NS masses from
the GW signal during inspiral, the determination of M/R will allow very strong
constraints to be placed on the equation of state of nuclear matter at high
densities.


title: An HST Survey of the mid-UV Morphology of Nearby Galaxies

abstract:
  (Abbreviated) We present an imaging survey of 37 nearby galaxies observed
with HST/WFPC2 in the mid-UV F300W filter and in F814W. 11 galaxies were also
imaged in F255W. These galaxies were selected to be detectable with WFPC2 in
one orbit, and cover a wide range of Hubble types and inclinations. The mid-UV
spans the gap between our groundbased optical/NIR images and far-UV images
available from the Astro/UIT missions. Our first qualitative results are:
  (1) Early-type galaxies show a significant decrease in surface brightness
going from the red to the mid-UV, and in some cases the presence of dust lanes.
Some galaxies would be classified different when viewed in the mid-UV, some
become dominated by a blue nuclear feature or point source.
  (2) Half of the mid-type spiral and star-forming galaxies appear as a later
morphological type in the mid-UV, as Astro/UIT also found in the far-UV. Some-
times these differences are dramatic. The mid-UV images show a considerable
range in the scale and surface brightness of individual star-forming regions.
Almost all mid-type spirals have their small bulges bi-sected by a dust-lane.
  (3) Most of the heterogeneous subset of late-type, irregular, peculiar, and
merging galaxies display F300W morphologies that are similar to those seen in
F814W, but with differences due to recognizable dust features absorbing the
bluer light, and due to UV-bright hot stars, star-clusters, and star-forming
ridges.
  In the rest-frame mid-UV, early- to mid-type galaxies are more likely to be
misclassified as later types than vice versa. This morphological K-correction
explains only part of the excess faint blue galaxies seen in deep HST fields.


title:
Extended Star Formation in Dwarf Spheroidal Galaxies: the Cases of
  Draco, Sextans, and Ursa Minor

abstract:
  Star formation and chemical enrichment histories of the dwarf spheroidal
galaxies (dSphs) Draco, Sextans, and Ursa Minor are investigated by means of
chemical evolution models and a simulation code for colour-magnitude diagrams
(CMDs). The CMD simulation code is designed to fully consider effects of the
chemical evolution on stellar evolution and photometric properties. Comparisons
between the chemical evolution models and the observed abundance patterns
reveal that the star formation rates were very low (1-5% of that of the solar
neighbourhood disc) and that the initial star formation continued for a long
duration (> 3.9-6.5 Gyr) in these dSphs. This star formation history can
reproduce morphologies of the observed CMDs, such as narrow red giant branches
and red horizontal branches. Hence, both of the abundance patterns and the
morphologies of the CMDs can be explained by the star formation histories
characterised by the low star formation rate and the long duration of the star
formation period. Because of the low star formation rates, plenty of gas
remains at the final epoch of star formation. We suggest that gas stripping by
the Galaxy results in termination of star formation in the dSphs.


title: Structure of Possible Long-lived Asteroid Belts

abstract:
  High resolution simulations are used to map out the detailed structure of two
long-lived stable belts of asteroid orbits in the inner Solar system. The
Vulcanoid belt extends from 0.09 to 0.20 astronomical units (au), though with a
gaps at 0.15 and 0.18 au corresponding to de-stabilising mean motion resonances
with Mercury and Venus. As collisional evolution proceeds slower at larger
heliocentric distances, kilometre-sized or larger Vulcanoids are most likely to
be found in the region between 0.16 and 0.18 au. The optimum location in which
to search for Vulcanoids is at geocentric ecliptic longitudes roughly between 9
and 10 degrees. Dynamically speaking, the Earth-Mars belt between 1.08-1.28 au
is an extremely stable repository for asteroids on nearly circular orbits. It
is interrupted at 1.21 au due to the 3:4 commensurability with the Earth, while
secular resonances with Saturn are troublesome beyond 1.17 au. These detailed
maps of the fine structure of the belts can be used to plan search
methodologies. Strategies for detecting members of the belts are discussed,
including the use of infrared wide-field imaging with VISTA, and forthcoming
European Space Agency satellite missions like GAIA and BepiColombo.


title:
Dust in the Photospheric Environment: Unified Cloudy Models of M, L, and
  T Dwarfs

abstract:
  We address the problem of how dust forms and how it could be sustained in the
static photospheres of cool dwarfs for a long time. In the cool and dense gas,
dust forms easily at the condensation temperature, T_cond, and the dust can be
in detailed balance with the ambient gas so long as it remains smaller than the
critical radius, r_cr. However, dust will grow larger and segregate from the
gas when it will be larger than r_cr somewhere at the lower temperature, which
we refer to as the critical temperature, T_cr. Then, the large dust grains will
precipitate below the photosphere and only the small dust grains in the region
of T_cr < T < T_cond can be sustained in the photosphere. Thus a dust cloud is
formed. Incorporating the dust cloud, non-grey model photo- spheres in
radiative-convective equilibrium are extended to T_eff as low as 800K. Observed
colors and spectra of cool dwarfs can consistently be accounted for by a single
grid of our cloudy models. This fact in turn can be regarded as supporting
evidence for our basic assumption on the cloud formation.


title: Two-stream Instability in Pulsar Magnetospheres

abstract:
  Creation of electron-positron pairs near the pulsar surface and the
parameters of plasma in pulsar magnetospheres are discussed. It is argued that
the pair creation process is nonstationary, and the pair plasma that flows out
from the pulsar environment is strongly nonhomogeneous and gathers into
separate clouds. Plasma instabilities in the outflowing plasma are reviewed.
The two-stream instability that develops due to strong nonhomogeneity of the
outflowing plasma is the most plausible reason for the generation of coherent
radio emission of pulsars. The development of the two-stream instability in
pulsar magnetospheres is considered.


title:
Rotation of Hot Horizontal Branch Stars in the Globular Clusters NGC
  1904, NGC 2808, NGC 6093 and NGC 7078

abstract:
  We present high resolution UVES+VLT spectroscopic observations of 56 stars in
the extended horizontal branch (EHB) of the Galactic globular clusters NGC
1904, NGC 2808, NGC 6093, and NGC 7078. Our data reveal for the first time the
presence in NGC 1904 of a sizable population of fast (vsini > 20 km/s)
horizontal branch (HB) rotators, confined to the cool end of the EHB, similar
to that found in M13. We also confirm the fast rotators already observed in NGC
7078. The cooler stars (Teff < 11,500 K) in these three clusters show a range
of rotation rates, with a group of stars rotating at ~ 15 km/s or less, and a
fast rotating group at ~ 30 km/s. Apparently, the fast rotators are relatively
more abundant in NGC 1904 and M13, than in NGC 7078. No fast rotators have been
identified in NGC 2808 and NGC 6093. All the stars hotter than Teff ~ 11,500 K
have projected rotational velocities vsini < 12 km/s, but less than 20% have
vsini < 2 km/s. The connection between photometric gaps in the HB and the
change in the projected rotational velocities is not confirmed by the new data.
However, our data are consistent with a relation between this discontinuity and
the HB jump. We discuss a number of possibilities for the origin of the stellar
rotation distribution along the HB. We conclude that none of them can yet
provide a satisfactory explanation of the observations.


title: The ROTSE-IIIa Telescope System

abstract:
  We report on the current operating status of the ROTSE-IIIa telescope,
currently undergoing testing at Los Alamos National Laboratories in New Mexico.
It will be shipped to Siding Spring Observatory, Australia, in first quarter
2002. ROTSE-IIIa has been in automated observing mode since early October,
2001, after completing several weeks of calibration and check-out observations.
Calibrated lists of objects in ROTSE-IIIa sky patrol data are produced
routinely in an automated pipeline, and we are currently automating analysis
procedures to compile these lists, eliminate false detections, and
automatically identify transient and variable objects. The manual application
of these procedures has already led to the detection of a nova that rose over
six magnitudes in two days to a maximum detected brightness of m_R~13.9 and
then faded two magnitudes in two weeks. We also readily identify variable
stars, includings those suspected to be variables from the Sloan Digital Sky
Survey. We report on our system to allow public monitoring of the telescope
operational status in real time over the WWW.


title: X-ray spectra produced by a hot plasma containing cold clouds

abstract:
  We compute the hard X-ray spectra from a hot plasma pervaded by small cold
dense clouds. The main cooling mechanism of the plasma is Compton cooling by
the soft thermal emission from the clouds. We compute numerically the
equilibrium temperature of the plasma together with the escaping spectrum. The
spectrum depends mainly on the amount of cold clouds filling the hot phase. The
clouds covering factor is constrained to be low in order to produce spectra
similar to those observed in Seyfert galaxies and X-ray binaries, implying that
an external reflector is required in order to reproduce the full range of
observed reflection amplitudes. We also derive analytical estimates for the
X-ray spectral slope and reflection amplitude using an escape probability
formalism.


title: Gamma-Ray Burst Afterglow emission with a decaying magnetic field

abstract:
  In models for gamma ray burst afterglows, it is normally assumed that the
external shock strongly amplifies the magnetic field and that this field
maintains a steady value throughout the shocked region. We discuss the effects
of modifying this (probably simplistic) assumption by allowing for a short
decay time. The observations are incompatible with a post-shock field that
decays too rapidly. However if the field pervades only a few percent of the
total thickness of the shocked shell (and the electrons undergo only inverse
Compton losses in the remainder) the model could be compatible with data. This
would suggest a strong dependence of model parameters on the uncertainties of
shock physics, therefore calling for independent external density estimates. We
claim that afterglow emission should be instead seen as a laboratory where we
can understand relativistic shock physics. The model we propose here together
with afterglow observations in all wavebands could help to pin down the field
structure.


title: The E-peak distribution of the GRBs detected by HETE FREGATE instrument

abstract:
  The FREGATE gamma ray detector of HETE-2 is sensitive to photons between 6
and 400 keV. This sensitivity range, extended towards low energies, allows us
to explore the emission of GRBs in hard X-rays. We fit the spectra of 23 GRBs
with Band's spectral function in order to derive the distribution of their peak
energies (E-peak). This distribution is then compared with the E-peak
distributions measured by BATSE and GINGA.


title:
Element abundances in cool white dwarfs. II. Ultraviolet observations of
  DZ white dwarfs

abstract:
  We present a small data base of homogeneously derived photospheric element
abundances of DZ white dwarfs and related objects. Our previous investigations
are supplemented with the analysis of ultraviolet spectra for nine white
dwarfs. Of particular interest is the detection of Lalpha absorption in van
Maanen 2 and a determination of the effective temperature of this star. The new
value is about 1000K lower than previous results due to the strong ultraviolet
absorption by metals which has to be considered consistently. The metal
abundances of our sample stars are compatible with the predictions from the
two-phase accretion model of Dupuis et al. (1992, 1993). Small deviations can
be observed for the abundance ratios in some objects. This could indicate
non-solar metal-to-metal ratios in the accreted material. Hydrogen can be
detected in virtually all of our objects. However, its average accretion rate
must be at least two orders of magnitude lower than the metal accretion rate.


title:
Discovery of Millisecond Variability in the Neutron-Star X-Ray Transient
  SAX J1750.8-2900

abstract:
  We report the discovery of millisecond oscillations in the X-ray emission
from the X-ray transient SAX J1750.8-2900. Millisecond quasiperiodic
oscillations (kHz QPOs) were present in the persistent emission with
frequencies ranging from 543 Hz to 1017 Hz. Oscillations at a frequency of
600.75 Hz were present in the brightest X-ray burst observed. We derive an
upper limit on the source distance of 6.3 +/- 0.7 kpc from this X-ray burst.


title:
Homogeneous age dating of 55 Galactic globular clusters. Clues to the
  Galaxy formation mechanisms

abstract:
  We present homogeneous age determinations for a large sample of 55 Galactic
globular clusters, which constitute about 30% of the total Galactic population.
A study of their age distribution reveals that all clusters from the most metal
poor ones up to intermediate metallicities are coeval, whereas at higher [Fe/H]
an age spread exists, together with an age-metallicity relationship. At the
same time, all clusters within a certain galactocentric distance appear coeval,
whereas an age spread is present further away from the Galactic centre, without
any correlation with distance. The precise value of [Fe/H] and galactocentric
distance for the onset of the age spread and the slope of the age-metallicity
relationship are strongly affected by the as yet uncertain [Fe/H] scale. We
discuss how differences in the adopted [Fe/H] scale and cluster sample size may
explain discrepant results about the clusters age distribution reached by
different authors. Taking advantage of the large number of objects included in
our sample, we also tested the possibility that age is the global second
parameter which determines the Horizontal Branch morphology, and found
indications that age could explain the global behaviour of the second parameter
effect.


title:
First results from dark matter search experiment with LiF bolometer at
  Kamioka Underground Laboratory

abstract:
  Tokyo group has performed first underground dark matter search experiment in
2001 through 2002 at Kamioka Observatory(2700m.w.e). The detector is eight LiF
bolometers with total mass 168g aiming for the direct detection of WIMPs via
spin-dependent interaction. With a total exposure of 4.1 kg days, we derived
the limits in the a_p-a_n (WIMP-nucleon couplings) plane and excluded a large
part of the parameter space allowed by the UKDMC experiment.


title:
Model atmospheres for type Ia supernovae: Basic steps towards realistic
  synthetic spectra

abstract:
  Type Ia supernovae are an important tool for studying the expansion history
of the universe. Advancing our yet incomplete understanding of the explosion
scenario requires detailed and realistic numerical models in order to interpret
and analyze the growing amount of observational data. Here we present first
results of our new NLTE model calculations for the expanding atmospheres of
type Ia supernovae that employ a detailed and consistent treatment of all
important NLTE effects as well as line blocking and blanketing. The comparison
of the synthetic spectra resulting from these models with observed data shows
that the employed methods represent an important step towards a more realistic
description of the atmospheres of supernovae Ia.


title:
Molecular Gas in Candidate Double Barred Galaxies I. The Diverse
  Morphology and Dynamics of NGC 2273 and NGC 5728

abstract:
  Double bars have been proposed as a means of transporting molecular gas past
inner Lindblad resonances into the nuclear regions, where it can fuel active or
starburst nuclei. Thus far, the existence of double bars has been determined
predominantly through analysis of near infrared images, which can tell us
little about the dynamics and inflow rates of these systems. We have observed
two double bar galaxy candidates (NGC 2273 and NGC 5728) in CO J=1-0 with the
Owens Valley Radio Observatory Millimeter Array. Despite the similarity in the
near infrared images of these galaxies, we see rather different nuclear
morphologies in the CO maps. NGC 2273 shows evidence of a nuclear gas bar,
aligned with the nuclear stellar bar seen in the near infrared images. Both the
nuclear gaseous and stellar bars are misaligned from the large scale bar by
approximately 90 degrees, which also allows the possibility that both are the
result of stars and gas populating the $x_2$ orbits of the primary bar.
Estimates using dynamical friction arguments and star formation rates suggest
significant gas inflow rates along the nuclear bar of NGC 2273. Conversely, NGC
5728 does not show any evidence for a nuclear molecular bar, but shows an arc
of CO clumps that peaks just to the south-west of the dynamical center and
curves to the south-east where it follows the dust lane to the south. Models of
double-barred galaxies suggest that these galaxies should contain large amounts
of molecular gas in their nuclei. Our calculations suggest that both galaxies
contain sufficient amounts of gas in their nuclei, but only NGC 2273 shows
evidence for a nuclear gas bar. This may be the result of past episodes of star
formation exhausting and dispersing the nuclear gas of NGC 5728, but is more
likely evidence that NGC 5728 has undergone a minor merger event.


title: The Inner Scale Length of Spiral Galaxy Rotation Curves

abstract:
  We use the tapering effect of Halpha/[NII] rotation curves of spiral galaxies
first noted by Goad & Roberts (1981) to investigate the internal extinction in
disks. The scale length of exponential fits to the inner part of rotation
curves depends strongly on the disk axial ratio. Preliminary modelling of the
effect implies substantial opacity of the central parts of disks at a
wavelength of 0.66 \mu. In addition, the average kinematic scale length of
rotation curves, when corrected to face--on perspective, has a nearly constant
value of about 1.7 h^{-1} kpc, for all luminosity classes. The interpretation
of that effect, as the result of the increasing dominance of the baryonic mass
in the inner parts of galaxies, yields a mean baryonic mass--to--light ratio in
the I band \Upsilon_I= 2.7h M_sun/L_{sun,I}, within the inner 1.7 h^{-1} kpc of
disks.


title: A Peculiar Linear Radio Feature in the Supernova Remnant N206

abstract:
  We present images of the supernova remnant N206 in the LMC, taken with ATCA
at wavelengths of 3 and 6 cm. Based on our data and previously published flux
densities, the spectral index of N206 is -0.20 +- 0.07. The 6-cm radio
morphology shows a filled center. Most interesting is the discovery of a
peculiar linear feature previously undetected at any wavelength. The feature
lies to the east of the center of the remnant, stretching from about one-fourth
to three-fourths of the remnant's radius. It is wedge-shaped, with a steady
opening angle from an apex on the eastern side. The feature resembles the
disturbance expected from an object moving through the material supersonically
at about 800 km/s. We present arguments suggesting that the linear feature
might have been produced by a low-mass star or compact object ejected from a
binary system which may have led to a Type Ic supernova.


title: Merger Sites of Double Neutron Stars and their Host Galaxies

abstract:
  Using the StarTrack population synthesis code we analyze the formation
channels possibly available to double neutron star binaries and find that they
can be richer than previously thought. We identify a group of short lived,
tight binaries, which do not live long enough to escape their host galaxies,
despite their large center-of-mass velocities. We present our most recent
results on all possible evolutionary paths leading to the formation of double
neutron stars, calculate their coalescence rates, and also revisit the question
of the distribution of merger sites around host galaxies. For a wide variety of
binary evolution models and galaxy potentials, we find that most of neutron
star mergers take place within galaxies. Our results stem from allowing for
radial and common envelope evolution of helium-rich stars (testable in the
future with detailed stellar-structure and hydrodynamic calculations) and
indicate that double neutron star binaries may not be excluded as Gamma-Ray
Burst (GRB) progenitors solely on the basis of their spatial distribution
around host galaxies. We also find, in contrast to Bethe & Brown (1998), that
in a significant fraction of common envelope (CE) phases neutron stars do not
accrete enough material to become black holes, and thus the channels involving
CEs are still open for the formation of double neutron stars.


title: The Great PV Ceph Outflow: A Case Study in Outflow-Cloud Interaction

abstract:
  We present a set of detailed molecular line maps of the region associated
with the giant Herbig-Haro flow HH 315, from the young star PV Cephei, aimed at
studying the outflow-cloud interaction. Our study clearly shows that the HH 315
flow is effecting the kinematics of its surrounding medium, and has been able
to redistribute considerable amounts of the surrounding medium-density gas in
its star-forming core as well at parsec-scale distances from the source. The
giant molecular outflow HH 315 is a highly asymmetric bipolar flow with a
projected linear extent of about 2 pc. Our results indicate that the two
outflow lobes are each interacting with the ambient medium in different ways.
The southern (redshifted) lobe interacts with a dense ambient medium, very
close to the young stellar outflow source, and its kinetic energy is comparable
to both the turbulent and gravitational binding energy of its host cloud. In
addition, we find evidence that the southern lobe is responsible for the
creation of a cavity in the 13CO emission. In contrast, the northern (mainly
blueshifted) outflow lobe extends farther from PV Ceph and interacts with
ambient gas much less dense than the southern lobe. There is very little 13CO
emission north of the outflow source, and the only prominent 13CO emission is a
shell-like structure coincident with the outer edge of the northern lobe, about
1.2 pc northwest of PV Ceph. It appears that the northern lobe of the HH 315
outflow has been able to ``push'' aside a substantial fraction of the gas in
the area, piling it in a dense shell-like structure at its edges. In addition,
we find that the northern outflow lobe is responsible for a velocity gradient
in the ambient gas.


title:
High Resolution X-ray Spectroscopy and the Nature of Warm Absorbers in
  AGN

abstract:
  Although soft X-ray absorption features in AGN were discovered almost ten
years ago, the nature and location of the gas creating them has remained
controversial. However, by making use of the newly-available high-resolution
spectra provided by XMM-Newton and Chandra, we should be able to make
substantial advances. The first such spectra indicate that multiple ionization
states coexist in the absorber; this is a natural consequence of
photoionization physics. Photoionized evaporation in the presence of a copious
mass source locks the ratio of ionizing intensity to pressure to a critical
value. A broad range of temperatures can all coexist in equilibrium for this
value of the ratio of ionizing intensity to pressure. Consequently, the flow is
expected to be strongly inhomogeneous in temperature. The inferred distance of
this material from the source of ionizing radiation depends on how much matter
exists at the highest-obtainable temperature. This distance can be measured by
monitoring how ionic column densities respond to changes in the ionizing
continuum on timescales of days to years.


title: Nearby quasar remnants and ultra-high energy cosmic rays

abstract:
  As recently suggested, nearby quasar remnants are plausible sites of
black-hole based compact dynamos that could be capable of accelerating
ultra-high energy cosmic rays (UHECRs). In such a model, UHECRs would originate
at the nuclei of nearby dead quasars, those in which the putative underlying
supermassive black holes are suitably spun-up. Based on galactic optical
luminosity, morphological type, and redshift, we have compiled a small sample
of nearby objects selected to be highly luminous, bulge-dominated galaxies,
likely quasar remnants. The sky coordinates of these galaxies were then
correlated with the arrival directions of cosmic rays detected at energies $>
40$ EeV. An apparently significant correlation appears in our data. This
correlation appears at closer angular scales than those expected when taking
into account the deflection caused by typically assumed IGM or galactic
magnetic fields over a charged particle trajectory. Possible scenarios
producing this effect are discussed, as is the astrophysics of the quasar
remnant candidates. We suggest that quasar remnants be also taken into account
in the forthcoming detailed search for correlations using data from the Auger
Observatory.


title: Keck Spectroscopy of Globular Clusters in the Sombrero Galaxy

abstract:
  We analyze high signal-to-noise spectra for 14 globular clusters (GCs) in the
Sombrero galaxy, NGC 4594 = M104, obtained with the LRIS spectrograph on the
Keck I telescope. We find generally good agreement between spectroscopic
metallicities and previous photometric metallicities based on V-I colors.
Further, we use measurements of various Balmer line indices on co-added spectra
of metal-poor and metal-rich GCs to estimate ages for the GC subpopulations and
find ages of 10-15 Gyr, with preferred ages around 11-12 Gyr and no detectable
differences between the metal-rich and metal-poor subpopulations. However,
because of model and measurement uncertainties, age differences of a few (2-3)
Gyrs cannot be be ruled out. We also measure alpha-to-iron abundance ratios
from Mg and TiO features and find enhancements on the order of +0.4 dex
relative to the Sun, similar to the alpha/Fe abundance ratios observed in other
old stellar populations. Finally, we combined our sample with radial velocities
for 34 GCs from Bridges et al. 1997 and obtain virial and projected masses for
the Sombrero of M(Vir) = 8.1+/-1.8 x 10^11 M(sun) and M(P) = 5.3+/-1.0 x 10^11
Msun within 17 kpc, respectively. Using 12 clusters within the central 4.5 kpc,
the corresponding numbers are M(Vir) = 2.1+/-1.1 x 10^11 Msun and M(P) =
2.0+/-1.3 x 10^11 Msun.


title:
The Scintillation Velocity of the Relativistic Binary Pulsar PSR
  J1141-6545

abstract:
  We report a dramatic orbital modulation in the scintillation timescale of the
relativistic binary pulsar J1141--6545 that both confirms the validity of the
scintillation speed methodology and enables us to derive important physical
parameters. We have determined the space velocity, the orbital inclination and
even the longitude of periastron of the binary system, which we find to be in
good agreement with that obtained from pulse timing measurements. Our data
permit two equally-significant physical interpretations of the system. The
system is either an edge-on binary with a high space velocity ($\sim 115$ km
s$^{-1}$) or is more face-on with a much slower velocity ($\sim 45$ km
s$^{-1}$). We favor the former, as it is more consistent with pulse timing and
the distribution of known neutron star masses. Under this assumption, the
runaway velocity of 115 km s$^{-1}$ is much greater than is expected if pulsars
do not receive a natal kick at birth. The derived inclination of the binary
system is (76\pm 2.5^{\circ}) degrees, implying a companion mass of 1.01 (\pm
)~0.02 M(_{\odot}) and a pulsar mass of 1.29 (\pm)~0.02 M(_{\odot}). Our
derived physical parameters indicate that this pulsar should prove to be an
excellent laboratory for tests of gravitational wave emission.


title:
The acceleration of cosmic-ray protons in the supernova remnant RX
  J1713.7-3946

abstract:
  Protons with energies up to 10^15 eV are the main component[1] of cosmic
rays, but evidence for the specific locations where they could have been
accelerated to these energies has been lacking[2]. Electrons are known to be
accelerated to cosmic-ray energies in supernova remnants[3, 4], and the shock
waves associated with such remnants, when they hit the surrounding interstellar
medium, could also provide the energy to accelerate protons. The signature of
such a process would be the decay of pions (pi0), which are generated when the
protons collide with atoms and molecules in an interstellar cloud: pion decay
results in g-rays with a particular spectral-energy distribution[5, 6]. Here we
report the observation of cascade showers of optical photons resulting
fromg-rays at energies of 10^12 eV hitting Earth's upper atmosphere, in the
direction of the supernova remnant RX J1713.7-3946. The spectrum is a good
match to that predicted by pion decay, and cannot be explained by other
mechanisms.


title:
Searching for the Physical Drivers of Eigenvector-1: From Quasars to
  Nano-Quasars

abstract:
  We point out an analogy between two accreting white dwarfs with jets (CH Cyg
and MWC 560) and powerful quasars. In spite of the enormous difference in the
mass of the central object (a factor about 10^7), the emission lines are
strikingly similar to those of I Zw1 (the prototype "Narrow Line Seyfert 1"
nucleus whose spectrum is widely used as an FeII template for almost all
quasars). The spectral similarity give us the unique possibility to consider
the optical Eigenvector-1 diagram using objects less massive by a factor of
millions. Our results reinforce the interpretation of the "Eigenvector-1
correlations" found for low redshift quasars as driven mainly by the source
luminosity to central compact object mass ratio(L/M). The accreting white
dwarfs CH Cyg and MWC 560, their jets and emission lines, may well represent
the low energy, non relativistic end of the accretion phenomena, which
encompass the most powerful quasars and the microquasars. The remarkable
similarities suggest that they may be legitimately considered "nano-quasars".


title:
Chemical evolution of starburst galaxies: How does star formation
  proceed?

abstract:
  We compute chemical evolution models to constrain the mode and the history of
star formation in starburst galaxies as a whole, i.e. over a large range of
mass and metallicity. To this end, we investigate the origin of the dispersion
observed in the evolution of both nitrogen-to-oxygen abundance ratio and galaxy
luminosity as a function of metallicity for a large sample of starburst
galaxies. We find that the variation of the star formation efficiency, in the
framework of continuous star formation models, produce a scatter equivalent to
what is observed in the N/O versus O/H diagram for low-mass HII galaxies only.
However, continous star formation models are unable to reproduce i) the scatter
observed for massive starburst and UV-selected galaxies in the N/O versus O/H
relation, and ii) the scatter in the luminosity versus O/H scaling relation
observed for the whole sample of starburst galaxies. The dispersion associated
with the distribution of N/O as a function of metallicity, for both low-mass
and massive galaxies, is well explained in the framework of bursting star
formation models. It is interpreted as a consequence of the time-delay between
the ejection of nitrogen and that of oxygen into the ISM. These models also
reproduce the spread observed in the luminosity-metallicity relation.
Metal-rich spiral galaxies differ from metal-poor ones by a higher star
formation efficiency and starburst frequency. Low-mass galaxies experienced a
few bursts of star formation whereas massive spiral galaxies experienced
numerous and extended powerful starbursts (abridged version).


title:
Quasar Microlensing at High Magnification and the Role of Dark Matter:
  Enhanced Fluctuations and Suppressed Saddlepoints

abstract:
  Contrary to naive expectation, diluting the stellar component of the lensing
galaxy in a highly magnified system with smoothly distributed ``dark'' matter
increases rather than decreases the microlensing fluctuations caused by the
remaining stars. For a bright pair of images straddling a critical curve, the
saddlepoint (of the arrival time surface) is much more strongly affected than
the associated minimum. With a mass ratio of smooth matter to microlensing
matter of 4:1, a saddlepoint with a macro-magnification of mu = 9.5 will spend
half of its time more than a magnitude fainter than predicted. The anomalous
flux ratio observed for the close pair of images in MG0414+0534 is a factor of
five more likely than computed by Witt, Mao and Schechter if the smooth matter
fraction is as high as 93%. The magnification probability histograms for
macro-images exhibit distinctly different structure that varies with the smooth
matter content, providing a handle on the smooth matter fraction. Enhanced
fluctuations can manifest themselves either in the temporal variations of a
lightcurve or as flux ratio anomalies in a single epoch snapshot of a multiply
imaged system. While the millilensing simulations of Metcalf and Madau also
give larger anomalies for saddlepoints than for minima, the effect appears to
be less dramatic for extended subhalos than for point masses. Morever,
microlensing is distinguishable from millilensing because it will produce
noticeable changes in the magnification on a time scale of a decade or less.


title:
QSO 2237+0305 VR light curves from Gravitational Lenses International
  Time Project optical monitoring

abstract:
  We present VR observations of QSO 2237+0305 conducted by the GLITP
collaboration from 1999 October 1 to 2000 February 3. The observations were
made with the 2.56 m Nordic Optical Telescope at Roque de los Muchachos
Observatory, La Palma (Spain). The PSF fitting method and an adapted version of
the ISIS subtraction method have been used to derive the VR light curves of the
four components (A-D) of the quasar. The mean errors range in the intervals
0.01-0.04 mag (PSF fitting) and 0.01-0.02 mag (ISIS subtraction), with the
faintest component (D) having the largest uncertainties. We address the
relatively good agreement between the A-D light curves derived using different
filters, photometric techniques, and telescopes. The new VR light curves of
component A extend the time coverage of a high magnification microlensing peak,
which was discovered by the OGLE team.


title: Observation of Kes 27: A Typical Mixed-Morphology SNR

abstract:
  We report here on the observation of Kes 27, a proto-typical mixed-morphology
SNR, using ASCA. It clearly shows a filled-center structure in the X-ray region
while a shell structure in the radio region. There are two radio bright
regions: one is in the center, while the other is in the east rim. The X-ray
intensity peak coincides well with the radio bright region at the center. The
X-ray spectrum was well-fitted by a collisional ionization equilibrium model
with solar abundances. Taking into account the ionization parameter (>10^{12}
cm^{-3} s) and the plasma density (0.39 cm^{-3}), we found that the age of the
SNR is longer than 8x10^4 yr. The hardness ratio map indicates that the inner
region shows a harder spectrum than that in the outer region, which does not
come from the heavier interstellar absorption feature, but from the higher
temperature. There is a temperature gradient from the innner region (0.84 keV)
toward outer region (0.59 keV), indicating that the thermal conduction does not
play an important role.


title:
Towards the automated reduction and calibration of SCUBA data from the
  James Clerk Maxwell Telescope

abstract:
  The Submillimetre Common User Bolometer Array (SCUBA) instrument has been
operating on the James Clerk Maxwell Telescope (JCMT) since 1997. The data
archive is now sufficiently large that it can be used to investigate
instrumental properties and the variability of astronomical sources. This paper
describes the automated calibration and reduction scheme used to process the
archive data with particular emphasis on `jiggle-map' observations of compact
sources. We demonstrate the validity of our automated approach at both 850- and
450-microns and apply it to several of the JCMT secondary flux calibrators. We
determine light curves for the variable sources IRC+10216 and OH231.8. This
automation is made possible by using the ORAC-DR data reduction pipeline, a
flexible and extensible data reduction pipeline that is used on UKIRT and the
JCMT.


title: RXTE View of the Starburst Galaxies M82 and NGC 253

abstract:
  The two nearby starburst galaxies M82 and NGC 253 were observed for 100 ksec
over a 10-month period in 1997. An increase of the M82 flux by a factor ~2 was
measured during the period July-November, when compared with the flux measured
earlier in 1997. The flux measured in the field centered on M82 includes ~38 of
the emission from the Seyfert 1 galaxy M81. The best-fitting model for the
earlier emission from M82 is thermal with kT = 6.7 +/- 0.1 keV. In the high
flux state, the emission additionally includes either an absorbed second
thermal component or absorbed power-law component, with the former providing a
much better fit. A likely origin for the temporal variability is a single
source in M82. The flux of NGC 253, which did not vary significantly during the
period of observations, can be well fit by either a thermal spectrum with kT ~
3.8 +/- 0.3 keV, or by a power law with photon index of 2.7 +/- 0.10. We have
also attempted fitting the measurements to more realistic composite models with
thermal and power-law components, such as would be expected from a dominant
contribution from binary systems, or Compton scattering of (far) IR radiation
by radio emitting electrons. However, the addition of any amount of a power-law
component, even with cutoff at 20 keV, only increases chi-square. The 90%
confidence upper limit for power law emission with (photon) index 1.5 is only
2.4% of the 2 -- 10 keV flux of M82; the corresponding limit for NGC 253, with
index 2.0, is 48%.


title:
Near-Infrared Photometric Variability of Stars Toward the Chamaeleon I
  Molecular Cloud

abstract:
  We present the results of a J, H, and K_s photometric monitoring campaign of
a 0.72 x 6 sq deg. area centered on the Chamaeleon I star forming region. Data
were obtained on 15 separate nights over a 4 month time interval using the
2MASS South telescope. Out of a total of 34,539 sources brighter than the
photometric completeness limits (J=16.0, H=15.2, K_s=14.8), 95 exhibit
near-infrared variability in one or more bands. The variables can be grouped
into a population of bright, red objects that are associated with the
Chamaeleon I association, and a population of faint, blue variables that are
dispersed over the full 6 deg of the survey and are likely field stars or older
pre-main-sequence stars unrelated to the present-day Chamaeleon I molecular
cloud. Ten new candidate members of Chamaeleon I, including 8 brown dwarf
candidates, have been identified based on variability and/or near-infrared
excess emission in the J-H vs. H-K_s color-color-diagram. We also provide a
compendium of astrometry and J, H, and K_s photometry for previously identified
members and candidate members of Chamaeleon I.