title:
$JHK'$ Imaging Photometry of Seyfert 1 AGNs and Quasars II: Observation
  of Long-Term Variability

abstract:
  Observations of 226 AGNs in the near-infrared $J$, $H$, and $K'$ bands are
presented along with the analysis of the observations for variability. Our
sample consists mainly of Seyfert 1 AGNs and QSOs. About a quarter of the
objects in each category are radio loud. The AGNs in the entire sample have the
redshifts spanning the range from $z=0$ to 1, and the absolute magnitudes from
$M_B=-29$ to -18. All the objects were observed twice and their variability was
measured by differential photometry.
  A reduction method of differential photometry, optimized to the analysis of
extended images, has been developed. The systematic error in variability
arising from AGNs of highly extended images is estimated to be less than 0.01
mag in each of the $J$, $H$, and $K'$ bands. The systematic error arising from
the flat fielding is negligible for most AGNs, although it is more than 0.1 mag
for some particular cases. The overall average flat fielding error is 0.03 mag
for the image pairs. We find that these systematic errors are superseded by
statistical errors, and the overall average total systematic and statistical
errors amounts to 0.05 mag in the measured variability in each band.
  We find that 58% of all the AGNs in the entire sample show variability of
more than $2\sigma$, and 44% of more than $3\sigma$. This result holds
independent of the $J$, $H$, and $K'$ bands. The detection rate of variability
is higher for a subsample of higher photometric accuracy, and there appears no
limit to this tendency. In particular, when we consider a subsample with small
photometric errors of $\sigma<0.03$ mag, the rate of $2\sigma$ detection is
80%, and 64% for $3\sigma$ detection. This suggests that most AGNs are variable
in the near-infrared.


title:
$JHK'$ Imaging Photometry of Seyfert 1 AGNs and Quasars III: Variability
  of Radio Quiet and Radio Loud AGNs

abstract:
  Variability of 226 AGNs in the near-infrared $J$, $H$, and $K'$ bands is
analyzed and discussed. An ensemble average for measured variabilities was
obtained for various samples of the AGNs divided by absolute $B$-magnitude
$M_B$, redshift $z$, and radio strength. All the samples in the $J$, $H$, and
$K'$ bands are found to give significant ensemble variability, but no
significant wavelength dependence is found. The ensemble variability in the
entire sample combining the $J$, $H$, and $K'$ samples is $\Delta m\approx
0.22$ mag, while $\Delta m\approx 0.18$ mag for the radio-quiet AGNs and
$\Delta m\approx 0.26$ mag for radio-loud AGNs. The ensemble variability for
the radio-quiet AGNs shows no significant $M_B$-dependence, while showing
positive $M_B$-dependence for the radio-loud AGNs. In any samples the measured
variability shows positive correlation among different passbands, with the
correlation coefficients of $r_{JH}$, $r_{HK'}$, and $r_{JK'}$ ranging from 0.6
to 0.9. For radio-quiet AGNs, the coefficient $r_{HK'}$ in a redshift range of
$0.1<z<0.3$ is significantly higher than $r_{JH}$ or $r_{JK'}$. The coefficient
for the radio-loud AGNs with $0.6<z<1.0$ is as high as 0.95, irrespective of
the passband. However, for the radio-quiet AGNs with $z>0.3$ and radio-loud
AGNs with $z<0.3$, we cannot confirm such strong correlation among different
passbands. All the features of near-infrared variability for the radio-quiet
AGNs are consistent with a simple dust reverberation model of the central
regions of AGNs. However, the features for the radio-loud AGNs are not fully
explained by such a model, and a non-thermal variable component is suggested as
a viable candidate for causing their large and fast variability in the
near-infrared region.


title:
Detailed Spectroscopic Analysis of SN 1987A: The Distance to the LMC
  using the SEAM method

abstract:
  Supernova 1987A remains the most well-studied supernova to date. Observations
produced excellent broad-band photometric and spectroscopic coverage over a
wide wavelength range at all epochs. We model the observed spectra from Day 1
to Day 81 using a hydrodynamical model. We show that good agreement can be
obtained at times up to about 60 days, if we allow for extended nickel mixing.
Later than about 60 days the observed Balmer lines become stronger than our
models can reproduce. We show that this is likely due to a more complicated
distribution of gamma-rays than we allow for in our spherically symmetric
calculations. We present synthetic light curves in UBVRIJHK and a synthetic
bolometric light curve. Using this broad baseline of detailed spectroscopic
models we find a distance modulus mu = 18.5 +/- 0.2 using the SEAM method of
determining distances to supernovae. We find that the explosion time agrees
with that of the neutrino burst and is constrained at 68% confidence to within
+/- 0.9 days. We argue that the weak Balmer lines of our detailed model
calculations casts doubt on the accuracy of the purely photometric EPM method.
We also suggest that Type IIP supernovae will be most useful as distance
indicators at early times due to a variety of effects.


title:
Superiority of the Lunar and Planetary Laboratory (LPL) over Steward
  Observatory (SO) at the University of Arizona

abstract:
  LPL dominance over Steward is demonstrated through several lines of evidence
including observations and modelling of previous April Fools day behavior. The
decrease in Steward coolness is attributed to the departure of interesting
graduate students from Steward that enrolled at LPL.


title: Direct X-ray Imaging of $\mu$m precision using Back-Illuminated CCD

abstract:
  A charge-coupled device (CCD) is a standard imager in optical region in which
the image quality is limited by its pixel size. CCDs also function in X-ray
region but with substantial differences in performance. An optical photon
generates only one electron while an X-ray photon generates many electrons at a
time. We developed a method to precisely determine the X-ray point of
interaction with subpixel resolution. In particular, we found that a
back-illuminated CCD efficiently functions as a fine imager. We present here
the validity of our method through an actual imaging experiment.


title: Optical Survey of Planetary Nebulae in the northern Galactic Bulge

abstract:
  We present preliminary results of an optical survey for Planetary Nebulae
(PNe) in the northern part of the Galactic Bulge. In particular, observations
at wavelengths corresponding to the [O III] 5007 emission line have been
carried out with the 0.3 m telescope at Skinakas Observatory, where we have
detected several new PNe and have rediscovered known and known-possible PNe
from that region.


title: N2H+ and C18O Depletion in a Cold Dark Cloud

abstract:
  We present sensitive, high angular resolution molecular-line observations of
C18O and N2H+ toward the dark globule B68. We directly compare these data with
the near-infrared extinction measurements of Alves, Lada, & Lada (2001) to
derive the first evidence for the depletion of N2H+, and by inference N2, in a
pre-stellar dark cloud. We also find widespread C18O depletion throughout the
centrally condensed core of the B68 cloud. Specifically, we find the N2H+
emission to peak in a shell partially surrounding the peak of dust extinction.
Moreover, the N2H+ peaks inside the much larger C18O depletion hole and has a
smaller depletion zone, confirming theoretical predictions. These data are
analyzed through a direct coupling of time dependent chemical models to a
radiation transfer code. This analysis highlights the importance of
photodissociation at cloud edges and suggests that the CO abundance declines by
two orders of magnitude from edge to center. In contrast N2H+ declines in
abundance, at minimum, by at least a factor of two. Indeed it is entirely
possible that both N2H+ and N2 are completely absent from the central regions
of the B68 core. The depletion of N2H+, and its parent molecule N2, opens the
possibility that the centers of dense cores, prior to the formation of a star,
may evade detection by conventional methods of probing cores using molecular
emission. Under these conditions H2D+ may be the sole viable molecular probe of
the innermost regions of star forming cores.


title: CMB and Cosmological Parameters: Current Status and Prospects

abstract:
  The last years have been an exciting period for the field of the Cosmic
Microwave Background (CMB) research. With recent CMB balloon-borne and
ground-based experiments we are entering a new era of 'precision' cosmology
that enables us to use the CMB anisotropy measurements to constrain the
cosmological parameters and test new theoretical scenarios.


title: Echoes in X-ray Binaries

abstract:
  We present a method of analysing the correlated X-ray and optical/UV
variability in X-ray binaries, using the observed time delays between the X-ray
driving lightcurves and their reprocessed optical echoes. This allows us to
determine the distribution of reprocessing sites within the binary. We model
the time-delay transfer functions by simulating the distribution of
reprocessing regions, using geometrical and binary parameters. We construct
best-fit time-delay transfer functions, showing the regions in the binary
responsible for the reprocessing of X-rays. We have applied this model to
observations of the Soft X-ray Transient, GRO j1655-40. We find the optical
variability lags the X-ray variability with a mean time delay of 19.3$pm{2.2}$
seconds. This means that the outer regions of the accretion disc are the
dominant reprocessing site in this system. On fitting the data to a simple
geometric model, we derive a best-fit disk half-opening angle of
13.5$^{+2.1}_{-2.8}$ degrees, which is similar to that observed after the
previous outburst by cite{orosz97}. This disk thickening has the effect of
almost entirely shielding the companion star from irradiation at this stage of
the outburst.


title: Phase Mixing in Unperturbed and Perturbed Hamiltonian Systems

abstract:
  This paper summarises a numerical investigation of phase mixing in
time-independent Hamiltonian systems that admit a coexistence of regular and
chaotic phase space regions, allowing also for low amplitude perturbations
idealised as periodic driving, friction, and/or white and colored noise. The
evolution of initially localised ensembles of orbits was probed through lower
order moments and coarse-grained distribution functions. In the absence of
time-dependent perturbations, regular ensembles disperse initially as a power
law in time and only exhibit a coarse-grained approach towards an invariant
equilibrium over comparatively long times. Chaotic ensembles generally diverge
exponentially fast on a time scale related to a typical finite time Lyapunov
exponent, but can exhibit complex behaviour if they are impacted by the effects
of cantori or the Arnold web. Viewed over somewhat longer times, chaotic
ensembles typical converge exponentially towards an invariant or near-invariant
equilibrium. This, however, need not correspond to a true equilibrium, which
may only be approached over very long time scales. Time-dependent perturbations
can dramatically increase the efficiency of phase mixing, both by accelerating
the approach towards a near-equilibrium and by facilitating diffusion through
cantori or along the Arnold web so as to accelerate the approach towards a true
equilibrium. The efficacy of such perturbations typically scales
logarithmically in amplitude, but is comparatively insensitive to most other
details, a conclusion which reinforces the interpretation that the
perturbations act via a resonant coupling.


title:
Active Nuclei and Star-Forming Objects at z>2: Metallicities, Winds, and
  Formation Histories

abstract:
  We present near-IR observations of AGN and star-forming objects in the field
of the radio galaxy 53W002 at z=2.39. The star-forming objects, of special
interest as candidate protogalactic objects, are uniformly very blue in
continuum slope, which fits with the strong Lyman alpha emission in indicating
metallicity less than half solar. They fall in a range of luminosity and
metallicity not populated by local objects. NICMOS spectroscopy detects [O III]
emission for two objects and sets interesting limits for the rest. These data
are satisfied by model stellar populations which have been forming stars for
the last 2-5 million years. We see no evidence for older populations, either in
broadband colors or as redder halos around the star-forming regions. These
results suggest that the compact star-forming objects we see at z=2.0-2.5 are
indeed early stages in the building of galaxies, rather than transient
star-forming events in larger systems. They also also permit an alternative
scheme, in which these low-mass systems are blowing winds rather than
self-enriching, and should fade rapidly with cosmic epoch. For the three
prominent AGN at z=2.39, emission-line ratios show metallicities just as high
as in nearby systems. The "ionization cones" appear in [O III] and H lines,
with continuum reflection in some cases as well. The contrast between the AGN
and fainter star-forming objects can be broadly accomodated in a hierarchical
formation picture, though there are still important unknowns as to the fate of
the star-forming objects.


title: First attempt at measuring the CMB cross-polarization

abstract:
  We compute upper limits on CMB cross-polarization by cross-correlating the
PIQUE and Saskatoon experiments. We also discuss theoretical and practical
issues relevant to measuring cross-polarization and illustrate them with
simulations of the upcoming BOOMERanG 2002 experiment. We present a method that
separates all six polarization power spectra (TT, EE, BB, TE, TB, EB) without
any other "leakage" than the familiar EE-BB mixing caused by incomplete sky
coverage. Since E and B get mixed, one might expect leakage between TE and TB,
between EE and EB and between BB and EB - our method eliminates this by
preserving the parity symmetry under which TB and EB are odd and the other four
power spectra are even.


title:
Prospects for Detection of Intracluster Gas Bulk Velocities Through the
  Sunyaev-Zel'dovich Effect

abstract:
  Intracluster gas velocity gradients have been recently detected by the
authors in the Centaurus cluster (Abell 3526) using the Doppler shift of X-ray
spectral lines with ASCA Solid-state Imaging Spectrometers. The velocity
gradient was found to be maximum along a line roughly perpendicular to the
direction of the incoming subgroup Cen 45 and has a correspondent velocity
difference of ~ (3.4+-1.1) x 1000 km/s within a ~10'-diameter region centered
on the cD galaxy NGC 4696. Such bulk velocities should Comptonize the Cosmic
Microwave Background Radiation producing variations of intensity and
temperature that can be detectable in the near future with bolometers such as
BOLOCAM . In this paper we realistically estimate the expected CMBR
Comptonization for the central region of Abell 3526, using ASCA and ROSAT data
to constrain the S-Z parameter expectations.


title:
Evolution of Hard X-Ray Radiation from Clusters of Galaxies:
  Bremsstrahlung or Inverse Compton Scattering?

abstract:
  We have calculated evolution of a non-thermal electron population from
super-thermal but weakly relativistic to highly relativistic energy range in
clusters of galaxies. We investigate evolution of hard X-ray radiation due to
both bremsstrahlung and inverse Compton scattering of the cosmic microwave
background photons. The bremsstrahlung component is more significant than the
inverse Compton scattering one when the momentum spectra of electron sources
are steeper than $\sim P_e^{-3.0}$ and vice versa in the case of Coma, where
$P_e$ is an electron momentum. The resultant hard X-ray spectra are flatter
when the bremsstrahlung component is dominant. When the spectral indices of the
source term are in the intermediate range ($ -2.5 \sim -3.5$), too much extreme
ultraviolet emission is produced. Inverse Compton dominant models can reproduce
Coma cluster results with reasonable injection rates, which are possible in
cluster mergers and/or ambient gas accretion.


title:
Tracing the Mass during Low-Mass Star Formation. III. Models of the
  Submillimeter Dust Continuum Emission from Class 0 Protostars

abstract:
  Seven Class 0 sources mapped with SCUBA at 850 and 450 micron are modeled
using a one dimensional radiative transfer code. The modeling takes into
account heating from an internal protostar, heating from the ISRF, realistic
beam effects, and chopping to model the normalized intensity profile and
spectral energy distribution. Power law density models, n(r) ~ r^{-p}, fit all
of the sources; best fit values are mostly p = 1.8 +/- 0.1, but two sources
with aspherical emission contours have lower values (p ~ 1.1). Including all
sources, <p> = 1.63 +/- 0.33. Based on studies of the sensitivity of the
best-fit p to variations in other input parameters, uncertainties in p for an
envelope model are \Delta p = +/- 0.2. If an unresolved source (e.g., a disk)
contributes 70% of the flux at the peak, p is lowered in this extreme case and
\Delta p = ^{+0.2}_{-0.6}. The models allow a determination of the internal
luminosity (<L_{int}> = 4.0 \lsun) of the central protostar as well as a
characteristic dust temperature for mass determination (<T_{iso}> = 13.8 +/-
2.4 K). We find that heating from the ISRF strongly affects the shape of the
dust temperature profile and the normalized intensity profile, but does not
contribute strongly to the overall bolometric luminosity of Class 0 sources.
There is little evidence for variation in the dust opacity as a function of
distance from the central source. The data are well-fitted by dust opacities
for coagulated dust grains with ice mantles (Ossenkopf & Henning 1994). The
density profile from an inside-out collapse model (Shu 1977) does not fit the
data well, unless the infall radius is set so small as to make the density
nearly a power-law.


title: The Dynamical Evolution of Substructure

abstract:
  The evolution of substructure embedded in non-dissipative dark halos is
studied through N-body simulations of isolated systems, both in and out of
initial equilibrium, complementing cosmological simulations of the growth of
structure. We determine by both analytic calculations and direct analysis of
the N-body simulations the relative importance of various dynamical processes
acting on the clumps, such as the removal of material by global tides,
clump-clump heating, clump-clump merging and dynamical friction. Our comparison
between merging and disruption processes implies that spiral galaxies cannot be
formed in a proto-system that contains a few large clumps, but can be formed
through the accretion of many small clumps; elliptical galaxies form in a more
clumpy environment than do spiral galaxies. Our results support the idea that
the central cusp in the density profiles of dark halos is the consequence of
self-limiting merging of small, dense halos. This implies that the collapse of
a system of clumps/substructure is not sufficient to form a cD galaxy, with an
extended envelope; plausibly subsequent accretion of large galaxies is
required. Persistent streams of material from disrupted clumps can be found in
the outer regions of the final system, and at an overdensity of around 0.75,
can cover 10% to 30% of the sky.


title:
Boron in the Small Magellanic Cloud: A Novel Test of Light Element
  Production

abstract:
  Hubble Space Telescope STIS observations of the B III resonance line at 2066A
have been obtained and analyzed for two Small Magellanic Cloud (SMC) B-type
stars. While boron is not detected in either star, upper limits to the boron
abundance are set, with 12+log(B/H) le 1.6 for both AV 304 and NGC 346-637. The
upper limits are consistent with the relationship between boron and oxygen
previously reported for Galactic disk stars. The SMC upper limits are discussed
in light of that galaxy's star formation history, present oxygen abundance, and
its present cosmic ray flux.
  The UV spectrum has also been used to determine the iron-group abundances in
the SMC stars. For AV 304, [Fe/H]=-0.6 pm 0.2, from both an absolute and a
differential analysis (with respect to the Galactic B-type star HD 36591). This
is consistent with results from A-F supergiants in the SMC. A lower iron
abundance is found for NGC 346-637, [Fe/H]=-1.0 pm 0.3, but this is in good
agreement with the supergiant iron abundances in NGC 330,another young SMC
cluster. We propose NGC 346-637 may be an unrecognized binary though, which
complicates its spectral analysis.


title: The Massive Disk Around OH 231.8+4.2

abstract:
  We have obtained 11.7 micron and 17.9 micron images at the Keck I telescope
of the circumstellar dust emission from OH 231.8+4.2, an evolved mass-losing
red giant with a well studied bipolar outflow. We detect both a central
unresolved point source and extended emission which is aligned with the bipolar
outflow seen on larger scales. We find that the unresolved central source can
be explained by an opaque, flared disk with an outer radius near 300 AU and an
outer temperature of about 130 K. One possible model to explain this flaring is
that the material in the disk is orbiting the central star and not simply
undergoing a radial expansion.


title: Secular bar formation in galaxies with significant amount of dark matter

abstract:
  Using high resolution N-body simulations of stellar disks embedded in
cosmologically motivated dark matter halos, we study the evolution of bars and
the transfer of angular momentum between halos and bars. We find that dynamical
friction results in some transfer of angular momentum to the halo, but the
effect is much smaller than previously found in low resolution simulations and
is incompatible with early analytical estimates. In simulations with millions
of particles reaching a resolution of 20-40 pc, the pattern speed may not
change over billions of years. Our high resolution models produce bars which
are fast rotators, where the ratio of the corotation radius to the bar major
semi-axis lies in the range R =1.2-1.7, marginally compatible with
observational results. In contrast to many previous simulations, we find that
bars are relatively short. As in many observed cases, the bar major semi-axis
is close to the exponential length of the disk. The transfer of angular
momentum between inner and outer parts of the disk plays a very important role
in the secular evolution of the disk and the bar. The bar formation increases
the exponential length of the disk by a factor of 1.2 -1.5. The transfer
substantially increases the stellar mass in the centre of the galaxy and
decreases the dark matter-to-baryons ratio. As the result, the central 2 kpc
region is always strongly dominated by the baryonic component. At intermediate
3-10kpc scales the disk is sub-dominant. In summary, realistic models produce
bar structure in striking agreement with observational results.


title:
Fuel-Supply-Limited Stellar Relaxation Oscillations: Application to
  Multiple Rings around AGB Stars and Planetary Nebulae

abstract:
  We describe a new mechanism for pulsations in evolved stars: relaxation
oscillations driven by a coupling between the luminosity-dependent mass-loss
rate and the H fuel abundance in a nuclear-burning shell. When mass loss is
included, the outward flow of matter can modulate the flow of fuel into the
shell when the stellar luminosity is close to the Eddington luminosity $L_{\rm
Edd}$. When the luminosity drops below $L_{\rm Edd}$, the mass outflow declines
and the shell is re-supplied with fuel. This process can be repetitive. We
demonstrate the existence of such oscillations and discuss the dependence of
the results on the stellar parameters. In particular, we show that the
oscillation period scales specifically with the mass of the H-burning
relaxation shell (HBRS), defined as the part of the H-burning shell above the
minimum radius at which the luminosity from below first exceeds the Eddington
threshold at the onset of the mass loss phase. For a stellar mass $M_*\sim
0.7\Msun$, luminosity $L_*\sim 10^4\Lsun$, and mass loss rate $|\dot M|\sim
10^{-5}\Msun$ yr$^{-1}$, the oscillations have a recurrence time $\sim 1400$
years $\sim 57\tau_{\rm fsm}$, where $\tau_{\rm fsm}$ is the timescale for
modulation of the fuel supply in the HBRS by the varying mass-loss rate. This
period agrees with the $\sim$ 1400-year period inferred for the spacings
between the shells surrounding some planetary nebulae, and the the predictied
shell thickness, of order 0.4 times the spacing, also agrees reasonably well.


title:
Time-series Spectroscopy of Pulsating sdB Stars II: Velocity Analysis of
  PG1605+072

abstract:
  We present the analysis of time-resolved spectroscopy of the pulsating sdB
star PG1605+072. From our main observing run of 16 nights we have detected
velocity variations at 5 frequencies that correspond to those found in
photometry. Based on these data, there appears to be change in amplitude of the
dominant modes over about a year. However, when we include extra observations
to improve the frequency resolution, we find that some of the frequencies are
split into two or three. Simulations suggest that the apparent amplitude
variation can be at least partially explained by a series of very closely
spaced frequencies around the two strongest modes. By combining observations
taken over ~300 days we conclude that some of the closely spaced modes are
caused by one mode whose amplitude is varying, however this frequency is still
within ~1 microHz of an apparently stable frequency. Because of this kind of
complexity and uncertainty we advise caution when trying to identify
oscillation modes in this star.


title: When can preheating affect the CMB?

abstract:
  We discuss the principles governing the selection of inflationary models for
which preheating can affect the CMB. This is a (fairly small) subset of those
models which have non-negligible entropy/isocurvature perturbations on large
scales during inflation. We study new models which belong to this class -
two-field inflation with negative nonminimal coupling and
hybrid/double/supernatural inflation models where the tachyonic growth of
entropy perturbations can lead to the variation of the curvature perturbation,
${\cal R}$, on super-Hubble scales. Finally we present evidence against recent
claims for the variation of ${\cal R}$ in the absence of substantial
super-Hubble entropy perturbations.


title: Polarisation of the Broad H alpha Wing in Symbiotic Stars

abstract:
  In many symbiotic stars there appear broad wings around H alpha, of which the
formation mechanism proposed thus far includes a fast outflow, the inner
accretion disc motion, electron scattering and Raman scattering of Ly beta. We
adopt a Monte Carlo technique to simulate the Raman scattering of UV photons
that are converted into optical photons around H alpha forming broad wings, and
compute its polarisation. Noting that many symbiotic stars exhibit a bipolar
nebular morphology and polarisation flip in the red wing part of the Raman
scattered O {\tiny{VI}} features, we assume that the neutral scattering region
is composed of the two components. The first component is a static cylindrical
shell with finite thickness and the other component is a finite slab that is
moving away with velocity v_p = 100 km s^{-1} along the symmetry axis of the
first component. The cylindrical shell component yields polarisation in the
direction parallel to the cylinder axis. The polarisation near the line-centre
is weaker than in the far wing regions because of the large Rayleigh scattering
numbers due to the large scattering cross sections near the line centre. The
receding polar scattering component produces strong polarisation in the
direction perpendicular to the cylinder axis. When the both scattering
components coexist, the polarisation is characterised by weak parallel
polarisation near the line-centre and strong perpendicular polarisation in the
red part. We discuss the observational implications of our computation.


title:
Variable stars in nearby galaxies. V. Search for Cepheids in Field A of
  NGC 6822

abstract:
  The results of a CCD survey for variability of stars in the nearby galaxy NGC
6822 are presented. The goal of the survey was to obtain good light curves of
Cepheids for Fourier decomposition and to detect shorter period Cepheids. Since
the program was carried out with a relatively small telescope, the Dutch 0.9 m
at ESO-La Silla, the observations were unfiltered (white light, or Wh-band).
The analysis revealed the presence of more than 130 variable stars. 21
population I Cepheids are detected; 6 of them were already known from previous
works (Kayser, 1967). For at least three Cepheids, however, the previous
identification or period was wrong. Some probable population II (W Vir) stars
are also identified. The dispersion of the fundamental mode Cepheid PL relation
appears to be small.


title:
Collisional Processes in Extrasolar Planetsimal Disks - Dust Clumps in
  Fomalhaut's Debris Disk

abstract:
  This paper presents a model for the outcome of collisions between
planetesimals in a debris disk and assesses the impact of collisional processes
on the structure and size distribution of the disk. The model is presented by
its application to Fomalhaut's collisionally replenished dust disk; a recent
450 micron image of this disk shows a clump embedded within it with a flux ~5
per cent of the total. The following conclusions are drawn: (i) SED modelling
is consistent with Fomalhaut's disk having a collisional cascade size
distribution extending from bodies 0.2 m in diameter down to 7 micron-sized
dust. (ii) Collisional lifetime arguments imply that the cascade starts with
planetesimals 1.5-4 km in diameter. Any larger bodies must be predominantly
primordial. (iii) Constraints on the timescale for the ignition of the cascade
are consistent with these primordial planetesimals having a distribution that
extends up to 1000km, resulting in a disk mass of 5-10 times the minimum mass
solar nebula. (iv) The debris disk is expected to be intrinsically clumpy,
since planetesimal collisions result in dust clumps. The intrinsic clumpiness
of Fomalhaut's disk is below current detection limits, but could be detectable
by future observatories such as the ALMA, and could provide the only way of
determining the primordial planetesimal population. (v) The observed clump
could have originated in a collision between two runaway planetesimals, both
larger than 1400 km diameter. It is unlikely that we should witness such an
event unless both the formation of these runaways and the ignition of the
collisional cascade occurred within the last ~10 Myr. (vi) Another explanation
for Fomalhaut's clump is that ~5 per cent of the planetesimals in the ring are
trapped in 1:2 resonance with a planet orbiting at 80 AU.


title:
Red-shifted H2O emission in NGC 3079: more evidence for a pc-scale
  circumnuclear torus?

abstract:
  Using the Effelsberg 100-m telescope, sensitive measurements of the H2O
megamaser in NGC 3079 are presented. During 2000 - 2001, `high velocity'
features are seen that are red-shifted up to 225 km/s with respect to the
systemic velocity of the galaxy (about 1120 km/s). Symmetrically bracketing the
systemic velocity, the H2O emission covers a velocity range of 450 km/s with
only one potential narrow gap (20 km/s) near the systemic velocity itself.
Velocity drifts of individual components are not convincingly detected. It is
shown that the presence of red-shifted emission and the absence of detectable
velocity drifts are not inconsistent with the existence of a rotating
circumnuclear maser disk at the very center of the galaxy. Significant
differences in the overall line profile compared to NGC 4258 and a complex
morphology of the radio continuum leave, however, space for scepticism.


title: Investigating the Flame Microstructure in Type Ia Supernovae

abstract:
  We present a numerical model to study the behavior of thermonuclear flames in
the discontinuity approximation. This model is applied to investigate the
Landau-Darrieus instability under conditions found in Type Ia supernova
explosions of Chandrasekhar mass white dwarfs. This is a first step to explore
the flame microstructure in these events. The model reproduces Landau's
linearized stability analysis in early stages of the flame evolution and the
stabilization in a cellular flame structure in the nonlinear stage.


title:
Gamma Ray Bursts and the Collapsar Model: a comment on astro-ph/0203391
  and astro-ph/0203467

abstract:
  In an essay published in 1997, M. J. Harris pointed out that the development
of a theoretical explanation, or "synthesis," of a group of astronomical
results can lead to a situation where subsequent observations are forced to fit
within that framework. Moreover, new results may be reported that fit within
the framework but which can no longer be reproduced following the advent of
more sensitive observations that overturn the synthesis. Although Harris
considered gamma-ray line transients, a similar situation regarding the
collapsar model for gamma-ray bursts now holds. In two recent papers posted on
astro-ph by J. S. Bloom et al., and by P. A. Price et al., the synthesis effect
is illustrated with respect to the collapsar model. These authors dismiss
observations that contradict the collapsar model, appeal to "simplicity" to
justify their preferred model, and dismiss (or better yet, ignore) competing
models with unscientific reasoning. Whether or not the collapsar model is
correct, these papers serve as textbook examples of the synthesis effect in
science.


title: Millimeter-band Surveys of Extragalactic Sources

abstract:
  Surveys at mm wavelengths emphasize rare classes of extragalactic radio
sources characterized by spectra keeping flat or inverted up to high
frequencies (such as blazars, GPS sources, advection dominated sources, or even
gamma-ray burst afterglows), which are are difficult to single out at lower
frequencies where the counts are dominated by far more numerous populations.
Such surveys may lead to the discovery of populations with extreme properties,
such as sources of the general GPS or blazar type but peaking at mm
wavelengths, whose existence is hinted by currently available data. At
relatively lower flux levels mm counts are dominated by high-redshift dusty
galaxies, such as those detected by SCUBA and MAMBO surveys. These data have
profound implications for our understanding of the formation and early
evolution of galaxies. High sensitivity surveys at cm/mm wavelengths may also
detect galaxy-scale Sunyaev-Zeldovich effects due to gas heated by central
active nuclei.


title: SAURON Observations of Disks in Spheroids

abstract:
  The panoramic integral-field spectrograph SAURON is currently being used to
map the stellar kinematics, gaseous kinematics, and stellar populations of a
large number of early-type galaxies and bulges. Here, we describe SAURON
observations of cold stellar disks embedded in spheroids (NGC3384, NGC4459,
NGC4526), we illustrate the kinematics and ionization state of large-scale
gaseous disks (NGC4278, NGC7742), and we show preliminary comparisons of SAURON
data with barred galaxy N-body simulations (NGC3623).


title:
Chaos caused by resonance overlap in the solar neighborhood -- Spiral
  structure at the Bar's 2:1 outer Lindblad resonance

abstract:
  We consider the nature of orbits near the solar neighborhood which are
perturbed by local spiral arms and the Milky Way bar. We present a simplified
Hamiltonian model which includes resonant terms from both types of
perturbations and is similar to the forced pendulum. Via numerical integration
of this model we construct Poincare maps to illustrate the nature and stability
of the phase space. We find that resonance overlap is most likely to cause
widespread chaos when the pattern of the spiral structure puts the solar
neighborhood near the 2:1 inner Lindblad resonance (ILR) in the case of a
2-armed pattern, or near the 4:1 ILR in the case of a 4-armed pattern. When
this happens both the quasiperiodic orbits which support the spiral structure
and those that oscillate with the bar are disrupted near the bar's 2:1 outer
Lindblad resonance (OLR). Consequently the pattern speed of spiral structure
which passes through the OLR must be faster than 0.45 times the solar
neighborhood angular rotation rate if it is 2-armed or faster than 0.75 times
this value if it is 4-armed. Alternatively the OLR may form a boundary between
spiral modes at different pattern speeds. In all cases we find that spiral
structure is disrupted by the OLR over a narrow range of radius and the extent
of the orbits aligned perpendicular to the bar at the OLR is limited by the
spiral perturbations.


title:
On the Utter Irrelevance of LPL Graduate Students: An Unbiased Survey by
  Steward Observatory Graduate Students

abstract:
  We present a new analysis of the irrelevance of Lunar and Planetary
Laboratory (LPL) graduate students at the University of Arizona. Based on
extensive Monte Carlo simulations we find that the actual number of useful
results from LPL graduate students is $0\pm0.01 (5\sigma)$. Their irrelevance
quotient far surpasses that of string theorists.


title: The Absence of Stars in Compact High-Velocity Clouds

abstract:
  We present the results of our search for faint Local Group dwarf galaxies in
compact high-velocity clouds (HVCs). We used digitized Palomar Observatory Sky
Survey (POSS) data to examine 1 square degree of sky around each of ~250
northern hemisphere HVCs. The POSS images were processed to remove foreground
stars and large-scale backgrounds, smoothed to enhance arcminute-sized low
surface brightness features, and then compared to the original plates. Using
this technique, we located 60 candidate dwarf galaxies in the ~250 square
degrees that we surveyed. Followup observations of these candidates have
revealed several distant clusters of galaxies and a number of possible Galactic
cirrus clouds, but no Local Group dwarfs. It appears that many of the low
surface brightness features in the sky survey data are plate flaws. The
second-generation red POSS plates are sensitive down to surface brightness
levels of 25-26 magnitudes per square arcsecond, and our followup images
reached 10-sigma limiting magnitudes of R = 21-23 for point sources. Given
these limits, all known Local Group galaxies except four of the very diffuse,
extended dwarf spheroidals located within 100 kpc of the Milky Way would have
been detected had they been in our survey. Therefore, we can rule out the
possibility that these HVCs are associated with normal but faint dwarf
galaxies. If compact HVCs do contain stars, they must have surface brightnesses
> 1 magnitude per square arcsecond fainter than most known Local Group
galaxies.


title:
Gravitational Lenses, the Distance Ladder and the Hubble Constant: A New
  Dark Matter Problem

abstract:
  In cold dark matter models, a galaxy's dark matter halo is more spatially
extended than its stars. However, even though the five well-constrained
gravitational lenses with time delay measurements must have similar dark matter
distributions, reconciling the Hubble constant estimated from their time delays
with local estimates is possible only if that dark matter distribution is as
compact as the luminous galaxy. The Hubble constant is H0=48-4+7 km/s Mpc (95%
confidence) if the lenses have flat rotation curves and H0=71+/-6 km/s Mpc (95%
confidence) if they have constant mass-to-light ratios, as compared to
H0=72+/-8 km/s Mpc (68% confidence) for local estimates by the HST Key Project.
Either all five H0 estimates based on the lenses are wrong, local estimates of
H0 are too high, or dark matter distributions are more concentrated than
expected. The average value for H0 including the uncertainties in the mass
distribution, H0=62+/-7 km/s Mpc, has uncertainties that are competitive with
local estimates. However, by selecting a value for H0 you also determine the
dark matter distribution of galaxies.


title: Can Reflection from Grains Diagnose the Albedo?

abstract:
  By radiation transfer models with a realistic power spectra of the projected
density distributions, we show that the optical properties of grains are poorly
constrained by observations of reflection nebulae. The ISM is known to be
hierarchically clumped from a variety of observations (molecules, H I,
far-infrared). Our models assume the albedo and phase parameter of the dust,
the radial optical depth of the sphere averaged over all directions, and random
distributions of the dust within the sphere. The outputs are the stellar
extinction, optical depth, and flux of scattered light as seen from various
viewing angles. Observations provide the extinction and scattered flux from a
particular direction.
  Hierarchical geometry has a large effect on the flux of scattered light
emerging from a nebula for a particular extinction of the exciting star. There
is a very large spread in both scattered fluxes and extinctions for any
distribution of dust. Consequently, an observed stellar extinction and
scattered flux can be fitted by a wide range of albedos. With hierarchical
geometry it is not completely safe to determine even relative optical constants
from multiwavelength observations of the same reflection nebula. The geometry
effectively changes with wavelength as the opacity of the clumps varies. Limits
on the implications of observing the same object in various wavelengths are
discussed briefly.
  Henry (2002) uses a recipe to determine the scattered flux from a star with a
given extinction. It is claimed to be independent of the geometry. It provides
considerably more scattering than our models, probably leading to an
underestimate of the grain albedos from the UV Diffuse Galactic Light.


title: Numerical Models of Viscous Accretion Flows Near Black Holes

abstract:
  We report on a numerical study of viscous fluid accretion onto a black hole.
The flow is axisymmetric and uses a pseudo-Newtonian potential to model
relativistic effects near the event horizon. The numerical method is a variant
of the ZEUS code. As a test of our numerical scheme, we are able to reproduce
results from earlier, similar work by Igumenshchev and Abramowicz and Stone et
al. We consider models in which mass is injected onto the grid as well as
models in which an initial equilibrium torus is accreted. In each model we
measure three ``eigenvalues'' of the flow: the accretion rate of mass, angular
momentum, and energy. We find that the eigenvalues are sensitive to r_{in}, the
location of the inner radial boundary. Only when the flow is always supersonic
on the inner boundary are the eigenvalues insensitive to small changes in
r_{in}. We also report on the sensitivity of the results to other numerical
parameters.


title: Chandra Observation of LMXBs in the elliptical galaxy M84

abstract:
  We present characteristics of the X-ray point source population in the M84
galaxy, observed by Chandra ACIS-S. We find an excess in the number of sources
centered on M84, with a spatial distribution closely corresponding to the M84
stellar light. Given an absence of recent star-formation, accreting binaries
are the only candidates for the M84 X-ray sources. The majority of M84 sources
(with luminosities exceeding 10^38 ergs/s) exhibit hardness ratios expected
from multi-temperature black-body disk emission. The most luminous sources,
which we attribute to accreting black holes exhibit X-ray colors typical of a
black body spectrum. We also identify the sources whose X-ray colors match the
expectations for constituents of the Cosmic X-ray Background. The number of
such sources agrees with that expected to be background sources. After
correcting for incompleteness in the source detection, we find a log(N)-log(S)
for M84 similar to that of the elliptical galaxy NGC4697, i.e. having a break
at a luminosity of L_b=2.4 (+0.6 -0.3) x10^38 ergs/s, approximately the
Eddington limit on the isotropic luminosity for accretion onto a neutron star.
The slope of the luminosity function above the break provides evidence for a
mass distribution in the M84 accreting black holes.


title:
The Starburst Nature of Lyman-Break Galaxies: Testing UV Extinction with
  X-rays

abstract:
  We derive the bolometric to X-ray correlation for a local sample of normal
and starburst galaxies and use it, in combination with several UV reddening
schemes, to predict the 2--8 keV X-ray luminosity for a sample of 24
Lyman-break galaxies in the HDF/CDF-N. We find that the mean X-ray luminosity,
as predicted from the Meurer UV reddening relation for starburst galaxies,
agrees extremely well with the Brandt stacking analysis. This provides
additional evidence that Lyman-break galaxies can be considered as scaled-up
local starbursts and that the locally derived starburst UV reddening relation
may be a reasonable tool for estimating the UV extinction at high redshift. Our
analysis shows that the Lyman-break sample can not have far-IR to far-UV flux
ratios similar to nearby ULIGs, as this would predict a mean X-ray luminosity
100 times larger than observed, as well as far-IR luminosities large enough to
be detected in the sub-mm. We calculate the UV reddening expected from the
Calzetti effective starburst attenuation curve and the radiative transfer
models of Witt & Gordon for low metallicity dust in a shell geometry with
homogeneous or clumpy dust distributions and find that all are consistent with
the observed X-ray emission. Finally, we show that the mean X-ray luminosity of
the sample would be under predicted by a factor of 6 if the the far-UV is
unattenuated by dust.


title: Self-Collimation and Magnetic Field Generation of Astrophysical Jets

abstract:
  A novel model for collimation and transport of electron-positron-ion jets is
presented. Analytical results show that the filamentary structures can be
sustained by self-induced toroidal magnetic fields permeating through the
filaments, whose widths significantly expand in the pair-dominant regimes. The
magnetic field strength reflects a characteristic of equipartition of excess
kinetic energy of the jets. It is also shown that growth of the hoselike
instability is strongly suppressed. Essential features derived from this model
are consistent with recent results observed by using very long baseline
telescopes.


title: Helium-like triplet diagnostics

abstract:
  The 1s2-1s2l lines are the most intense He-like ions lines. They are used as
spectroscopic diagnostics for solar active regions as well as for different
laboratory plasmas. Nowadays, it exits very high spectral resolution
instruments and, for intense X-ray sources, one can do spectroscopic
diagnostics from line ratios. With XMM (RGS) and Chandra (LETGS, HETGS)
spectral resolutions and for several atomic elements, it is particularly
possible to separate a 3 blended line set, the so-called He-like triplet:
Resonance (r), Intercombination (i) and Forbidden (f), which are dominated
respectively by lines issued from the following levels : 1s2p 1P1, 1s2p 3P1,2
and 1s2s 3S1. We shall show that the measurement of two different ratios
between these 3 lines (R = f/i and G = (f + i)/r) give quantitative
informations on the nature of the emitting plasma (photo-ionized or
collisional) and on its electronic density and temperature. A more refined
analysis must also include satellite line contributions.


title:
BeppoSAX observations of the young pulsar in the Kes 75 Supernova
  Remnant

abstract:
  We present the results of BeppoSAX observations of the young X-ray pulsar PSR
J1846-0258, recently discovered at the center of the composite supernova
remnant Kes 75. The pulsar (plus nebula) spectrum can be fitted by an absorbed
power law with photon index alpha_ph=2.16+/-0.15, N_H=(4.7+/-0.8) x 10^22
cm^-2, and unabsorbed flux ~3.9x10^-11 erg cm^-2 s^-1 (2-10 keV). By joining
two observations taken at an interval of two weeks we have been able to obtain
a precise measurement of the spin period (P=324.818968+/-0.000006 ms). This
value, when combined with previous measurements, cannot be fitted by a smooth
frequency evolution with a canonical braking index n=3. With the hypothesis of
no glitches and/or significant timing noise, the braking index would be
n=1.86+/-0.08 and, assuming a short initial period, the pulsar age would be
\~1700 years, closer to that of the supernova remnant than the simple estimate
\tau=P/2\pdot=723 years. Other likely possibilities involve the presence of
glitches and lead to a wide range of acceptable ages. For example, we obtain n
in the range 1.8-2.5, if a glitch occurred near MJD 51500, while for a glitch
between October 1993 and March 1999 we can only get a lower limit of n>1.89.


title:
VLA Detection of RRLs from the radio nucleus of NGC 253 : Ionization by
  a weak AGN, an obscured SSC or a compact SNR ?

abstract:
  We have imaged the H92alpha and H75alpha radio recombination line (RRL)
emissions from the starburst galaxy NGC 253 with a resolution of ~4 pc. The
peak of the RRL emission at both frequencies coincides with the unresolved
radio nucleus. Both lines observed towards the nucleus are extremely wide, with
FWHM of ~200 km /s. Modeling the RRL and radio continuum data for the radio
nucleus shows that the lines arise in gas whose density is ~10^4 \cc and mass
is few thousand Msun, which requires an ionizing flux of (6-20)x10^{51} photons
/s. We consider a SNR expanding in a dense medium, a star cluster and also an
AGN as potential ionizing sources. Based on dynamical arguments, we rule out an
SNR as a viable ionizing source. A star cluster model was considered and the
dynamics of the ionized gas in a stellar-wind driven structure was
investigated. Such a model is consistent with the properties of the ionized gas
only for a cluster younger than ~10^5 years. The existence of such a young
cluster at the nucleus seems improbable. The third model assumes the ionizing
source to be an AGN at the nucleus. In this model, it was shown that the
observed X-ray flux is too weak to account for the required ionizing photon
flux. However, the ionization requirement can be explained if the accretion
disk is assumed to have a Big Blue Bump in its spectrum. Hence, we favor an AGN
at the nucleus as the source responsible for ionizing the observed RRLs. A
hybrid model consisting of a inner ADAF disk and an outer thin disk is
suggested, which could explain the radio, UV and the X-ray luminosities of the
nucleus.


title: The Phoenix galaxy: UGC4203 re-birth from its ashes?

abstract:
  We report on a dramatic transition between a Compton-thick,
reflection-dominated state and a Compton-thin state in the Seyfert 2 galaxy
UGC4203, discovered by comparing a recent (May 2001) XMM-Newton observation
with ASCA observations performed about six years earlier. This transition can
be explained either as a change in the column density of the absorber, maybe
due to moving clouds in a clumpy torus, or as the revival of a transient active
nucleus, which was in a phase of very low activity when observed by ASCA. If
the latter explanation is correct, spectral transitions of this kind provide
observational support to the idea that Compton-thick and Compton-thin regions
coexist in the same source, the former likely to be identified with the
"torus", the latter with dust lanes on much larger scales.


title: Microlensing Neutron Stars

abstract:
  We investigate the chances that neutron stars act as the lense in a
gravitational microlensing event towards the galactic bulge or a spiral arm.
The observation of neutron stars by means of gravitational microlensing would
allow the estimation of neutron star masses independently of the property of
being a pulsar in a binary system. We estimate the contribution of neutron
stars to the optical depth and the lensing rate based on two different models
of the pulsar distribution in the galaxy. Since only a small fraction of all
neutron stars are pulsars, it is unlikely to find a pulsar that acts as a
microlense by chance. A position comparison of known radio pulsars with
observed microlensing candidates towards the galactic bulge and spiral arms
shows no candidate pair, which is consistent with the theoretical expectation.
To improve the probability of microlensing a pulsar, we suggest to search for
gravitational microlensing events of known nearby high proper motion pulsars.
The pulsar PSR J1932+1059 is a good candidate for an astrometric detection of
gravitational lensing.


title: NGC1052 - A study of the pc-scale twin jet

abstract:
  We present results of a VLBA multi-frequency study of the pc-scale twin jet
in NGC1052. We observed this object at epoch 1998.99 with the VLBA at 5, 8.4,
22 and 43 GHz both in total and linearly polarized intensity. The spectral
analysis confirms the necessity of a free-free absorbing medium, obscuring the
innermost part of both jets. At 5 GHz we found a compact linearly polarized
emission region at the base of the eastern jet with a degree of polarization of
1.5%. At higher frequencies there is no evidence for polarization in our data.
A core shift analysis constrains the position of the central engine to ~0.03
pc. The shift rates of the apparent core position with frequency confirm the
strong influence of free-free absorption in conjunction with steep pressure
gradients at the bases of both jets.


title:
Stellar Masses and Star Formation Histories for 10^5 Galaxies from the
  Sloan Digital Sky Survey

abstract:
  We develop a new method to constrain the star formation histories, dust
attenuation and stellar masses of galaxies. It is based on two stellar
absorption line indices, the 4000 Angstrom break strength and the Balmer
absorption line index Hdelta_A. Together, these indices allow us to constrain
the mean stellar ages of galaxies and the fractional stellar mass formed in
bursts over the past few Gyr. A comparison with broad band photometry then
yields estimates of dust attenuation and of stellar mass. We generate a large
library of Monte Carlo realizations of different star formation histories,
including starbursts of varying strength and a range of metallicities. We use
this library to generate median likelihood estimates of burst mass fractions,
dust attenuation strengths, stellar masses and stellar mass-to-light ratios for
a sample of 122,208 galaxies drawn from the Sloan Digital Sky Survey. The
typical 95% confidence range in our estimated stellar masses is +-40%. We study
how the stellar mass-to-light ratios of galaxies vary as a function of absolute
magnitude, concentration index and photometric pass-band and how dust
attenuation varies as a function of absolute magnitude and 4000 Angstrom break
strength. We also calculate how the total stellar mass of the present Universe
is distributed over galaxies as a function of their mass, size, concentration,
colour, burst mass fraction and surface mass density. We find that most of the
stellar mass in the local Universe resides in galaxies that have stellar masses
\~5\times 10^10 M_sol, half light radii ~3 kpc, and half- light surface mass
densities ~10^9 M_sol/kpc^2. The distribution of D(4000) is strongly bimodal,
showing a clear division between galaxies dominated by old stellar populations
and galaxies with more recent star formation.


title:
The role of damped Alfven waves on magnetospheric accretion models of
  young stars

abstract:
  We examine the role of Alfven wave damping in heating the plasma in the
magnetic funnels of magnetospheric accretion models of young stars. We study
four different damping mechanisms of the Alfven waves: nonlinear, turbulent,
viscous-resistive and collisional. Two different possible origins for the
Alfven waves are discussed: 1) Alfven waves generated at the surface of the
star by the shock produced by the infalling matter; and 2) Alfven waves
generated locally in the funnel by the Kelvin-Helmholtz instability. We find
that, in general, the damping lengths are smaller than the tube length. Since
thermal conduction in the tube is not efficient, Alfven waves generated only at
the star's surface cannot heat the tube to the temperatures necessary to fit
the observations. Only for very low frequency Alfven waves ~10^{-5} the ion
cyclotron frequency, is the viscous-resistive damping length greater than the
tube length. In this case, the Alfven waves produced at the surface of the star
are able to heat the whole tube. Otherwise, local production of Alfven waves is
required to explain the observations. The turbulence level is calculated for
different frequencies for optically thin and thick media. We find that
turbulent velocities varies greatly for different damping mechanisms, reaching
\~100 km s^{-1} for the collisional damping of small frequency waves.


title: Characterising the complex absorber in NGC 4151

abstract:
  We present a detailed analysis of the complex absorption apparent in the 2-6
keV X-ray spectrum of the bright nearby Seyfert galaxy NGC 4151. We first
utilize the large bandpass and medium spectral resolution afforded by BeppoSAX
data to construct a 1-100 keV spectral template, which assumes the absorption
arises in both warm (i.e. partially photoionized) and cold gas present in the
line of sight to the active nucleus of the source. Application of this spectral
model to an ASCA "long-look" observation of NGC 4151 reveals a partial
correlation between the underlying continuum flux and the ionization state of
the warm absorber. Such a correlation is an intrinsic property of a warm
absorber and argues strongly in favour of this interpretation for the complex
absorbing column over alternative partial covering models. The inferred
relatively low density for the warm gas, implies an equilibration timescale for
the dominant ions of the same order or longer than the timescale of the
continuum variability. It follows that the warm component will invariably be
observed in a non-equilibrium ionization state.
  We also find that (i) the reported hardening of the spectrum of NGC 4151 as
the continuum level falls may be simply due to the presence of an underlying
(hard and relatively constant) Compton-reflection component and (ii) the iron
Ka line has a relatively narrow Gaussian profile and a line flux that remains
constant over both short (days) and long (months to years) timescales - a
relativistically broadened iron Ka feature was not required in our modelling.


title:
Luminous matter may arise from a turbulent plasma state of the early
  universe

abstract:
  The almost perfect uniformity of the cosmic microwave background (CMB)
radiation, discovered by Penzias and Wilson in 1965 appears to present clearcut
evidence that the universe was uniform and in equilibrium at the decoupling
transition when a plasma of protons and electrons condensed into a gas of
Hydrogen. COBE indicates that only very small ripples of order 10^{-5} existed
at decoupling. Gravity then caused hydrogen to cluster and possibly reheat
parts of the universe to form the luminous matter that we observe today. We
suggest an alternative scenario, where a spatially intermittent structure of
extremely hot matter already existed in an otherwise uniform plasma state at
the decoupling transition. The plasma was not in equilibrium but in a very high
Reynolds number turbulent state. The sparse bursts would not affect the
uniformity of the CMB radiation. Luminous matter originates from localized hot
bursts already present in the plasma state prior to decoupling. No reheating,
and no exotic matter is needed to get luminous matter.


title: Dark 2002 and Beyond

abstract:
  Salient aspects of the meeting are summarized, including our knowledge of
dark matter at different cosmological and astrophysical distance scales,
ranging from large-scale structure to the cores of galaxies, and our
speculations on particle candidates for dark matter, including neutrinos,
neutralinos, axinos, gravitinos and cryptons. Comments are also made on
prospects for detecting dark matter particles and on the dark energy problem.


title: Mapping the submillimeter spiral wave in NGC 6946

abstract:
  We have analysed SCUBA 850\mum images of the (near) face-on spiral galaxy NGC
6946, and found a tight correlation between dust thermal emission and molecular
gas. The map of visual optical depth relates well to the distribution of
neutral gas (HI+H2) and implies a global gas-to-dust ratio of 90. There is no
significant radial variation of this ratio: this can be understood, since the
gas content is dominated by far by the molecular gas. The latter is estimated
through the CO emission tracer, which is itself dependent on metallicity,
similarly to dust emission. By comparing the radial profile of our visual
optical depth map with that of the SCUBA image, we infer an emissivity (dust
absorption coefficient) at 850\mum that is 3 times lower than the value
measured by COBE in the Milky Way, and 9 times lower than in NGC 891. A
decomposition of the spiral structure half way out along the disk of NGC 6946
suggests an interarm optical depth of between 1 and 2. These surprisingly high
values represent 40-80% of the visual opacity that we measure for the arm
region (abridged).


title:
Fundamental Properties and Distances of LMC Eclipsing Binaries: III.
  EROS 1044

abstract:
  We present results from a detailed analysis of a third eclipsing binary (EB)
system in the Large Magellanic Cloud, EROS 1044 (~B2 IV-V + ~B2 III-IV). Our
study combines the "classical" EB study of light and radial velocity curves
with detailed modeling of the observed spectral energy distribution, and yields
an essentially complete picture of the stellar properties of the system and a
determination of its distance. The observational data exploited include optical
photometry, space-based UV spectroscopy, and UV/optical spectrophotometry. The
advantages of our technique include numerous consistency checks and, in the
case of the distance determinations, the absence of zero point uncertainties
and adjustable parameters. We find the EROS 1044 system to consist of a pair of
normal, mildly-evolved ~21000 K stars, whose derived properties are consistent
with stellar evolution calculations. The distance to the system is 47.5+/-1.8
kpc. We discuss the implications of our results for three EB systems (HV 2274,
HV 982, and EROS 1044) on the general distance to the Large Magellanic Cloud.


title: The Role of Millimeter VLBI Observations in AGN Research

abstract:
  VLBI at millimeter wavelengths (mm-VLBI) allows the detailed imaging of
compact galactic and extragalactic radio sources with micro-arcsecond scale
resolution, unaccessible by other observing techniques. Here we discuss the
scientific potential of mm-VLBI for present and future research on `Active
Galactic Nuclei' (AGN) and their powerful relativistic jets. With the new
generation of large radio telescopes and interferometer arrays operating in the
millimeter radio bands (e.g. ALMA), the ultimate vicinity of super massive
Black Holes, and eventually even their event horizon, could be imaged. With its
large collecting area, and in combination with these future telescopes, the
Sardinia Radio Telescope could form the World's `sharpest' astronomical imaging
machine.


title:
Candidate Pre-Mainsequence F Stars with Circumstellar Dust Identified
  Using Combined 2MASS and uvby Data

abstract:
  We propose a method that uses near-infrared plus uvby photometry to identify
potentially extensive circumstellar dusty environment about F and A stars. The
method has been applied to a sample of ~900 metal rich reddened F stars with
2MASS and uvby data, suggesting the presence of circumstellar dust emitting in
the near infrared for ~70 stars. The log T_e - M_V diagram suggests that most,
if not all, of them are likely pre-mainsequence (PMS). They seem to be
consistent with being a continuation of the class of Herbig Ae/Be PMS stars
into the spectral type F. Their number drops sharply downward of log T_e ~ 3.84
(spectral types later than ~F5), which may provide new clues to the PMS
evolution of stars with 1 to 2 solar mass. We present a list of 21 most
conspicuous candidate stars with circumstellar dust. About half of them are
associated with the extended star-forming region around rho Oph. The brightest
of these 21 stars, with V < 7.5, turn out to be IRAS sources, suggesting the
presence of heated dust emitting in the far infrared. Also in this list, HD
81270 is reported as a very unusual star moving away from the Galactic plane at
a projected speed of 70 km/sec.


title: Sketching the inflaton potential

abstract:
  Based on solutions of the Stewart-Lyth inverse problem it is argued that in
the CMB data analysis the parametrization of the primordial spectra from
inflation must include the `running' of both, scalar and tensorial, spectral
indices if information beyond the exponential potential model is wanted to be
detected.


title: Characterization of M,L and T dwarfs in the Sloan Digital Sky Survey

abstract:
  An extensive sample of M, L and T dwarfs identified in the Sloan Digital Sky
Survey (SDSS) has been compiled. The sample of 718 dwarfs includes 677 new
objects (629 M dwarfs, 48 L dwarfs) together with 41 that have been previously
published. All new objects and some of the previously published ones have new
optical spectra obtained either with the SDSS spectrographs or with the Apache
Point Observatory 3.5m ARC telescope. Spectral types and SDSS colors are
available for all objects; approximately 35% also have near-infrared magnitudes
measured by 2MASS or on the Mauna Kea system. We use this sample to
characterize the color--spectral type and color--color relations of late type
dwarfs in the SDSS filters, and to derive spectroscopic and photometric
parallax relations for use in future studies of the luminosity and mass
functions based on SDSS data. We find that the (i*-z*) and (i*-J) colors
provide good spectral type and absolute magnitude (M_i*) estimates for M and L
dwarfs. Our distance estimates for the current sample indicate that SDSS is
finding early M dwarfs out to about 1.5 kpc, L dwarfs to approximately 100 pc
and T dwarfs to near 20 pc. The T dwarf photometric data show large scatter and
are therefore less reliable for spectral type and distance estimation.


title: Is power-law inflation really attractive?

abstract:
  It is argued that the order of the analytic expressions for the calculation
of the primordial perturbations from inflation exerts a strong influence upon
the results of the analysis of observables dynamics based on these expressions
and, therefore, upon some predictions sometimes taken for granted as generic
for the inflationary scenario.


title: The Discovery of Time Variability in OH Megamasers

abstract:
  We report the discovery of variability in the OH megamaser in IRAS 21272+2514
at z=0.15. This is the first OH megamaser (OHM) observed to vary in time. The
variation is broadband, spanning 0.5-1.5 MHz or 100-300 km/s in the rest frame,
and strong, showing rms modulations of 10%-15% while the largest change in flux
density between extremal epochs is 34%. Timescales sampled range from 39 to 821
days, and the characteristic modulation timescale is likely to be less than the
shortest time baseline. The source of modulation is currently ambiguous,
although we favor interstellar scintillation. Best estimates of the size scales
of the 1667 MHz OH line features obtained from refractive interstellar
scintillation models constrain variable features to be smaller than 2 pc, and
quiescent features to be larger than a few pc. Compact masers account for
roughly 27%-58% of the total OH emission in this source. Accelerations in
spectral lines are generally constrained to be less than 3 km/s/yr, but
acceleration of this magnitude is suggested in one of the quiescent spectral
components and merits further study.


title:
Weak Lensing of the CMB: Extraction of Lensing Information from the
  Trispectrum

abstract:
  We discuss the four-point correlation function, or the trispectrum in Fourier
space, of CMB temperature and polarization anisotropies due to the weak
gravitational lensing effect by intervening large scale structure. We discuss
the squared temperature power spectrum as a probe of this trispectrum and, more
importantly, as an observational approach to extracting the power spectrum of
the deflection angle associated with the weak gravitational lensing effect on
the CMB. We extend previous discussions on the trispectrum and associated weak
lensing reconstruction from CMB data by calculating non-Gaussian noise
contributions, beyond the previously discussed dominant Gaussian noise.
Non-Gaussian noise contributions are generated by lensing itself and by the
correlation between the lensing effect and other foreground secondary
anisotropies in the CMB such as the Sunyaev-Zel'dovich (SZ) effect. When the SZ
effect is removed from temperature maps using its spectral dependence, we find
these additional non-Gaussian noise contributions to be an order of magnitude
lower than the dominant Gaussian noise. If the noise-bias due to the dominant
Gaussian part of the temperature squared power spectrum is removed, then these
additional non-Gaussian contributions provide the limiting noise level for the
lensing reconstruction. The temperature squared power spectrum allows a high
signal-to-noise extraction of the lensing deflections and a confusion-free
separation of the curl (or B-mode) polarization due to inflationary
gravitational waves from that due to lensed gradient (or E-mode) polarization.
The small angular scale temperature and polarization anisotropy measurements
provide a novel approach to weak lensing studies, complementing the approach
based on galaxy ellipticities.


title:
Possible link between the changing fine-structure constant and the
  accelerating universe via scalar-tensor theory

abstract:
  In 1976, Shlyakhter showed that the Sm data from Oklo results in the upper
bound on the time-variability of the fine-structure constant:
$|\dot{\alpha}/\alpha| \lsim 10^{-17}{\rm y}^{-1}$, which has ever been the
most stringent bound. Since the details have never been published, however, we
recently re-analyzed the latest data according to Shlyakhter's recipe. We
nearly re-confirmed his result. To be more precise, however, the Sm data gives
either an upper-bound or an "evidence" for a changing $\alpha$:
$\dot{\alpha}/\alpha = -(0.44 \pm 0.04)\times 10^{-16}{\rm y}^{-1}$. A remark
is made to a similar re-analysis due to Damour and Dyson. We also compare our
result with a recent "evidence" due to Webb et al, obtained from distant QSO's.
We point out a possible connection between this time-dependence and the
behavior of a scalar field supposed to be responsible for the acceleration of
the universe, also revealed recently.


title: AGN Outflows: Analysis of the Absorption Troughs

abstract:
  With the advent of Chandra and XMM, X-ray lines spectroscopy of AGN outflows
is off to an exciting start. In this paper we illuminate some of the
complications involved in extracting the outflow's physical conditions
(ionization equilibrium, total column density, chemical abundances) from such
spectroscopic data. To do so we use the example provided by high-quality FUSE
and HST observations of the outflow seen in NGC 985.
  We show how simple determinations of the column density in the UV absorption
lines often severely underestimate the real column densities. This is due to
strong non-black saturation of the absorption troughs, where in many cases the
UV line profile mainly reflects the velocity-dependent covering factor rather
than the column density distribution. We then show that underestimating
individual ionic column densities by a factor of 5 can cause a two orders of
magnitude error in the inferred total column density of the outflow. In some
case this will be enough to associate the UV and X-ray absorber with the same
outflowing material.
  Finally, we note that the UV spectra of NGC 985 have 10--20 times the
resolution and 2--5$\times$ the S/N per resolution element compared with the
best available Chandra spectra of similar objects. Therefore, in the X-ray band
non-black saturation and velocity-dependent covering factor effects will only
become abundantly clear using vastly more capable future X-ray telescopes.
However, by taking into consideration the lessons learned from the UV band, we
can greatly improve the quality of physical constraints we extract from current
X-ray data of AGN outflows.


title:
Velocity Structure of the ISM as Seen by the Spectral Correlation
  Function

abstract:
  (Abridged) We use the statistical tool known as the ``Spectral Correlation
Function" [SCF] to intercompare simulations and observations of the atomic
interstellar medium. The simulations considered mimic three distinct sets of
physical conditions. One of them (run "ISM") is intended to represent a mixture
of cool and warm atomic gas, and includes self-gravity and magnetic fields. For
each simulation, H I spectral-line maps are synthesized and intercompared, both
with each other, and with observations, using the SCF. We find that, when
thermal broadening is large in comparison with fine-scale turbulent velocity
structure, it masks sub-thermal velocity sub-structure in the synthesized
spectra. The H I observations we use here for comparison are of the North
Celestial Pole (NCP) Loop. None of the simulations match the NCP Loop data very
well. The most realistic sets of line profiles and SCF statistics comes from
artifically rescaling the velocity axis of run ISM. Without rescaling, almost
all velocity structure is smeared out by thermal broadening. However, if the
velocity axis is expanded by a factor of 6, the SCF distributions of run ISM an
the NCP Loop match up fairly well. This means that the ratio of thermal to
turbulent pressure in run ISM is much too large as it stands, and that the
simulation is deficient in turbulent energy. This is a consequence of run ISM
not including the effects of supernovae. We conclude that the SCF is a useful
tool for understanding and fine-tuning simulations of interstellar gas, and in
particular that realistic simulations of the atomic ISM need to include the
effects of energetic stellar winds (e.g. supernovae) in order for the ratio of
thermal-to-turbulent pressure to give spectra representative of the observed
interstellar medium in our Galaxy.


title: Molecular gas in NGC6946

abstract:
  We present imaging of molecular gas emission in the star-forming spiral
galaxy NGC6946. Our CO(1-0) and CO(3-2) images, made at 22" resolution with the
IRAM 30-m and the Heinrich Hertz 10-m radio telescopes, are the most extensive
CO observations of this galaxy and are among the most extensive observations of
molecular gas in any spiral galaxy. The molecular component in NGC6946 is
unusually massive, with a ratio of molecular to atomic Hydrogen of 0.57. A star
formation efficiency image for NGC6946 ranges by over two orders of magnitude
with highest values found in the northeastern spiral arm, and anticorrelates
with the 6cm polarized emission image, which traces the regular part of the
magnetic field. We analyse the ISM in NGC6946's disk by making 1-D and 2-D
comparisons of images made in several wavebands. A point-by-point correlation
technique finds that the molecular gas is closely associated with the
7micron-emitting dust. The high correlation found between the MIR emission and
the radio continuum at 6cm cannot be due to dust heating and gas ionization in
star-forming regions because the thermal radio emission is less correlated with
the MIR than the nonthermal emission. A coupling of magnetic fields to gas
clouds is proposed as a possible scenario.


title: The truncation of stellar discs: the magnetic hypothesis

abstract:
  We propose a hypothesis of the truncation of stellar discs based on the
magnetic model of the rotation curve of spiral galaxies. Once the disc had
formed and acquired its present structure, approximately, three balanced forces
were acting on the initial gas: gravity and magnetic forces, inwards, and
centrifugal force. When stars are formed from this gas, the magnetic force is
suddenly suppressed. Gravitation alone cannot retain the newly-formed stars and
at birth places beyond a certain galactocentric radius they escape to
intergalactic space. This radius is the so-called ``truncation radius'', which
is predicted to be at about 4-5 disc radial scale lengths, in promising
agreement with observations.


title: Recent Advances in Large-Scale Structure and Galaxy Formation Studies

abstract:
  I review at the non-specialist level recent progress in the study of the
large-scale structure of the Universe, covering the following areas: (1)
Results from recently completed or ongoing redshift surveys of galaxies and
X-ray clusters; (2) Measurements of the power spectrum of fluctuations
approaching Gpc scales; (3) Redshift-space distortions and their cosmological
use; (4) Structure at high redshifts and its connection to galaxy formation.


title:
The Signature of Supernova Ejecta Measured in the X-ray Afterglow of
  Gamma-Ray Burst 011211

abstract:
  Since their identification with cosmological distances, Gamma-ray bursts
(GRBs) have been recognised as the most energetic phenomena in the Universe,
with an isotropic burst energy as high as 10^54 ergs. However, the progenitors
responsible for the bursts remain elusive, favoured models ranging from a
neutron star binary merger, to the collapse of a massive star. Crucial to our
understanding of the origins of GRBs is the study of the afterglow emission,
where spectroscopy can reveal details of the environment of the burst. Here we
report on an XMM-Newton observation of the X-ray afterglow of GRB 011211. The
X-ray spectrum reveals evidence for emission lines of Magnesium, Silicon,
Sulphur, Argon, Calcium, and possibly Nickel, arising in enriched material with
an outflow velocity of order 0.1c. This is the first direct measurement of
outflowing matter in a gamma ray burst. The observations strongly favour models
where a supernova explosion from a massive stellar progenitor precedes the
burst event and is responsible for the outflowing matter.


title:
ROSAT X-ray sources in the field of the LMC. II.Statistics of background
  AGN and X-ray binaries

abstract:
  About 200 X-ray sources from a sample of spectrally hard ROSAT PSPC sources,
given in the catalog of Haberl & Pietsch (1999), and observed in a ~60 square
degree field of the LMC during several archival pointed observations with a
wide range of exposure times have been reanalyzed. For these sources accurate
count rates and hardness ratios have been recalculated. In comparison to Haberl
& Pietsch (1999) we used merged data from all available observations and we
derived average source parameters by investigating each source individually.
  From a simulation powerlaw spectral tracks have been derived in the HR1 - HR2
plane and ~170 sources have been classified as background X-ray sources or as
LMC X-ray binaries. 80% of the spectrally hard X-ray sources with more than 50
observed counts have been found to be consistent with background X-ray sources
and 20% with LMC X-ray binaries (53 sources with AGN and 15 with X-ray
binaries). The discovery of a new supersoft source RX J0529.4-6713 at the
southern HI boundary of the supergiant shell LMC4 is reported. We find two new
candidate X-ray binary systems which are associated with the optical bar of the
LMC and additional candidate X-ray binaries which are associated with
supergiant shells.


title:
Orbital dynamics of three-dimensional bars: I. The backbone of 3D bars.
  A fiducial case

abstract:
  In this series of papers we investigate the orbital structure of 3D models
representing barred galaxies. In the present introductory paper we use a
fiducial case to describe all families of periodic orbits that may play a role
in the morphology of three-dimensional bars. We show that, in a 3D bar, the
backbone of the orbital structure is not just the x1 family, as in 2D models,
but a tree of 2D and 3D families bifurcating from x1. Besides the main tree we
have also found another group of families of lesser importance around the
radial 3:1 resonance. The families of this group bifurcate from x1 and
influence the dynamics of the system only locally. We also find that 3D orbits
elongated along the bar minor axis can be formed by bifurcations of the planar
x2 family. They can support 3D bar-like structures along the minor axis of the
main bar. Banana-like orbits around the stable Lagrangian points build a forest
of 2D and 3D families as well. The importance of the 3D x1-tree families at the
outer parts of the bar depends critically on whether they are introduced in the
system as bifurcations in $z$ or in $\dot{z}$.


title:
Orbital dynamics of three-dimensional bars: II. Investigation of the
  parameter space

abstract:
  We investigate the orbital structure in a class of 3D models of barred
galaxies. We consider different values of the pattern speed, of the strength of
the bar and of the parameters of the central bulge of the galactic model. The
morphology of the stable orbits in the bar region is associated with the degree
of folding of the x1-characteristic. This folding is larger for lower values of
the pattern speed. The elongation of rectangular-like orbits belonging to x1
and to x1-originated families depends mainly on the pattern speed. The detailed
investigation of the trees of bifurcating families in the various models shows
that major building blocks of 3D bars can be supplied by families initially
introduced as unstable in the system, but becoming stable at another energy
interval. In some models without radial and vertical 2:1 resonances we find,
except for the x1 and x1-originated families, also families related to the
z-axis orbits, which support the bar. Bifurcations of the x2 family can build a
secondary 3D bar along the minor axis of the main bar. This is favoured in the
slow rotating bar case.


title: Deep optical observations of G 65.3+5.7

abstract:
  We present the first CCD mosaic of the supernova remnant G 65.3+5.7 in the
optical emission lines of [O II] and [O III]. The new images reveal several
diffuse and filamentary structures both inside and outside the extent of the
remnant as defined by its X-ray and radio emission. The medium ionization line
of [O III] 5007 provides the sharpest view to the system, while the remnant
appears less filamentary in the emission line of [O II]. There are significant
morphological differences between the two images strongly suggesting the
presence of incomplete shock structures. Deep long-slit spectra were taken at
several different positions of G 65.3+5.7. All spectra originate from shock
heated gas, while the majority of them is characterized by large [O III]/Hbeta
ratios. The sulfur line ratios indicate electron densities below ~200 cm^{-3},
while estimates of the shock velocities lie in the range of 90-140 km/s.
Finally, the observed variations of the Halpha/Hbeta ratios may reflect the
presence of intrinsic absorption affecting the optical spectra.


title: On the Dyadosphere of Black Hole

abstract:
  Basic energy requirements of Gamma Ray Burst(GRB) sources can be easily
accounted for by a pair creation process occurring in the "Dyadosphere" of a
Black Hole endowed with an electromagnetic field (abbreviated to EMBH for
"electromagnetic Black Hole"). This includes the recent observations of
GRB971214 by Kulkarni et al. The "Dyadosphere" is defined as the region outside
the horizon of an EMBH where the electromagnetic field exceeds the critical
value for e^+ e^- pair production. In a very short time $\sim O(hbar mc^2}),
very large numbers of pairs are created there. Further evolution then leads
naturally to a relativistically expanding pair-electromagnetic-pulse
(PEM-pulse). Specific examples of Dyadosphere parameters are given for 10 and
10^5 solar mass EMBH's. This process does occur for EMBH with charge-to-mass
ratio larger than 2.210^{-5} and strictly smaller than one. From a fundamental
point of view, this process represents the first mechanism proved capable of
extracting large amounts of energy from a Black Hole with an extremely high
efficiency (close to 100%).


title: Theoretical thermal X-ray spectra of relativistic MHD jets

abstract:
  Highly relativistic jets are most probably driven by strong magnetic fields
and launched from the accretion disk surrounding a central black hole. Applying
the jet flow parameters (velocity, density, temperature) calculated from the
magnetohydrodynamic (MHD) equations, we derive the thermal X-ray luminosity
along the inner jet flow in the energy range 0.2-10.1 keV. Here, we concentrate
on the case of Galactic microquasars emitting highly relativistic jets. For a 5
solar masses central object and a jet mass flow rate of 10^{-8} solar
masses/year we obtain a jet X-ray luminosity L_x ~ 10^{33} erg\sec. Emission
lines of Fe XXV and Fe XXVI are clearly visible. Relativistic effects such as
Doppler shift and Doppler boosting were considered for different inclinations
of the jet axis. Due to the chosen geometry of the MHD jet the inner X-ray
emitting part is not yet collimated. Therefore, depending on the viewing angle,
the Doppler boosting does not play a major role in the total spectra.


title:
Stellar Archaeology: a Keck Pilot Program on Extremely Metal-Poor Stars
  From the Hamburg/ESO Survey. I Stellar Parameters

abstract:
  In this series of two papers we present a high dispersion spectroscopic
analysis of 8 candidate extremely metal poor stars selected from the
Hamburg/ESO Survey and of 6 additional very metal poor stars. We demonstrate
that with suitable vetting using moderate-resolution spectra the yield of this
survey for stars with [Fe/H] $\le -3.0$ dex is very high; three out of the
eight stars observed thus far at high resolution from the HES are actually that
metal poor, three more have [Fe/H] $\le -2.8$ dex, and the remainder are only
slightly more metal rich. In preparation for a large scale effort to mine the
Hamburg/ESO Survey database for such stars about to get underway, we lay out in
this paper the basic principles we intend to use to determine in a uniform way
the stellar parameters Teff, surface grav, and reddening.


title:
Stellar Archaeology: a Keck Pilot Program on Extremely Metal-Poor Stars
  from the Hamburg/ESO Survey. II. Abundance Analysis

abstract:
  We present a detailed abundance analysis of 8 stars selected as extremely
metal poor candidates from the Hamburg/ESO Survey (HES). For comparison, we
have also analysed 3 extremely metal-poor candidates from the HK survey, and 3
additional bright metal-poor stars. With this work, we have doubled the number
of extremely metal-poor stars ([Fe/H]$\le 3.0$) with high-precision abundance
analyses. Our sample of extremely metal-poor candidates from the HES contains 3
stars with [Fe/H] $\le -3.0$, 3 more with [Fe/H]$\le -2.8$, and 2 stars that
are only slightly more metal rich. Thus, the chain of procedures that led to
the selection of these stars from the HES successfully provides a high fraction
of extremely metal-poor stars. We verify that our stellar parameters, derived
in Paper I, lead to acceptable ionization and excitation balances for Fe,
ruling out substantial non-LTE effects in Fe. For the $\alpha-$elements Mg, Si,
Ca, Ti, the light element Al, the iron-peak elements Sc, Cr, Mn, and the
neutron capture elements Sr and Ba, we find trends in abundance ratios [X/Fe]
similar to those found by previous studies. However,the scatter in most of
these ratios, even at [Fe/H]$\le -3.0$ dex, is surprisingly small. Only Sr and
Ba show scatter larger than the expected errors. Future work (the 0Z project)
will provide much stronger constraints on the scatter (or lack thereof) in
abundances for a greater number of stars. We discuss the implications of these
results for the early chemical evolution of the Galaxy, including such issues
as the number of contributing SN, and the sizes of typical fragments in which
they were born. In addition, we have identified a very metal poor star that
appears to be the result of the s-process chain, operating in a very metal-poor
environment, with extremely enhanced C, Ba, and Pb, and somewhat enhanced Sr.


title: LBQS 0015+0239: A Binary Quasar with Small Angular Separation

abstract:
  We present spectroscopic observations with Keck/LRIS of LBQS 0015+0239, a
pair of quasars at z = 2.45 with a separation of $\Delta\theta = 2.2$ arcsec
(projected linear distance of 17.8 $h_{70}^{-1}$ kpc, for $\Omega_m = 0.3$,
$\Lambda = 0.7$). Lensing is an unlikely interpretation for the images, since
the spectra show significant differences in the NV and CIV emission line
profiles, and there is no luminous galaxy at the anticipated lens position.
Rather, we interpret this pair as the highest redshift known example of a
binary quasar. The redshift difference of 661+/-173 km/s between the two
components is inconsistent with the lensing expectation, but is consistent with
the line of sight velocity difference of a bound pair of galaxies. The spectra
show associated, narrow metal absorption in highly ionized species of C and N,
with a systemic velocity difference of 492+/-6 km/s. It is likely that this
absorption arises in a group or cluster of galaxies surrounding the quasar
pair. After a thorough search, the Large Bright Quasar Survey (LBQS) is known
to contain one gravitational lens and four probable binary pairs. The existence
of close binaries is evidence that quasar activity can be triggered by galaxy
interactions. We speculate that the close pair LBQS 0015+0239 is a rare example
of the pre-merger state of two supermassive black holes.


title: Emission of SN 1006 produced by accelerated cosmic rays

abstract:
  The nonlinear kinetic model of cosmic ray (CR) acceleration in supernova
remnants (SNRs) is used to describe the properties of the remnant of SN 1006.
It is shown, that the theory fits the existing data in a satisfactory way
within a set of parameters which is consistent with the idea that SN 1006 is a
typical source of Galactic CR nucleons, although not necessarily of CR
electrons. The adjusted parameters are those that are not very well determined
by present theory or not directly amenable to astronomical observations. The
calculated expansion law and the radio-, X-ray and gamma-ray emissions produced
by the accelerated CRs in SN 1006 agree quite well with the observations. A
rather large interior magnetic field B_d\approx 100 \muG is required to give a
good fit for the radio and X-ray synchrotron emission. In the predicted TeV
gamma-ray flux from SN 1006, the pi^0-decay gamma-rays, generated by the
nuclear CR component, dominate over the inverse Compton (IC) gamma-rays,
generated by the CR electrons in the cosmic microwave background. The predicted
source morphology in high energy gamma-rays roughly corresponds to that of the
synchrotron emission. The predicted integral gamma-ray flux F \propto e^-1
extends up to energies 100 TeV if CR diffusion is as strong as the Bohm limit.
Only if the interior magnetic field is much lower in the SNR, B_d\approx 10
\muG, then the observed gamma-ray emission can be due to the accelerated
electron component alone. In this case, not plausible physically in our view,
the lowest permissible value of the electron to proton ratio is rather high,
and the maximum individual energy and total energy content of accelerated
nucleons so small, that SN 1006 can not be considered as a typical source of
the nuclear Galactic CRs.


title: The effect of lensing on the identification of bright SCUBA galaxies

abstract:
  Spectroscopic surveys of luminous submillimetre-selected sources have
uncovered optically-bright galaxies at z<1 close to the positions of several
submillimetre (submm) sources. Naive statistical analyses suggest that these
galaxies are associated with the submm emission. However, in some cases, it is
difficult to understand this association given the relatively modest redshifts
and unpreposessing spectral characteristics of the galaxies. These are in stark
constrast to those expected from the massive dust-enshrouded starbursts and AGN
thought to power the bulk of the bright submm population. We present new
observations of optically-bright counterparts to two luminous submm sources,
along with a compilation of previously proposed optically-bright counterparts
with z<1. We suggest that the majority of these associations between bright
galaxies and submm sources may be due to the action of the foreground galaxies
as gravitational lenses on the much fainter and more distant submm sources. We
discuss the implications of this conclusion for our understanding of the SCUBA
population.


title:
The Temperature Structure in Ionized Nebulae and the Chemical Evolution
  of Galaxies

abstract:
  A few results that indicate the presence of temperature variations in gaseous
nebulae are reviewed. The evidence is based on: a) temperatures derived from
different methods, and b) on comparisons of abundances predicted by models of
galactic chemical evolution with abundances derived from observations.


title: VLA Observations of H I in the Helix Nebula (NGC 7293)

abstract:
  We report the detection of 21-cm line emission from H I in the planetary
nebula NGC 7293 (the Helix). The observations, made with the Very Large Array,
show the presence of a ring of atomic hydrogen that is associated with the
outer portion of the ionized nebula. This ring is most probably gas ejected in
the AGB phase that has been subsequently photodissociated by radiation from the
central star. The H I emission spreads over about 50 km/s in radial velocity.
The mass in H I is approximately 0.07 solar masses, about three times larger
than the mass in molecular hydrogen and comparable with the mass in ionized
hydrogen.


title:
Using Supernovae to Determine the Equation of State of the Dark Energy:
  Is Shallow Better than Deep?

abstract:
  Measurements of the flux and redshifts of Type Ia supernovae have provided
persuasive evidence that the expansion of the universe is accelerating. If
true, then in the context of standard FRW cosmology this suggests that the
energy density of hte universe is dominated by "dark energy" -- a component
with negative pressure of magnitude comparable to its energy density. To
further investigate this phenomenon, more extensive surveys of supernovae are
being planned. Given the likely timescales for completion, by the time data
from these surveys are available some important cosmological parameters will be
known to high precision from CMB measurements. Here we consider the impact of
that foreknowledge on the design of supernova surveys. In particular we show
that, despite greater opportunities to multiplex, purely from the point of view
of statistical errors, a deep survey may not obviously be better than a shallow
one.


title: Large Scale Structure in an Era of Precision CMB Measurements

abstract:
  The advent of high signal-to-noise cosmic microwave background (CMB)
anisotropy experiments now allow detailed studies on the statistics related to
temperature fluctuations. The existence of acoustic oscillations in the
anisotropy power spectrum is now established with the clear detection of the
first, and to a lesser confidence the second and the third, peak. Beyond the
acoustic peak structure associated with CMB photon temperature fluctuations, we
study the possibility for an observational detection of oscillations in the
large scale structure (LSS) matter power spectrum due to baryons. We also
suggest a new cosmological test using the angular power spectrum of dark matter
halos, or clusters of galaxies detected via wide-field surveys of the large
scale structure. The standard rulers of the proposed test involve overall shape
of the matter power spectrum and baryon oscillation peaks in projection. The
test allows a measurement of the angular diameter distance as a function of
redshift, similar to the distance to the last scattering surface from the first
acoustic peak in the temperature anisotropy power spectrum. The simultaneous
detection of oscillations in both photons and baryons will provide a strong,
and a necessary, confirmation of our understanding related to the physics
during the recombination era. The proposed studies can be carried out with a
combined analysis of CMB data from missions such as the MAP and the large scale
structure data from missions such as the DUET.


title:
Extrasolar Trojans: The Viability and Detectability of Planets in the
  1:1 Resonance

abstract:
  We explore the possibility that extrasolar planets might be found in the 1:1
mean-motion resonance. There are a variety of stable co-orbtial configurations,
and we specifically examine three different versions of the 1:1 resonance.
These include tadpole and horseshoe type orbits, as well as a more exotic
configuration which occurs when one planet has a highly eccentric orbit while
the other planet moves on a nearly circular orbit. We show that pairs of
planets in 1:1 resonance yield characteristic radial velocity signatures which
are not prone to the sin(i) degeneracy. Indeed, Keplerian fits to the radial
velocities cannot reveal the presence of two planets in the 1:1 resonance. We
discuss a dynamical fitting method for such systems, and illustrate its use
with a simulated data set. Finally, we argue that hydrodynamical simulations
and torqued three-body calculations indicate that 1:1 resonant pairs might
readily form and migrate within protostellar disks.


title:
Non-Gaussian Features of Transmitted Flux of QSO's Ly$\alpha$
  Absorption: Intermittent Exponent

abstract:
  We calculate the structure function and intermittent exponent of the 1.) Keck
data, which consists of 29 high resolution, high signal to noise ratio (S/N)
QSO Ly$\alpha$ absorption spectra, and 2.)the Ly$\alpha$ forest simulation
samples produced via the pseudo hydro scheme for the low density cold dark
matter (LCDM) model and warm dark matter (WDM) model with particle mass
$m_W=300, 600, 800$ and 1000 eV. These two measures detect not only
non-gaussianities, but also the type of non-gaussianty in the the field. We
find that, 1.) the structure functions of the simulation samples are
significantly larger than that of Keck data on scales less than about 100
h$^{-1}$ kpc, 2.) the intermittent exponent of the simulation samples is more
negative than that of Keck data on all redshifts considered, 3.) the
order-dependence of the structure functions of simulation samples are closer to
the intermittency of hierarchical clustering on all scales, while the Keck data
are closer to a lognormal field on small scales. These differences are
independent of noise and show that the intermittent evolution modeled by the
pseudo-hydro simulation is substantially different from observations, even
though they are in good agreement in terms of second and lower order
statistics. (Abridged)