title: The effects of blending on the light curve shape of Cepheids

abstract:
  A short analysis is presented of the effects on the cepheid light curve
shape, i.e. on the Fourier parameters usually adopted for its description, of
the blending of the stellar image with other close stars. The conclusion is
that, within reasonable error, the effects are in general small and the Fourier
decomposition is confirmed to be a useful tool for pulsation mode
discrimination. A large effect has been found on the phase differences in a
narrow period range corresponding to the known resonance centers between
pulsation modes.


title:
Passive spiral formation from halo gas starvation: Gradual
  transformation into S0s

abstract:
  Recent spectroscopic and high resolution $HST$-imaging observations have
revealed significant numbers of ``passive'' spiral galaxies in distant
clusters, with all the morphological hallmarks of a spiral galaxy (in
particular, spiral arm structure), but with weak or absent star formation.
Exactly how such spiral galaxies formed and whether they are the progenitors of
present-day S0 galaxies is unclear. Based on analytic arguments and numerical
simulations of the hydrodynamical evolution of a spiral galaxy's halo gas
(which is a likely candidate for the source of gas replenishment for star
formation in spirals), we show that the origin of passive spirals may well be
associated with halo gas stripping. Such stripping results mainly from the
hydrodynamical interaction between the halo gas and the hot intracluster gas.
Our numerical simulations demonstrate that even if a spiral orbits a cluster
with a pericenter distance $\sim$ 3 times larger than the cluster core radius,
$\sim$ 80 % of the halo gas is stripped within a few Gyr and, accordingly,
cannot be accreted by the spiral. Furthermore, our study demonstrates that this
dramatic decline in the gaseous infall rate leads to a steady increase in the
$Q$ parameter for the disk, with the spiral arm structure, although persisting,
becoming less pronounced as the star formation rate gradually decreases. These
results suggest that passive spirals formed in this way, gradually evolve into
red cluster S0s.


title:
Extended HI spiral structure and the figure rotation of triaxial dark
  halos

abstract:
  The HI disk of the blue compact dwarf (BCD) galaxy NGC 2915 extends to
  22 optical scalelengths and shows spiral arms reaching far beyond the optical
component. None of the previous theories for spiral structure provide likely
explanations for these very extended spiral arms. Our numerical simulations
first demonstrate that such large spiral arms can form in an extended gas disk
embedded in a massive triaxial dark matter halo with slow figure rotation,
through the strong gravitational torque of the rotating halo. We then show that
the detailed morphological properties of the developed spirals and rings depend
strongly on the pattern speed of the figure rotation, the shape of the triaxial
halo, and the inclination of the disk with respect to the plane including the
triaxial halo's long and middle axes. These results strongly suggest that the
dark matter halo of NGC 2915 is triaxial and has figure rotation. Based on
these results, we also suggest that dynamical effects of triaxial halos with
figure rotation are important in various aspect of galaxy formation and
evolution, such as formation of polar ring galaxies, excitation of
non-axisymmetric structures in low surface-brightness galaxies, and gas fueling
to the central starburst regions of BCDs.


title:
Properties of Disk Galaxies in Phenomenological Models of Galaxy
  Formation

abstract:
  We present a phenomenological model for understanding the origins and
evolution of galaxy morphologies from a phenomenological perspective. The model
includes an observationally motivated prescription for star formation in galaxy
disks, as well as a merger-driven starburst mode of star formation. We consider
the formation of bulges and ellipticals both in mergers and by global
instabilities in disks. We use our model to investigate the fundamental
properties of disk galaxies and the effects of surface-brightness limits on
large galaxy surveys.


title:
Probing Dust around Brown Dwarfs: The naked LP 944-20 and the Disk of
  Cha Ha2

abstract:
  We present the first mid-infrared (MIR) detection of a field brown dwarf (BD)
and the first ground-based MIR measurements of a disk around a young BD
candidate. We prove the absence of warm dust surrounding the field BD LP
944-20. In the case of the young BD candidate Cha Ha2, we find clear evidence
for thermal dust emission from a disk. Surprisingly, the object does not
exhibit any silicate feature as previously predicted. We show that the flat
spectrum can be explained by an optically thick flat dust disk.


title:
A comparison of designs of off-axis Gregorian telescopes for mm-wave
  large focal plane arrays

abstract:
  We compare the diffraction-limited field of view (FOV) provided by four types
of off-axis Gregorian telescopes: the classical Gregorian, the aplanatic
Gregorian, and designs that cancel astigmatism and both astigmatism and coma.
The analysis is carried out using telescope parameters that are appropriate for
satellite and balloon-borne millimeter and sub-millimeter wave astrophysics. We
find that the design that cancels both coma and astigmatism provides the
largest flat FOV, about 21 square degrees. We also find that the FOV can be
increased by about 15% by optimizing the shape and location of the focal
surface.


title: Modelling the spectral evolution of classical double radio sources

abstract:
  The spectral evolution of powerful double radio galaxies (FR II's) is thought
to be determined by the acceleration of electrons at the termination shock of
the jet, their transport through the bright head region into the lobes and the
production of the radio emission by synchrotron radiation in the lobes. Models
presented to date incorporate some of these processes in prescribing the
electron distribution which enters the lobes. We have extended these models to
include a description of electron acceleration at the relativistic termination
shock and a selection of transport models for the head region. These are
coupled to the evolution of the electron spectrum in the lobes under the
influence of losses due to adiabatic expansion, by inverse Compton scattering
on the cosmic background radiation and by synchrotron radiation. The
evolutionary tracks predicted by this model are compared to observation using
the power/source-size (P-D) diagram. We find that the simplest scenario, in
which accelerated particles suffer adiabatic losses in the head region which
become more severe as the source expands produces P-D-tracks which conflict
with observation, because the power is predicted to decline too steeply with
increasing size. Agreement with observation can be found by assuming that
adiabatic losses are compensated during transport between the termination shock
and the lobe by a re-acceleration process distributed throughout the head
region.


title:
The CORALIE survey for southern extra-solar planets IX. A 1.3-day period
  brown dwarf disguised as a planet

abstract:
  In this article we present the case of HD 41004 AB, a system composed of a
K0V star and a 3.7-magnitude fainter M-dwarf companion separated by only 0.5
arcsec. An analysis of CORALIE radial-velocity measurements has revealed a
variation with an amplitude of about 50m/s and a periodicity of 1.3days. This
radial-velocity signal is consistent with the expected variation induced by the
presence a very low mass giant planetary companion to HD 41004 A, whose light
dominates the spectra. The radial-velocity measurements were then complemented
with a photometric campaign and with the analysis of the bisector of the
CORALIE Cross-Correlation Function (CCF). While the former revealed no
significant variations within the observational precision of 0.003-0.004 mag
(except for an observed flare event), the bisector analysis showed that the
line profiles are varying in phase with the radial-velocity. This latter
result, complemented with a series of simulations, has shown that we can
explain the observations by considering that HD 41004 B has a brown-dwarf
companion orbiting with the observed 1.3-day period. If confirmed, this
detection represents the first discovery of a brown dwarf in a very short
period (1.3-day) orbit around an M dwarf. Finally, this case should be taken as
a serious warning about the importance of analyzing the bisector when looking
for planets using radial-velocity techniques.


title:
Astrometry with Hubble Space Telescope: A Parallax of the Fundamental
  Distance Calibrator delta Cephei

abstract:
  We present an absolute parallax and relative proper motion for the
fundamental distance scale calibrator, delta Cep. We obtain these with
astrometric data from FGS 3, a white-light interferometer on HST. Utilizing
spectrophotometric estimates of the absolute parallaxes of our astrometric
reference stars and constraining delta Cep and reference star HD 213307 to
belong to the same association (Cep OB6, de Zeeuw et al. 1999), we find
pi_{abs} = 3.66 +/- 0.15 mas. The larger than typical astrometric residuals for
the nearby astrometric reference star HD 213307 are found to satisfy Keplerian
motion with P = 1.07 +/- 0.02 years, a perturbation and period that could be
due to a F0V companion ~7 mas distant from and ~4 magnitudes fainter than the
primary. Spectral classifications and VRIJHKT$_2$M and DDO51 photometry of the
astrometric reference frame surrounding delta Cep indicate that field
extinction is high and variable along this line of sight. However the
extinction suffered by the reference star nearest (in angular separation and
distance) to delta Cep, HD 213307, is lower and nearly the same as for delta
Cep. Correcting for color differences, we find <A_V> = 0.23 +/- 0.03 for delta
Cep, hence, an absolute magnitude M_V = -3.47 +/- 0.10. Adopting an average V
magnitude, <V> = 15.03 +/- 0.03, for Cepheids with log P = 0.73 in the LMC from
Udalski et al. (1999), we find a V-band distance modulus for the LMC, m-M =
18.50 +/- 0.13 or, 18.58 +/- 0.15, where the latter value results from a highly
uncertain metallicity correction (Freedman et al. 2001). These agree with our
previous RR Lyr HST parallax-based determination of the distance modulus of the
LMC.


title: Relativistic models and the jet velocity field in the radio galaxy 3C 31

abstract:
  We show that the principal differences in appearance of the main and
counter-jets within 30 arcsec of the nucleus of the low-luminosity radio galaxy
3C 31 can result entirely from the effects of relativistic aberration in two
symmetrical, antiparallel, axisymmetric, time-stationary relativistic flows. We
develop empirical parameterized models of the jet geometry and the
three-dimensional distributions of the velocity, emissivity and magnetic-field
structure and optimize their parameters by fitting the predicted synchrotron
intensity and polarization to deep 8.4-GHz VLA observations. We conclude that
the jets are at roughly 52 degrees to the line of sight, that they decelerate
and that they have transverse velocity gradients. They have three regions with
distinct kinematics: a narrow inner region; a flaring region of rapid expansion
followed by recollimation and a conical outer region. There is a discontinuity
in the flow between inner and flaring regions. The on-axis velocity is close to
0.8c until the end of the flaring region, where it drops abruptly to 0.55c,
thereafter falling more slowly to 0.25c at the end of the modelled region.
Throughout the flaring and outer regions, the velocity at the edge of the jet
is 0.7 of its on-axis value. The magnetic field has primarily toroidal and
longitudinal components except in the flaring region, where there is a
significant radial component at the jet edge. Simple adiabatic models fail in
the inner and flaring regions. The inferred transverse velocity profiles and
field structure in the flaring region support the idea that the jets decelerate
by entraining the external medium. We demonstrate the appearance of our model
at other angles to the line of sight and argue that other low-luminosity radio
galaxies resemble 3C 31 seen at different orientations. [Abridged]


title: Extra-solar planets around HD196050, HD216437 and HD160691

abstract:
  We report precise Doppler measurements of the stars HD 216437, HD 196050 and
HD 160691 obtained with the Anglo-Australian Telescope using the UCLES
spectrometer together with an iodine cell as part of the Anglo-Australian
Planet Search. Our measurements reveal periodic Keplerian velocity variations
that we interpret as evidence for planets in orbit around these solar type
stars. HD 216437 has a period of 1294$\pm$250 d, a semi-amplitude of 38$\pm$4 m
s$^{-1}$ and of an eccentricity of 0.33$\pm$0.09. The minimum (M sin $i$) mass
of the companion is 2.1$\pm$0.3 M$_{\rm JUP}$ and the semi-major axis is
2.4$\pm$0.5 au. HD 196050 has a period of 1288$\pm$230 d, a semi-amplitude of
54$\pm$8 m s$^{-1}$ and an eccentricity of 0.28$\pm$0.15. The minimum mass of
the companion is 3.0$\pm$0.5 M$_{\rm JUP}$ and the semi-major axis is
2.3$\pm$0.5 au. We also report further observations of the metal rich planet
bearing star HD 160691. Our new solution confirms the previously reported
planet and shows a trend indicating a second, longer-period companion. These
discoveries add to the growing numbers of midly-eccentric, long-period
extra-solar planets around Sun-like stars. As seems to be typical of stars with
planets, both stars are metal-rich.


title:
Morphology of the Secondary CMB Anisotropies: the Key to "Smoldering"
  Reionization

abstract:
  We show how the morphological analysis of the maps of the secondary CMB
anisotropies can detect an extended period of ``smoldering'' reionization,
during which the universe remains partially ionized. Neither radio observations
of the redshifted 21cm line nor IR observations of the redshifted Lyman-alpha
forest will be able to detect such a period. The most sensitive to this kind of
non-gaussianity parameters are the number of regions in the excursion set, the
perimeter of the excursion set, and the genus of the largest (by area) region.
For example, if the universe reionized fully at z=6, but maintained about 1/3
mean ionized fraction since z=20, then a 2 arcmin map with 500x500 pixel
resolution and a signal-to-noise ratio S/N=1/2 allows to detect the
non-gaussianity due to reionization with better than 99% confidence level.


title: Thin discs, thick discs and transition zones

abstract:
  Accretion onto a compact object must occur through a disc when the material
has some initial angular momentum. Thin discs and the thicker low radiative
efficiency accretion flows are solutions to this problem that have been widely
studied and applied. This is an introduction to these accretion flows within
the context of X-ray binaries and cataclysmic variables.


title: The Molecular Line Opacity of MgH in Cool Stellar Atmospheres

abstract:
  A new, complete, theoretical rotational and vibrational line list for the A-X
electronic transition in MgH is presented. The list includes transition
energies and oscillator strengths for all possible allowed transitions and was
computed using the best available theoretical potential energies and dipole
transition moment function with the former adjusted to account for experimental
data. The A-X line list, as well as new line lists for the B'-X and the X-X
(pure rovibrational) transitions, were included in comprehensive stellar
atmosphere models for M, L, and T dwarfs and solar-type stars. The resulting
spectra, when compared to models lacking MgH, show that MgH provides
significant opacity in the visible between 4400 and 5600 Angstrom. Further,
comparison of the spectra obtained with the current line list to spectra
obtained using the line list constructed by Kurucz (1993) show that the Kurucz
list significantly overestimates the opacity due to MgH particularly for the
bands near 5150 and 4800 Angstrom with the discrepancy increasing with
decreasing effective temperature.


title: Discovery of a 136 millisecond radio and X-ray pulsar in SNR G54.1+0.3

abstract:
  We report the discovery of a pulsar with period P = 136 ms and dispersion
measure 308 pc/cc in a deep observation of the supernova remnant (SNR)
G54.1+0.3 with the Arecibo radio telescope. Timing measurements of the new
pulsar, J1930+1852, reveal a characteristic age of Pdt/2dP = 2900 yr and
spin-down luminosity dE/dt = 1.2e37 erg/s. We have subsequently searched
archival ASCA X-ray data of this SNR, and detect pulsations with a consistent
period. These findings ensure that PSR J1930+1852 is the pulsar that powers the
"Crab-like" SNR G54.1+.3. Together with existing Chandra observations of the
SNR, we derive an X-ray pulsed fraction (2-10 keV) of ~27%. We also find that
the cooling efficiency of the pulsar wind nebula (PWN) is intermediate between
those of the Vela and Crab PWNe: Lx (2-10 keV) ~0.002 dE/dt. PSR J1930+1852 is
a very weak radio source, with period-averaged flux density at 1180 MHz of 60
microJy. For a distance of 5 kpc, its luminosity, ~1 mJy kpc^2, is among the
lowest for known young pulsars.


title: The Low-Mass X-ray Binary-Globular Cluster connection in NGC 4472

abstract:
  We have analyzed the low mass X-ray binary (LMXB) candidates in a Chandra
observation of the giant elliptical galaxy NGC 4472. In a region observed by
the Hubble Space Telescope, approximately 40% of the bright (L_X >= 10^37
ergs/s) LMXBs are associated with optically identified globular clusters (GC).
This is significantly higher than the fraction of bright LMXBs in Galactic GCs
and confirms that GCs are the dominant sites of LMXB formation in early type
galaxies. The approximately 4% of NGC 4472 GCs hosting bright LMXBs, on the
other hand, is remarkably similar to the fraction of GCs with LMXBs in every
other galaxy. Although statistical tests suggest that the luminosity of a
cluster is an important driver of LMXB formation in GCs, this appears largely
to be a consequence of the greater number of stars in bright clusters. The
metallicity of GCs is a strong determinant of LMXB specific frequency, with
metal-rich clusters about 3 times more likely to host LMXBs than metal-poor
ones. There are weaker dependences on the size of a GC and its distance from
the center of the galaxy. The X-ray luminosity does not depend significantly on
the properties of the host GC. Furthermore, the spatial distribution and X-ray
luminosity function of LMXBs within and outside GCs are indistinguishable. The
X-ray luminosity function of both GC-LMXBs and non-GC-LMXBs reveal a break at
approximately 3x10^38 ergs/s strongly suggesting that the brightest LMXBs are
black hole accretors.


title: Supermassive Black Holes

abstract:
  After a brief historical introduction, we summarize current efforts and
accomplishments in the study of supermassive black holes.


title:
Narrow Components within the Fe Kalpha Profile of NGC 3516: Evidence for
  the Importance of General Relativistic Effects?

abstract:
  We present results from a simultaneous Chandra HETG and XMM-Newton
observation of NGC 3516. We find evidence for several narrow components of Fe
Kalpha along with a broad line. We consider the possibility that the lines
arise in an blob of material ejected from the nucleus with velocity ~0.25c. We
also consider an origin in a neutral accretion disk, suffering enhanced
illumination at 35 and 175 gravitational radii, perhaps due to magnetic
reconnection. The presence of these narrow features indicates there is no
Comptonizing region along the line-of-sight to the nucleus. This in turn is
compelling support for the hypothesis that broad Fe Kalpha components are, in
general, produced by strong gravity.


title:
Brane World Cosmologies and Statistical Properties of Gravitational
  Lenses

abstract:
  Brane world cosmologies seem to provide an alternative explanation for the
present accelerated stage of the Universe with no need to invoke either a
cosmological constant or an exotic \emph{quintessence} component. In this paper
we investigate statistical properties of gravitational lenses for some
particular scenarios based on this large scale modification of gravity. We show
that a large class of such models are compatible with the current lensing data
for values of the matter density parameter $\Omega_{\rm{m}} \leq 0.94$
($1\sigma$). If one fixes $\Omega_{\rm{m}}$ to be $\simeq 0.3$, as suggested by
most of the dynamical estimates of the quantity of matter in the Universe, the
predicted number of lensed quasars requires a slightly open universe with a
crossover distance between the 4 and 5-dimensional gravities of the order of
$1.76 H_o^{-1}$.


title:
Spectroscopic Target Selection in the Sloan Digital Sky Survey: The Main
  Galaxy Sample

abstract:
  We describe the algorithm that selects the main sample of galaxies for
spectroscopy in the Sloan Digital Sky Survey from the photometric data obtained
by the imaging survey. Galaxy photometric properties are measured using the
Petrosian magnitude system, which measures flux in apertures determined by the
shape of the surface brightness profile. The metric aperture used is
essentially independent of cosmological surface brightness dimming, foreground
extinction, sky brightness, and the galaxy central surface brightness. The main
galaxy sample consists of galaxies with r-band Petrosian magnitude r < 17.77
and r-band Petrosian half-light surface brightness < 24.5 magnitudes per square
arcsec. These cuts select about 90 galaxy targets per square degree, with a
median redshift of 0.104. We carry out a number of tests to show that (a) our
star-galaxy separation criterion is effective at eliminating nearly all stellar
contamination while removing almost no genuine galaxies, (b) the fraction of
galaxies eliminated by our surface brightness cut is very small (0.1%), (c) the
completeness of the sample is high, exceeding 99%, and (d) the reproducibility
of target selection based on repeated imaging scans is consistent with the
expected random photometric errors. (abridged)


title: Mass Profile of the Infall Region of the Abell 2199 Supercluster

abstract:
  Using a redshift survey of 1323 galaxies (1092 new or remeasured) in a region
of 95 square degrees centered on the nearby galaxy cluster Abell 2199, we
analyze the supercluster containing A2199, A2197, and an X-ray group. The
caustic technique accurately reproduces the true mass profiles of simulated
simple superclusters (i.e., superclusters where the virial mass of one cluster
is 2-10 times the virial mass of all other clusters in the supercluster). We
calculate the masses of the two main components of A2197 (A2197W and A2197E)
using archival X-ray observations and demonstrate that the A2199 supercluster
is simple and thus that the caustic technique should yield an accurate mass
profile. The mass profile is uncertain by ~30% within 3 Mpc/h and by a factor
of two within 8 Mpc/h and is one of only a few for a supercluster on such large
scales. Independent X-ray mass estimates agree with our results at all radii
where they overlap. The mass profile strongly disagrees with an isothermal
sphere profile but agrees with profiles suggested by simulations. We discuss
the interplay of the supercluster dynamics and the dynamics of the bound
subclusters. The agreement between the infall mass profile and other techniques
shows that the caustic technique is surprisingly robust for simple
superclusters (abridged).


title: Is The Enigmatic Source 3EG J1828+0142 a Galactic Microblazar ?

abstract:
  The unidentified EGRET source 3EG J1828+0142, located at (l,b) ~ (31.9,5.8)
(Hartman et al. 1999), is particularly enigmatic since it displays very high
variability over timescales of months (Torres et al. 2000, Tompkins 1999) yet
no blazar has been found within the 95% confidence contour of the gamma-ray
location error-box (Punsly et al 2000). It also has an unusually steep
gamma-ray spectral index of Gamma=2.76 +/- 0.39. It's relatively low latitude
may be indicative of a galactic origin of the variable GeV flux. A
multifrequency study of this source has been initiated and may reveal the
presence of a novel type of compact object: a galactic 'microblazar'. X-ray
data, especially those of high spatial resolution from CHANDRA, would be
particularly useful in establishing such a connection.


title:
On the Unique Solution of Planet and Star Parameters from an Extrasolar
  Planet Transit Light Curve

abstract:
  There is a unique solution of the planet and star parameters from a planet
transit light curve with two or more transits if the planet has a circular
orbit and the light curve is observed in a band pass where limb darkening is
negligible. The existence of this unique solution is very useful for current
planet transit surveys for several reasons. First, there is an analytic
solution that allows a quick parameter estimate, in particular of Rp. Second,
the stellar density can be uniquely derived from the transit light curve alone.
The stellar density can be used to immediately rule out a giant star (and hence
a much larger than planetary companion) and can also be used to put an upper
limit on the stellar and planet radius even considering slightly evolved stars.
Third, the presence of an additional fully blended star that contaminates an
eclipsing system to mimic a planet transit can be largely ruled out from the
transit light curve given a spectral type for the central star. Fourth, the
period can be estimated from a single-transit light curve and a measured
spectral type. All of these applications can be used to select the best planet
transit candidates for mass determination by radial velocity follow-up. To use
these applications in practice, the photometric precision and time sampling of
the light curve must be high (better than 0.005 mag precision and 5 minute time
sampling).


title: Subaru optical observations of the old pulsar PSR B0950+08

abstract:
  We report the B band optical observations of an old (17.5 Myr) radiopulsar
PSR B0950+08 obtained with the Suprime-Cam at the Subaru telescope. We detected
a faint object, B=27.07(16). Within our astrometrical accuracy it coincides
with the radio position of the pulsar and with the object detected earlier by
Pavlov et al. (1996) in UV with the HST/FOC/F130LP. The positional coincidence
and spectral properties of the object suggest that it is the optical
counterpart of PSR B0950+08. Its flux in the B band is two times higher than
one would expect from the suggested earlier Rayleigh-Jeans interpretation of
the only available HST observations in the adjacent F130LP band. Based on the B
and F130LP photometry of the suggested counterpart and on the available X-ray
data we argue in favour of nonthermal origin of the broad-band optical spectrum
of PSR B0950+08, as it is observed for the optical emission of the younger,
middle-aged pulsars PSR B0656+14 and Geminga. At the same time, the optical
efficiency of PSR B0950+08, estimated from its spin-down power and the detected
optical flux, is by several orders of magnitude higher than for these pulsars,
and comparable with that for the much younger and more energetic Crab pulsar.
We cannot exclude the presence of a compact, about 1'', faint pulsar nebula
around PSR B0950+08, elongated perpendicular to the vector of its proper
motion, unless it is not a projection of a faint extended object on the pulsar
position.


title: Protostellar Jets Driven by a Disorganized Magnetic Field

abstract:
  We have proposed a viscoelastic model of the Maxwell stresses due to the
disorganized magnetic field in MRI-driven MHD turbulence. Viscoelastic fluids
in the laboratory are known to produce jet-like structures under the action of
a rotating sphere. Here we argue that a similar mechanism may help explain jets
in protostellar systems. Such jets would be driven not by large-scale organized
magnetic fields, but by the mean-field stresses of small-scale tangled magnetic
fields.


title:
A QSO survey via optical variability and zero proper motion in the M92
  field. IV. More QSOs due to improved photometry

abstract:
  We continue the QSO search in the 10 square degrees Schmidt field around M92
based on variability and proper motion (VPM) constraints. We have re-reduced
162 digitised B plates with a time-baseline of more than three decades and have
considerably improved both the photometric accuracy and the star-galaxy
separation at B>19. QSO candidates are selected and marked with one out of
three degrees of priority based on the statistical significance of their
measured variability and zero proper motion. Spectroscopic follow-up
observations of 84 new candidates with B>19 revealed an additional 37 QSOs and
7 Seyfert1s. In particular, all 92 high-priority candidates are
spectroscopically classified now; among them are 70 QSOs and 9 Seyfert1s
(success rate 86%). We expect that 87% (55%) of all QSOs with B<19.0 (19.8) are
contained in this high-priority subsample. For the combined sample of
high-priority and medium-priority objects, a completeness of 89% is estimated
up to B_lim=19.5. The sample of all AGNs detected in the framework of the VPM
search in the M92 field contains now 95 QSOs and 14 Seyfert1s with B<19.9.
Although the VPM QSOs were selected by completely different criteria, their
properties do not significantly differ from those of QSOs found by more
traditional optical survey techniques. In particular, the spectra and the
optical broad band colours do not provide any hints on a substantial population
of red QSOs up to the present survey limit.


title:
Halting Planet Migration in the Evacuated Centers of Protoplanetary
  Disks

abstract:
  Precise Doppler searches for extrasolar planets find a surfeit of planets
with orbital periods of 3-4 days, and no planets with orbital periods less than
3 days. The circumstellar distance, R_0, where small grains in a protoplanetary
disk reach sublimation temperature (~1500 K) corresponds to a period of ~6
days. Interior to R_0, turbulent accretion due to magneto-rotational
instability may evacuate the disk center. We suggest that planets with orbital
periods of 3-4 days are so common because migrating planets halt once this
evacuated region contains the sites of their exterior 2:1 Lindblad resonances.


title:
Stellar and Wind Properties of LMC WC4 stars - A metallicity dependence
  for Wolf-Rayet mass-loss rates

abstract:
  We use ultraviolet space-based (FUSE, HST) and optical/IR ground-based (2.3m
MSSSO, NTT) spectroscopy to determine the physical parameters of six WC4-type
Wolf-Rayet stars in the Large Magellanic Cloud. Stellar parameters are revised
significantly relative to Grafener et al. (1998) based on improved observations
and more sophisticated model atmosphere codes, which account for line
blanketing and clumping. We find that stellar luminosities are revised upwards
by up to 0.4 dex, with surface abundances spanning a lower range of
0.1<C/He<0.35 (20-45% carbon by mass) and O/He<0.06 (<10% oxygen by mass).
Relative to Galactic WC5-8 stars at known distance, and analysed in a similar
manner, LMC WC4 stars possess systematically higher stellar luminosities,
0.2dex lower wind densities, yet a similar range of surface chemistries. We
illustrate how the classification CIII 5696 line is extremely sensitive to wind
density, such that this is the principal difference between the subtype
distribution of LMC and Galactic early-type WC stars. Temperature differences
do play a role, but carbon abundance does not affect WC spectral types. We
illustrate the effect of varying temperature and mass-loss rate on the WC
spectral type for HD32257 (WC4, LMC) and HD156385 (WC7, Galaxy) which possess
similar abundances and luminosities.
  Using the latest evolutionary models, pre-supernova stellar masses in the
range 11-19 Mo are anticipated for LMC WC4 stars, with 7-14 Mo for Galactic WC
stars with known distances. These values are consistent with pre-cursors of
bright Type-Ic supernovae such as SN1998bw (alias GRB 980425) for which a
minimum total mass of C and O of 14Mo has been independently derived.


title:
Weak Gravitational Lensing by a Sample of X-Ray Luminous Clusters of
  Galaxies -- II. Comparison with Virial Masses

abstract:
  Dynamic velocity dispersion and mass estimates are given for a sample of five
X-ray luminous rich clusters of galaxies at intermediate redshifts (z~0.3)
drawn from a sample of 39 clusters for which we have obtained gravitational
lens mass estimates. The velocity dispersions are determined from between 9 and
20 redshifts measured with the LDSS spectrograph of the William Herschel
Telescope, and virial radii are determined from imaging using the UH8K mosaic
CCD camera on the University of Hawaii 2.24m telescope.
  Including clusters with velocity dispersions taken from the literature, we
have velocity dispersion estimates for 12 clusters in our gravitational lensing
sample. For this sample we compare the dynamical velocity dispersion estimates
with our estimates of the velocity dispersions made from gravitational lensing
by fitting a singular isothermal sphere profile to the observed tangential weak
lensing distortion as a function of radius. In all but two clusters, we find a
good agreement between the velocity dispersion estimates based on spectroscopy
and on weak lensing.


title: Low-energy X-ray emission from the Abell 2199 cluster of galaxies

abstract:
  In a recent Letter, Berghoefer & Bowyer rediscussed the analysis of BeppoSAX
LECS data of the cluster of galaxies Abell 2199 as presented by Kaastra et al.,
in particular the detection of a soft X-ray excess. Berghoefer & Bowyer stated
that their analysis method is better suited and does not show evidence for a
soft X-ray excess. Here we find it necessary to publish a rebuttal, because it
can be demonstrated that the method used by Berghoefer & Bowyer is
oversimplified, leading to an erroneous result. As a consequence, their
statement that our initial analysis is incorrect is invalid and the detection
of a soft X-ray excess in A 2199 is still confirmed.


title: High-Energy Gamma-ray Sources and the Quest for their Identification

abstract:
  The 3rd EGRET catalogue lists 271 sources and provides an identification for
101 of them. Thus, the unidentified sources are the majority in the gamma-ray
sky, as we currently know it. Solving the mystery of the unidentified gamma-ray
sources is a major challenge for all fields of astronomy. Here we shall review
the different approaches towards source identification as well as the results
achieved so far.


title: High resolution spectroscopy of nearby AGN

abstract:
  In this paper the potential of high resolution spectroscopy of nearby AGN
with XEUS is discussed. The focus is upon the energy resolution that is needed
in order to disentangle the different spectral components. It is shown that
there is an urgent need for high spectral resolution, and that a spectral
resolution of 1 eV, if possible, leads to a significant increase in diagnostic
power as compared to 2 eV resolution.


title: The HI Content of the Virgo Cluster Galaxies

abstract:
  Because of its proximity and richness on late-type galaxies, the Virgo
cluster has been the subject of numerous studies exploring the effect of the
intracluster environment on galaxy evolution. First discovered nearly three
decades ago by Davies & Lewis (1973), the neutral hydrogen (HI) deficiency of
the Virgo galaxies is now a well-established observational phenomenon also
observed on many other rich clusters. A number of studies on the neutral
hydrogen 21-cm line of Virgo cluster galaxies --from the lenticular and largest
spiral types through the faintest dwarf irregulars-- show that a significant
number of these objects have lost a substantial fraction of their atomic
hydrogen and are HI-deficient when compared with galaxies of the same optical
properties in less dense environments.


title:
On the Heating of the Solar Corona and the Acceleration of the Low-Speed
  Solar Wind by Acoustic Waves Generated in Corona

abstract:
  We investigate possibilities of solar coronal heating by acoustic waves
generated not at the photosphere but in the corona, aiming at heating in the
mid- to low-latitude corona where the low-speed wind is expected to come from.
Acoustic waves of period tau ~ 100s are triggered by chromospheric
reconnection, one model of small scale magnetic reconnection events recently
proposed by Sturrock. These waves having a finite amplitude eventually form
shocks to shape sawtooth waves (N-waves), and directly heat the surrounding
corona by dissipation of their wave energy. Outward propagation of the N-waves
is treated based on the weak shock theory, so that the heating rate can be
evaluated consistently with physical properties of the background coronal
plasma without setting a dissipation length in an ad hoc manner. We construct
coronal structures from the upper chromosphere to the outside of 1AU for
various inputs of the acoustic waves having a range of energy flux of F_{w,0} =
(1-20) times 10^5 erg cm^{-2} s^{-1} and a period of tau = 60-300s. The heating
by the N-wave dissipation effectively works in the inner corona and we find
that the waves of F_{w,0} >= 2 times 10^5 erg cm^{-2} s^{-1} and tau >= 60s
could maintain peak coronal temperature, T_{max} > 10^6 K. The model could also
reproduce the density profile observed in the streamer region. However, due to
its short dissipation length, the location of T_{max} is closer to the surface
than the observation, and the resultant flow velocity of the solar wind is
lower than the observed profile of the low-speed wind. The cooperations with
other heating and acceleration sources with the larger dissipation length are
inevitable to reproduce the real solar corona.


title:
The Structure of Radiative Shock Waves. IV. Effects of Electron Thermal
  Conduction

abstract:
  We considered the structure of steady-state radiative shock waves propagating
in the partially ionized hydrogen gas with density rho1 = 1e-10 gm/cm^3 and
temperature 3000K <= T1 <= 8000K. The radiative shock wave models with electron
thermal conduction in the vicinity of the viscous jump are compared with pure
radiative models. The threshold shock wave velocity above of which effects of
electron thermal conduction become perceptible is of U1=70 km/s and corresponds
to the upstream Mach numbers from M1= 6 at T1=8000K to M1=11 at T1=3000K. In
shocks with efficient electron heat conduction more than a half of hydrogen
atoms are ionized in the radiative precursor, whereas behind the viscous jump
the hydrogen gas undergoes the full ionization. The existence of the electron
conductive precursor leads to the enhancement of the Lyman continuum flux
trapped in the surroundings of the discontinuous jump. For upstream velocities
ranged within 70 km/s <= U1 <= 85 km/s the partially ionized hydrogen gas of
the radiative precursor undergoes the additional ionization (<= 5%), whereas
the total radiave flux emerging from the shock wave increases by 10% <=
delta(FRad) <= 25% .


title: The origin of the radio emission from beta Lyrae

abstract:
  In this paper we present new observational evidence that supports the
presence of an extra source of continuum emission in the binary system beta
Lyrae. New VLA and IRAM observations, together with published data from the
literature and ISO archive data, allow us to build the Spectral Energy
Distribution of the binary between 5x10^9 Hz and 5x10^15Hz. The
radio-millimeter part of the spectrum is consistent with free-free emission
from a symbiotic-like wind associated with the primary component and ionized by
the radiation field of the hidden companion. Furthermore, we also consider the
possibility that the observed radio flux originates from collimated radio
structures associated with the mass gaining component and its disk (Conical
thermal jets). An extrapolation of this emission to the far-IR part of the
spectrum indicates that in both cases the free-free contribution at these
frequencies cannot explain the observations and that the observed infrared
excess flux is due principally to the secondary component and its associated
disk.


title: Jet/cloud collision, 3D gasdynamic simulations of HH 110

abstract:
  We present 3D, gasdynamic simulations of jet/cloud collisions, with the
purpose of modelling the HH 270/110 system. From the models, we obtain
predictions of H$\alpha$ and H$_2$ 1-0 s(1) emission line maps, which
qualitatively reproduce some of the main features of the corresponding
observations of HH 110. We find that the model that better reproduces the
observed structures corresponds to a jet that was deflected at the surface of
the cloud $\sim 1000$ yr ago, but is now boring a tunnel directly into the
cloud. This model removes the apparent contradiction between the jet/cloud
collision model and the lack of detection of molecular emission in the crossing
region of the HH 270 and HH 110 axes.


title: Lensing and the Centers of Distant Early-Type Galaxies

abstract:
  Gravitational lensing provides a unique probe of the inner 10-1000 pc of
distant galaxies (z=0.2-1). Lens theory predicts that every strong lens system
should have a faint image near the center of the lens galaxy, which should be
visible in radio lenses but have not been observed. We study these ``core''
images using models derived from the stellar distributions in nearby early-type
galaxies. We find that realistic galaxies predict a remarkably wide range of
core images, with lensing magnifications spanning some six orders of magnitude.
More concentrated galaxies produce fainter core images, although not with any
simple, quantitative, model independent relation. Some real galaxies have
diffuse cores and predict bright core images (magnification mu>~0.1), but more
common are galaxies that predict faint core images (mu<~0.001). Thus, stellar
mass distributions alone are probably concentrated enough to explain the lack
of observed core images, and may require observational sensitivity to improve
by an order of magnitude before detections of core images become common.
Two-image lenses will tend to have brighter core images than four-image lenses,
so they will be the better targets for finding core images and exploiting these
tools for studying the central mass distributions of distant galaxies.


title: Galaxies: The Third Dimension -- Conference Summary

abstract:
  ``Galaxies: the Third Dimension'' continues a tradition which started in
Marseilles 1994 with the ``Tridimensional Optical Spectroscopic Methods in
Astrophysics'' meeting, followed by ``Imaging the Universe in Three
Dimensions'' at Walnut Creek in 1999. Since then, there have been developments
both in instrumentation and in the way astronomy is conducted, and these need
to be seen against a broad canvas. As we emphasize below, one of the main
reasons for satisfaction is the trend towards talks focused on scientific
results rather than on `yet another 3D spectroscopic technology.'


title: Cosmic Shear: The Dark Side of the Universe

abstract:
  We discuss the present status and future prospects for cosmic shear
observations and their cosmological constraints. We review the evidences
supporting the cosmological origin of the measured signal, and discuss the
possible problems coming from intrinsic alignment and from the actual
limitations of theoretical predictions.


title: Lithium abundances from the 6104A line in cool Pleiades stars

abstract:
  Lithium abundances determined by spectral synthesis from both the 6708A
resonance line and the 6104 subordinate line are reported for 11 late-type
Pleiades stars, including spectra previously analysed by Russell (1996). We
report a 0.7 dex scatter in the abundances from 6708A, and a scatter at least
as large from the 6104A line. We find a reasonable correllation between the
6104A and 6708A Li abundances, although four stars have 6104A-determined
abundances which are significantly larger than the 6708-determined values, by
up to 0.5 dex, suggesting problems with the homogeneous, one-dimensional
atmospheres being used. We show that these discrepancies can be explained,
although probably not uniquely, by the presence of star spots with plausible
coverage fractions. The addition of spots does not significantly reduce the
apparent scatter in Li abundances, leaving open the possibility that at least
some of the spread is caused by real star-to-star differences in pre-main-
sequence Li depletion.


title: Constraining Dark Matter with the Long-Term Variability of Quasars

abstract:
  By comparing the results of numerical microlensing simulations to the
observed long-term variability of quasars, strong upper limits on the
cosmological density of compact objects in the mass range 0.01 to 0.0001 solar
masses may be imposed. Using recently developed methods to better approximate
the amplification of large sources, we investigate in what way the constraints
are affected by assumptions concerning the size of the optical
continuum-emitting region of quasars in the currently favored (Omega_M=0.3,
Omega_Lambda=0.7) cosmology.


title: A photometric method to determine supermassive black hole masses

abstract:
  We report the discovery of a strong correlation between the shape of a
bulge's light-profile and the mass of its central supermassive black hole
(M_{bh}). We find that log(M_{bh}/M_{sun}) = 2.91(+/-0.38)log(n) +
6.37(+/-0.21), where `n' is the Sersic r^{1/n} shape index of the bulge. This
correlation is marginally stronger than the relationship between the logarithm
of the stellar velocity dispersion and log(M_{bh}) and has comparable scatter.
It therefore offers a cheap (in terms of telescope time) alternative to
estimating the masses of supermassive black holes.


title:
High Resolution Soft X-ray Spectroscopy of M87 with the Reflection
  Grating Spectrometers on XMM-Newton

abstract:
  We present high-resolution X-ray spectroscopic observations of M87 with the
Reflection Grating Spectrometers on XMM-Newton. We detect strong K-shell line
emission from N, O, Ne, Mg, some emission from He-like Si, a fully resolved set
of Fe L-shell emission spectra, and some emission from C. The angular intensity
distributions of the strong emission lines are detectably resolved on scales
(15-160) arcsec. The gas in the inner arcmin of M87 has a multi-phase
structure, as indicated by the similarity of the emission line profiles of Fe L
shell ions with widely separated ionization potentials. The global Fe L
spectrum is approximately consistent with an isothermal plasma at kT_e ~ 1.8
keV, in addition to a component with a temperature distribution appropriate to
an isobaric cooling flow, but with a minimum temperature cutoff of kT_min ~ 600
eV. The behaviour of this cooling-flow component is qualitatively similar to
what is seen in other cooling flow clusters. Finally, we do not find any strong
evidence for a spatial variation in abundances due to resonance scattering
redistribution in the inner arcminute of the core.


title:
FUSE Observations of the Magellanic Bridge Gas toward Two Early-Type
  Stars: Molecules, Physical Conditions, and Relative Abundance

abstract:
  We discuss FUSE observations of two early-type stars, DI1388 and DGIK975, in
the low density and low metallicity gas of Magellanic Bridge (MB). Toward
DI1388, the FUSE observations show molecular hydrogen, O VI, and numerous other
atomic or ionic transitions in absorption, implying the presence of multiple
gas phases in a complex arrangement. The relative abundance pattern in the MB
is attributed to varying degrees of depletion onto dust similar to that of halo
clouds. The N/O ratio is near solar, much higher than N/O in damped Ly-alpha
systems, implying subsequent stellar processing to explain the origin of
nitrogen in the MB. The diffuse molecular cloud in this direction has a low
column density and low molecular fraction. H2 is observed in both the
Magellanic Stream and the MB, yet massive stars form only in the MB, implying
significantly different physical processes between them. In the MB some of the
H2 could have been pulled out from the SMC via tidal interaction, but some also
could have formed in situ in dense clouds where star formation might have taken
place. Toward DGIK975, the presence of neutral, weakly and highly ionized
species suggest that this sight line has also several complex gas phases. The
highly ionized species of O VI, C IV, and Si IV toward both stars have very
broad features, indicating that multiple components of hot gas at different
velocities are present. Several sources (a combination of turbulent mixing
layer, conductive heating, and cooling flows) may be contributing to the
production of the highly ionized gas in the MB. Finally, this study has
confirmed previous results that the high-velocity cloud HVC 291.5-41.2+80 is
mainly ionized composed of weakly and highly ions. The high ion ratios are
consistent with a radiatively cooling gas in a fountain flow model.


title: On Validating an Astrophysical Simulation Code

abstract:
  We present a case study of validating an astrophysical simulation code. Our
study focuses on validating FLASH, a parallel, adaptive-mesh hydrodynamics code
for studying the compressible, reactive flows found in many astrophysical
environments. We describe the astrophysics problems of interest and the
challenges associated with simulating these problems. We describe methodology
and discuss solutions to difficulties encountered in verification and
validation. We describe verification tests regularly administered to the code,
present the results of new verification tests, and outline a method for testing
general equations of state. We present the results of two validation tests in
which we compared simulations to experimental data. The first is of a
laser-driven shock propagating through a multi-layer target, a configuration
subject to both Rayleigh-Taylor and Richtmyer-Meshkov instabilities. The second
test is a classic Rayleigh-Taylor instability, where a heavy fluid is supported
against the force of gravity by a light fluid. Our simulations of the
multi-layer target experiments showed good agreement with the experimental
results, but our simulations of the Rayleigh-Taylor instability did not agree
well with the experimental results. We discuss our findings and present results
of additional simulations undertaken to further investigate the Rayleigh-Taylor
instability.


title:
The Modelling of Intermediate Age Stellar Populations. II. Average
  spectra for upper AGB stars, and their use

abstract:
  The upper Asymptotic Giant Branch is populated with oxygen rich and carbon
rich Long Period Variables. These stars are essential contributors to the
near-IR light of intermediate age stellar populations. Individual observed
spectra of LPVs are so diverse that they cannot be used directly in the
synthesis of galaxy spectra. In this paper, the library of individual spectra
of Lancon and Wood (2000) is used to construct averages that can be
incorporated conveniently in population synthesis work. The connection between
such spectra and stellar evolution tracks is discussed [...]. For instance, we
address: (i) the bolometric corrections and temperature scales needed to
associate a spectrum with a given point on a theoretical stellar evolution
track (or isochrone), (ii) the simplifying assumptions that will be implicitely
made when using the average spectra, (iii) potential biases in the sample of
Lan\c{c}on & Wood and their effects, (iv) the small contribution of LPVs to the
interstellar hydrogen emission lines in galaxies. It is emphasized that an a
posteriori calibration of the effective temperature scale remains necessary,
until consistent models for the evolution, the pulsation and the spectral
appearance of LPVs become available.


title: Wind Accretion and State Transitions in Cygnus X-1

abstract:
  We present the results of a spectroscopic monitoring program (from 1998 to
2002) of the H-alpha emission strength in HDE 226868, the optical counterpart
of the black hole binary, Cyg X-1. The H-alpha profiles consist of (1) a P
Cygni component associated with the wind of the supergiant, (2) emission
components that attain high velocity at the conjunctions and that probably form
in enhanced outflows both towards and away from the black hole, and (3) an
emission component that moves in anti-phase with the supergiant's motion. We
argue that the third component forms in accreted gas near the black hole, and
the radial velocity curve of the emission is consistent with a mass ratio of
M_X / M_opt = 0.36 +/- 0.05. We find that there is a general anti-correlation
between the H-alpha emission strength and X-ray flux in the sense that when the
H-alpha emission is strong (W_\lambda < -0.5 Angstroms) the X-ray flux is
weaker and the spectrum harder. On the other hand, there is no correlation
between H-alpha emission strength and X-ray flux when H-alpha is weak. During
the low/hard X-ray state, the strong wind is fast and the accretion rate is
relatively low, while in the high/soft state the weaker, highly ionized wind
attains only a moderate velocity and the accretion rate increases. We argue
that the X-ray transitions from the normal low/hard to the rare high/soft state
are triggered by episodes of decreased mass loss rate in the supergiant donor
star.


title:
BOOMERANG: A Balloon-borne Millimeter Wave Telescope and Total Power
  Receiver for Mapping Anisotropy in the Cosmic Microwave Background

abstract:
  We describe BOOMERANG; a balloon-borne microwave telescope designed to map
the Cosmic Microwave Background (CMB) at a resolution of 10' from the Long
Duration Balloon (LDB) platform. The millimeter-wave receiver employs new
technology in bolometers, readout electronics, cold re-imaging optics,
millimeter-wave filters, and cryogenics to obtain high sensitivity to CMB
anisotropy. Sixteen detectors observe in 4 spectral bands centered at 90, 150,
240 and 410 GHz. The wide frequency coverage, the long duration flight, the
optical design and the observing strategy provide strong rejection of
systematic effects. We report the flight performance of the instrument during a
10.5 day stratospheric balloon flight launched from McMurdo Station, Antarctica
that mapped ~2000 square degrees of the sky.


title:
Chandra View of the Dynamically Young Cluster of Galaxies A1367 I.
  Small-Scale Structures

abstract:
  The 40 ks \emph{Chandra} ACIS-S observation of A1367 provides new insights
into small-scale structures and point sources in this dynamically young
cluster. Here we concentrate on small-scale extended structures. A ridge-like
structure around the center (``the ridge'') is significant in the \chandra\
image. The ridge, with a projected length of $\sim$ 8 arcmin (or 300
h$_{0.5}^{-1}$ kpc), is elongated from northwest (NW) to southeast (SE), as is
the X-ray surface brightness distribution on much larger scales ($\sim$ 2
h$_{0.5}^{-1}$ Mpc). The ridge is cooler than its western and southern
surroundings while the differences from its eastern and northern surroundings
are small. We also searched for small-scale structures with sizes $\sim$
arcmin. Nine extended features, with sizes from $\sim$ 0.5$'$ to 1.5$'$, were
detected at significance levels above 4 $\sigma$. Five of the nine features are
located in the ridge and form local crests. The nine extended features can be
divided into two types. Those associated with galaxies (NGC 3860B, NGC 3860 and
UGC 6697) are significantly cooler than their surroundings (0.3 - 0.9 keV vs. 3
- 4.5 keV). The masses of their host galaxies are sufficient to bind the
extended gas. These extended features are probably related to thermal halos or
galactic superwinds of their host galaxies. The existence of these relatively
cold halos imply that galaxy coronae can survive in cluster environment (e.g.,
Vikhlinin et al. 2001). Features of the second type are not apparently
associated with galaxies. Their temperatures may not be significantly different
from those of their surroundings. This class of extended features may be
related to the ridge. We consider several possibilities for the ridge and the
second type of extended features. The merging scenario is preferred.


title:
Parameter constraints for flat cosmologies from CMB and 2dFGRS power
  spectra

abstract:
  We constrain flat cosmological models with a joint likelihood analysis of a
new compilation of data from the cosmic microwave background (CMB) and from the
2dF Galaxy Redshift Survey (2dFGRS). Fitting the CMB alone yields a known
degeneracy between the Hubble constant h and the matter density Omega_m, which
arises mainly from preserving the location of the peaks in the angular power
spectrum. This `horizon-angle degeneracy' is considered in some detail and
shown to follow a simple relation Omega_m h^{3.4} = constant. Adding the 2dFGRS
power spectrum constrains Omega_m h and breaks the degeneracy. If tensor
anisotropies are assumed to be negligible, we obtain values for the Hubble
constant h=0.665 +/- 0.047, the matter density Omega_m=0.313 +/- 0.055, and the
physical CDM and baryon densities Omega_c h^2 = 0.115 +/- 0.009, Omega_b h^2 =
0.022 +/- 0.002 (standard rms errors). Including a possible tensor component
causes very little change to these figures; we set a upper limit to the
tensor-to-scalar ratio of r<0.7 at 95% confidence. We then show how these data
can be used to constrain the equation of state of the vacuum, and find w<-0.52
at 95% confidence. The preferred cosmological model is thus very well
specified, and we discuss the precision with which future CMB data can be
predicted, given the model assumptions. The 2dFGRS power-spectrum data and
covariance matrix, and the CMB data compilation used here, are available from
http://www.roe.ac.uk/~wjp/


title:
Revised Stellar Temperatures for Magellanic Cloud O Supergiants from
  FUSE and VLT-UVES Spectroscopy

abstract:
  We have undertaken quantitative analysis of four LMC and SMC O4--9.7 extreme
supergiants using far-ultraviolet FUSE, ultraviolet IUE/HSTand optical VLT UVES
spectroscopy. Extended, non-LTE model atmospheres that allow for the consistent
treatment of line blanketing are used to analyse wind & photospheric spectral
features simultaneously. Using Halpha to constrain dM/dt, HeI-II photospheric
lines reveal T_eff's which are systematically (5-7.5kK) & substantially
(15-20%) lower than previously derived from unblanketed, plane-parallel,
non-LTE photospheric studies. We have confidence in these revisions, since
derived T_eff's generally yield consistent fits across the entire 912-7000Ang
observed spectral range. In particular, we are able to resolve previous
UV-optical T_eff discrepancies. `Of' classification criteria are directly
linked to (strong) nitrogen enrichment (via NIII 4097) & (weak) carbon
depletion (via CIII 4647-51), providing evidence for mixing of unprocessed and
CNO processed material at their stellar surfaces. Oxygen abundances are more
difficult to constrain, except via OII lines in the O9.7 supergiant for which
it is also found to be somewhat depleted. The effect of wind clumping is also
investigated, for which PV 1118-28 potentially provides a useful diagnostic in
O-star winds. Revised stellar properties affect existing calibrations of (i)
Lyman continuum photons - a factor of two lower for the O4 supergiant; and (ii)
kinetic energy released into the ISM by O supergiants. Our results also have
importance for the calibration of the wind momentum-luminosity relationship for
OB stars.


title: Long-term evolution of isolated N-body sytems

abstract:
  We report results of N-body simulations of isolated star clusters, performed
up to the point where the clusters are nearly completely dissolved. Our main
focus is on the post-collapse evolution of these clusters. We find that after
core collapse, isolated clusters evolve along nearly a single sequence of
models whose properties are independent of the initial density profile and
particle number. Due to the slower expansion of high-N clusters, relaxation
times become almost independent of the particle number after several core
collapse times, at least for the particle range of our study. As a result, the
dissolution times of isolated clusters exhibit a surprisingly weak dependence
on N.
  We find that most stars escape due to encounters between single stars inside
the half-mass radius of the cluster. Encounters with binaries take place mostly
in the cluster core and account for roughly 15% of all escapers. Encounters
between single stars at intermediate radii are also responsible for the build
up of a radial anisotropic velocity distribution in the halo. For clusters
undergoing core oscillations, escape due to binary stars is efficient only when
the cluster center is in a contracted phase. Our simulations show that it takes
about 10^5 N-body time units until the global anisotropy reaches its maximum
value. The anisotropy increases with particle number and it seems conceivable
that isolated star clusters become vulnerable to radial orbit instabilities for
large enough N. However, no indication for the onset of such instabilities was
seen in our runs.


title:
MEDEA: Automated Measure and on-line Analysis in Astronomy and
  Astrophysics for Very Large Vision Machine

abstract:
  MEDEA is a software architecture to detect luminosity variations connected
with the discovery of new planet outside the Solar System. Taking into account
the enormous number of stars to monitor for our aim traditional approaches are
very demanding in terms of computing time; here, the implementation of an
automatic vision and decision system, which allows to perform an on-line
discrimination of possible events by using two levels of trigger and a
quasi-on-line data analysis, is presented. MEDEA becomes very profitable when
dealing with large or deep surveys and provides to obtain soon results with its
powerful data analysis tools.


title:
Long-Term Dynamics and the Orbital Inclinations of the Classical Kuiper
  Belt Objects

abstract:
  We numerically integrated the orbits of 1458 particles in the region of the
classical Kuiper Belt (41 AU < a < 47 AU) to explore the role of dynamical
instabilities in sculpting the inclination distribution of the classical Kuiper
Belt Objects (KBOs). We find that the selective removal of low-inclination
objects by overlapping secular resonances (nu_17 and nu_18) acts to raise the
mean inclination of the surviving population of particles over 4 billion years
of interactions with Jupiter, Saturn, Uranus and Neptune, though these
long-term dynamical effects do not themselves appear to explain the discovery
of KBOs with inclinations near 30 degrees. Our integrations also imply that
after 3 billion years of interaction with the massive planets, high inclination
KBOs more efficiently supply Neptune-encountering objects, the likely
progenitors of short-period comets, Centaurs, and scattered KBOs. The secular
resonances at low inclinations may indirectly cause this effect by weeding out
objects unprotected by mean motion resonances during the first 3 billion years.


title: Nonlinear Turbulent Magnetic Diffusion and Mean-Field Dynamo

abstract:
  The nonlinear coefficients defining the mean electromotive force (i.e., the
nonlinear turbulent magnetic diffusion, the nonlinear effective velocity, the
nonlinear kappa-tensor, etc.) are calculated for an anisotropic turbulence. A
particular case of an anisotropic background turbulence (i.e., the turbulence
with zero mean magnetic field) with one preferential direction is considered.
It is shown that the toroidal and poloidal magnetic fields have different
nonlinear turbulent magnetic diffusion coefficients. It is demonstrated that
even for a homogeneous turbulence there is a nonlinear effective velocity which
exhibits diamagnetic or paramagnetic properties depending on anisotropy of
turbulence and level of magnetic fluctuations in the background turbulence.
Analysis shows that an anisotropy of turbulence strongly affects the nonlinear
mean electromotive force. Two types of nonlinearities (algebraic and dynamic)
are also discussed. The algebraic nonlinearity implies a nonlinear dependence
of the mean electromotive force on the mean magnetic field. The dynamic
nonlinearity is determined by a differential equation for the magnetic part of
the alpha-effect. It is shown that for the alpha-Omega axisymmetric dynamo the
algebraic nonlinearity alone cannot saturate the dynamo generated mean magnetic
field while the combined effect of the algebraic and dynamic nonlinearities
limits the mean magnetic field growth. Astrophysical applications of the
obtained results are discussed.


title:
Accurate results for primordial black holes from spectra with a
  distinguished scale

abstract:
  We perform an accurate computation of the production rate for primordial
black holes (PBHs). The reason is that the underlying mass variance had been
overestimated systematically, as was shown recently. For scale-free powerlaw
primordial spectra, and for a Universe with critical density, the mass variance
is less than 34% of its value thought earlier for the spectral index in the
range $1\leq n\leq 1.3$. We then extend our study to spectra with a
characteristic scale and find the accurate shape of the corresponding mass
variance. For a pure step in the primordial spectrum, the step in the variance
is smoothed around the characteristic scale $k_s$. For a spectrum with large
oscillations near $k_s$, we find a pronounced bump in the variance. This could
yield a significant part of the cold dark matter in the form of PBHs with mass
$M$ in the range $5\times 10^{15} {\rm g}\lesssim M \lesssim 10^{21} {\rm g}$.


title: Microlensing of Relativistic Knots in the Quasar HE1104-1805

abstract:
  We present 3 years of photometry of the ``Double Hamburger'' lensed quasar,
HE1104-1805, obtained on 102 separate nights using the OGLE 1.3-m telescope.
Both the A and B images show variations, but with substantial differences in
the lighcurves at all time delays. At the 310 day delay reported by Wisotzki
and collaborators the difference lightcurve has an rms amplitude of 0.060 mag.
The structure functions for the A and B images are quite different, with image
A more than twice as variable as image B (a factor of 4 in structure function)
on timescales of less than a month. Adopting microlensing as a working
hypothesis for the uncorrelated variability, the short timescale argues for the
relativistic motion of one or more components of the source. We argue that the
small amplitude of the fluctuations is due to the finite size of the source
with respect to the microlenses.


title:
Chandra Detection of OVIII Ly-alpha Absorption from an Overdense Region
  in the Intergalactic Medium

abstract:
  We report the first detection of an OVIII Ly-alpha absorption line associated
with an overdense region in the intergalactic medium (IGM) along the sightline
towards PKS 2155-304 with the Chandra Low Energy Transmission Grating
Spectrometer (LETGS). The absorption line is detected at 4.5 sigma level with
cz~16,600 km/s. At the same velocity Shull et al.(1998) detected a small group
of spiral galaxies (with an overdensity of delta_gal ~ 100) and low metallicity
HI Ly-alpha clouds. We constrain the intragroup gas that gives rise to the
OVIII Ly-alpha line to a baryon density in the range 1e-5 < n_b < 7.5e-5 cm^-3
(50 < delta_b < 350) and a temperature of (4-5) x 10^6 K, assuming 0.1 solar
abundance. These estimates are in accordance with those of the warm/hot
intergalactic medium (WHIM) that are predicted from hydrodynamic simulations.
Extrapolating from this single detection implies a large fraction of the
``missing baryons'' (~ 10%, or ~ 30-40% of the WHIM) are probed by the OVIII
absorber.


title:
Non-Oscillatory Central Difference and Artificial Viscosity Schemes for
  Relativistic Hydrodynamics

abstract:
  High resolution, non-oscillatory, central difference (NOCD) numerical schemes
are introduced as alternatives to more traditional artificial viscosity (AV)
and Godunov methods for solving the fully general relativistic hydrodynamics
equations. These new approaches provide the advantages of Godunov methods in
capturing ultra-relativistic flows without the cost and complication of Riemann
solvers, and the advantages of AV methods in their speed, ease of
implementation, and general applicability without explicitly using artificial
viscosity for shock capturing. Shock tube, wall shock, and dust accretion
tests, all with adiabatic equations of state, are presented and compared
against equivalent solutions from both AV and Godunov based codes. In the
process we address the accuracy of time-explicit NOCD and AV methods over a
wide range of Lorentz factors.


title: The Light-cone Effect on the Shapiro Time Delay

abstract:
  We investigate the light-cone effect on the Shapiro time delay. The extra
time delay caused by Jupiter on the 8th of September 2002 can be measured by
advanced VLBI (very long baseline interferometry). Our expression for the delay
is in complete agreement with that of Kopeikin (2001), in which he argued that
the excess time delay was due to the propagation of gravity. The present
letter, however, shows that the excess comes from nothing but the propagation
of light, namely the light-cone effect. To make a robust confirmation of
general relativity by the coming Jupiter event, it is important to take account
of the light-cone effect on the Shapiro time delay.


title:
Images for a Binary Gravitational Lens from a Single Real Algebraic
  Equation

abstract:
  It is shown that the lens equation for a binary gravitational lens being a
set of two coupled real fifth-order algebraic equations (equivalent to a single
complex equation of the same order) can be reduced to a single real fifth-order
algebraic equation, which provides a much simpler way to study lensing by
binary objects.


title: High-Energy Neutrinos from Cosmic Rays

abstract:
  We introduce neutrino astronomy from the observational fact that Nature
accelerates protons and photons to energies in excess of 10^{20} and 10^{13}
eV, respectively. Although the discovery of cosmic rays dates back close to a
century, we do not know how and where they are accelerated. We review the facts
as well as the speculations about the sources. Among these gamma ray bursts and
active galaxies represent well-motivated speculations because these are also
the sources of the highest energy gamma rays, with emission observed up to 20
TeV, possibly higher.
  We discuss why cosmic accelerators are also expected to be cosmic beam dumps
producing high-energy neutrino beams associated with the highest energy cosmic
rays. Cosmic ray sources may produce neutrinos from MeV to EeV energy by a
variety of mechanisms. The important conclusion is that, independently of the
specific blueprint of the source, it takes a kilometer-scale neutrino
observatory to detect the neutrino beam associated with the highest energy
cosmic rays and gamma rays. The technology for commissioning such instruments
exists.


title:
Radio Halo Formation through Magneto-turbulent Particle Acceleration in
  Clusters of Galaxies

abstract:
  We developed a magneto-turbulent model for the cosmic ray (CR) electrons seen
in the radio halo clusters of galaxies. Steady state momentum distribution
functions of the CR electrons are calculated for given spectra of the turbulent
Alfven waves. The radio spectrum produced by the obtained CR electron
distribution is compared to the observed radio spectrum of the Coma radio halo.
We find that the observed radio spectrum of the Coma cluster is well reproduced
when the spectral index of the turbulent Alfven waves is 2.8. The obtained
energy spectrum of the turbulent Alfven waves is steeper than that expected
from the turbulence theory, suggesting back reaction of the particle
acceleration. The fitting procedure constraints the amplitude of the turbulent
Alfven waves as well as the spectral index. Then we estimate the dissipation of
the turbulent Alfven waves, which is found to be less than the cooling rate by
X-ray radiation. We suggest that the turbulence which is sufficient for
particle acceleration is developed in the clusters containing the radio halo.
It is most likely that cluster mergers create the turbulence and seed
relativistic electrons.


title:
Distant star forming galaxies, next generation radio telescopes and the
  radio universe before re-ionisation

abstract:
  I present the various capabilities of upgraded and next generation radio
telescopes, in particular their ability to detect and image distant star
forming galaxies. I demonstrate that e-MERLIN, EVLA and LOFAR can detect
systems similar to Arp 220 out to cosmological distances. The SKA can detect
such systems out to any reasonable redshift that they might be expected to
exist. Employing very long integration times on the multiple-beam SKA will
require the array to be extended beyond the current specification - simply to
avoid confusion noise limitations at 1.4 GHz. Other arguements for extending
the SKA baseline length are also presented. As well as going ``deeper'' all
these instruments (especially LOFAR and the SKA) will also go ``wider'' -
detecting many tens of thousands of galaxies in a single day's observing. I
briefly comment on the prospects of detecting radio emission at much earlier
epochs, just before the epoch of re-ionisation.


title: Improved Exclusion Limits from the EDELWEISS WIMP Search

abstract:
  The EDELWEISS experiment has improved its sensitivity for the direct search
for WIMP dark matter. In the recoil energy range relevant for WIMP masses below
10 TeV/c2, no nuclear recoils were observed in the fiducial volume of a
heat-and-ionization cryogenic Ge detector operated in the low-background
environment of the Laboratoire Souterrain de Modane in the Frejus Tunnel,
during an effective exposure of 7.4 kg.days. This result is combined with the
previous EDELWEISS data to derive a limit on the cross-section for
spin-independent interaction of WIMPs and nucleons as a function of WIMP mass,
using standard nuclear physics and astrophysical assumptions. This limit
excludes at more than 99.8%CL a WIMP candidate with a mass of 44 GeV/c2 and a
cross-section of 5.4 x 10-6 pb, as reported by the DAMA collaboration. A first
sample of supersymmetric models are also excluded at 90%CL.


title: Cluster-Group Interaction in the Virgo Cluster

abstract:
  We present two projects related to interaction in the Virgo cluster. In the
first section we draw a quantitative comparison of the distribution of the
galaxies and the intra-cluster gas taking into account that the Virgo cluster
has an irregular structure consisting of several subclusters. In the second
section we show hydrodynamic simulations of the interaction (ram pressure
stripping) of a galaxy like M86 with the intra-cluster gas.


title: Gas accretion on spiral galaxies: bar formation and renewal

abstract:
  The effects of gas accretion on spiral disk dynamics and stability are
studied through N-body simulations, including star formation and gas/stars mass
exchange. The detailed processes of bar formation, bar destruction and bar
re-formation are followed, while in the same time the disk to bulge ratio is
varying. The accreted gas might be first prevented to flow inwards to the
center by the bar gravity torques, which maintains it to the outer Lindblad
resonance. While the first bar is weakening, the accreted gas replenishes the
disk, increasing the disk-to-bulge ratio, and the disk self-gravity. A second
bar is then unstable, with a higher pattern speed, due both to the increased
mass, and shorter bar length. Three or four bar episodes have been followed
over a Hubble time. Their strength is decreasing with time, while their pattern
speed is increasing. Detailed balance of the angular momentum transfer and
evolution can account for these processes. The gas recycled through star
formation, and rejected through stellar mass loss plays also a role in the disk
dynamics. Implications on the spiral galaxy dynamics and evolution along the
Hubble sequence, and as a function of redshift are discussed.


title:
Non-radial instabilities of isothermal Bondi accretion with a shock:
  vortical-acoustic cycle vs post-shock acceleration

abstract:
  The linear stability of isothermal Bondi accretion with a shock is studied
analytically in the asymptotic limit of high incident Mach number M_1. The flow
is unstable with respect to radial perturbations as expected by Nakayama
(1993), due to post-shock acceleration. Its growth time scales like the
advection time from the shock r_sh to the sonic point r_son. The growth rate of
non-radial perturbations l=1 is higher by a factor M_1^{2/3}, and is therefore
intermediate between the advection and acoustic frequencies. Besides these
instabilities based on post-shock acceleration, our study revealed another
generic mechanism based on the cycle of acoustic and vortical perturbations
between the shock and the sonic radius, independently of the sign of post-shock
acceleration. The vortical-acoustic instability is fundamentally non-radial. It
is fed by the efficient excitation of vorticity waves by the isothermal shock
perturbed by acoustic waves. The growth rate exceeds the advection rate by a
factor log M_1. Unstable modes cover a wide range of frequencies from the
fundamental acoustic frequency ~c/r_sh up to a cut-off ~c/r_son associated with
the sonic radius. The highest growth rate is reached for l=1 modes near the
cut-off. The additional cycle of acoustic waves between the shock and the sonic
radius is responsible for variations of the growth rate by a factor up to 3
depending on its phase relative to the vortical-acoustic cycle. The instability
also exists, with a similar growth rate, below the fundamental acoustic
frequency down to the advection frequency, as vorticity waves are efficiently
coupled to the region of pseudosound. These results open new perspectives to
address the stability of shocked accretion flows.


title:
More evidence for hidden spiral and bar features in bright early-type
  dwarf galaxies

abstract:
  Following the discovery of spiral structure in IC3328 (Jerjen et al.~2000),
we present further evidence that a sizable fraction of bright early-type dwarfs
in the Virgo cluster are genuine disk galaxies, or are hosting a disk
component. Among a sample of 23 nucleated dwarf ellipticals and dS0s observed
with the Very Large Telescope in $B$ and $R$, we found another four systems
exhibiting non-axisymmetric structures, such as a bar and/or spiral arms,
indicative of a disk (IC0783, IC3349, NGC4431, IC3468). Particularly remarkable
are the two-armed spiral pattern in IC0783 and the bar and trailing arms in
NGC4431. For both galaxies the disk nature has recently been confirmed by a
rotation velocity measurement (Simien & Prugniel 2002). Our photometric search
is based on a Fourier decomposition method and a specific version of unsharp
masking. Some ``early-type'' dwarfs in the Virgo cluster seem to be former
late-type galaxies which were transformed to early-type morphology, e.g. by
``harassment'', during their infall to the cluster, while maintaining part of
their disk structure.


title:
Kinematic study of the disrupting globular cluster Palomar 5 using VLT
  spectra

abstract:
  Wide-field photometric data from the Sloan Digital Sky Survey have recently
revealed that the Galactic globular cluster Palomar 5 is in the process of
being tidally disrupted (Odenkirchen et al. 2001). Here we investigate the
kinematics of this sparse remote star cluster using high resolution spectra
from the Very Large Telescope (VLT). Twenty candidate cluster giants located
within 6 arcmin of the cluster center have been observed with the UV-Visual
Echelle Spectrograph (UVES) on VLT-UT2. The spectra provide radial velocities
with a typical accuracy of 0.15 km/s. We find that the sample contains 17
certain cluster members with very coherent kinematics, two unrelated field
dwarfs, and one giant with a deviant velocity, which is most likely a cluster
binary showing fast orbital motion. From the confirmed members we determine the
heliocentric velocity of the cluster as -58.7 +- 0.2 km/s. The total
line-of-sight velocity dispersion of the cluster stars is 1.1 +- 0.2 km/s (all
members) or 0.9 +- 0.2 km/s (stars on the red giant branch only). This is the
lowest velocity dispersion that has so far been measured for a stellar system
classified as a globular cluster. The shape of the velocity distribution
suggests that there is a significant contribution from orbital motions of
binaries and that the dynamical part of the velocity dispersion is therefore
still substantially smaller than the total dispersion. ... (abridged)


title: X-ray Spectroscopy of the IP PQ Gem

abstract:
  Using RXTE and ASCA data, we investigate the roles played by occultation and
absorption in the X-ray spin pulse profile of the Intermediate Polar PQ Gem.
  From the X-ray light curves and phase-resolved spectroscopy, we find that the
intensity variations are due to a combination of varying degrees of absorption
and the accretion regions rotating behind the visible face of the white dwarf.
These occultation and absorption effects are consistent with those expected
from the accretion structures calculated from optical polarisation data. We can
reproduce the changes in absorber covering fraction either from geometrical
effects, or by considering that the material in the leading edge of the
accretion curtain is more finely fragmented than in other parts of the curtain.
We determine a white dwarf mass of ~1.2 using the RXTE data.


title:
Probing Intracluster Magnetic Fields with Cosmic Microwave Background
  Polarization

abstract:
  Intracluster magnetic fields with $ \sim \mu G $ strength induce Faraday
rotation on the cosmic microwave background
  (CMB) polarization. Measurements of this effect can potentially probe the
detailed structure of intracluster magnetic fields across clusters, since the
CMB polarization is a continuously varying field on the sky, in contrast to the
conventional method restricted by the limited number of radio sources behind or
inside a cluster. We here construct a method for extracting information on
magnetic fields from measurements of the effect, combined with possible
observations of the Sunyaev-Zel'dovich effect and X-ray emission for the same
cluster which are needed to reconstruct the electron density fields.
  Employing the high-resolution magneto-hydrodynamic simulations performed by
Dolag, Bartelmann & Lesch (1999) as a realistic model of magnetized
intracluster gas distribution, we demonstrate how our reconstruction technique
can well reproduce the magnetic fields, i.e., the spherically average radial
profiles of the field strength and the coherence length.


title:
Carbon Recombination Lines near 327 MHz I: "Diffuse" CII regions in the
  Galactic Disk

abstract:
  In earlier papers (Roshi & Anantharamaiah 2000, 2001a), we presented
extensive surveys (angular resolution -- 2\deg $\times$ 2\deg & 2\deg $\times$
6\arcmin) of radio recombination lines (RRLs) near 327 MHz in the longitude
range $l = $ 332\deg $\to$ 89\deg using the Ooty Radio Telescope. These surveys
have detected carbon lines mostly between $l = $ 358\deg $\to$ 20\deg and in a
few positions at other longitudes. This paper presents the observed carbon line
parameters in the high-resolution survey and a study of the galactic
distribution and angular extent of the line emission observed in the surveys.
The carbon lines detected in the surveys arise in ``diffuse'' \CII regions. The
\lv diagram and radial distribution constructed from our carbon line data shows
similarity with that obtained from hydrogen recombination lines at 3 cm from
\HII regions indicating that the distribution of the diffuse \CII regions in
the inner Galaxy resembles the distribution of the star-forming regions. We
estimated the [CII] 158 micron emission from diffuse \CII regions and find that
upto 95 % of the total observed [CII] 158 micron emission can arise in diffuse
\CII regions if the temperature of the latter $\sim 80$ K. Our high-resolution
survey data shows that the carbon line emitting regions have structures on
angular scale $\sim$ 6\arcmin. Analysis of the dual-resolution observations
toward a 2\deg wide field centered at $l = $ 13\deg.9 and toward the longitude
range $l = $ 1\deg.75 to 6\deg.75 shows the presence of narrow ($\Delta V \le $
15 \kms) carbon line emitting regions extending over several degrees in $l$ and
$b$. The physical size perpendicular to the line-of-sight of an individual
diffuse \CII region in these directions is $>$ 200 pc.


title: SAURON: Observations of E/S0/Sa galaxies

abstract:
  We present results from a new and unique integral-field spectrograph, SAURON.
It has a large field of view and high throughput and is primarily built for the
study of stellar & gaseous kinematics and stellar populations in galaxies. Its
aim is to carry out a systematic survey of the velocity fields, velocity
dispersions, and line-strength distributions of nearby ellipticals, lenticular
galaxies and spiral bulges. Its wide field is especially useful for the study
of complicated velocity structures. Together with other spectroscopic data,
images, and dynamical modelling, SAURON will help to constrain the intrinsic
shapes, mass-to-light ratios, and stellar populations of early-type galaxies
and spiral bulges.


title:
A radiation-hydrodynamics scheme valid from the transport to the
  diffusion limit

abstract:
  We present in this paper the numerical treatment of the coupling between
hydrodynamics and radiative transfer. The fluid is modeled by classical
conservation laws (mass, momentum and energy) and the radiation by the grey
moment $M_1$ system. The scheme introduced is able to compute accurate
numerical solution over a broad class of regimes from the transport to the
diffusive limits. We propose an asymptotic preserving modification of the HLLE
scheme in order to treat correctly the diffusion limit. Several numerical
results are presented, which show that this approach is robust and have the
correct behavior in both the diffusive and free-streaming limits. In the last
numerical example we test this approach on a complex physical case by
considering the collapse of a gas cloud leading to a proto-stellar structure
which, among other features, exhibits very steep opacity gradients.


title: Statistical characteristics of Large Scale Structure

abstract:
  We investigate the mass functions of different elements of the Large Scale
Structure -- walls, pancakes, filaments and clouds -- and the impact of
transverse motions -- expansion and/or compression -- on their statistical
characteristics. Using the Zel'dovich theory of gravitational instability we
show that the mass functions of all structure elements are approximately the
same and the mass of all elements is found to be concentrated near the
corresponding mean mass. At high redshifts, both the mass function and the mean
mass of formed elements depend upon the small scale part of the initial power
spectrum and, in particular, upon the mass of dominant fraction of dark matter
(DM) particles. These results generalize the Press-Schechter approach and are
used to obtain independent estimates of probable redshifts of the reionization
and reheating periods of the Universe. We show that the transverse motions do
not significantly change the redshift evolution of the observed mass function
and the mean linear number density of low mass pancakes related to absorption
lines in the spectra of the farthest quasars. We apply this approach to the
observed Lyman-$\alpha$ clouds and obtain direct estimates of the variance of
initial density perturbations and the shape of initial power spectrum on small
scale. In turn, these estimates restrict the mass of dominant fraction of DM
particles.


title: Asteroseismology and calibration of alpha Cen binary system

abstract:
  Using the oscillation frequencies of alpha Cen A recently discovered by
Bouchy & Carrier, the available astrometric, photometric and spectroscopic
data, we tried to improve the calibration of the visual binary system alpha
Cen. With the revisited masses of Pourbaix et al. (2002) we do not succeed to
obtain a solution satisfying all the seismic observational constraints.
Relaxing the constraints on the masses, we have found an age t_alpha
Cen=4850+-500 Myr, an initial helium mass fraction Y_i = 0.300+-0.008, and an
initial metallicity (Z/X)_i=0.0459+-0.0019, with M_A=1.100+-0.006M_o and
M_B=0.907+-0.006M_o for alpha Cen A&B.


title: X-ray emission from old and intermediate age brown dwarfs

abstract:
  According to the paradigm of solar-type dynamo action brown dwarfs should not
exhibit magnetic activity as they are fully convective. Indeed, Halpha
observations of ultracool field dwarfs indicate a decline of activity setting
in near the substellar limit. X-ray emission traditionally serves as another
means to examine magnetic activity on stars. The substellar regime can now be
accessed with the new generation of X-ray instruments onboard XMM-Newton and
Chandra. We report on two recent XMM-Newton observations of brown dwarfs in the
Pleiades cluster and in the field aiming to constrain the age and effective
temperature dependence of X-ray emission from substellar objects.


title: Improving the triaxial bulge model of M31

abstract:
  A detailed hydrodynamical model of the gas flow in the triaxial gravitational
potential of the bulge of the Andromeda galaxy (M31) has recently been proposed
by Berman (2001) astro-ph/0103209, and shown to provide excellent agreement
with the CO emission line velocities observed along its major axis. In the
present paper, we confirm the validity of that model by showing that it can
also reproduce the CO velocities observed off the major axis - a much more
robust test. The CO observations, however, tend to span a wider range of
velocities than a direct application of the original model of Berman would
suggest. This situation can be improved significantly if the molecular disk is
made thicker, a requirement already encountered in dynamical simulations of
other spiral galaxies, and typically attributed to a broadening of the
molecular layer in galactic fountain-like processes. In the central regions of
M31, however, it is unclear whether there actually is a thick molecular disk,
or whether broadening the molecular layer is merely an artificial theoretical
means of accounting for some disk warping. Other effects not included in the
model, such as hydraulic jumps, might also contribute to a widening of the
velocities.


title:
New results on source and diffusion spectral features of Galactic cosmic
  rays: I- B/C ratio

abstract:
  In a previous study (Maurin et al., 2001), we explored the set of parameters
describing diffusive propagation of cosmic rays (galactic convection,
reacceleration, halo thickness, spectral index and normalization of the
diffusion coefficient), and we identified those giving a good fit to the
measured B/C ratio. This study is now extended to take into account a sixth
free parameter, namely the spectral index of sources. We use an updated version
of our code where the reacceleration term comes from standard minimal
reacceleration models. The goal of this paper is to present a general view of
the evolution of the goodness of fit to B/C data with the propagation
parameters. In particular, we find that, unlike the well accepted picture, and
in accordance with our previous study, a Kolmogorov-like power spectrum for
diffusion is strongly disfavored. Rather, the $\chi^2$ analysis points towards
$\delta\gtrsim 0.7$ along with source spectra index $\lesssim 2.0$. Two
distinct energy dependences are used for the source spectra: the usual
power-law in rigidity and a law modified at low energy, the second choice being
only slightly preferred. We also show that the results are not much affected by
a different choice for the diffusion scheme. Finally, we compare our findings
to recent works, using other propagation models. This study will be further
refined in a companion paper, focusing on the fluxes of cosmic ray nuclei.


title: Topological defects: A problem for cyclic universes?

abstract:
  We study the behaviour of cosmic string networks in contracting universes,
and discuss some of their possible consequences. We note that there is a
fundamental time asymmetry between defect network evolution for an expanding
universe and a contracting universe. A string network with negligible loop
production and small-scale structure will asymptotically behave during the
collapse phase as a radiation fluid. In realistic networks these two effects
are important, making this solution only approximate. We derive new scaling
solutions describing this effect, and test them against high-resolution
numerical simulations. A string network in a contracting universe, together
with the gravitational radiation background it has generated, can significantly
affect the dynamics of the universe both locally and globally. The network can
be an important source of radiation, entropy and inhomogeneity. We discuss the
possible implications of these findings for bouncing and cyclic cosmological
models.


title:
Timing diagrams and correlations in gamma-ray bursts signal jets from
  accretion into black holes

abstract:
  The temporal properties of a sample of 498 bright gamma-ray bursts (GRBs)
with durations between 0.05 s and 674 s were analysed. The large range in
duration (T90) is accompanied by a similarly large range in the median values
of the pulse timing properties including rise time, fall time, FWHM and
separation between the pulses. Four timing diagrams relating these pulse
properties to T90 are presented and show the power law relationships between
the median values of the 4 pulse timing properties and T90, but also that the
power laws depend in a consistent manner on the number of pulses per GRB. The
timing diagrams are caused by the correlated properties of the pulses in the
burst and can be explained by a combination of factors including the Doppler
boost factor Gamma, a viewing effect caused by a jet and different progenitors.
GRBs with similar values of T90 have a wide range in the number of pulses. GRBs
with the large number of short and spectrally hard pulses may occur either from
a homogeneous jet with a higher average value of Gamma or close to the axis of
an inhomogeneous jet with higher values of Gamma near the rotation axis. The
less luminous GRBs with fewer pulses may originate further from the axis of the
inhomogeneous jet. The pulses in GRBs have six distinctive statistical
properties including correlations between time intervals, correlations between
pulse amplitudes, an anticorrelation between pulse amplitudes and time
intervals, and a link to intermittency in GRS 1915+105. The timing diagrams and
correlated pulses suggest that GRBs are powered by accretion processes
signalling jets from the formation of black holes.


title:
Absolute Proper Motions to B~22.5: V. Detection of Sagittarius Dwarf
  Spheroidal Debris in the Direction of the Galactic Anticenter

abstract:
  We have detected a population of predominantly blue (B-V <= 1.1) stars in the
direction l = 167 deg., b = -35 deg. (Kapteyn Selected Area 71) that cannot be
accounted for by standard starcount models. Down to V ~ 20, the colors and
magnitudes of these stars are similar to those of the southern overdensity
detected by the Sloan Digital Sky Survey, and identified as stripped material
from the Sagittarius dwarf spheroidal galaxy. We present absolute proper
motions for the stars in SA 71, and we find that the excess blue stars
represent a distinct, kinematically cooler component than the Galactic field,
and in reasonable agreement with predictions of Sgr disruption models. The
density of the excess SA 71 stars at V ~ 18.8 and B-V <=1.1 is within a factor
of two of the density of the SDSS-south Sgr stripped material, and of that
predicted by the Helmi and White disruption model. Three additional anticenter
fields (SA 29, 45 and 118) show very good agreement with standard starcount
models.


title: EUVE Phase-Resolved Spectroscopy of V834 Centauri

abstract:
  (abridged) The Extreme Ultraviolet Explorer (EUVE) satellite was employed in
1999 February to acquire phase-resolved EUV photometric and spectroscopic
observations of the AM Her-type cataclysmic variable V834 Centauri. Although we
do not understand the EUV light curves in detail, they are explained
qualitatively by a simple model of accretion from a ballistic stream along the
field lines of a tilted magnetic dipole centered on the white dwarf. The 75-140
Angstrom EUVE spectra are well described by either a blackbody or a pure-H
stellar atmosphere absorbed by a neutral hydrogen column density, but
constraints on the size of the EUV emission region and its UV brightness favor
the blackbody interpretation with temperature kT ~ 17.6 eV, hydrogen column
density N_H ~ 7.4x10^{19} cm^{-2}, fractional emitting area f ~ 10^{-3}, and
luminosity L_soft ~ 7.2x10^{32} (d/100 pc)^2 erg s^{-1}. The ratio of the EUV
to X-ray luminosities is L_soft/L_hard ~ 40, signaling that some mechanism
other than irradiation (e.g., blob heating) dominates energy input into the
accretion spot.


title:
Large-Amplitude X-ray Outbursts from Galactic Nuclei: A Systematic
  Survey Using ROSAT Archival Data

abstract:
  In recent years, luminous X-ray outbursts with variability amplitudes as high
as ~ 400 have been serendipitously detected from a small number of active and
inactive galaxies. These outbursts may result from the tidal disruptions of
stars by supermassive black holes as well as accretion-disk instabilities. In
order to place the first reliable constraints on the rate of such outbursts in
the Universe and test the stellar tidal disruption hypothesis, we have
performed a systematic and complete survey for them by cross-correlating ROSAT
All-Sky Survey (RASS) and pointed PSPC data. We have detected five galaxies
that were in outburst during the RASS, three of which show no signs of nuclear
activity; these objects had been reported on individually in previous studies.
After making reasonable corrections for the complicated selection effects, we
conclude that the rate of large-amplitude X-ray outbursts from inactive
galaxies in the local Universe is ~ 9.1 x 10^{-6} galaxy^{-1} yr^{-1}. This
rate is consistent with the predicted rate of stellar tidal disruption events
in such galaxies. When only the two active galaxies are considered, we find a
rate for active galaxies of ~ 8.5 x 10^{-4} galaxy^{-1} yr^{-1}. In order to
place tighter constraints on these rates, additional outbursts must be
detected.