title: Dynamics of triaxial galaxies with a central density cusp

abstract:
  Cuspy triaxial potentials admit a large number of chaotic orbits, which
moreover exhibit extreme "stickiness" that makes the process of chaotic mixing
surprisingly inefficient. Environmental effects, modeled as noise and/or
periodic driving, help accelerate phase space transport but probably not as
much as in simpler potentials. This could mean that cuspy triaxial ellipticals
cannot exist as time-independent systems.


title: BeppoSAX observations of LINER-2 galaxies

abstract:
  We present BeppoSAX observations of 6 ``type-2'' LINER and ``transition''
galaxies (NGC3379, NGC3627, NGC4125, NGC4374, NGC5195 and NGC5879)from the
  Ho et al. (1997) spectroscopic sample of nearby galaxies. All objects are
detected in the 2-10 keV band, having luminosities in the range L(2-10 keV)
  ~ 1x10^{39}- 1x10^{40} erg s-1. The PDS upper limits above 10 keV place
constraints on the presence of a heavily obscured AGN in the case of NGC3379
and NGC4125. No significant variability is detected in any of the objects.
  The spectra are described in most cases by a simple power-law model with a
spectral slope of 1.7-2.5 while there is evidence neither for a significant
absorption above the Galactic nor for an FeK emission line. Therefore, based on
the spectral properties alone, it is difficult to differentiate between a
low-luminosity AGN or a star-forming galaxy scenario.
  However, imaging observations of NGC3627 and NGC5195 with
  Chandra ACIS-S reveal very weak nuclear sources while most of the X-ray flux
originates either in off-nuclear point sources or in diffuse emission. The
above clearly argue in favour of a star-forming origin for the bulk of the
X-ray emission, at least in the above two sources.


title: A Chandra Search for X-Ray Jets in Redshift 6 Quasars

abstract:
  We have searched for X-ray jets in the recent Chandra observations of three
Sloan Digital Sky Survey (SDSS) quasars at redshift z ~ 6. All 3 quasars were
detected in X-rays in these relatively short observations. SDSS 1030+0524 is
not consistent with a point source, and may be a gravitationally lensed system.
We find a possible jet-like feature 23" from the quasar SDSS 1306+0356. We can
explain the emission by inverse Compton scattering off the Cosmic Microwave
Background, assuming that the intrinsic properties of the system are similar to
other X-ray jets at z<1. Deeper observations to confirm the interpretation as a
jet will be practical.


title: On the Formation of Globular Cluster Systems in a Hierarchical Universe

abstract:
  We have investigated the formation of globular cluster (GC) systems in the
fiducial semi-analytic galaxy formation model of Cole et al. We assume that GCs
are formed at high-redshift (z > 5) in proto-galactic fragments, and during the
subsequent gas-rich merging of these fragments. We find that the mean ages of
the metal-rich GCs are dependent upon host galaxy luminosity and halo circular
velocity, whereas the mean ages of the metal-poor GCs are not. We find that
gaseous merging of the proto-galactic fragments leads to a significant
age-spread amongst the metal-rich GCs, which increases for lower-luminosity
galaxies. We find the total GC populations scale with host galaxy luminosity as
L^1.25, due to the systematic increase in the mass-to-light ratios (with mass)
of the galaxy haloes in the model. A comparison between the luminosity growth
of the model ellipticals and their GC formation indicates that mergers do not
significantly effect S_N at z < 2. We conclude that gaseous merging, the bulk
of which occurs at 1 < z < 4 in the Lambda-CDM model, leads to the formation of
the metal-rich peak of the GC systems of elliptical galaxies. We suggest that
the formation and subsequent truncation of the metal-poor GCs is closely
related to the star formation rate in the proto-galactic fragments, which may
have been significantly higher at early times (abridged).


title: 2D spectroscopy of double-barred galaxies

abstract:
  The first results of the observational program of the study of 2D-kinematics
in double-barred galaxies are presented. We show that, for the main part of the
sample, the inner bars do not affect the circumnuclear stellar kinematics.
Therefore, they are not dynamically decoupled structures. Various types of
non-circular gas motion were found in many galaxies. The analysis of the
ground-based and HST optical and NIR images reveals mini-spirals in about half
of the investigated objects. We suggest that so called ``double-barred
galaxies'' are, in fact, galaxies with very different circumnuclear structure.


title: Fabry-Perot observations at the 6m telescope

abstract:
  A current status of the observations with Interferometer Fabry-Perot (IFP) at
the 6m telescope are described. A reduction of the data obtaining with a new
focal reducer SCORPIO in IFP mode are outlined.


title: Imaging planets around nearby white dwarfs

abstract:
  We suggest that Jovian planets will survive the late stages of stellar
evolution, and that white dwarfs will retain planetary systems in wide orbits
(>5AU). Utilising evolutionary models for Jovian planets, we show that
infra-red imaging with 8m class telescopes of suitable nearby white dwarfs
should allow us to resolve and detect companions >3Mjup. Detection of massive
planetary companions to nearby white dwarfs would prove that such objects can
survive the final stages of stellar evolution, place constraints on the
frequency of main sequence stars with planetary systems dynamically similar to
our own and allow direct spectroscopic investigation of their composition and
structure.


title: Formation and evolution of galaxy disks: what is wrong with CDM?

abstract:
  We find that the density distribution of high and low surface brightness (SB)
galaxy disks formed within LCDM halos under the assumption of detailed angular
momentum conservation is in rough agreement with observations. The
luminous-to-dark matter ratio of the model galaxies increases with SB. The
lowest SB models tend to be minimum disks, but the high SB models hardly attain
the maximum disk solution. With the introduction of shallow cores in the halos,
high SB models become maximum disks. The shallow cores also help to improve the
inner SB profiles of bulge-less low SB models and the zero-point of the
Tully-Fisher relation. The models predict well this relation and its scatter,
as well as the small correlation among the residuals of this and the
luminosity-radius relation, in spite of the dependence of the rotation curve
shapes on SB.


title:
Time Dependence of the Ultraviolet Radiation Field in the Local
  Interstellar Medium

abstract:
  Far Ultraviolet radiation has been recognized as the main source of heating
of the neutral interstellar gas, and, as a consequence, it determines whether
the thermal balance of the neutral gas results in cold ($T\sim 50 - 100 K$)
clouds (CNM), warm ($T \sim 10^4 K$) clouds (WNM), or a combination of the two.
High FUV fields convert the neutral gas to WNM, while low fields result in CNM.
The sources of FUV radiation are the short-lived massive stars that generally
originate in associations that form in Giant Molecular Clouds present in the
galactic disk. Using McKee & Williams' (1997) distribution of birthrates for OB
associations in the Galaxy, we determine the expected behavior of the
time-dependent FUV field for random positions in the local ISM. The FUV field
is calculated in two bands (912-1100 \AA and 912-2070 \AA) and at the
wavelength 1400 \AA. Our median value for the [912-2070 \AA] band is $G_0=1.6$
times Habing's (1968) value for the radiation field at the solar circle in this
band, and quite close to Draine's (1976) value, $G_0=1.7$. Due to attenuation
by dust, only associations within about 500 pc contribute significantly to the
energy density at a given point. The FUV field is asymmetric at a given point,
and the asymmetry grows for higher fields. The FUV field fluctuates with a
variety of amplitudes, the larger ones being less frequent. The mean field is
about twice the median field because of these fluctuations, or spikes, in the
radiation field. These spikes, which last $\sim 30$ Myr, are caused by the
infrequent birth of nearby associations. We also model shorter duration spikes
caused by runaway OB stars. The presence of a fluctuating heating rate created
by the fluctuating FUV field converts CNM to WNM and vice versa.


title:
Spiral Molecular Front in Galaxies: Quick Transition from Atomic to
  Molecular Hydrogen in Spiral Arms

abstract:
  We derived a two-dimensional map of the molecular fraction, fmol, (the ratio
of molecular-gas density to that of total gas) in the spiral galaxy M51, and
examined the behavior of molecular fronts (MF), where MF represents the place
where fmol changes drastically from nearly zero to unity and vice versa. We
show that the MF phenomenon occurs not only radial, but also in the azimuth
direction through the spiral arms, and fmol changes rapidly in the
arm-to-inter-arm transition regions. The existence of the azimuthal MF
indicates that the atomic gas (HI) is quicklytransformed to molecular gas (H_2)
during the passage through spiral arms. We performed a numerical simulation of
MF based on an HI-to-H_2 phase transition theory, and reproduced the
observations. We estimated a azimuthal scale length of the transition to be
less than 200 pc, corresponding to a time scale of about 2 Myr for H_2 gas
formation. The azimuthal width of a molecular arm is estimated to be at most
2.5 kpc, where the gas can remain in molecular phase for about 25 Myr.


title: Not Color Blind: Using Multiband Photometry to Classify Supernovae

abstract:
  Large numbers of supernovae (SNe) have been discovered in recent years, and
many more will be found in the near future. Once discovered, further study of a
SN and its possible use as an astronomical tool (e.g., as a distance estimator)
require knowledge of the SN type. Current classification methods rely almost
solely on the analysis of SN spectra to determine their type. However,
spectroscopy may not be possible or practical when SNe are faint, numerous, or
discovered in archival studies. We present a classification method for SNe
based on the comparison of their observed colors with synthetic ones,
calculated from a large database of multi-epoch optical spectra of nearby
events. We discuss the capabilities and limitations of this method. For
example, type Ia SNe at redshifts z < 0.1 can be distinguished from most other
SN types during the first few weeks of their evolution, based on V-R vs. R-I
colors. Type II-P SNe have distinct (very red) colors at late (t > 100 days)
stages. Broadband photometry through standard Johnson-Cousins $UBVRI$ filters
can be useful to classify SNe out to z ~ 0.6. The use of Sloan Digital Sky
Survey (SDSS) ugriz filters allows the extension of our classification method
to even higher redshifts (z = 0.75), and the use of infrared bands, to z = 2.5.
We demonstrate the application of this method to a recently discovered SN from
the SDSS. Finally, we outline the observational data required to further
improve the sensitivity of the method, and discuss prospects for its use on
future SN samples. Community access to the tools developed is provided by a
dedicated website (http://wise-obs.tau.ac.il/~dovip/typing) .


title:
Clusters of Galaxies at Sharp Focus: Cooling Flows and Radio Sources
  Unveiled by Chandra

abstract:
  Chandra images of galaxy clusters have revealed a wealth of structure unseen
by previous generations of low resolution X-ray observatories. In the cores of
clusters, bright, irregular X-ray emission is now routinely seen within central
dominant galaxies (CDGs) harboring powerful radio sources. The radio sources
are interacting with and are often displacing the hot gas leaving cavities in
their wakes. The cavities rise buoyantly, transporting up to 10E61 ergs of
energy to the intracluster medium over the life of a cluster. The dynamically
important magnetic fields observed in cooling flows may have originated from
these cavities. The cooling rates found by Chandra and XMM-Newton are much
smaller than previously reported, and they are more in line with the levels of
cold gas and star formation seen in other bandpasses. I discuss the emerging
correlation between extended H-alpha emission, star formation, and bright X-ray
emission at locations where the cooling time of the keV gas approaches a few
hundred million years. Data from a variety of disciplines suggest repeated,
short duration bursts of cooling and star formation are occurring, possibly
induced and regulated in some instances by the central radio source. Finally, I
discuss the interesting possibility that radio sources quench cooling flows,
while emphasizing the difficulties with some proposed scenarios.


title: Neutrino flux predictions for known Galactic microquasars

abstract:
  It has been proposed recently that Galactic microquasars may be prodigious
emitters of TeV neutrinos that can be detected by upcoming km^2 neutrino
telescopes. In this paper we consider a sample of identified microquasars and
microquasar candiates, for which available data enables rough determination of
the jet parameters. By employing the parameters inferred from radio
observations of various jet ejection events, we determine the neutrino fluxes
that should have been produced during these events by photopion production in
the jet. Despite the large uncertainties in our analysis, we demonstrate that
in several of the sources considered, the neutrino flux at Earth, produced in
events similar to those observed, would exceed the detection threshold of a
km^2 neutrino detector. The class of microquasars may contain also sources with
bulk Lorentz factors larger than those characteristic of the sample considered
here, directed along our line of sight. Such sources, which may be very
difficult to resolve at radio wavelengths and hence may be difficult to
identify as microqusar candidates, may emit neutrinos with fluxes significantly
larger than typically obtained in the present analysis. These sources may
eventually be identified through their neutrino and gamma-ray emission.


title: Heating of the intracluster medium by quasar outflows

abstract:
  We study the possibility of quasar outflows in clusters and groups of
galaxies heating the intracluster gas in order to explain the recent
observation of excess entropy in this gas. We use the extended Press-Schechter
formalism to estimate the number of quasars that become members of a group of
cluster of a given mass and formation epoch. We also estimate the fraction of
mechanical energy in the outflows that is imparted to the surrounding medium as
a function of the density and temperature of this gas. We finally calculate the
total amount of non-gravitational heating from such outflows as a function of
the cluster potential and formation epoch. We show that outflows from broad
absorption line (BAL) and radio loud quasars can provide the required amount of
heating of the intracluster gas. We find that in this scenario most of the
heating takes place at $z \sim 1\hbox{--}4$, and that this ``preheating'' epoch
is at lower redshift for lower mass clusters.


title: Chandra Detection of Highest Redshift (z~6) Quasars in X-rays

abstract:
  We report on Chandra observations of three quasars SDSSP J083643+005453,
SDSSP J103027+052455, and SDSSP J130608+035626 at redshifts 5.82, 6.28 and 5.99
respectively. All the three sources are clearly detected in the X-ray band, up
to rest frame energies of ~55 keV. These observations demonstrate the
unprecedented sensitivity of Chandra to detect faint sources in relatively
short exposure times (5.7--8.2 ksec). The broad band X-ray properties of these
highest redshift quasars do not appear to be any different from their lower
redshift cousins. Spectra of the sources could not be determined with only few
counts detected. Observations with XMM-Newton will be able to constrain the
spectral shapes, if they are simple. Determination of complex spectra in a
reasonable amount of time, however, will have to await next generation of X-ray
missions.


title: The Massive Wolf-Rayet Binary SMC WR7

abstract:
  We present a study of optical spectra of the Wolf--Rayet star AzV 336a (= SMC
WR7) in the Small Magellanic Cloud. Our study is based on data obtained at
several Observatories between 1988 and 2001. We find SMC WR7 to be a double
lined WN+O6 spectroscopic binary with an orbital period of 19.56 days. The
radial velocities of the He absorption lines of the O6 component and the strong
He{\sc ii} emission at $\lambda$4686\AA of the WN component describe antiphased
orbital motions. However, they show a small phase shift of $\sim$ 1 day. We
discuss possible explanations for this phase shift. The amplitude of the radial
velocity variations of He {\sc ii} emission is twice that of the absorption
lines. The binary components have fairly high minimum masses, $\sim$ 18
$\modot$ and 34 $\modot$ for the WN and O6 components, respectively.


title:
Subaru Deep Survey II. Luminosity Functions and Clustering Properties of
  Lya Emitters at z=4.86 in the Subaru Deep Field

abstract:
  We report on early results from deep and wide-field narrow-band imaging on a
543 arcmin^2 area of the Subaru Deep Field. We find 87 Lya emitters (LAEs) at
z=4.86(+/-0.03) which are photometrically selected by a combination of two
broad bands (R and i') and one narrow band (NB711; 7126A FWHM=73A). We derive
the luminosity functions (LFs) of the LAEs at Lya luminosity and at
UV-continuum (1700A) luminosity. The LFs show little evolution between z=3.4
and z=4.86 either in Lya or UV-continuum emission. The amplitude of the LAE LF
tends to decline at the bright magnitudes more rapidly than that of the LBG LF
at similar redshifts. We calculate the angular correlation function of our LAEs
up to ~15 arcmin separations. The angular correlation w(theta) is found to
increase with decreasing angular separations, showing a clear signal of
clustering. It is also found that the distribution of LAEs shows a large
density gradient with a scale of >~15 arcmin, which would indicate the
existence of a large-scale structure of LAEs on >~20h^(-1) Mpc scales.We fit
the observed correlation function by Aw theta^(-0.8) to find Aw=29arcsec^(0.8).
The estimated correlation length is r0=3.5(+/-0.3)h^(-1)Mpc in comoving units
(Omega_m=0.3 and Omega_Lambda=0.7), which is slightly larger than the value for
z~4 LBGs with i'<26. We calculate the angular correlation function for two
sub-samples of the 87 LAEs divided by Lya luminosity, UV-continuum luminosity,
and Lya equivalent width (EW). The Lya bright sub-sample shows a larger
correlation amplitude than the Lya faint sub-sample, while no significant
difference is found for the sub-samples divided by UV-continuum luminosity or
EW.


title: Energy Dependence of a Low Frequency QPO in GRS 1915+105

abstract:
  We analyze a set of three RXTE Target of Opportunity observations of the
Galactic microquasar GRS 1915+105, observed on April 2000, during a
multi-wavelength campaign.
  During the three observations, a strong, variable low frequency (2-9 Hz)
quasi periodic oscillation (hereafter QPO), often referred to as the ubiquitous
QPO, is detected together with its first harmonic. We study the spectral
properties of both features, and show that : 1) their frequency variations are
better correlated with the soft X-ray flux (2-5 keV), favoring thus the
location of the QPO in the accretion disk; 2) the QPO affects more the hard
X-rays, usually taken as the signature of an inverse compton scattering of the
soft photons in a corona; 3) the fundamental and its harmonic do not behave in
the same manner: the fundamental sees its power increase with the energy up to
40 keV, whereas the harmonic increases up to $\sim 10$ keV. The results
presented here could find an explanation in the context of the
Accretion-Ejection Instability, which could appear as a rotating spiral or hot
point located in the disk, between its innermost edge and the corotation
radius. The presence of the harmonic could then be a signature of the
non-linear behavior of the instability. The high-energy (>40 keV) decrease of
the fundamental would favor an interpretation where most or all of the
quasi-periodic modulation at high energies comes, not from the comptonized
corona as usually assumed, but from a hot point in the optically thick disk


title:
Study of X-ray reflection features in a sample of Sy 1s observed by
  BeppoSAX

abstract:
  The ionized disc reflection model of Ross & Fabian is applied to a sample of
five Seyfert 1 galaxies observed by BeppoSAX. Good fits were obtained for all
the objects in the sample. NGC 4051 and Mkn 335 (usually classified as NLSy 1s)
show evidence of a highly ionized accretion disc (xi ~ 350 erg cm s^{-1} and xi
\~ 800 erg cm s^{-1}). While NGC 3783 seems to be a ``pure Sy 1'' characterized
by a highly ionized accretion disc (xi ~ 500 erg cm s^{-1}). All the sources
are consistent with having a face-on disc. The accurate determination of the
continuum emission allows us to investigate the spectral variability in the
case of Mkn 509.


title:
A synoptic spectral study of Cassiopeia-A based on XMM-Newton and
  BeppoSax observations

abstract:
  In this paper we present recent image and spectral data of Cas-A obtained
with XMM-Newton and BeppoSAX. Analysis of the hard X-ray continuum does not
support an interpretation of the hard X-radiation as synchrotron emission
produced in the primary shock, non-thermal Bremsstrahlung is a plausible
alternative. Moreover, a recent 500 kilosecond deep observation of the hard
X-ray continuum by BeppoSAX has revealed the positive detection of the 44Sc
nuclear decay lines at 67.9 and 78.4 keV. Appropriate modelling of the hard
X-ray continuum leads to an estimate of the initial 44Ti mass of (0.8-2.5)E-4
solar masses. We also present ionisation age, temperature, abundances maps. The
observed elemental abundance ratio patterns can be reconciled best with a type
Ib SNe, arising from a 60 solar mass progenitor (ZAMS) with high-mass-loss. The
accurate modeling of the image-resolved emission line spectra has enabled us to
derive reliable Doppler velocities for the bright Si-K, S-K, and Fe-K line
complexes.


title: Weak homology of elliptical galaxies

abstract:
  We start by studying a small set of objects characterized by photometric
profiles that have been pointed out to deviate significantly from the standard
R^{1/4} law. For these objects we confirm that a generic R^{1/n} law, with n a
free parameter, can provide superior fits (the best-fit value of n can be lower
than 2.5 or higher than 10), better than those that can be obtained by a pure
R^{1/4} law, by an R^{1/4}+exponential model, and by other dynamically
justified self--consistent models. Therefore, strictly speaking, elliptical
galaxies should not be considered homologous dynamical systems. Still, a case
for "weak homology", useful for the interpretation of the Fundamental Plane of
elliptical galaxies, could be made if the best-fit parameter n, as often
reported, correlates with galaxy luminosity L, provided the underlying
dynamical structure also follows a systematic trend with luminosity. We
demonstrate that this statement may be true even in the presence of significant
scatter in the correlation n(L). Preliminary indications provided by a set of
"data points" associated with a sample of 14 galaxies suggest that neither the
strict homology nor the constant stellar mass--to--light solution are a
satisfactory explanation of the observed Fundamental Plane (abridged).


title: XMM-Newton observation of the bursting pulsar GRO J1744-28 in quiescence

abstract:
  The XMM-Newton X-ray observatory performed a pointed observation of the
bursting pulsar GRO J1744-28 in April 2001 for about 10 ks during a program
devoted to the scan of the Galactic center region. After the discovery of this
source by BATSE in December 1995 during a very active bursting phase, it has
been in quiescence since April 1997. We present here the first detection of GRO
J1744-28 in its quiescent state at a position which is consistent with previous
high-energy positions (but not consistent with a proposed IR counterpart). The
observed luminosity of the source in quiescence is about 6 orders of magnitude
weaker than the luminosity in outburst.


title:
Non-thermal bremsstrahlung as the dominant hard X-ray continuum emission
  from the supernova remnant MSH14-63 (RCW 86)

abstract:
  We present an analysis of the X-ray emission of the supernova remnant
MSH14-63, which was partially covered by four observations with XMM-Newton. The
detection of Fe K emission at 6.4 keV, and the lack of spatial correlation
between hard X-ray and radio emission is evidence against a dominant X-ray
synchrotron component. We argue that the hard X-ray continuum is best explained
by non-thermal bremsstrahlung from a supra-thermal tail to an otherwise cool
electron gas. The existence of low electron temperatures, required to explain
the absence of line emission, is supported by low temperatures found in other
parts of the remnant, which are as low as 0.2 keV in some regions.


title: XMM-Newton observations of the Lockman Hole : Spectral analysis

abstract:
  We present the results of the X-ray spectral analysis of the deep survey
obtained with the XMM-Newton observatory on the Lockman Hole. The X-ray data
and the cumulative source counts were reported by Hasinger et al. (2001). Our
sample contains 104 sources with a count limit of 70 of which 55 have redshift
identification. The redshift distribution peaks at z ~ 0.8, with a strong
excess of low z AGN and a deficiency of sources at z > 2 compared to population
synthesis models for the X-ray background. The type 2 (obscured) AGN have
weaker soft X-ray and optical fluxes. They cluster around z ~ 1. There is a
clear separation between the classical/type 1 AGN and the obscured/type 2 ones
in several diagnostics involving X-ray colour, X-ray flux, optical/near IR
colour and optical brightness. Using the z subsample, we show that this
separation between the AGN populations is a consequence of different absorption
column densities. The two populations have the same average spectral index,
Gamma ~ 1.9. At the 70 count detection limit, there is also a strong overlap
between the two populations in hard X-ray flux and near IR brightness. These
diagnostics should enable the classification of obscured/type 2 AGN very faint
optically.


title:
Photospheric Abundances of the Hot Stars in NGC1399 and Limits on the
  Fornax Cluster Cooling Flow

abstract:
  We present far-UV spectroscopy of the giant elliptical galaxy NGC 1399,
obtained with the Far Ultraviolet Spectroscopic Explorer. Of all quiescent
ellipticals, NGC 1399 has the strongest known ``UV upturn'' -- a sharp spectral
rise shortward of 2500 A. It is now well-established that this emission comes
from hot horizontal branch (HB) stars and their progeny; however, the chemical
composition of these stars has been the subject of a long-standing debate. For
the first time in observations of any elliptical galaxy, our spectra clearly
show photospheric metallic absorption lines within the UV upturn. The abundance
of N is at 45% solar, Si is at 13% solar, and C is at 2% solar. Such abundance
anomalies are a natural consequence of gravitational diffusion. These
photospheric abundances fall in the range observed for subdwarf B stars of the
Galactic field.
  Although NGC1399 is at the center of the Fornax cluster, we find no evidence
for O VI cooling flow emission. The upper limit to 1032,1038 emission is
3.9E-15 erg/s/cm2, equivalent to 0.14 M_sun/yr, and less than that predicted by
simple cooling flow models of the NGC 1399 X-ray luminosity.


title: A Unified Description of the Timing Features of Accreting X-ray Binaries

abstract:
  We study an empirical model for a unified description of the power spectra of
accreting neutron stars and black holes. This description is based on a
superposition of multiple Lorentzians and offers the advantage that all QPO and
noise components are dealt with in the same way, without the need of deciding
in advance the nature of each component. This approach also allows us to
compare frequencies of features with high and low coherences in a consistent
manner and greatly facilitates comparison of power spectra across a wide range
of source types and states. We apply the model to six sources, the
low-luminosity X-ray bursters 1E 1724-3045, SLX 1735-269 and GS 1826-24, the
high-latitude transient XTE J1118+480, the bright system Cir X-1, and the Z
source GX 17+2. We find that it provides a good description of the observed
spectra, without the need for a scale-free (1/f) component. We update
previously reported correlations between characteristic frequencies of timing
features in the light of this new approach and discuss similarities between
different types of systems which may point towards similar underlying physics.


title:
Discovery and analysis of p-mode and g-mode oscillations in the A-type
  primary of the eccentric binary HD 209295

abstract:
  We have discovered both intermediate-order gravity mode and low-order
pressure mode pulsation in the same star, HD 209295. It is therefore both a
Gamma Doradus and a Delta Scuti star, which makes it the first pulsating star
to be a member of two classes.
  The star is a single-lined spectroscopic binary with an orbital period of
3.10575 d and an eccentricity of 0.352. Weak pulsational signals are found in
both the radial velocity and line-profile variations, allowing us to show that
the two highest-amplitude Gamma Doradus pulsation modes are consistent with l=1
and |m|=1.
  In our 280 h of BVI multi-site photometry we detected ten frequencies in the
light variations, one in the Delta Scuti regime and nine in the Gamma Doradus
domain. Five of the Gamma Doradus frequencies are exact integer multiples of
the orbital frequency. This observation leads us to suspect they are tidally
excited. Results of theoretical modeling (stability analysis, tidal excitation)
were consistent with the observations.
  We could not detect the secondary component of the system in infrared
photometry, suggesting that it may not be a main-sequence star. Archival data
of HD 209295 show a strong ultraviolet excess, the origin of which is not
known. The orbit of the primary is consistent with a secondary mass of M > 1.04
Msun indicative of a neutron star or a white dwarf companion.


title: Dynamics of Cosmological Perturbations in Position Space

abstract:
  We show that the linear dynamics of cosmological perturbations can be
described by coupled wave equations, allowing their efficient numerical and, in
certain limits, analytical integration directly in position space. The linear
evolution of any perturbation can then be analyzed with the Green's function
method. Prior to hydrogen recombination, assuming tight coupling between
photons and baryons, neglecting neutrino perturbations, and taking isentropic
(adiabatic) initial conditions, the obtained Green's functions for all metric,
density, and velocity perturbations vanish beyond the acoustic horizon. A
localized primordial cosmological perturbation expands as an acoustic wave of
photon-baryon density perturbation with narrow spikes at its acoustic
wavefronts. These spikes provide one of the main contributions to the cosmic
microwave background radiation anisotropy on all experimentally accessible
scales. The gravitational interaction between cold dark matter and baryons
causes a dip in the observed temperature of the radiation at the center of the
initial perturbation. We first model the radiation by a perfect fluid and then
extend our analysis to account for finite photon mean free path. The resulting
diffusive corrections smear the sharp features in the photon and baryon density
Green's functions over the scale of Silk damping.


title:
The Contribution of HI-rich Galaxies to the Damped Lyman-alpha Absorber
  Population at z=0

abstract:
  We present a study of the expected properties of the low redshift damped
Lyman-alpha absorber population determined from a sample of HI-selected
galaxies in the local universe. Because of a tight correlation between the HI
mass and HI cross-section, which we demonstrate spans all galaxy types, we can
use our HI-selected sample to predict the properties of the absorption line
systems. We use measurements of the number density and HI cross-section of
galaxies to show that the total HI cross-section at column densities sufficient
to produce damped Lyman-alpha absorption is consistent with no evolution of the
absorber population. We also find that the dN/dz distribution is dominated by
galaxies with HI masses near 10^9 Msolar. However, because of the large
dispersion in the correlation between HI mass and stellar luminosity, we find
that the distribution of dN/dz as a function of L_J is fairly flat.
Additionally, we examine the line widths of the HI-selected galaxies and show
that there may be evolution in the kinematics of HI-rich galaxies, but it is
not necessary for the higher redshift population to contain a greater
proportion of high mass galaxies than we find locally.


title: Deflationary $\Lambda(t)$ cosmology: observational expressions

abstract:
  We discuss the classical cosmological tests for a large class of FRW type
models driven by a decaying vacuum energy density. Analytic expressions for the
lookback time, age of the universe, luminosity distance, angular diameter, and
galaxy number counts versus redshift are derived and their meaning discussed in
detail. It is found that the standard FRW results are significantly altered,
showing that such tests may constrain the physical parameters of these models
which are also in agreement to the accelerated expansion suggested by the
latest SNe type Ia observations.


title:
Constraints on primordial black holes and primeval density perturbations
  from the epoch of reionization

abstract:
  We investigate the constraint on the abundance of primordial black holes
(PBHs) and the spectral index $n$ of primeval density perturbations given by
the ionizing photon background at the epoch of reionization. Within the
standard inflationary cosmogony, we show that the spectral index $n$ of the
power-law power spectrum of primeval density perturbations should be $n<$1.27.
Since the universe is still optical thick at the reionization redshift $z\sim
6$ - 8, this constraint is independent of the unknown parameter of reheating
temperature of the inflation. The ionizing photon background from the PBHs can
be well approximated by a power law spectrum $J(\nu)\propto{\nu}^3$, which is
greatly different from those given by models of massive stars and quasars.


title: Planetary system around Vega

abstract:
  We applied our earlier numerical method to compute the thermal emission from
a dusty resonant structure around Vega and compared the new observational
evidence for a ring arc at 95 AU near Vega with our modeling. Our high
resolution simulations indicate that Vega may have an outerm ost planet at a
distance of 90-100 AU with coordinates near 18 35'16.25" (right ascension,
B1950) and 38 44'15" (declination). Another symmetrical position, 18 35'14.75"
and 38 44'32.5", of the planet is also possible. Radii of the observed clumps
(and planet's orbital radius) may be smaller, e.g. ~60-75 AU. In this case the
planet stays approximately on the line between the two possible positions
above. From our modeling we make following conclusions: 1.Dust clumps rotate
around Vega exactly wi th the planet orbital speed, 0.6-1.2 deg/year, as
function of orbital radius of parent planet. 2. Orbital radius of the planet is
approximately the same as the orbital radius of clumps (90-100 AU from
observation by Koerner, Sargent & Ostroff, 2001 or 60-75 AU from observation by
Wilner, Holman, Ho & Kuchner, 2002). 3. The most dense clump is ahead of the
planet in the direction of the orbital motion. 4. The orbit of the planet may
be circular or with a small eccentricity. 5. Absence of dust i n the inner part
of Vega planetary system is a signature of inner planet(s) with orbital radii
<50-60 AU.


title:
XMM-Newton GT and AO-1 observations of SHARC galaxy clusters : RX
  J1120.1+4318 and RX J0256.5+0006

abstract:
  We present the follow-up of two galaxy clusters from the Bright and Southern
SHARC surveys observed with the XMM-Newton satellite. We studied the galaxy
cluster RX J1120.1+4318 which seems to be a relaxed cluster at high redshift
according to its surface brightness profile and to its temperature profile
which is flat up to 950 kpc. Its mean temperature is measured at 5.3 keV. The
other galaxy cluster RX J0256.5+0006 shows two components. We discuss possible
scenario.


title: Gamma-Ray Imaging by Silicon Detectors in Space: the AREM Method

abstract:
  We present the Agile REconstruction Method (AREM) for gamma-ray (30 MeV - 50
GeV) direction reconstruction applicable to high-resolution Silicon Tracker
detectors in space. It can be used in a "fast mode", independently of Kalman
filters techniques, or in an "optimized mode", including Kalman filter
algorithms for track identification. AREM correctly addresses three points of
the analysis which become relevant for off-axis incidence angles: (1) intrinsic
ambiguity in the identification of the 3-dimensional $e^+/e^-$ tracks; (2)
proper identification of the 3-dimensional pair production plane and
reconstructed direction; (3) careful choice of an energy weighting scheme for
the 3-dimensional tracks. We apply our method to simulated gamma-rays in the
AGILE detector. The excellent spatial resolution obtained by the AGILE Silicon
Tracker, providing crucial analog information, makes it possible to improve the
spatial resolution of previous detectors (e.g. EGRET) by a factor of ~ 2 in
containment radius at gamma energy ~ 400 MeV. In this paper we present the
results of our 3D-method for a selected sample of photon incidence angles and
energies. A more comprehensive and complete discussion including the use of
Kalman filter algorithms will be the subject of forthcoming papers.


title: Simulation of the AGILE gamma-ray imaging detector performance: part I

abstract:
  We present in this paper the results of a comprehensive GEANT simulation of
the Gamma-Ray Imaging Detector (GRID) being developed for the AGILE space
astrophysics mission. The GRID is designed to be sensitive in the 30 MeV - 50
GeV energy range, with excellent imaging and timing capabilities, and with a
very large field-of-view (~3 sr). In this paper (Paper I) we present the GRID
baseline geometry, a model for the charged particle and albedo-photon
backgrounds for an equatorial orbit of 550-600 km altitude, and the main
results of the first level (Level-1 Trigger) on-board data processing. Our
simulations show that the GRID Level-1 data processing is expected to be
capable of decreasing by a factor of ~ 20 the charged particle background (from
\~2 kHz to below 100 Hz), and by a factor of ~ 30 the albedo-photon background.
The gamma-ray photon detection efficiency by the imaging GRID is simulated to
be particularly efficient, varying between 39% and 17% depending on photon
energies and incident directions.


title: Simulation of the AGILE gamma-ray imaging detector performance: Part II

abstract:
  In this paper (Paper II) we complete our discussion on the results of a
comprehensive GEANT simulation of the scientific performance of the AGILE
Gamma-Ray Imaging Detector (GRID), operating in the 30 MeV - 50 GeV energy
range in an equatorial orbit of height near 550 km. Here we focus on the
on-board Level-2 data processing and discuss possible alternative strategies
for event selection and their optimization. We find that the dominant particle
background components after our Level-2 processing are electrons and positrons
of kinetic energies between 10 and 100 MeV penetrating the GRID instrument from
directions almost parallel to the Tracker planes (incidence angles > 90
degrees) or from below. The analog (charge) information available on-board in
the GRID Tracker is crucial for a reduction by almost three orders of magnitude
of protons (and heavier ions) with kinetic energies near 100 MeV. We also
present in this paper the telemetry structure of the GRID photon and particle
events, and obtain the on-board effective area for photon detection in the
energy range ~30 MeV - 50 GeV.


title: On the cosmological variation of the fine structure constant

abstract:
  A phenomenological model is proposed to explain the recent observed
cosmological variation of the fine structure constant as an effect of the
quantum vacuum, assuming a flat universe with cosmological constant $\Lambda$
in the cases ($\Omega_M, \Omega_\Lambda$) equal to (0.3,0.7) and (1,0). Because
of the fourth Heisenberg relation, the lifetime of the virtual pairs of the
zero-point radiation must depend on the gravitational potential, so that the
quantum vacuum changes its density and acquires a relative permittivity
different from one. Since the matter was more concentrated in the past, the
gravitational potential of all the universe was stronger and the optical
density of the vacuum higher, the electron charge being then more renormalized
and smaller than now. The model is based on a first order Newtonian
approximation that is valid for the range of the observations, but not for very
high redshift, its prediction being that $\Delta \alpha /\alpha$ is
proportional to $\Omega_M[a(t)^{-1}-1]-2\Omega_\Lambda [a(t)^2-1]$, $a(t)$
being the scale factor. This agrees with the observations.


title: A Hall--Drift Induced Magnetic Field Instability

abstract:
  In the presence of a strong magnetic field and under conditions as realized
in the crust and the superfluid core of neutron stars the Hall--drift dominates
the field evolution. We show by a linear analysis that for a sufficiently
strong large--scale background field depending at least quadratically on
position in a plane conducting slab an instability occurs which rapidly
generates small--scale fields. Their growth rates depend on the choice of the
boundary conditions, increase with the background field strength and may reach
$10^3$ times the ohmic decay rate. The effect of that instability on the
rotational and thermal evolution of neutron stars is discussed.


title:
The first detection of weak gravitational shear in infrared
  observations: Abell 1689

abstract:
  We present the first detection of weak gravitational shear at infrared
wavelengths, using observations of the lensing cluster Abell 1689, taken with
the SofI camera on the ESO-NTT telescope. The imprint of cluster lenses on the
shapes of the background galaxy population has previously been harnessed at
optical wavelengths, and this gravitational shear signal enables cluster mass
distributions to be probed, independent of whether the matter is luminous or
dark. At near-infrared wavelengths, the spectrophotometric properties of
galaxies facilitate a clean selection of background objects for use in the
lensing analysis. A finite-field mass reconstruction and application of the
aperture mass (Map) statistic are presented. The probability that the peak of
the Map detection S/N~5, arises from a chance alignment of background sources
is only ~4.5*10^-7. The velocity dispersion of the best-fit singular isothermal
sphere model for the cluster is sigma_1D=1030^{+70}_{-80} km/s, and we find a
K-band mass-to-light ratio of ~40 M_solar/L_solar inside a 0.44 Mpc radius.


title: Radiative Transfer Effects in He I Emission Lines

abstract:
  We consider the effect of optical depth of the 2 ^{3}S level on the nebular
recombination spectrum of He I for a spherically symmetric nebula with no
systematic velocity gradients. These calculations, using many improvements in
atomic data, can be used in place of the earlier calculations of Robbins. We
give representative Case B line fluxes for UV, optical, and IR emission lines
over a range of physical conditions: T=5000-20000 K, n_{e}=1-10^{8} cm^{-3},
and tau_{3889}=0-100. A FORTRAN program for calculating emissivities for all
lines arising from quantum levels with n < 11 is also available from the
authors.
  We present a special set of fitting formulae for the physical conditions
relevant to low metallicity extragalactic H II regions: T=12,000-20,000 K,
n_{e}=1-300 cm^{-3}, and tau_{3889} < 2.0. For this range of physical
conditions, the Case B line fluxes of the bright optical lines 4471 A, 5876 A,
and 6678 A, are changed less than 1%, in agreement with previous studies.
However, the 7065 A corrections are much smaller than those calculated by
Izotov & Thuan based on the earlier calculations by Robbins. This means that
the 7065 A line is a better density diagnostic than previously thought. Two
corrections to the fitting functions calculated in our previous work are also
given.


title: Submillimeter Galaxies

abstract:
  A cosmologically significant population of very luminous high-redshift
galaxies has recently been discovered at submm wavelengths. Advances in submm
detector technologies have opened this new window on the distant Universe. Here
we discuss the properties of the high-redshift submm galaxies, their
significance for our understanding of the process of galaxy formation, and the
selection effects that apply to deep submm surveys. The submm galaxies generate
a significant fraction of the energy output of all galaxies in the early
Universe. We emphasize the importance of studying a complete sample of submm
galaxies, and stress that because they are typically very faint in other
wavebands, these follow-up observations are very challenging. Finally, we
discuss the surveys that will be made using the next generation of submm-wave
instruments under development.


title:
Constraints on the Extremely High-Energy Cosmic Ray Accelerators from
  Classical Electrodynamics

abstract:
  We find the general requirements, set by classical electrodynamics, to the
sources of extremely high-energy cosmic rays (EHECRs). It is shown that the
parameters of EHECR accelerators are strongly limited not only by the particle
confinement in large-scale magnetic field or by the difference in electric
potentials (generalized Hillas criterion), but also by the synchrotron
radiation, the electro-bremsstrahlung, or the curvature radiation of
accelerated particles. Optimization of these requirements in terms of
accelerator's size and magnetic field strength results in the ultimate lower
limit to the overall source energy, which scales as the fifth power of
attainable particle energy. Hard gamma-rays accompanying generation of EHECRs
can be used as a probe for potential acceleration sites. We apply the results
to several populations of astrophysical objects -- potential EHECR sources --
and discuss their ability to accelerate protons to $10^{20}$ eV and beyond. A
possibility to gain from ultrarelativistic bulk flows is emphasized, with
Active Galactic Nuclei and Gamma-Ray Bursts being the examples.


title:
An X-ray Reprocessing Model of Disk Thermal Emission in Type 1 Seyfert
  Galaxies

abstract:
  Using a geometry consisting of a hot central Comptonizing plasma surrounded
by a thin accretion disk, we model the optical through hard X-ray spectral
energy distributions of the type 1 Seyfert galaxies NGC 3516 and NGC 7469. As
in the model proposed by Poutanen, Krolik, & Ryde for the X-ray binary Cygnus
X-1 and later applied to Seyfert galaxies by Zdziarski, Lubi\'nski, & Smith,
feedback between the radiation reprocessed by the disk and the thermal
Comptonization emission from the hot central plasma plays a pivotal role in
determining the X-ray spectrum, and as we show, the optical and ultraviolet
spectra as well. Seemingly uncorrelated optical/UV and X-ray light curves,
similar to those which have been observed from these objects can be explained
by variations in the size, shape, and temperature of the Comptonizing plasma.
Furthermore, by positing a disk mass accretion rate which satisfies a condition
for global energy balance between the thermal Comptonization luminosity and the
power available from accretion, one can predict the spectral properties of the
hard X-ray continuum above $\sim 50$ keV in type 1 Seyfert galaxies.
Forthcoming measurements of the hard X-ray continuum by more sensitive hard
X-ray and soft $\gamma$-ray telescopes, in conjunction with simultaneous
optical, UV, and soft X-ray monitoring, will allow the mass accretion rates to
be directly constrained for these sources in the context of this model.


title: X-Ray Supernovae

abstract:
  We present a review of X-ray observations of supernovae (SNe). By observing
the (~0.1-100 keV) X-ray emission from young SNe, physical key parameters such
as the circumstellar matter (CSM) density, mass-loss rate of the progenitor and
temperature of the outgoing and reverse shock can be derived as a function of
time. Despite intensive search over the last ~25 years, only 15 SNe have been
detected in X-rays. We review the individual X-ray observations of these SNe
and discuss their implications as to our understanding of the physical
processes giving rise to the X-ray emission.


title: Interaction of High-Velocity Pulsars with Supernova Remnant Shells

abstract:
  Hydrodynamical simulations are presented of a pulsar wind emitted by a
supersonically moving pulsar. The pulsar moves through the interstellar medium
or, in the more interesting case, through the supernova remnant created at its
birth event. In both cases there exists a three-fold structure consisting of
the wind termination shock, contact discontinuity and a bow shock bounding the
pulsar wind nebula. Using hydrodynamical simulations we study the behaviour of
the pulsar wind nebula inside a supernova remnant, and in particular the
interaction with the outer shell of swept up interstellar matter and the blast
wave surrounding the remnant. This interaction occurs when the pulsar breaks
out of the supernova remnant. We assume the remnant is in the Sedov stage of
its evolution. Just before break-through, the Mach number associated with the
pulsar motion equals ${\cal M}_{\rm psr} = 7/\sqrt{5}$, {\em independent} of
the supernova explosion energy and pulsar velocity. The bow shock structure is
shown to survive this break-through event.


title: Building a CCD Spectrograph for Educational or Amateur Astronomy

abstract:
  We discuss the design of an inexpensive, high-throughput CCD spectrograph for
a small telescope. By using optical fibers to carry the light from the
telescope focus to a table-top spectrograph, one can minimize the weight
carried by the telescope and simplify the spectrograph design. We recently
employed this approach in the construction of IntroSpec, an instrument built
for the 16-inch Knowles Telescope on the Harvard College campus.


title: Evolution of "51Peg b-like" Planets

abstract:
  About one-quarter of the extrasolar giant planets discovered so far have
orbital distances smaller than 0.1 AU. These ``51Peg b-like'' planets can now
be directly characterized, as shown by the planet transiting in front the star
HD209458. We review the processes that affect their evolution.
  We apply our work to the case of HD209458b, whose radius has been recently
measured. We argue that its radius can be reproduced only when the deep
atmosphere is assumed to be unrealistically hot. When using more realistic
atmospheric temperatures, an energy source appears to be missing in order to
explain HD209458b's large size. The most likely source of energy available is
not in the planet's spin or orbit, but in the intense radiation received from
the parent star. We show that the radius of HD209458b can be reproduced if a
small fraction (~1%) of the stellar flux is transformed into kinetic energy in
the planetary atmosphere and subsequently converted to thermal energy by
dynamical processes at pressures of tens of bars.


title:
Exploratory Chandra Observations of the Three Highest Redshift Quasars
  Known

abstract:
  We report on exploratory Chandra observations of the three highest redshift
quasars known (z = 5.82, 5.99, and 6.28), all found in the Sloan Digital Sky
Survey. These data, combined with a previous XMM-Newton observation of a z =
5.74 quasar, form a complete set of color-selected, z > 5.7 quasars. X-ray
emission is detected from all of the quasars at levels that indicate that the
X-ray to optical flux ratios of z ~ 6 optically selected quasars are similar to
those of lower redshift quasars. The observations demonstrate that it will be
feasible to obtain quality X-ray spectra of z ~ 6 quasars with current and
future X-ray missions.


title: Atmospheric Circulation and Tides of "51Peg b-like" Planets

abstract:
  We examine the properties of the atmospheres of extrasolar giant planets at
orbital distances smaller than 0.1 AU from their stars. We show that these
``51Peg b-like'' planets are rapidly synchronized by tidal interactions, but
that small departures from synchronous rotation can occur because of
fluid-dynamical torques within these planets. Previous radiative-transfer and
evolution models of such planets assume a homogeneous atmosphere. Nevertheless,
we show using simple arguments that, at the photosphere, the day-night
temperature difference and characteristic wind speeds may reach ~500 K and ~2
km/s, respectively. Substantial departures from chemical equilibrium are
expected. The cloud coverage depends sensitively on the dynamics; clouds could
exist predominantly either on the dayside or nightside, depending on the
circulation regime. Radiative-transfer models that assume homogeneous
conditions are therefore inadequate in describing the atmospheric properties of
51Peg b-like planets. We present preliminary three-dimensional, nonlinear
simulations of the atmospheric circulation of HD209458b that indicate plausible
patterns for the circulation and generally agree with our simpler estimates.
Furthermore, we show that kinetic energy production in the atmosphere can lead
to the deposition of substantial energy in the interior, with crucial
consequences for the evolution of these planets. Future measurements of
reflected and thermally-emitted radiation from these planets will help test our
ideas.


title: Short-Period Waves That Heat the Corona Detected at the 1999 Eclipse

abstract:
  As a part of a study of the cause of solar coronal heating, we searched for
high-frequency (~1 Hz) intensity oscillations in coronal loops in the [Fe XIV]
coronal green line. We summarize results from observations made at the 11
August 1999 total solar eclipse from Ramnicu-Valcea, Romania, through clear
skies. We discuss the image reduction and analysis through two simultaneous
series of coronal CCD images digitized at 10 Hz for a total time of about 140
s. One series of images was taken through a 3.6 A filter isolating the 5303 A
[Fe XIV] coronal green line and the other through a 100 A filter in the nearby
K-corona continuum. Previous observations, described in Pasachoff et al.
(2000), showed no evidence for oscillations in the [Fe XIV] green line at a
level great than 2% of coronal intensity. We describe several improvements made
over the 1998 eclipse that led to increased image clarity and sensitivity. The
corona was brighter in 1999 with the solar maximum, further improving the data.
We use Fourier analysis to search in the [Fe XIV] channel for intensity
oscillations in loops at the base of the corona. Such oscillations in the 1-Hz
range are predicted as a result of density fluctuations from the resonant
absorption of MHD waves. The dissipation of a significant amount of mechanical
energy from the photosphere into the corona through this mechanism could
provide sufficient energy to hear the corona. A Monte-Carlo model of the data
suggests the presence of enhanced power, particularly in the 0.75-1.0 Hz range,
and we conclude that MHD waves remain a viable method for coronal heating.


title: Accretion onto the Supermassive Black Hole in M87

abstract:
  Chandra X-ray observations of the giant elliptical galaxy M87 resolve the
thermal state of the hot interstellar medium into the accretion (Bondi) radius
of its central 3 10^9 Msun black hole. We measure the X-ray gas temperature and
density profiles and calculate the Bondi accretion rate, Mdot_Bondi \sim 0.1
Msun/yr. The X-ray luminosity of the active nucleus of M87 observed with
Chandra is L_{x, 0.5-7 \keV} \sim 7 \times 10^{40}erg/s. This value is much
less than the predicted nuclear luminosity, L_{Bondi} \sim 5 \times 10^{44}
erg/s, for accretion at the Bondi rate with a canonical accretion radiative
efficiency of 10%. If the black hole in M87 accretes at this rate it must do so
at a much lower radiative efficiency than the canonical value. The
multiwavelength spectrum of the nucleus is consistent with that predicted by an
advection-dominated flow. However, as is likely, the X-ray nucleus is dominated
by jet emission then the properties of flow must be modified, possibly by
outflows. We show that the overall energetics of the system are just consistent
with the predicted Bondi nuclear power. This suggests that either most of the
accretion energy is released in the relativistic jet or that the central engine
of M87 undergoes on-off activity cycles. We show that, at present, the energy
dumped into the ISM by the jet may reduce the accretion rate onto the black
hole by a factor \propto (v_j/c_s)^{-2}, where v_j is the jet velocity and c_s
the ISM sound speed, and that this is sufficient to account for the low nuclear
luminosity.


title: FUSE Observations of Degree-Scale Variations in Galactic Halo O VI

abstract:
  We report Far Ultraviolet Spectroscopic Explorer (FUSE) observations of
interstellar O VI absorption in the halo of the Milky Way towards 12 early-type
stars in the Large Magellanic Cloud (LMC) and 11 in the Small Magellanic Cloud
(SMC). The mean column densities of O VI associated with the Galactic halo
towards the LMC and SMC are log<N(OVI)> = 14.52(+0.10,-0.14) and
14.13(+0.14,-0.20), respectively, where the uncertainties represent the
standard deviations of the individual measurements about the means. Significant
variations in the O VI column densities are observed over all of the angular
scales probed by our observations: 0.5-5.0 degrees towards the LMC and 0.05-3.3
degrees towards the SMC. The maximum factors by which the O VI varies between
sight lines towards the LMC and SMC are ~2.8 and ~4.2, respectively. Though
low-, intermediate-, and high-velocity clouds are present along most of the
sight lines towards the LMC, the variations in O VI column densities are found
in all of these O VI absorbing structures. The column density variations trace
the structure of the hot ionized medium in the Galactic halo on scales of <<80
to 800 pc towards the LMC and <<6 to 400 pc towards the SMC (assuming the
absorption arises within the first 5 kpc above the Galactic plane).


title:
Planetary Nebulae in the Magellanic Clouds: Probing Stellar Evolution
  and Populations

abstract:
  This review contains: (1) the scientific motivations for studying Planetary
Nebulae in the Magellanic Clouds; (2) a review of this field of study, from the
origins to the most recent results, focusing on the papers that have been
published since the last IAU Symposium on Planetary Nebulae; (3) a review of
the Hubble contribution to the field, from the early results to our own
Magellanic Cloud Planetary Nebula program.


title: The 2-10 keV luminosity as a Star Formation Rate indicator

abstract:
  Radio and far infrared luminosities of star forming galaxies follow a tight
linear relation. Making use of BeppoSAX and ASCA observations of a well-defined
sample of star forming galaxies, we argue that a tight linear relation holds
between the 2-10 keV X-ray luminosity and both the radio and far infrared ones.
It is suggested that the hard X-ray emission is directly related to the Star
Formation Rate. Preliminary results obtained from deep Chandra and radio
observations of the Hubble Deep Field North show that a similar relation might
hold also at high (0.2<z<1.2) redshift.


title: Stars and singularities: Stellar phenomena near a massive black hole

abstract:
  This is a pedagogical review of recent results on the interactions of central
massive black holes with stars very near them, focused on the black hole in the
center of the Milky Way. Table of contents: [1] Introduction [2] Stellar
dynamics near a black hole [2.1] Physical scales [2.2] A relaxed stellar system
around a MBH [3] The stellar collider in the Galactic Center [3.1] The case for
a dense stellar cusp in the Galactic Center [3.2] Tidal spin-up [3.3] Tidal
scattering [4] The gravitational telescope in the Galactic Center [4.1]
Gravitational lensing by a point mass [4.2] Pinpointing the MBH with lensed
images [4.3] The detection of gravitational lensing [4.4] Magnification bias
[4.5] Beyond the point mass lens approximation [5] Summary


title: Stellar Outflows Driven by Magnetized Wide-Angle Winds

abstract:
  We present two-dimensional, cylindrically symmetric simulations of
hydrodynamic and magnetohydrodynamic (MHD) wide-angle winds interacting with a
collapsing environment. These simulations have direct relevance to young
stellar objects (YSOs). The results may also be of use in the study of
collimated outflows from proto-planetary and planetary nebulae. We study a
range of wind configurations consistent with asymptotic MHD wind collimation.
The degree of collimation is parameterized by the ratio of the wind density at
the pole to that of the equator. We find that a toroidal magnetic field can
have a significant influence on the resulting outflow, giving rise to a very
dense, jet-like flow in the post-shock region. The properties of the flow in
this region are similar to the asymptotic state of a collimated MHD wind. We
conclude that wide-angle MHD winds are quite likely capable of driving
molecular outflows. Due to difficulty in treating MHD winds ab-initio in
simulations we choose magnetic field strengths in the wind consistent slow
magnetic rotators. While MHD launched winds will be in the fast rotator regime
we discuss how our results, which rely on toroidal pinch effects, will hold for
stronger field strengths.


title: White dwarfs and Galactic dark matter

abstract:
  We discuss the recent discovery by Oppenheimer et al (2001) of old, cool
white dwarf stars, which may be the first direct detection of Galactic halo
dark matter. We argue here that the contribution of more mundane white dwarfs
of the stellar halo and thick disk would contribute sufficiently to explain the
new high velocity white dwarfs without invoking putative white dwarfs of the
dark halo. This by no means rules out that the dark matter has been found, but
it does constrain the overall contribution by white dwarfs brighter than M_V ~
16 to significantly less than 1% of the Galactic dark matter. This work
confirms a similar study by Reyle et al (2001).


title:
First Results from a XMM-Newton Survey of a Distance-Limited (D<22 Mpc)
  Sample of Seyfert Galaxies: I- the Agns

abstract:
  We report here preliminary results from a survey of nearby Seyfert galaxies
using the EPIC CCDs on board XMM-Newton. The total sample consists of 28
Seyfert galaxies, and constitute a well-defined, complete (B<12.5 mag), and
volume-limited (D<22 Mpc) sample of Seyfert galaxies in the northern (Delta > 0
deg.) hemisphere. The survey has been initiated in June, 2001, and we report
here the results for the 6 objects analyzed so far, namely: NGC3185, NGC3486,
NGC3941, NGC4138, NGC4565, and NGC5033. The main goal of this survey is to
obtain a better and unbiased understanding of the ``typical'' Seyfert X-ray
spectrum (e.g. the distribution of their absorption column density) in the
local Universe. This is crucial to verify the predictions and, thus, to
validate unified models, and is a fundamental parameter of synthesis models for
the X-ray background. A companion poster (paper II: L. Foschini et al., these
proceedings) illustrates how this survey will also allow a comprehensive
spectral study of the brightest (highest-luminosity) off-nuclear sources in the
galaxies.


title:
Hydrodynamic stability in accretion disks under the combined influence
  of shear and density stratification

abstract:
  The hydrodynamic stability of accretion disks is considered. The particular
question is whether the combined action of a (stable) vertical density
stratification and a (stable) radial differential rotation gives rise to a new
instability for nonaxisymmetric modes of disturbances. The existence of such an
instability is not suggested by the well-known Solberg-Hoiland criterion. It is
also not suggested by a local analysis for disturbances in general
stratifications of entropy and angular momentum which is presented in our
Section 2 confirming the results of the Solberg-Hoiland criterion also for
nonaxisymmetric modes within the frame of ideal hydrodynamics but only in the
frame of a short-wave approximation for small m. As a necessary condition for
stability we find that only conservative external forces are allowed to
influence the stable disk. As magnetic forces are never conservative, linear
disk instabilities should only exist in the magnetohydrodynamical regime which
indeed contains the magnetorotational instability as a much-promising
candidate. To overcome some of the used approximations in a numerical
approach,the equations of the compressible adiabatic hydrodynamics are
integrated imposing initial nonaxisymmetric velocity perturbations with m=1 to
m=200.
  Only solutions with decaying kinetic energy are found. The system always
settles in a vertical equilibrium stratification according to pressure balance
with the gravitational potential of the central object. keywords: accretion
disks -- hydrodynamic instabilities -- turbulence


title:
First Results from a XMM-Newton Survey of a Distance-Limited (D < 22
  Mpc) Sample of Seyfert Galaxies. II - The Galactic Serendipitous Sources

abstract:
  We present preliminary results from a study with XMM-Newton of the galactic
serendipitous sources in a sample of 28 nearby Seyfert galaxies (with D < 22
Mpc). We concentrate here on a subset of four galaxies, namely: NGC3185,
NGC3486, NGC3941, and NGC4565. In these galaxies we found six ultraluminous
X-ray source (ULX). The large collecting area of XMM-Newton makes the
statistics sufficient to perform spectral fitting with simple models. We
shortly discuss the results obtained so far.


title: Diamagnetic Screening of the Magnetic Field in Accreting Neutron Stars

abstract:
  A possible mechanism for screening of the surface magnetic field of an
accreting neutron star, by the accreted material, is investigated. In
particular, we investigate the nature of the evolution of the internal field
configuration in the case of a) a polar cap accretion and b) a spherical
accretion.


title:
Photometry of symbiotic stars X. EG And, Z And, BF Cyg, CH Cyg, V1329
  Cyg, AG Dra, RW Hya, AX Per and IV Vir

abstract:
  We present new photometric observations of EG And, Z And, BF Cyg, CH Cyg,
V1329 Cyg, AG Dra, RW Hya, AX Per and IV Vir made in standard Johnson UBVR
system. The current issue summarizes observations of these onjects to 2001
December.


title: Satellite decay in flattened dark matter haloes

abstract:
  We carry out a set of self-consistent N-body calculations to compare the
decay rates of satellite dwarf galaxies orbiting a disc galaxy embedded in a
dark matter halo (DMH). We consider both spherical and oblate axisymmetric DMHs
of aspect ratio q_h=0.6. The satellites are given different initial orbital
inclinations, orbital periods and mass. The live flattened DMHs with embedded
discs and bulges are set-up using a new fast algorithm, MaGalie (Boily, Kroupa
and Pe\~{n}arrubia 2001).
  We find that the range of survival times of satellites within a flattened DMH
becomes of the order of 100% larger than the same satellites within a spherical
DMH. In the oblate DMH, satellites on polar orbits have the longest survival
time, whereas satellites on coplanar prograde orbits are destroyed most
rapidly. The orbital plane of a satellite tilts as a result of anisotropic
dynamical friction, causing the satellite's orbit to align with the plane of
symmetry of the DMH. Polar orbits are not subjected to alignment. Therefore the
decay of a satellites in an axisymmetric DMH may provide a natural explanation
for the observed lack of satellites within (0-30) degrees of their host
galaxy's disc (Holmberg 1969; Zaritsky and Gonz\'alez 1999).
  The computations furthermore indicate that the evolution of the orbital
eccentricity $e$ is highly dependent of its initial value e(t=0) and the DMH's
shape. We also discuss some implications of flattened DMHs for satellite debris
streams.


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

abstract:
  We describe the algorithm for selecting quasar candidates for optical
spectroscopy in the Sloan Digital Sky Survey. Quasar candidates are selected
via their non-stellar colors in "ugriz" broad-band photometry, and by matching
unresolved sources to the FIRST radio catalogs. The automated algorithm is
sensitive to quasars at all redshifts lower than z=5.8. Extended sources are
also targeted as low-redshift quasar candidates in order to investigate the
evolution of Active Galactic Nuclei (AGN) at the faint end of the luminosity
function. Nearly 95% of previously known quasars are recovered (based on 1540
quasars in 446 square degrees). The overall completeness, estimated from
simulated quasars, is expected to be over 90%, whereas the overall efficiency
(quasars:quasar candidates) is better than 65%. The selection algorithm targets
ultraviolet excess quasars to i^*=19.1 and higher-redshift (z>3) quasars to
i^*=20.2, yielding approximately 18 candidates per square degree. In addition
to selecting ``normal'' quasars, the design of the algorithm makes it sensitive
to atypical AGN such as Broad Absorption Line quasars and heavily reddened
quasars.


title: The OI Line Emission in Active Galactic Nuclei Revisited

abstract:
  UV, visible, and near-infrared spectroscopy is used to study the transitions
of neutral oxygen leading to the emission of broad OI $\lambda$8446,
$\lambda$11287 and $\lambda$1304 in Active Galactic Nuclei. From the strength
of the former two lines, contrary to the general belief, we found that in six
out of seven galaxies, L-beta fluorescence is not the only mechanism
responsible for the formation of these three lines. Because OI $\lambda$13165
is almost reduced to noise level, continuum fluorescence is ruled out as an
additional excitation mechanism, but the presence of OI $\lambda$7774 in one of
the objects suggests that collisional ionization may have an important role in
the formation of OI $\lambda$8446. The usefulness of the OI lines as a reliable
reddening indicator for the broad line region is discussed. The values of
E(B-V) derived from the OI $\lambda 1304/\lambda$8446 ratio agree with those
obtained using other reddening indicators. The observations point toward a
break in the one-to-one photon relation between OI $\lambda$8446 and OI
$\lambda$1304, attributable to several destruction mechanisms that may affect
the latter line.


title:
Using a Hipparcos derived HR diagram to limit the metallicity scatter of
  stars in the Hyades -- Are Stars Polluted?

abstract:
  Hipparcos parallaxes and proper motions have made it possible to construct
Hertzsprung-Russell (HR) diagrams of nearby clusters with unprecedented
accuracy. The standard deviation of high fidelity non-binary non-variable stars
about a model stellar evolution isochrone in the Hyades cluster is about 0.04
magnitudes. We use this deviation to estimate an upper limit on the scatter in
metallicities in stars in this cluster. From the gradient of the isochrones
evolution in the HR diagram we estimate an upper limit for the scatter of
metallicities Delta [Fe/H] <~ 0.03 dex, a smaller limit than has been measured
previously spectroscopically. This suggests that stars in open clusters are
formed from gas that is nearly homogeneous in its metallicity. We consider the
hypothesis that processes associated with planet formation can pollute the
convection zone of stars. If the position on the HR diagram is insensitive to
the metallicity of the convection zone and atmosphere, then stars which have
very polluted convection zones can be identified from a comparison between
their metallicity and position on the HR diagram. Alternatively if the
pollution of the star by metals results in a large change in the position of
the star on the HR diagram in a direction perpendicular to the isochrone, then
the low scatter of stars in the Hyades can be used to place constraints on
quantity of high-Z material that could have polluted the stars.


title: Gamma Ray Bursts and Cosmic Ray Origin

abstract:
  This paper presents the theoretical basis of the fireball/blast wave model,
and some implications of recent results on GRB source models and cosmic-ray
production from GRBs. BATSE observations of the prompt gamma-ray luminous
phase, and Beppo-SAX and long wavelength afterglow observations of GRBs are
briefly summarized. Derivation of spectral and temporal indices of an adiabatic
blast wave decelerating in a uniform surrounding medium in the limiting case of
a nonrelativistic reverse shock, both for spherical and collimated outflows, is
presented as an example of the general theory. External shock model fits for
the afterglow lead to the conclusion that GRB outflows are jetted. The external
shock model also explains the temporal duration distribution and clustering of
peak energies in prompt spectra of long-duration GRBs, from which the redshift
dependence of the GRB source rate density can be derived. Source models are
reviewed in light of the constant energy reservoir result of Frail et al. that
implies a total GRB energy of a few times 10^{51} ergs and an average beaming
fraction of ~1/500 of full sky. Paczynski's isotropic hypernova model is ruled
out. The Vietri-Stella model two-step collapse process is preferred over a
hypernova/collapsar model in view of the X-ray observations of GRBs and the
constant energy reservoir result. Second-order processes in GRB blast waves can
accelerate particles to ultra-high energies. GRBs may be the sources of UHECRs
and cosmic rays with energies above the knee of the cosmic ray spectrum.
High-energy neutrino and gamma-ray observations with GLAST and ground-based
gamma-ray telescopes will be crucial to test GRB source models.


title: 3C 129 at 90cm: Evidence for a Radio Relic?

abstract:
  We present a new wide-field map of the radio galaxy 3C 129 and its companion
galaxy 3C 129.1 at lambda=90 cm. We see a distinct steep-spectrum feature near
the head of 3C 129, extending in a direction perpendicular to the radio tails.
We propose that this Crosspiece might consist of fossil radio plasma, which has
been re-energized by the compression of the bow shock of the supersonically
moving galaxy 3C 129. One possible origin of the fossil radio plasma could be
the tail of a nearby head-tail radio galaxy. We discuss the implications of,
and give testable predictions for this scenario.


title: Is the Universe Inflating? Dark Energy and the Future of the Universe

abstract:
  We consider the fate of the observable universe in the light of the discovery
of a dark energy component to the cosmic energy budget. We extend results for a
cosmological constant to a general dark energy component and examine the
constraints on phenomena that may prevent the eternal acceleration of our patch
of the universe. We find that the period of accelerated cosmic expansion has
not lasted long enough for observations to confirm that we are undergoing
inflation; such an observation will be possible when the dark energy density
has risen to between 90% and 95% of the critical. The best we can do is make
cosmological observations in order to verify the continued presence of dark
energy to some high redshift. Having done that, the only possibility that could
spoil the conclusion that we are inflating would be the existence of a
disturbance (the surface of a true vacuum bubble, for example) that is moving
toward us with sufficiently high velocity, but is too far away to be currently
observable. Such a disturbance would have to move toward us with speed greater
than about 0.8c in order to spoil the late-time inflation of our patch of the
universe and yet avoid being detectable.


title: Brownian Motion in Gravitationally-Interacting Systems

abstract:
  We derive a model that describes the motion of a Brownian particle in a
system which is dominated by gravitational forces. An example of such a system
is a massive black hole immersed in a cluster of stars. We compute the
dispersion in the position and velocity of such a black hole, and examine
whether it achieves a state of equipartition of kinetic energy with the stars.
This problem has been considered before only for stellar systems with an
isothermal Maxwellian distribution of velocities; here we study other examples
and confirm our calculations with N-body simulations. In certain cases,
depending on the stellar distribution function, the black hole can acquire a
steady state kinetic energy which is very far from equipartition relative to
the stars.


title:
Long Term Variability of Cyg X-1 I. X-ray spectral-temporal correlations
  in the hard state

abstract:
  We present the long term evolution of the timing properties of the black hole
candidate Cygnus X-1 in the 0.002-128 Hz frequency range as monitored from 1998
to 2001 with the RXTE. The hard state power spectral density (PSD) is well
modeled as the sum of four Lorentzians, which describe distinct broad noise
components. Before 1998 July, Cyg X-1 was in a "quiet" hard state characterized
primarily by the first three of these broad Lorentzians. Around 1998 May, this
behavior changed: the total fractional rms amplitude decreased, the peak
frequencies of the Lorentzians increased, the average time lag slightly
increased, and the X-ray spectrum softened. The change in the timing parameters
is mainly due to a strong decrease in the amplitude of the third Lorentzian.
Since then, an unusually large number of X-ray flares have been observed.
During these "failed state transitions", the X-ray power spectrum changes to
that of the intermediate state. Modeling this PSD with the four Lorentzians, we
find that the first Lorentzian component is suppressed relative to the second
and third Lorentzian. Also the frequency-dependent time lags increase
significantly. We confirm the interpretation as failed state transitions with
observations from the 2001 Jan. and 2001 Oct. soft states. Such behavior
suggests that some or all of the Lorentzian components are associated with the
accretion disk corona. We discuss the physical interpretation of our results.


title:
B,V Photometry of Variable Stars in the Northeast Arm of the Small
  Magellanic Cloud

abstract:
  B and V photometry has been obtained for variable stars in the northeast arm
of the Small Magellanic Cloud (SMC). Periods and lightcurves have been
determined for 237 periodic variables, including 201 Cepheids, 68 of which are
newly discovered. Fundamental mode Cepheids and first overtone mode Cepheids
are generally well separated in the B,V color-magnitude diagram, with the
latter having bluer mean colors than the former. The Cepheid period-color
relationship for this outlying SMC field is indistinguishable from that seen in
more centrally located SMC fields, and is bluer than theoretical predictions.
The red edge to the populated portion of the instability strip shifts to bluer
colors for fainter Cepheids. There is support from our sample for a previously
reported steepening in the slope of the period-luminosity relation for
fundamental mode Cepheids near a period of 2 days. The Cepheids of the
northeast arm may be closer to us than are those of the main body of the SMC,
but the difference is smaller than or equal to about 4 kpc, comparable to the
tidal radius of the SMC.


title:
Deflationary cosmology: constraints from angular size and ages of
  globular clusters

abstract:
  Observational constraints to a large class of decaying vacuum cosmologies are
derived using the angular size data of compact radio sources and the latest age
estimates of globular clusters. For this class of deflationary $\Lambda(t)$
models, the present value of the vacuum energy density is quantified by a
positive $\beta$ parameter smaller than unity. In the case of milliarcsecond
compact radio-sources, we find that the allowed intervals for $\beta$ and the
matter density parameter $\Omega_m$ are heavily dependent on the value of the
mean projected linear size $l$. For $l \simeq 20h^{-1} - 30h^{-1}$ pc, the best
fit occurs for $\beta \sim 0.58$, $\Omega_{\rm{m}} \sim 0.58$, and $\beta \sim
0.76$, $\Omega_{\rm{m}} \sim 0.28$, respectively. This analysis shows that if
one minimizes $\chi^{2}$ for the free parameters $l$, $\Omega_{\rm{m}}$ and
$\beta$, the best fit for these angular size data corresponds to a decaying
$\Lambda(t)$ with $\Omega_{\rm{m}} = 0.54$ $\beta=0.6$ and $l = 22.64h^{-1}$
pc. Constraints from age estimates of globular clusters and old high redshift
galaxies are not so restrictive, thereby suggesting that there is no age crisis
for this kind of $\Lambda(t)$ cosmologies.


title:
Radio-wave propagation through a medium containing electron-density
  fluctuations described by an anisotropic Goldreich-Sridhar spectrum

abstract:
  We study the propagation of radio waves through a medium possessing density
fluctuations that are elongated along the ambient magnetic field and described
by an anisotropic Goldreich-Sridhar power spectrum. We derive general formulas
for the wave phase structure function, visibility, angular broadening,
diffraction-pattern length scales, and scintillation time scale for arbitrary
distributions of turbulence along the line of sight, and specialize these
formulas to idealized cases.


title: Spectral Components of the Radio Composite Supernova Remnant G11.2-0.3

abstract:
  We present a high-resolution radio study of the supernova remnant (SNR)
G11.2-0.3 using archival VLA data. Spectral tomography is performed to
determine the properties of this composite-type SNR's individual components,
which have only recently been distinguished through X-ray observations. Our
results indicate that the spectral index of the pulsar wind nebula (PWN), or
plerion, is alpha_P ~ 0.25. We observe a spectral index of alpha_S ~ 0.56
throughout most of the SNR shell region, but also detect a gradient in alpha in
the south-eastern component. We compare the spectral index and flux density
with recent single-dish radio data of the source. Also, the radio efficiency
and morphological properties of this PWN are found to be consistent with
results for other known PWN systems.


title: New Problems for a New Century

abstract:
  A summary is presented of a symposium held to review recent progress in X-ray
astronomy and to discuss prospects for the next generation of X-ray missions.
The summary is organized around ten general, astrophysical questions that may
provide scientific drivers for the design of new facilities.


title: Current High Energy Emission from Black Holes

abstract:
  Two related topics are discussed. 1. Accretion onto black holes at low and
high (though not very high) rates is believed to proceed adiabatically ({\em
ie} non-radiatively). It is argued that the liberated energy is carried off by
an outflow, probably involving almost all of the gas that is supplied. Two
dimensional, fluid, accretion disks, in which mass, angular momentum and energy
are transported to the disk surface, are summarized. It is conjectured that
relatively minor changes are needed to describe magnetised disks. By contrast,
the disk surface physics is argued to dictate the character of the outflow. 2.
Ultrarelativistic jets appear to be produced by active galactic nuclei (AGN),
pulsars and $\gamma$-ray bursts (GRB). In all three cases, it is argued that
the power is generated electromagnetically by a magnetic rotator, (in a DC not
AC form), and transported in this manner to the emission site. A model of a
relativistically expanding electromagnetic shell is described and used to
provide a simple model of a GRB in which the $\gamma$-rays are produced by
unstable electrical currents flowing along the rotation axis. The shell drives
a relativistic blast wave into the surrounding medium with a speed that varies
with latitude and whose afterglow emission may exhibit achromatic breaks.
Similar processes may be at work in non-relativistic plerions like the Crab
Nebula and, possibly, AGN jets. The observational implications of these two
classes of model and the prospects for performing instructive, numerical
experiments to elucidate them further are briefly outlined.


title: To the Lighthouse

abstract:
  The extreme hypothesis that essentially all types of ultrarelativistic
outflow -- specifically AGN jets, pulsar wind nebulae and GRB --are
electromagnetic, rather than gas dynamical, phenomena is considered.
Electromagnetic flows are naturally anisotropic and self-collimating so as to
produce jet-like features. The relativistic force-free description of these
flows, which is simpler than the relativistic MHD description, is explained. It
is suggested that the magnetic field associated with AGN jets and GRB is quite
extensively distributed in latitude, without necessarily increasing by much the
total power. It is also proposed that the observed emission from these sources
traces out regions of high current density where global instabilities drive a
turbulence spectrum that is ultimately responsible for the particle
acceleration and the synchrotron, inverse Compton and synchro-Compton emission.
The direct extraction of spin energy from a black hole is re-examined and an
electromagnetic model of GRB explosions is developed. It is also suggested that
some GRB ``lighthouses'' be identified with accretion-induced collapse of a
neutron star to form a black hole in a binary system.


title:
The Millennium Arecibo 21-cm Absorption Line Survey: Extolling the
  Analysis Procedures

abstract:
  We have recently completed the analysis of a survey of the HI line in
emission/absorption against 79 radio sources. Our CNM temperatures are about
half those of previous authors and we find a substantial quantity of thermally
unstable WNM. These results are somewhat controversial. Here we discuss the
analysis procedures to illustrate explicitly why the results are reliable.


title: Galaxy Evolution from Emission Linewidths

abstract:
  The major thrust of the Tully-Fisher (TF) surveys of distant galaxies is the
measurement of linewidths rather than mere redshifts or colors. Linewidths are
a measure of galaxy mass and should therefore be a more stable indicator of
size than galaxy brightness, which can be badly affected by luminosity
evolution. Masses may provide the best way to relate galaxies at different
epochs, but for such a program to work, we must control systematic effects that
could bias linewidth measurements at high redshift and skew comparisons with
local Tully-Fisher calibrations. Potential sources of confusion in TF studies
of galaxy structure and evolution include central or extended star bursts,
infalling gas, turbulence and outflows, dust extinction, calibration of
emission linewidths, and improper application of local TF calibrations to high
redshift galaxies.


title:
HST observations rule out the association between Cir X-1 and SNR
  G321.9-0.3

abstract:
  Cir X-1 is one of the most intriguing galactic X-ray sources. It is a ~16.6
days variable X/radio source, a type-I X-ray burster and a QPO emitter. In
spite of an uncertain optical counterpart classification, all these properties
identify the source as an LMXB. The morphology of the surrounding radio nebula
has suggested an association with the nearby (~25 arcmin) SNR G321.9-0.3,
implying that Cir X-1 is a runaway binary originated from the supernova
explosion 10^5 years ago. To investigate this hypothesis, we carried out a
proper motion measurement of the Cir X-1 m ~19 optical counterpart using a set
of HST/WFC and WFPC2 observations taken ~8.6 years apart. We obtained a 3 sigma
upper limit of ~5 mas/yr on the source proper motion. Since the runaway
hypothesis would have implied a proper motion due North ranging between 15 and
75 mas/yr, depending on the actual age of the SNR, our result definitively
rules out the association between Cir X-1 and SNR G321.9-0.3.


title:
Formation of the Galactic disk globular clusters in early dissipative
  minor merging

abstract:
  The origin of metal-rich, highly flattened, and rapidly rotating disk
globular cluster system in the Galaxy is one of longstanding issues in the
context of the Galaxy formation. Our numerical simulations suggest a new
``two-fold'' scenario that the disk globular clusters are firstly formed in the
high-pressure, dense central region of a gas-rich dwarf galaxy, as induced
during the tidal interaction with the pre-existing, young thin disk of the
Galaxy, and then dispersed into the disk region owing to the final tidal
destruction of the merging dwarf. We also demonstrate that spatial
distribution, total number, and metallicity distribution of the clusters formed
in this minor merging depend on the mass ratio of the host to dwarf galaxy and
the orbital configuration of merging. Based on these results, we discuss
whether a minor merging event about 10 Gyr ago can explain both the Galactic
thick disk and the disk globular clusters. Several other implications for the
possible relation between the properties of disk galaxies and their disk
globular clusters are also discussed.


title:
Gas Dynamics in NGC 5248: Fueling a Circumnuclear Starburst Ring of
  Super Star Clusters

abstract:
  Through observations and modeling, we demonstrate how the recently discovered
large-scale bar in NGC 5248 generates spiral structure which extends from 10
kpc down to 100 pc, fuels star formation on progressively smaller scales, and
drives disk evolution. Deep inside the bar, two massive molecular spirals cover
nearly 180 degrees in azimuth, show streaming motions of 20--40 km/s and feed a
starburst ring of super star clusters at 375 pc. They also connect to two
narrow K-band spirals which delineate the UV-bright star clusters in the ring.
The data suggest that the K-band spirals are young, and the starburst has been
triggered by a bar-driven spiral density wave (SDW). The latter may even have
propagated closer to the center where a second Halpha ring and a dust spiral
are found. The molecular and HST data support a scenario where stellar winds
and supernovae efficiently clear out gas from dense star-forming regions on
timescales less than a few Myrs. We have investigated the properties of massive
CO spirals within the framework of bar-driven SDWs, incorporating the effect of
gas self-gravity. We find good agreement between the model predictions and the
observed morphology, kinematics, and pitch angle of the spirals. This
combination of observations and modeling provides the best evidence to date for
a strong dynamical coupling between the nuclear region and the surrounding
disk. It also confirms that a low central mass concentration, which may be
common in late-type galaxies, is particularly favorable to the propagation of a
bar-driven gaseous SDW deep into the central region of the galaxy, whereas a
large central mass concentration favors other processes, such as the formation
and decoupling of nuclear bars.


title:
Removing 1/f noise stripes in cosmic microwave background anisotropy
  observations

abstract:
  Removal of systematic effects is crucial in present and future CMB
experiments mapping large fraction of the sky. Accurate CMB measurements ask
for multi-feed array instruments observing the sky with a redundant scanning
strategy covering the same region of the sky on different time scales and with
different detectors for a better control of systematic effects. We investigate
here the capability to suppress 1/f noise features in Time Ordered Data (TOD)
by using the destriping technique described in Maino et al. (1999), under
realistic assumptions for crossing condition between different scan circles and
sky signal fluctuations on small angular scales. We consider as working case,
Planck-LFI simulated observations with few arminutes pixel size convolved with
LFI beam resolutions. We also extend the analysis to high values of the
knee-frequency and found a residual additional noise rms ~31% larger than the
pure white noise rms at fk=1 Hz which could be a critical issue in the
extraction of the CMB angular power spectrum. Furthermore we verified that
destriping quality does not significantly depend on the receiver sensitivity
whereas it improves proportionally to the improvement of sampling rate.
Therefore given a noise level, the higher the sampling rate, the better the
destriping quality.


title: Evolution and structure of magnetic fields in simulated galaxy clusters

abstract:
  We use cosmological magneto-hydrodynamic simulations to study the evolution
of magnetic fields in galaxy clusters in two different cosmological models, a
standard-CDM and a $\Lambda$-CDM model. We show that the magnetic field
strength profiles closely follow the cluster density profiles outside a core
region of radius $\sim200\kpc$. The magnetic field has a correlation length of
order $50\kpc$ and reverses on scales of $\sim100\kpc$ along typical
lines-of-sight. The power spectrum of the magnetic field can well be
approximated by a steep power law with an exponent of $\sim-2.7$. The mean
magnetic field in the cluster cores grows roughly exponentially with decreasing
redshift, $B\sim10^{-2.5z} \muG$. Merger events have a pronounced effect on
magnetic field evolution, which is strongly reflected in measurable quantities
like the Faraday rotation. The field evolution in the two different cosmologies
proceeds virtually identically. All our cluster models very well reproduce
observed Faraday rotation measurements when starting with nG seed fields.


title: Are There Unstable Planetary Systems Around White Dwarfs?

abstract:
  The presence of planets around solar-type stars suggests that many white
dwarfs should have relic planetary systems. While planets closer than $\sim$
5~AU will most likely not survive the post-main sequence lifetime of its parent
star, any planet with semimajor axis $>$ 5~AU will survive, and its semimajor
axis will increase as the central star loses mass. Since the stability of
adjacent orbits to mutual planet-planet perturbations depends on the ratio of
the planet mass to the central star's mass, some planets in previously stable
orbits around a star undergoing mass loss will become unstable. We show that
when mass loss is slow, systems of two planets that are marginally stable can
become unstable to close encounters, while for three planets the timescale for
close approaches decreases significantly with increasing mass ratio. These
processes could explain the presence of anomalous IR excesses around white
dwarfs that cannot be explained by close companions, such as G29-38, and may
also be an important factor in explaining the existence of DAZ white dwarfs.
The onset of instability through changing mass-ratios will also be a
significant effect for planetary embryos gaining mass in protoplanetary disks.


title: A multi-epoch spectrophotometric atlas of symbiotic stars

abstract:
  A multi-epoch, absolute-fluxed spectral atlas extending from about 3200 to
9000 Ang is presented for 130 symbiotic stars, including members of the LMC,
SMC and Draco dwarf galaxies. The fluxes are accurate to better than 5% as
shown by comparison with Tycho and ground-based photometric data. The spectra
of 40 reference objects (MKK cool giant standards, Mira and Carbon stars,
planetary nebulae, white dwarfs, hot sub-dwarfs, Wolf-Rayet stars, classical
novae, VV Cep and Herbig Ae/Be objects) are provided to assist the
interpretation of symbiotic star spectra. Astrometric positions and
counterparts in astrometric catalogues are derived for all program symbiotic
stars.


title: Modeling Stellar Populations in Star Clusters and Galaxies

abstract:
  Combining population synthesis models with simple Montecarlo simulations of
stochastic effects in the number of stars occupying sparsely populated stellar
evolutionary phases in the HRD, I show that the scatter observed in the
photometric magnitudes and colors of LMC and NGC 7252 star clusters can be
understood in the framework of current stellar evolution theory. The use of a
high resolution stellar spectral atlas in population synthesis models improves
considerably the quality of the fits to observed galaxy SEDs, making the
assignment of a spectroscopic age to stellar populations more reliable than
with low spectral resolution models.


title: Tidal interaction of a rotating 1 Msun star with a binary companion

abstract:
  We calculate the tidal torque on a uniformly rotating 1 Msun star at various
stages of core hydrogen burning by an orbiting companion. We apply the
`traditional approximation' and solve the radial part of the tidal
perturbations by matrix inversion of the set of finite difference equations on
a very fine grid. We have identified resonances with gravity- and
quasi-toroidal modes with up to 1000 radial nodes in the more evolved stellar
models. For low forcing frequencies we find significant tidal response due to
viscous damping of inertial modes in the convective envelope of the solar-type
star. We conclude that effects due to stellar rotation (including resonance
locking) may considerably enhance the speed of tidal evolution in solar-type
stars.


title: Discovery of Soft X-Ray Emission from Io, Europa and the Io Plasma Torus

abstract:
  We report the discovery of soft (0.25--2 keV) x-ray emission from the
Galilean satellites Io and Europa, probably Ganymede, and from the Io Plasma
Torus (IPT). Bombardment by energetic (>10 keV) H, O, and S ions from the
region of the IPT seems the likely source of the x-ray emission from the
Galilean satellites. According to our estimates, fluorescent x-ray emission
excited by solar x-rays, even during flares from the active Sun,
charge-exchange processes, previously invoked to explain Jupiter's x-ray aurora
and cometary x-ray emission, and ion stripping by dust grains fail to account
for the observed emission. On the other hand, bremsstrahlung emission of soft
X-rays from non-thermal electrons in the few hundred to few thousand eV range
may account for a substantial fraction of the observed x-ray flux from the IPT.