title: Space-time Evolution and CMB Anisotropies from Quantum Gravity

abstract:
  We propose an evolutional scenario of the universe which starts from quantum
states with conformal invariance, passing through the inflationary era, and
then makes transition to the conventional Einstein space-time. The space-time
dynamics is derived from the renormalizable higher-derivative quantum gravity
developed on the basis of a renormalizable conformal gravity in four
dimensions. Based on the linear perturbation theory in the inflationary
background, we simulate evolutions of gravitational scalar, vector and tensor
perturbations, and evaluate the spectra at the transition point located at the
beginning of the big bang. The obtained spectra cover the range of the
primordial spectra for explaining the tiny anisotropy in the homogeneous CMB.


title:
Dynamical Expansion of Ionization and Dissociation Front around a
  Massive Star : A Starburst Mechanism

abstract:
  We quantitatively examine the significance of star formation triggered in the
swept-up shell around an expanding HII region. If the swept-up molecular gas is
sufficiently massive, new OB stars massive enough to repeat the triggering
process will form in the shell. We determine the lower limit (M_thr) for the
mass of the star that sweeps up the molecular gas, where at least one new star
with mass M_* > M_thr forms after the shell fragmentation. To calculate the
threshold stellar mass, M_thr, we examine how massive molecular shells can form
around various central stars, by performing detailed numerical radiation
hydrodynamics calculations. The mass of the photodissociated gas is generally
larger than the mass of the photoionized gas. However, the swept-up molecular
mass exceeds the photodissociated mass with a higher-mass star of M_* > 20
Msun. The accumulated molecular mass generally increases with the stellar mass,
and amounts to 10^{4-5} Msun for M_* > 20 Msun with an ambient density of n
\sim 100/cc. The threshold stellar mass is M_thr \sim 18 Msun with the
star-formation efficiency of \epsilon \sim 0.1 and n \sim 100/cc. We examine
the generality of this mode of run-away triggering for different sets of
parameters, and found that M_thr \sim 15-20 Msun in various situations. If the
ambient density is too high or the star-formation efficiency is too low, the
triggering is not run-away, but a single event.


title:
Evolution of Collapse Nonuniformity for Rotating Magnetic Interstellar
  Clouds

abstract:
  We investigate the formation and evolution of isothermal collapse
nonuniformity for rotating magnetic interstellar clouds. The initial and
boundary conditions correspond to the statement of the problem of homogeneous
cloud contraction from a pressure equilibrium with the external medium. The
initial uniform magnetic field is collinear with the angular velocity. Fast and
slow magnetosonic rarefaction waves are shown to be formed and propagate from
the boundary of the cloud toward its center in the early collapse stages. The
front of the fast rarefaction wave divides the gas mass into two parts. The
density, angular velocity, and magnetic field remain uniform in the inner
region and have nonuniform profiles in the outer region. The rarefaction wave
front surface can take both prolate and oblate shapes along the rotation axis,
depending on the relationship between the initial angular velocity and magnetic
field. We derive a criterion that separates the two regimes of rarefaction wave
dynamics with the dominant role of electromagnetic and centrifugal forces.
Based on analytical estimations and numerical calculations, we discuss possible
scenarios for the evolution of collapse nonuniformity for rotating magnetic
interstellar clouds.


title: Sensitivity and figures of merit for dark energy supernovae surveys

abstract:
  Tracking the origin of the accelerating expansion of the Universe remains one
of the most challenging research activities today. The final answer will depend
on the precision and on the consistency of future data. The sensitivity of
future surveys and the control of the errors are crucial. We focus on futur
supernovae surveys in the light of the figure of merit defined by the Dark
Energy Task Force. We compare different optimisation and emphasize the
importance of the understanding of the systematic error level in this approach
and their impact on the conclusions. We discuss different representations of
the results to distinguish $\Lambda$CDM from other theoretical models. We
conclude that all representations should be controlled through combined
analyses and consistency checks to avoid some bias.


title: DK And: Reclassification as EW Binary from CCD Observations

abstract:
  This paper describes the reclassification of DK And, formerly classified as a
RRc type star, as EW binary. 1599 CCD unfiltered and filtered (V and R band)
observations between 1999 and 2005 show, that the star is actually an eclipsing
binary star with a period of P = 0.4892224 +/- 0.0000002 [d] with epoch E0 =
2451435.4353 +/- 0.0010 (if all historic data were taken into account). From
our new observations 12 timings of minimum light are given.


title: SuperWASP Observations of the Transiting Extrasolar planet XO-1b

abstract:
  We report on observations of 11 transit events of the transiting extrasolar
planet XO-1b by the SuperWASP-North observatory. From our data, obtained during
May-September 2004, we find that the XO-1b orbital period is 3.941634 +/-
0.000137 days, the planetary radius is 1.34 +/- 0.12 Rjup and the inclination
is 88.92 +/- 1.04 degrees, in good agreement with previously published values.
We tabulate the transit timings from 2004 SuperWASP and XO data, which are the
earliest obtained for XO-1b, and which will therefore be useful for future
investigations of timing variations caused by additional perturbing planets. We
also present an ephemeris for the transits. See http://www.superwasp.org for
general project details.


title:
Average hard X-ray emission from NS LMXBs: Observational evidence of
  different spectral states in NS LMXBs

abstract:
  We studied and compared the long-term average hard X-ray (>20keV) spectra of
a sample of twelve bright low-mass X-ray binaries hosting a neutron star (NS).
Our sample comprises the six well studied Galactic Z sources and six Atoll
sources, four of which are bright ("GX") bulge sources while two are weaker
ones in the 2-10keV range (H1750-440 and H1608-55). For all the sources of our
sample, we analysed available public data and extracted average spectra from
the IBIS/ISGRI detector on board INTEGRAL. We can describe all the spectral
states in terms of the bulk motion Comptonisation scenario. We find evidence
that bulk motion is always present, its strength is related to the accretion
rate and it is suppressed only in the presence of high local luminosity. The
two low-dim Atoll source spectra are dominated by photons up-scattered
presumably due to dynamical and thermal Comptonisation in an optically thin,
hot plasma. For the first time, we extend the detection of H1750-440 up to
150keV. The Z and bright "GX" Atoll source spectra are very similar and are
dominated by Comptonised blackbody radiation of seed photons, presumably coming
from the accretion disc and NS surface, in an optically thick cloud with plasma
temperature in the range of 2.5-3keV. Six sources show a hard tail in their
average spectrum: CygX-2 (Z), GX340+0 (Z), GX17+2 (Z), GX5-1 (Z), ScoX-1 (Z)
and GX13+1 (Atoll). This is the first detection of a hard tail in the X-ray
spectrum of the peculiar GX13+1. Using radio data from the literature we find,
in all Z sources and bright "GX" Atolls, a systematic positive correlation
between the X-ray hard tail (40-100keV) and the radio luminosity. This suggests
that hard tails and energetic electrons causing the radio emission may have the
same origin, most likely the Compton cloud located inside the NS magnetosphere.


title: Pulsating pre-main sequence stars in IC 4996 and NGC 6530

abstract:
  Asteroseismology of pulsating pre-main sequence (PMS) stars has the potential
of testing the validity of current models of PMS structure and evolution. As a
first step, a sufficiently large sample of pulsating PMS stars has to be
established, which allows to select candidates optimally suited for a detailed
asteroseismological analysis based on photometry from space or ground based
network data.
  A search for pulsating PMS members in the young open clusters IC 4996 and NGC
6530 has been performed to improve the sample of known PMS pulsators. As both
clusters are younger than 10 million years, all members with spectral types
later than A0 have not reached the zero-age main sequence yet. Hence, IC 4996
and NGC 6530 are most suitable to search for PMS pulsation among their A- and
F-type cluster stars.
  CCD time series photometry in Johnson B and V filters has been obtained for
IC 4996 and NGC 6530. The resulting light curves for 113 stars in IC 4996 and
194 stars in NGC 6530 have been subject to detailed frequency analyses.
  2 delta Scuti-like PMS stars have been discovered in IC 4996 and 6 in NGC
6530. For another PMS star in each cluster, pulsation can only be suspected.
According to the computed pulsation constants, the newly detected PMS stars
seem to prefer to pulsate in a similar fashion to the classical delta Scuti
stars, and with higher overtone modes.


title:
Wavelet analysis of MCG-6-30-15 and NGC 4051: a possible discovery of
  QPOs in 2:1 and 3:2 resonance

abstract:
  Following our previous work of Lachowicz & Czerny (2005), we explore further
the application of the continuous wavelet transform to X-ray astronomical
signals. Using the public archive of the XMM-Newton satellite, we analyze all
available EPIC-pn observations for nearby Seyfert 1 galaxies MCG-6-30-15 and
NGC 4051. We confine our analysis to 0.002-0.007 Hz frequency band in which, on
the way of theoretically motivated premises, some quasi-periodic oscillations
(QPOs) are expected to be found. We find that indeed wavelet power histogram
analysis reveals such QPOs centered at two frequencies of ~2.5E-3 Hz and 4-6E-3
Hz, respectively. We show that these quasi-periodic features can be
disentangled from the Poisson noise contamination level what is hardly to
achieve with the standard Fourier analysis. Interestingly, we find some of them
to be in 2:1 or 3:2 ratio. If real, our finding may be considered as a link
between QPOs observed in AGN and kHz QPOs seen in X-ray binary systems.


title: The Influence of X-ray Emission on the Stellar Wind of O Stars

abstract:
  We study the influence of X-ray radiation on the wind parameters of O stars.
For this purpose we use our own NLTE wind code. The X-ray emission (assumed to
be generated in wind shocks) is treated as an input quantity. We study its
influence on the mass-loss rate, terminal velocity and ionization state of the
stellar wind of Galactic O stars.


title:
Spectral-timing evidence for a Very High State in the Narrow Line
  Seyfert 1 Ark 564

abstract:
  We use a 100 ks long XMM-Newton observation of the Narrow-Line Seyfert 1
galaxy Ark 564 and combine it with the month-long monitoring of the same source
produced by ASCA, to calculate the phase lags and coherence between different
energy bands, over frequencies ~ 10^{-6} to 10^{-3} Hz. This is the widest
frequency range for which these spectral-timing properties have been calculated
accurately for any AGN. The 0.7-2 and 2--0 keV ASCA light curves, and the
XMM-Newton light curves in corresponding energy bands, are highly coherent (~
0.9) over most of the frequency range studied. We observe time lags between the
energy bands, increasing both with time-scale and with energy separation of the
bands. The time lag spectrum shows a broad peak in the 10^{-5} - 5x10^{-4} Hz
frequency range, where the time lags follow a power law slope ~ -0.7. Above ~ 5
x 10^{-4} Hz the lags drop below this relation significantly. This change in
slope resembles the shape of the lag spectra of black hole X-ray binaries
(BHXRB) in the very high or intermediate state. The lags increase linearly with
the logarithm of the separation of the energy bands, which poses one more
similarity between this AGN and BHXRBs.


title:
HST Proper Motions and Stellar Dynamics in the Core of the Globular
  Cluster 47 Tucanae

abstract:
  We have used HST imaging of the central regions (R<100 arcsec, about 5 core
radii) of the globular cluster 47 Tucanae to derive proper motions and U- and
V-band magnitudes for 14,366 cluster members. We also present a catalogue of
astrometry and F475W photometry for nearly 130,000 stars in a rather larger
central area. These data are made available in their entirety, in the form of
downloadable electronic tables. We use them first to obtain a new estimate for
the position of the cluster center and to define the stellar density profile
into essentially zero radius. We then search in particular for any very
fast-moving stars, such as might be expected to result from very close stellar
encounters. Likely fewer than 0.1% (and no more than about 0.3%) of stars have
total speeds above the nominal central escape velocity in 47 Tuc, and at lower
speeds the velocity distribution is described very well by a regular King
model. Considerations of only the proper-motion velocity dispersion then lead
to a number of results: (1) Blue stragglers in the core of 47 Tuc have a
velocity dispersion lower than that of the cluster giants by a factor of
sqrt{2}. (2) The velocity distribution in the cluster center is essentially
isotropic, as expected. (3) Using a sample of radial velocities for stars in
the core, we estimate the distance to 47 Tuc: D = 4.0 +/- 0.35 kpc. And (4) we
infer a 1-sigma upper limit of M<1000-1500 solar masses for any central,
intermediate-mass black hole. We can neither confirm nor refute the hypothesis
that 47 Tuc might lie on an extension of the M-sigma relation observed for
supermassive black holes in galaxy bulges. [Abridged]


title:
Supernova Remnants in the Magellanic Clouds. VII. Infrared Emission from
  SNRs

abstract:
  We have used the instruments on the Spitzer Space Telescope to study the
Large Magellanic Cloud supernova remnants (SNRs) N11L, N44, N49, N206, N63A,
and N157B. The two large SNRs N44 and N206 were not detected in any IRAC or
MIPS wavebands; the remainder were detected at one or more wavelengths. In
particular, the SNRs N49 and N63A each had features that were evident in all
available IRAC and MIPS bands. Each of these two also displayed faint limb
emission in the MIPS 24 micron band only. IRS spectra obtained for the N49 SNR
showed a number of prominent lines, with little continuum contribution. We
therefore suggest that N49, and possibly N63A, are dominated by line emission,
with thermal emission from hot dust being at most a secondary component.


title: Evolution of HII regions in hierarchically structured molecular clouds

abstract:
  We present observations of the H91$\alpha$ recombination line emission
towards a sample of nine HII regions associated with 6.7-GHz methanol masers,
and report arcsecond-scale emission around compact cores. We derive physical
parameters for our sources, and find that although simple hydrostatic models of
region evolution reproduce the observed region sizes, they significantly
underestimate emission measures. We argue that these findings are consistent
with young source ages in our sample, and can be explained by existence of
density gradients in the ionised gas.


title: Heliospheric Response to Different Possible Interstellar Environments

abstract:
  At present, the heliosphere is embedded in a warm low density interstellar
cloud that belongs to a cloud system flowing through the local standard of rest
with a velocity near ~18 km/s. The velocity structure of the nearest
interstellar material (ISM), combined with theoretical models of the local
interstellar cloud (LIC), suggest that the Sun passes through cloudlets on
timescales of < 10^3 - 10^4 yr, so the heliosphere has been, and will be,
exposed to different interstellar environments over time. By means of a
multi-fluid model that treats plasma and neutral hydrogen self-consistently,
the interaction of the solar wind with a variety of partially ionized ISM is
investigated, with the focus on low density cloudlets such as are currently
near the Sun. Under the assumption that the basic solar wind parameters
remain/were as they are today, a range of ISM parameters (from cold neutral to
hot ionized, with various densities and velocities) is considered. In response
to different interstellar boundary conditions, the heliospheric size and
structure change, as does the abundance of interstellar and secondary neutrals
in the inner heliosphere, and the cosmic ray level in the vicinity of Earth.
Some empirical relations between interstellar parameters and heliospheric
boundary locations, as well as neutral densities, are extracted from the
models.


title: Anatomy of A Dark Burst - The Afterglow of GRB 060108

abstract:
  We report the first detection of an optical afterglow of a GRB (060108) that
would have been classified as 'dark' in the absence of deep, rapid ground-based
optical imaging with the 2-m robotic Faulkes Telesscope (FTN). Our
multiwavelength analysis reveals an X-ray light curve typical of many Swift
long GRBs (3-segments plus flare). Its optical afterglow, however, was already
fainter than the detection limit of the UVOT within 100s of the burst. Optical
imaging in BVRi' filters with the FTN began 2.75 minutes after the burst and
resulted in the detection of the optical afterglow at 5.3 minutes, with a UKIRT
K-band identification at ~45 mins. R and i'-band light curves are consistent
with a single power law decay in flux, F(t) prop t^-a where a=0.43+/-0.08, or a
2-segment light curve with a steep decay a_1 <0.88, flattening to a_2 ~ 0.31,
with evidence for rebrightening at i' band. Deep VLT R-band imaging at ~12 days
reveals a faint, extended object (R ~23.5 mag) at the location of the
afterglow. Although the brightness is compatible with the extrapolation of the
a_2 slow decay, significant flux is likely due to a host galaxy. This implies
that the optical light curve had a break before 12 days, akin to what observed
in the X-rays. We derive a maximum photometric redshift z<3.2 for GRB 060108
and a best-fitting optical-to-X-ray SED at 1000 s after the burst consistent
with a power law with index beta_OX = 0.54 and a small amount of extinction.
The unambiguous detection at B-band and the derived photometric redshift rule
out a high redshift as the reason for the optical faintness of GRB 060108.
Instead, the hard opt/X-ray spectral index confirms it as one of the
optically-darkest bursts detected and with modest host extinction explains the
UVOT non-detection (abridged).


title: Measuring Flexion

abstract:
  We describe practical approaches to measuring flexion in observed galaxies.
In particular, we look at the issues involved in using the Shapelets and HOLICs
techniques as means of extracting 2nd order lensing information. We also
develop an extension of HOLICs to estimate flexion in the presence of noise,
and with a nearly isotropic PSF. We test both approaches in simple simulated
lenses as well as a sample of possible background sources from ACS observations
of A1689. We find that because noise is weighted differently in shapelets and
HOLICs approaches, that the correlation between measurements of the same object
is somewhat diminished, but produce similar scatter due to measurement noise.


title:
A Radio Study of the Seyfert galaxy Markarian 6: Implications for
  Seyfert life-cycles

abstract:
  We have carried out an extensive radio study with the Very Large Array on the
Seyfert 1.5 galaxy Mrk 6 and imaged a spectacular radio structure in the
source. The radio emission occurs on three different spatial scales, from ~7.5
kpc bubbles to ~1.5 kpc bubbles lying nearly orthogonal to them and a ~1 kpc
radio jet lying orthogonal to the kpc-scale bubble. To explain the complex
morphology, we first consider a scenario in which the radio structures are the
result of superwinds ejected by a nuclear starburst. However, recent Spitzer
observations of Mrk 6 provide an upper limit to the star formation rate (SFR)
of ~5.5 M_sun/yr, an estimate much lower than the SFR of ~33 M_sun/yr derived
assuming that the bubbles are a result of starburst winds energized by
supernovae explosions. Thus, a starburst alone cannot meet the energy
requirements for the creation of the bubbles in Mrk 6. We show that a single
plasmon model is energetically infeasible, and we argue that a jet-driven
bubble model while energetically feasible does not produce the complex radio
morphologies. Finally, we consider a model in which the complex radio structure
is a result of an episodically-powered precessing jet that changes its
orientation. This model is the most attractive as it can naturally explain the
complex radio morphology, and is consistent with the energetics, the spectral
index and the polarization structure. Radio emission in this scenario is a
short-lived phenomenon in the lifetime of a Seyfert galaxy which results due to
an accretion event.


title: Matter density perturbations in interacting quintessence models

abstract:
  Models with dark energy decaying into dark matter have been proposed to solve
the coincidence problem in cosmology. We study the effect of such coupling in
the matter power spectrum. Due to the interaction, the growth of matter density
perturbations during the radiation dominated regime is slower compared to
non-interacting models with the same ratio of dark matter to dark energy today.
This effect introduces a damping on the power spectrum at small scales
proportional to the strength of the interaction and similar to the effect
generated by ultrarelativistic neutrinos. The interaction also shifts
matter--radiation equality to larger scales. We compare the matter power
spectrum of interacting quintessence models with the measurments of 2dFGRS. We
particularize our study to models that during radiation domination have a
constant dark matter to dark energy ratio.


title:
Empirical distributions of galactic $\lambda$ spin parameters from the
  SDSS

abstract:
  Using simple dimensional arguments for both spiral and elliptical galaxies,
we present formulas to derive an estimate of the halo spin parameter $\lambda$
for any real galaxy, in terms of common observational parameters. This allows a
rough estimate of $\lambda$, which we apply to a large volume limited sample of
galaxies taken from the SDSS data base. The large numbers involved (11,597)
allow the derivation of reliable $\lambda$ distributions, as signal adds up
significantly in spite of the errors in the inferences for particular galaxies.
We find that if the observed distribution of $\lambda$ is modeled with a
log-normal function, as often done for this distribution in dark matter halos
that appear in cosmological simulations, we obtain parameters $\lambda_{0}=0.04
\pm 0.005$ and $\sigma_{\lambda}=0.51 \pm 0.05$, interestingly consistent with
values derived from simulations. For spirals, we find a good correlation
between empirical values of $\lambda$ and visually assigned Hubble types,
highlighting the potential of this physical parameter as an objective
classification tool.


title:
The Pseudo-continuum Bound-free Opacity of Hydrogen and its Importance
  in Cool White Dwarf Atmospheres

abstract:
  We investigate the importance of the pseudo-continuum bound-free opacity from
hydrogen atoms in the atmospheres of cool white dwarfs. This source of
absorption, when calculated by the occupation probability formalism applied in
the modeling of white dwarf atmospheres with $T_{\rm eff}\rm <17000 K$,
dominates all other sources of opacity at optical wavelengths. This is
unrealistic and not observed. On the other hand, a significant flux suppression
in the blue part of the spectra of cool white dwarfs has been reported, and
mainly interpreted as a result of the pseudo-continuum absorption from atomic
hydrogen. We investigate this problem by proposing a new, more realistic
approach to calculating this source of opacity. We show that this absorption is
orders of magnitude smaller than that predicted by current methods. Therefore,
we rule out the pseudo-continuum opacity as a source of the flux deficiency
observed in the spectra of cool white dwarfs.


title:
Accurate Extra-Galactic Distances and Dark Energy: Anchoring the
  Distance Scale with Rotational Parallaxes

abstract:
  We investigate how the uncertainty on the Hubble constant (H_0) affects the
uncertainty in the Equation of State (EOS) of Dark Energy and the total density
of the Universe (Omega_tot). We use the approximate relations between the
cosmological parameters [Spergel etal (2007)] and use error-propagation to
estimate the effects of improving the CMB parameters and H_0 on the EOS of Dark
Energy (DE). First we assume that the additional data does not improve
significantly, but decrease the error on H_0 by a factor <~10. Second, we allow
improved additional data but current H_0 errors (i.e., the DE Task Force case).
In the 1st scenario, improvements of the CMB parameters hardly change the
accuracy of the EOS and Omega_tot, unless H_0 can be measured with an accuracy
of a few %. We find that a combination of moderate improvements for both H_0
and other data significantly constrains the evolution of dark energy, but at a
reduced cost. We review several methods (and their strengths and weaknesses)
that might yield extra-galactic distances with errors of about 1%. We review:
the Velocity Field method, two Maser methods, two Light Echo techniques, the
Binary Star method, and the Rotational Parallax (RP) technique. Because these
methods substantially rely on geometry rather than astrophysics or cosmology,
their results are quite robust. We focus on the advantages of the RP technique
which can provide single-step, bias-free distances to nearby spirals. These
distances can be used to improve the zero-point for other methods which in turn
allow for a much improved H_0 errors. Achieving an accuracy of ~2% in the
distances to M31, M33 and the LMC by the RP method requires proper motions from
future astrometric missions (SIM, GAIA and OBSS, or the SKA).


title: R3 fluids

abstract:
  With regard to large-scale astrophysical systems, the current paper deals
with (i) formulation of tensor virial equations from the standpoint of
analytical mechanics; (ii) investigation on the role of systematic and random
motions for virial equilibrium configurations; (iii) extent to which systematic
and random motions are equivalent in changing a fluid shape. The tensor virial
equations are formulated using analytical mechanics, and the self
potential-energy tensor is shown to be symmetric. The role of systematic and
random motions in collisionless, ideal, self-gravitating fluids, is analysed in
detail including radial and tangential velocity dispersion on the equatorial
plane. R3 fluids are defined as ideal, self-gravitating fluids in virial
equilibrium, with systematic rotation around a principal axis of inertia, and
ihe related virial equations are formulated. A unified theory of systematic and
random motions is developed for R3 fluids, taking into consideration imaginary
rotation. The effect of random motion excess is shown to be equivalent to an
additional real or imaginary rotation, respectively, inducing flattening or
elongation. R3 fluids are found to admit adjoint configurations with isotropic
random velocity distribution. Further constraints are established on the amount
of random velocity anisotropy along the principal axes, for triaxial
configurations. A necessary condition is formulated for the occurrence of
bifurcation points from axisymmetric to triaxial configurations in virial
equilibrium, which is independent of the anisotropy parameters. In the special
case of homeoidally striated Jacobi ellipsoid, some previously known results
are reproduced.


title: A Universal Decline Law of Classical Novae

abstract:
  We calculate many different nova light curves for a variety of white dwarf
masses and chemical compositions, with the assumption that free-free emission
from optically thin ejecta dominates the continuum flux. We show that all these
light curves are homologous and a universal law can be derived by introducing a
``time scaling factor.'' The template light curve for the universal law has a
slope of the flux, F \propto t^{-1.75}, in the middle part (from ~2 to ~6 mag
below the optical maximum), but it declines more steeply, F \propto t^{-3.5},
in the later part (from ~6 to ~10 mag). This break on the light curve is due to
a quick decrease in the wind mass-loss rate. The nova evolutions are
approximately scaled by the time of break. Once the time of break is
observationally determined, we can derive the various timescales of novae such
as the period of a UV burst phase, the duration of optically thick wind phase,
and the turnoff date of hydrogen shell-burning. We have applied our template
light curve model to the three well-observed novae, V1500 Cyg, V1668 Cyg, and
V1974 Cyg. Our theoretical light curves show excellent agreement with the
optical y and infrared J, H, K light curves. The WD mass is estimated, from the
light curve fitting, to be 1.15 M_\sun for V1500 Cyg, 0.95 ~M_\sun for V1668
Cyg, and 0.95-1.05 M_\sun for V1974 Cyg.


title:
A Gravitational Instability-Driven Viscosity in Self-Gravitating
  Accretion Disks

abstract:
  We derive a viscosity from gravitational instability in self-gravitating
accretion disks, which has the required properties to account for the observed
fast formation of the first super-massive black holes in highly redshifted
quasars and for the cosmological evolution of the black hole-mass distribution.


title: Window To The Stars

abstract:
  We present Window To The Stars, a graphical user interface to the popular
TWIN single/binary stellar evolution code, for novices, students and
professional astrophysicists.
  It removes the drudgery associated with the traditional approach to running
the code, while maintaining the power, output quality and flexibility a modern
stellar evolutionist requires. It is currently being used for cutting edge
research and interactive teaching.


title: The large-scale jet-powered radio nebula of Circinus X-1

abstract:
  We present multi-epoch observations of the radio nebula around the neutron
star X-ray binary Circinus X-1 made at 1.4 and 2.5 GHz with the Australia
Telescope Compact Array between October 2000 and September 2004. The nebula can
be seen as a result of the interaction between the jet from the system and the
interstellar medium and it is likely that we are actually looking toward the
central X-ray binary system through the jet-powered radio lobe. The study of
the nebula thus offers a unique opportunity to estimate for the first time
using calorimetry the energetics of a jet from an object clearly identified as
a neutron star. An extensive discussion on the energetics of the complex is
presented: a first approach is based on the minimum energy estimation, while a
second one employs a self-similar model of the interaction between the jets and
the surrounding medium. The results suggest an age for the nebula of \leq 10^5
years and a corresponding time-averaged jet power \geq 10^{35} erg s^{-1}.
During periodic flaring episodes, the instantaneous jet power may reach values
of similar magnitude to the X-ray luminosity.


title:
VLT/UVES spectroscopy of Wray 977, the hypergiant companion to the X-ray
  pulsar GX301-2

abstract:
  Model atmosphere fits to high-resolution optical spectra of Wray 977 confirm
the B hypergiant classification of the massive companion to the X-ray pulsar
GX301-2. The models give a radius of 62 Rsun, an effective temperature of
18,100 K and a luminosity of 5 x 10^^5 Lsun. The deduced mass-loss rate and
terminal velocity of the stellar wind are 10^^-5 Msun/yr and 305 km/s,
respectively. The interstellar Na I D absorption indicates that Wray 977 is
located behind the first intersection with the Sagittarius-Carina spiral arm
(1-2.5 kpc) and probably belongs to the stellar population of the Norma spiral
arm at a distance of 3-4 kpc. The spectra obtained with UVES on the Very Large
Telescope (VLT) cover a full orbit of the system, including periastron passage,
from which we derive the radial-velocity curve of the B hypergiant. The
measured radial-velocity amplitude is 10 +/-3 km/s yielding a mass ratio q =
0.046 +/- 0.014. The absence of an X-ray eclipse results in a lower limit to
the mass of Wray 977 of 39 Msun. An upper limit of 53 Msun is derived for the
mass of Wray 977 adopting a maximum neutron star mass of 2.5 Msun. The
``spectroscopic'' mass of Wray 977 is 43 +/- 10 Msun, consistent with the range
in mass derived from the binarity constraints. The mass of the neutron star is
1.85 +/- 0.6 Msun. Time series of spectral lines formed in the dense stellar
wind indicate the presence of a gas stream trailing the neutron star in its
orbit. The long-term behaviour of the H alpha equivalent width exhibits strong
variations in wind strength; the sampling of the data is insufficient to
conclude whether a relation exists between wind mass-loss rate and pulsar spin
period.


title:
Search for radio pulsations in four Anomalous X-ray Pulsars and
  discovery of two new pulsars

abstract:
  We report on observations of four southern Anomalous X-ray Pulsars, (1RXS
J170849.0-400910, 1E 1048.1-5937, 1E 1841-045 and AX J1845-0258), obtained at
1.4 GHz using the Parkes radio telescope. Radio pulsations from these sources
have been searched (i) by directly folding the time series at a number of trial
periods centered on the value of the spin rate obtained from the X-ray
observations; (ii) by performing a blind search; (iii) using a code sensitive
to single dedispersed pulses, in the aim to detect signals similar to those of
the recently discovered Rotating RAdio Transients. No evidence for radio
pulsations with an upper limit of ~0.1 mJy for any of the four targets has been
found. The blind search led to the serendipitous discovery of two new pulsars,
rotating with a spin period of about 0.7 s and of 92 ms respectively, and to
the further detection of 18 known pulsars, two of which were also detected in
the single-pulse search.


title:
Diagnostics of active galaxies: I. Modeling the infrared properties of
  dusty cores of starburst galaxies

abstract:
  An evolutionary model of star formation in ULIRGs was created using existing
star formation and radiative transfer codes (STARBURST99, RADMC and RADICAL) as
building blocks. The results of the simulations are compared to data from two
IRAS catalogs. From the simulations it is found that the dust surrounding the
starburst region is made up from two components. There is a low optical depth
(tau=0.1, which corresponds to 0.1% of the total dust mass), hot (T~400K)
non-grey component close to the starburst (scale size 10pc) and a large scale,
colder grey component (100pc, 75K) with a much larger column (tau=10). The
simulations also show that starburst galaxies can be powered by massive star
formation. The parameters for this star forming region are difficult to
determine, since the IR continuum luminosity is only sensitive to the total UV
input. Therefore, there is a degeneracy between the total starburst mass and
the initial mass function (IMF) slope. A less massive star formation with a
shallower IMF will produce the same amount of OB stars and therefore the same
amount of irradiating UV flux. Assuming the stars are formed according to a
Salpeter IMF (Psi(M) ~ M^-2.35), the star formation region should produce 10^9
Msun of stars (either in one instantaneous burst, or in a continuous process)
in order to produce enough IR radiation.


title:
Anomalous H_2CO Absorption Towards the Galactic Anticenter: A Blind
  Search for Dense Molecular Clouds

abstract:
  We have carried out a blind search in the general direction of the Galactic
Anticenter for absorption of the Cosmic Microwave Background (CMB) radiation
near 4.83 GHz by molecular clouds containing gaseous ortho-formaldehyde
(H_2CO). The observations were done using the 25-m radio telescope at Onsala in
Sweden, and covered strips in Galactic latitude -1 < b < +1 at several
longitudes in the region 170 < l < 190 . Spectra were obtained in these strips
with a grid spacing corresponding to the telescope resolution of 10'. We have
detected H_2CO CMB absorption at ~ 10% of the survey pointings. This detection
rate is likely to increase with further improvements in sensitivity, and may
become comparable to the detection rate expected from a blind CO survey with a
corresponding sensitivity limit. We have mapped some of these detections in
more detail and compared the H_2CO absorption to existing maps of CO(1-0)
emission in the same regions. There appears to be a rough correlation between
the velocity-integrated line strength of the CO(1-0) emission and that of the
H_2CO absorption. However, the scatter in this correlation is significantly
larger than the measurement errors, indicating differences of detail at and
below the linear resolution of our observations (~ 4 - 9 pc). Although these
two tracers are expected to have similar excitation requirements on the
microscopic level characteristic of warm, T_K > 10K, dense, 10^3 < n < 10^5
cm^{-3} condensations in molecular clouds, the CO(1-0) line is expected to be
optically thick, whereas the H_2CO line is not. This latter difference is
likely to be responsible for a significant part of the scatter in the
correlation we have found.


title:
A Database of 2MASS Near-Infrared Colors of Magellanic Cloud Star
  Clusters

abstract:
  The (rest-frame) near-IR domain contains important stellar population
diagnostics and is often used to estimate masses of galaxies at low as well as
high redshifts. However, many stellar population models are still relatively
poorly calibrated in this part of the spectrum. To allow an improvement of this
calibration we present a new database of integrated near-infrared JHKs
magnitudes for 75 star clusters in the Magellanic Clouds, using the 2-Micron
All-Sky Survey (2MASS). The majority of the clusters in our sample have robust
age and metallicity estimates from color-magnitude diagrams available in the
literature, and populate a range of ages from 10 Myr to 15 Gyr and a range in
[Fe/H] from -2.17 to +0.01 dex. A comparison with matched star clusters in the
2MASS Extended Source Catalog (XSC) reveals that the XSC only provides a good
fit to the unresolved component of the cluster stellar population. We also
compare our results with the often-cited single-channel JHK photometry of
Persson and collaborators, and find significant differences, especially for
their 30"-diameter apertures up to ~2.5 mag in the K-band, more than 1 mag in
J-K, and up to 0.5 mag in H-K. Using simulations to center apertures based on
maximum light throughput (as performed by Persson et al, we show that these
differences can be attributed to near-IR-bright cluster stars (e.g., Carbon
stars) located away from the true center of the star clusters. The wide age and
metallicity coverage of our integrated JHKs photometry sample constitutes a
fundamental dataset for testing population synthesis model predictions, and for
direct comparison with near-IR observations of distant stellar populations.


title:
The redshift distribution of SWIFT Gamma-Ray Bursts: evidence for
  evolution

abstract:
  We predict the redshift distribution of long Gamma-Ray Bursts (GRBs) with
Monte Carlo simulations. Our improved analysis constrains free parameters with
three kinds of observation: (i) the log(N)-log(P) diagram of BATSE bursts; (ii)
the peak energy distribution of bright BATSE bursts; (iii) the HETE2 fraction
of X-ray rich GRBs and X-ray flashes. The statistical analysis of the Monte
Carlo simulation results allow us to carefully study the impact of the
uncertainties in the GRB intrinsic properties on the redshift distribution. The
comparison with SWIFT data then leads to the following conclusions. The Amati
relation should be intrinsic, if observationally confirmed by SWIFT. The
progenitor and/or the GRB properties have to evolve to reproduce the high mean
redshift of SWIFT bursts. Our results favor an evolution of the efficiency of
GRB production by massive stars, that would be ~6-7 times higher at z~7 than at
z~2. We finally predict around 10 GRBs detected by SWIFT at redshift z>6 for a
three year mission. These may be sufficient to open a new observational window
over the high redshift Universe.


title:
Simulation of neutrino and charged particle production and propagation
  in the atmosphere

abstract:
  A precise evaluation of the secondary particle production and propagation in
the atmosphere is very important for the atmospheric neutrino oscillation
studies. The issue is addressed with the extension of a previously developed
full 3-Dimensional Monte-Carlo simulation of particle generation and transport
in the atmosphere, to compute the flux of secondary protons, muons and
neutrinos. Recent balloon borne experiments have performed a set of accurate
flux measurements for different particle species at different altitudes in the
atmosphere, which can be used to test the calculations for the atmospheric
neutrino production, and constrain the underlying hadronic models. The
simulation results are reported and compared with the latest flux measurements.
It is shown that the level of precision reached by these experiments could be
used to constrain the nuclear models used in the simulation. The implication of
these results for the atmospheric neutrino flux calculation are discussed.


title:
X-Ray Observations of Type Ia Supernovae with Swift: Evidence for
  Circumstellar Interaction for SN 2005ke

abstract:
  We present a study of the early (days to weeks) X-ray and UV properties of
eight Type Ia supernovae (SNe Ia) which have been extensively observed with the
X-Ray Telescope (XRT) and UV/Optical Telescope (UVOT) onboard Swift, ranging
from 5-132 days after the outburst. SN 2005ke is tentatively detected (at a
3-3.6 sigma level of significance) in X-rays based on deep monitoring with the
XRT ranging from 8 to 120 days after the outburst. The inferred X-ray
luminosity [(2+/-1) x 10^{38} ergs/s; 0.3-2 keV band] is likely caused by
interaction of the SN shock with circumstellar material (CSM), deposited by a
stellar wind from the progenitor's companion star with a mass-loss rate of ~ 3
x 10^{-6} M_sun/yr (v_w/10 km/s). Evidence of CSM interaction in X-rays is
independently confirmed by an excess of UV emission as observed with the UVOT
onboard Swift, starting around 35 days after the explosion. The non-detection
of SN 2005ke with Chandra 105 days after the outburst implies a rate of decline
steeper than L_x \propto t^{-0.75}, consistent with the decline expected from
the interaction of the SN shock with a spherically symmetric CSM (t^{-1}). None
of the other seven SNe Ia is detected in X-rays or shows a UV excess, which
allows us to put tight constraints on the mass-loss rates of the progenitor
systems.


title: Status and Perspectives of Dark Matter Searches

abstract:
  In the last year many collaborations searching for the dark matter
constituent have published results from their experiments. Here I give a review
of direct detection searches reported by the DAMA, KIMS, CDMS-II, EDELWEISS-I,
CRESST-II and ZEPLIN-I collaborations. I also outline the future plans of each
collaboration as well as the XENON10 collaboration.


title:
Formation and Collapse of Nonaxisymmetric Protostellar Cores in Planar
  Magnetic Interstellar Clouds: Formulation of the Problem and Linear Analysis

abstract:
  We formulate the problem of the formation and collapse of nonaxisymmetric
protostellar cores in weakly ionized, self-gravitating, magnetic molecular
clouds. In our formulation, molecular clouds are approximated as isothermal,
thin (but with finite thickness) sheets. We present the governing dynamical
equations for the multifluid system of neutral gas and ions, including
ambipolar diffusion, and also a self-consistent treatment of thermal pressure,
gravitational, and magnetic (pressure and tension) forces. The dimensionless
free parameters characterizing model clouds are discussed. The response of
cloud models to linear perturbations is also examined, with particular emphasis
on length and time scales for the growth of gravitational instability in
magnetically subcritical and supercritical clouds. We investigate their
dependence on a cloud's initial mass-to-magnetic-flux ratio (normalized to the
critical value for collapse), the dimensionless initial neutral-ion collision
time, and also the relative external pressure exerted on a model cloud. Among
our results, we find that nearly-critical model clouds have significantly
larger characteristic instability lengthscales than do more distinctly sub- or
supercritical models. Another result is that the effect of a greater external
pressure is to reduce the critical lengthscale for instability. Numerical
simulations showing the evolution of model clouds during the linear regime of
evolution are also presented, and compared to the results of the dispersion
analysis. They are found to be in agreement with the dispersion results, and
confirm the dependence of the characteristic length and time scales on
parameters such as the initial mass-to-flux ratio and relative external
pressure.


title: Free-free absorption in the gravitational lens JVAS B0218+357

abstract:
  We address the issue of anomalous image flux ratios seen in the double-image
gravitational lens JVAS B0218+357. From the multi-frequency observations
presented in a recent study (Mittal et al. 2006) and several previous
observations made by other authors, the anomaly is well-established in that the
image flux-density ratio (A/B) decreases from 3.9 to 2.0 over the observed
frequency range from 15 GHz to 1.65 GHz. In Mittal et al. (2006), the authors
investigated whether an interplay between a frequency-dependent structure of
the background radio-source and a gradient in the relative image-magnification
can explain away the anomaly. Insufficient shifts in the image centroids with
frequency led them to discard the above effect as the cause of the anomaly. In
this paper, we first take this analysis further by evaluating the combined
effect of the background source extension and magnification gradients in the
lens plane in more detail. This is done by making a direct use of the observed
VLBI flux-distributions for each image to estimate the image flux-density
ratios at different frequencies from a lens-model. As a result of this
investigation, this mechanism does not account for the anomaly. Following this,
we analyze the effects of mechanisms which are non-gravitational in nature on
the image flux ratios in B0218+357. These are free-free absorption and
scattering, and are assumed to occur under the hypothesis of a molecular cloud
residing in the lens galaxy along the line-of-sight to image A. We show that
free-free absorption due to an H II region covering the entire structure of
image A at 1.65 GHz can explain the image flux ratio anomaly. We also discuss
whether H II regions with physical parameters as derived from our analysis are
consistent with those observed in Galactic and extragalactic H II regions.


title: X-ray binaries

abstract:
  We review the nuclear astrophysics aspects of accreting neutron stars in
X-ray binaries. We summarize open astrophysical questions in light of recent
observations and their relation to the underlying nuclear physics. Recent
progress in the understanding of the nuclear physics, especially of X-ray
bursts, is also discussed.


title: The importance of nuclear masses in the astrophysical rp-process

abstract:
  The importance of mass measurements for astrophysical capture processes in
general, and for the rp-process in X-ray bursts in particular is discussed. A
review of the current uncertainties in the effective lifetimes of the major
waiting points 64Ge, 68Se, and 72Kr demonstrates that despite of recent
measurements uncertainties are still significant. It is found that mass
measurements with an accuracy of the order of 10 keV or better are desirable,
and that reaction rate uncertainties play a critical role as well.


title: Accelerated expansion from structure formation

abstract:
  We discuss the physics of backreaction-driven accelerated expansion. Using
the exact equations for the behaviour of averages in dust universes, we explain
how large-scale smoothness does not imply that the effect of inhomogeneity and
anisotropy on the expansion rate is small. We demonstrate with an analytical
toy model how gravitational collapse can lead to acceleration. We find that the
conjecture of the accelerated expansion being due to structure formation is in
agreement with the general observational picture of structures in the universe,
and more quantitative work is needed to make a detailed comparison.


title: Non-Gaussianity of the primordial perturbation in the curvaton model

abstract:
  We use the delta N -formalism to investigate the non-Gaussianity of the
primordial curvature perturbation in the curvaton scenario for the origin of
structure. We numerically calculate the full probability distribution function
allowing for the non-instantaneous decay of the curvaton and compare this with
analytic results derived in the sudden-decay approximation. We also present
results for the leading-order contribution to the primordial bispectrum and
trispectrum. In the sudden-decay approximation we derive a fully non-linear
expression relating the primordial perturbation to the initial curvaton
perturbation. As an example of how non-Gaussianity provides additional
constraints on model parameters, we show how the primordial bispectrum on CMB
scales can be used to constrain variance on much smaller scales in the curvaton
field. Our analytical and numerical results allow for multiple tests of
primordial non-Gaussianity, and thus they can offer consistency tests of the
curvaton scenario.


title: A Linear Perturbation Theory of Inhomogeneous Reionization

abstract:
  We develop an analytic approach to study inhomogeneous reionization on large
scales by solving the equations of ionization balance and radiative transfer to
first order in perturbations. Given the spatial distribution and spectrum of
the ionizing sources, our formalism can be used to predict the large scale
power spectra of fluctuations in the abundances of HII, HI and radiation. Our
approach avoids common approximations/assumptions in existing analytic methods
-- for instance, we do not assume a specific ionization topology from the
outset; nor do we make a step-function bubble-like approximation to the HII
distribution. Applying our formalism to sources biased according to the
Press-Schechter prescription, we find: 1. reionization always proceeds
``inside--out'', with dense regions more highly ionized, at least on large
scales; 2. on sufficiently large scales, HII, HI and radiation exhibits a scale
independent bias relative to dark matter; 3. the bias is suppressed on scales
comparable to or smaller than the mean free path of the ionizing photons; 4. if
the ionizing source spectrum is sufficiently soft, the HII bias closely tracks
the source bias for most of the reionization process but drops precipitously
after percolation; 5. if the ionizing source spectrum is sufficiently hard, the
HII bias drops in a more steady fashion throughout the reionization process.
The tools developed here will be useful for interpreting future 21 cm, CMB and
Lyman-alpha forest observations, both to learn about the reionization
astrophysics (such as the hardness of the source spectrum and therefore the
nature of the ionizing sources) and to possibly extract interesting
cosmological information.


title:
The 2dF-SDSS LRG and QSO survey: Evolution of the Luminosity Function of
  Luminous Red Galaxies to z=0.6

abstract:
  We present new measurements of the luminosity function (LF) of Luminous Red
Galaxies (LRGs) from the Sloan Digital Sky Survey (SDSS) and the 2dF-SDSS LRG
and Quasar (2SLAQ) survey. We have carefully quantified, and corrected for,
uncertainties in the K and evolutionary corrections, differences in the colour
selection methods, and the effects of photometric errors, thus ensuring we are
studying the same galaxy population in both surveys. Using a limited subset of
6326 SDSS LRGs (with 0.17<z<0.24) and 1725 2SLAQ LRGs (with 0.5 <z<0.6), for
which the matching colour selection is most reliable, we find no evidence for
any additional evolution in the LRG LF, over this redshift range, beyond that
expected from a simple passive evolution model. This lack of additional
evolution is quantified using the comoving luminosity density of SDSS and 2SLAQ
LRGs, brighter than M_r - 5logh = -22.5, which are 2.51+/-0.03 x 10^-7 L_sun
Mpc^-3 and 2.44+/-0.15 x 10^-7 L_sun Mpc^-3 respectively (<10% uncertainty). We
compare our LFs to the COMBO-17 data and find excellent agreement over the same
redshift range. Together, these surveys show no evidence for additional
evolution (beyond passive) in the LF of LRGs brighter than M_r - 5logh = -21
(or brighter than L*). We test our SDSS and 2SLAQ LFs against a simple ``dry
merger'' model for the evolution of massive red galaxies and find that at least
half of the LRGs at z=0.2 must already have been well-assembled (with more than
half their stellar mass) by z=0.6. This limit is barely consistent with recent
results from semi-analytical models of galaxy evolution.


title:
MegaZ-LRG: A photometric redshift catalogue of one million SDSS Luminous
  Red Galaxies

abstract:
  We describe the construction of MegaZ-LRG, a photometric redshift catalogue
of over one million luminous red galaxies (LRGs) in the redshift range 0.4 < z
< 0.7 with limiting magnitude i < 20. The catalogue is selected from the
imaging data of the Sloan Digital Sky Survey Data Release 4. The 2dF-SDSS LRG
and Quasar (2SLAQ) spectroscopic redshift catalogue of 13,000
intermediate-redshift LRGs provides a photometric redshift training set,
allowing use of ANNz, a neural network-based photometric-redshift estimator.
The rms photometric redshift accuracy obtained for an evaluation set selected
from the 2SLAQ sample is sigma_z = 0.049 averaged over all galaxies, and
sigma_z = 0.040 for a brighter subsample (i < 19.0). The catalogue is expected
to contain ~5 per cent stellar contamination. The ANNz code is used to compute
a refined star/galaxy probability based on a range of photometric parameters;
this allows the contamination fraction to be reduced to 2 per cent with
negligible loss of genuine galaxies. The MegaZ-LRG catalogue is publicly
available on the World Wide Web from http://www.2slaq.info .


title: The 2dF-SDSS LRG and QSO (2SLAQ) Luminous Red Galaxy Survey

abstract:
  We present a spectroscopic survey of almost 15,000 candidate
intermediate-redshift Luminous Red Galaxies (LRGs) brighter than i=19.8,
observed with 2dF on the Anglo-Australian Telescope. The targets were selected
photometrically from the Sloan Digital Sky Survey (SDSS) and lie along two
narrow equatorial strips covering 180 sq deg. Reliable redshifts were obtained
for 92% of the targets and the selection is very efficient: over 90% have
redshifts between 0.45 and 0.8. More than 80% of the ~11,000 red galaxies have
pure absorption-line spectra consistent with a passively-evolving old stellar
population. The redshift, photometric and spatial distributions of the LRGs are
described. The 2SLAQ data will be released publicly from mid-2006, providing a
powerful resource for observational cosmology and the study of galaxy
evolution.


title: The Hubble Ultra Deep Field

abstract:
  This paper presents the Hubble Ultra Deep Field (HUDF), a one million second
exposure of an 11 square minute-of-arc region in the southern sky with the
Hubble Space Telescope. The exposure time was divided among four filters, F435W
(B435), F606W (V606), F775W (i775), and F850LP (z850), to give approximately
uniform limiting magnitudes mAB~29 for point sources. The image contains at
least 10,000 objects presented here as a catalog. Few if any galaxies at
redshifts greater than ~4 resemble present day spiral or elliptical galaxies.
Using the Lyman break dropout method, we find 504 B-dropouts, 204 V-dropouts,
and 54 i-dropouts. Using these samples that are at different redshifts but
derived from the same data, we find no evidence for a change in the
characteristic luminosity of galaxies but some evidence for a decrease in their
number densities between redshifts of 4 and 7. The ultraviolet luminosity
density of these samples is dominated by galaxies fainter than the
characteristic luminosity, and the HUDF reveals considerably more luminosity
than shallower surveys. The apparent ultraviolet luminosity density of galaxies
appears to decrease from redshifts of a few to redshifts greater than 6. The
highest redshift samples show that star formation was already vigorous at the
earliest epochs that galaxies have been observed, less than one billion years
after the Big Bang.


title:
The Evolution of Optical Depth in the Ly-alpha Forest: Evidence Against
  Reionization at z~6

abstract:
  We examine the evolution of the IGM Ly-alpha optical depth distribution using
the transmitted flux probability distribution function (PDF) in a sample of 63
QSOs spanning absorption redshifts 1.7 < z < 5.8. The data are compared to two
theoretical optical depth distributions: a model distribution based on the
density distribution of Miralda-Escude et al. (2000) (MHR00), and a lognormal
distribution. We assume a uniform UV background and an isothermal IGM for the
MHR00 model, as has been done in previous works. Under these assumptions, the
MHR00 model produces poor fits to the observed flux PDFs at redshifts where the
optical depth distribution is well sampled, unless large continuum corrections
are applied. However, the lognormal optical depth distribution fits the data at
all redshifts with only minor continuum adjustments. We use a simple
parametrization for the evolution of the lognormal parameters to calculate the
expected mean transmitted flux at z > 5.4. The lognormal optical depth
distribution predicts the observed Ly-alpha and Ly-beta effective optical
depths at z > 5.7 while simultaneously fitting the mean transmitted flux down
to z = 1.6. If the evolution of the lognormal distribution at z < 5 reflects a
slowly-evolving density field, temperature, and UV background, then no sudden
change in the IGM at z ~ 6 due to late reionization appears necessary. We have
used the lognormal optical depth distribution without any assumption about the
underlying density field. If the MHR00 density distribution is correct, then a
non-uniform UV background and/or IGM temperature may be required to produce the
correct flux PDF. We find that an inverse temperature-density relation greatly
improves the PDF fits, but with a large scatter in the equation of state index.
[Abridged]


title: High Resolution Simulations of Supersonic Turbulence in Molecular Clouds

abstract:
  We present the results of three-dimensional simulations of supersonic Euler
turbulence with grid resolutions up to 1024^3 points. Our numerical experiments
describe nonmagnetized driven turbulent flows with an isothermal equation of
state and an rms Mach number of 6. We demonstrate that the inertial range
scaling properties of turbulence in this strongly compressible regime deviate
substantially from a Kolmogorov-like behavior previously recovered for mildly
compressible transonic flows.


title: Cosmic Dust Induced Flux Fluctuations: Bad and Good Aspects

abstract:
  Cosmic dust extinction alters the flux of type Ia supernovae. Inhomogeneities
in the dust distribution induce correlated fluctuations of the SN fluxes. We
find that such correlation can be up to 60% of the signal caused by
gravitational lensing magnification, with an opposite sign. Therefore if not
corrected, cosmic dust extinction is the dominant source of systematic
uncertainty for future SNe Ia lensing measurement limiting the overall S/N to
be $\la 10$. On the other hand, SN flux correlation measurements can be used in
combination with other lensing data to infer the level of dust extinction. This
will provide a viable method to eliminate gray dust contamination from the SN
Ia Hubble diagram.


title:
Size and properties of the narrow-line region in Seyfert-1 galaxies from
  spatially-resolved optical spectroscopy

abstract:
  Spatially resolved emission-line spectroscopy is a powerful tool to determine
the physical conditions in the narrow-line region (NLR) of active galactic
nuclei (AGNs). We recently used optical long-slit spectroscopy to study the
NLRs of a sample of six Seyfert-2 galaxies. We have shown that such an
approach, in comparison to the commonly used [OIII] narrow-band imaging alone,
allows us to probe the size of the NLR in terms of AGN photoionisation.
Moreover, several physical parameters of the NLR can be directly accessed. We
here apply the same methods to study the NLR of six Seyfert-1 galaxies and
compare our results to those of Seyfert-2 galaxies. We employ diagnostically
valuable emission-line ratios to determine the physical properties of the NLR,
including the core values and radial dependencies of density, ionisation
parameter, and reddening. Tracking the radial change of emission-line ratios in
diagnostic diagrams allows us to measure the transition between AGN-like and
HII-like line excitation, and thus we are able to measure the size of the NLR.
In the diagnostic diagrams, we find a transition between line ratios falling in
the AGN regime and those typical for HII regions in two Seyfert-1 galaxies,
thus determining the size of the NLR. The central electron temperature and
ionisation parameter are in general higher in type-1 Seyferts than in type 2s.
In almost all cases, both electron density and ionisation parameter decrease
with radius. In general, the decrease is faster in Seyfert-1 galaxies than in
type 2s. In several objects, the gaseous velocity distribution is
characteristic for rotational motion in an (inclined) emission-line disk in the
centre. We give estimates of the black hole masses. We discuss our findings in
detail for each object.


title:
The Detailed Star Formation History in the Spheroid, Outer Disk, and
  Tidal Stream of the Andromeda Galaxy

abstract:
  Using the Advanced Camera for Surveys on the Hubble Space Telescope, we have
obtained deep optical images reaching stars well below the oldest main sequence
turnoff in the spheroid, tidal stream, and outer disk of the Andromeda Galaxy.
We have reconstructed the star formation history in these fields by comparing
their color-magnitude diagrams to a grid of isochrones calibrated to Galactic
globular clusters observed in the same bands. Each field exhibits an extended
star formation history, with many stars younger than 10 Gyr but few younger
than 4 Gyr. Considered together, the star counts, kinematics, and population
characteristics of the spheroid argue against some explanations for its
intermediate-age, metal-rich population, such as a significant contribution
from stars residing in the disk or a chance intersection with the stream's
orbit. Instead, it is likely that this population is intrinsic to the inner
spheroid, whose highly-disturbed structure is clearly distinct from the
pressure-supported metal-poor halo that dominates farther from the galaxy's
center. The stream and spheroid populations are similar, but not identical,
with the stream's mean age being ~1 Gyr younger; this similarity suggests that
the inner spheroid is largely polluted by material stripped from either the
stream's progenitor or similar objects. The disk population is considerably
younger and more metal-rich than the stream and spheroid populations, but not
as young as the thin disk population of the solar neighborhood; instead, the
outer disk of Andromeda is dominated by stars of age 4 - 8 Gyr, resembling the
Milky Way's thick disk. The disk data are inconsistent with a population
dominated by ages older than 10 Gyr, and in fact do not require any stars older
than 10 Gyr.


title:
The distribution of the ISM in the Milky Way A three-dimensional
  large-scale model

abstract:
  We use the COBE/DIRBE (1.2, 2.2, 60, 100, 140, and 240 $\mu$m) maps and the
COBE/FIRAS spectra (for the wavelength range 100 - 1000 $\mu$m) to constrain a
model for the spatial distribution of the dust, the stars, and the gas in the
Milky Way. By assuming exponential axisymmetric distributions for the dust and
the stars and by performing the corresponding radiative transfer calculations
we closely (given the simple geometry of the model) reproduce the FIR and NIR
maps of the Milky Way. Similar distributions for the atomic and molecular
hydrogen in the disk are used (with an inner cut-off radius for the atomic
hydrogen) to fit the gas data. The star formation rate as a function of the
Galactic radius is derived from the FIR emission and is well in agreement with
existing estimates from various star formation tracers. The gas surface density
is plotted against the star formation rate density and an ``intrinsic''
Galactic Schmidt law is derived with excellent agreement with the ``external''
Schmidt law found for spiral galaxies. The Milky Way is found to consume $\sim
1%$ and $\sim 10%$ of its gas in the outer and inner regions respectively (for
a period of 0.1 Gyr) to make stars. The dust-induced B-V color excess observed
in various directions and distances (up to $\sim 6.5$ kpc) with well-studied
Cepheid stars is compared with the model predictions showing a good agreement.
The simple assumption of exponential distributions of stars and dust in the
Galaxy is found to be quite instructive and adequate in modeling all the
available data sets from 0.45 $\mu$m (B-band) to 1000 $\mu$m.


title: Dark matter and dark energy as a effects of Modified Gravity

abstract:
  We explain the effect of dark matter (flat rotation curve) using modified
gravitational dynamics. We investigate in this context a low energy limit of
generalized general relativity with a nonlinear Lagrangian ${\cal L}\propto
R^n$, where $R$ is the (generalized) Ricci scalar and $n$ is parameter
estimated from SNIa data. We estimate parameter $\beta$ in modified
gravitational potential $V(r) \propto -\frac{1}{r}(1+(\frac{r}{r_c})^{\beta})$.
Then we compare value of $\beta$ obtained from SNIa data with $\beta$ parameter
evaluated from the best fitted rotation curve. We find $\beta \simeq 0.7$ which
becomes in good agreement with an observation of spiral galaxies rotation
curve. We also find preferred value of $\Omega_{m,0}$ from the combined
analysis of supernovae data and baryon oscillation peak. We argue that although
amount of "dark energy" (of non-substantial origin) is consistent with SNIa
data and flat curves of spiral galaxies are reproduces in the framework of
modified Einstein's equation we still need substantial dark matter. For
comparison predictions of the model with predictions of the $\Lambda$CDM
concordance model we apply the Akaike and Bayesian information criteria of
model selection.


title:
The Parkes multibeam pulsar survey: VI. Discovery and timing of 142
  pulsars and a Galactic population analysis

abstract:
  [ABRIDGED] We present the discovery and follow-up observations of 142 pulsars
found in the Parkes 20-cm multibeam pulsar survey of the Galactic plane. These
new discoveries bring the total number of pulsars found by the survey to 742.
In addition to tabulating spin and astrometric parameters, along with pulse
width and flux density information, we present orbital characteristics for 13
binary pulsars which form part of the new sample. Combining these results from
another recent Parkes multibeam survey at high Galactic latitudes, we have a
sample of 1008 normal pulsars which we use to carry out a determination of
their Galactic distribution and birth rate. We infer a total Galactic
population of 30000 +/- 1100 potentially detectable pulsars (i.e. those beaming
towards us) having 1.4-GHz luminosities above 0.1 mJy kpc squared. Using a
pulsar current analysis, we derive the birth rate of this population to be 1.4
+/- 0.2 pulsars per century. An important conclusion from our work is that the
inferred radial density function of pulsars depends strongly on the assumed
distribution of free electrons in the Galaxy. As a result, any analyses using
the most recent electron model of Cordes & Lazio predict a dearth of pulsars in
the inner Galaxy. We show that this model can also bias the inferred pulsar
scale height with respect to the Galactic plane. Combining our results with
other Parkes multibeam surveys we find that the population is best described by
an exponential distribution with a scale height of 330 pc.


title: Mechanical Model for Relativistic Blast Waves

abstract:
  Relativistic blast waves can be described by a mechanical model. In this
model, the "blast" -- the compressed gas between the forward and reverse shocks
-- is viewed as one hot body. Equations governing its dynamics are derived from
conservation of mass, energy, and momentum. Simple analytical solutions are
obtained in the two limiting cases of ultra-relativistic and non-relativistic
reverse shock. Equations are derived for the general explosion problem.


title:
Does Radiative Feedback by the First Stars Promote or Prevent Second
  Generation Star Formation?

abstract:
  We study the effect of starlight from the first stars on the ability of other
minihaloes in their neighborhood to form additional stars. The question of what
the dynamical consequences were for these target minihaloes, of their exposure
to the ionizing and dissociating starlight from the Pop III star requires a
full radiation-hydrodynamics calculation. Towards this end, we have performed a
series of detailed, 1D, radiation-hydrodynamical simulations. We have varied
the distance to the source (and, hence, the flux) and the mass and evolutionary
stage of the target haloes to quantify this effect. We find: (1) trapping of
the I-front and its transformation from R-type to D-type, preceded by a shock
front; (2) photoevaporation of the ionized gas (i.e. all gas originally located
outside the trapping radius); (3) formation of an H_2 precursor shell which
leads the I-front, stimulated by partial photoionization; and (4) the
shock-induced formation of H_2 in the minihalo neutral core when the shock
speeds up and partially ionizes the gas. The fate of the neutral core is mostly
determined by the response of the core to this shock front, which leads to
molecular cooling and collapse that, when compared to the same halo without
external radiation, is either: (a) expedited, (b) delayed, (c) unaltered, or
(d) reversed or prevented, depending upon the flux (i.e. distance to the
source) and the halo mass and evolutionary stage. Roughly speaking, most haloes
that were destined to cool, collapse, and form stars in the absence of external
radiation are found to do so even when exposed to the first Pop III star in
their neighborhood, while those that would not have done so are still not able
to. (abridged)


title: Bulk viscosity of spin-one color superconductors with two quark falvors

abstract:
  We consider the contribution of the Urca-type processes to the bulk viscosity
of several spin-one color-superconducting phases of dense two-flavor quark
matter. In the so-called transverse phases which are suggested to be
energetically favorable at asymptotic densities, the presence of ungapped
quasiparticle modes prevents that spin-one color superconductivity has a large
effect on the bulk viscosity. When all modes are gapped, as for one particular
color-spin-locked phase, the effect on the viscosity can be quite large, which
may have important phenomenological implications.


title:
Observational Constraints on the Angular and Spectral Distributions of
  Photons in Gamma-Ray Burst Sources

abstract:
  The typical spectra of gamma-ray bursts (GRBs) are discussed in the context
of the compactness problem for GRB sources and how it is resolved in the
popular fireball model. In particular, observational (model-independent)
constraints on the collimation of the gamma-rays and the dependence of the
collimation angle on the photon energy are considered. The fact that the
threshold for the creation of $e^{-}e^{+}$ pairs depends on the angle between
the momenta of the annihilating photons in the GRB source provides an
alternative solution to the compactness problem. A new approach to explaining
GRBs, taking into account the angular dependence for pair creation, is
proposed, and the main features of a scenario describing a GRB source with a
total (photon) energy smaller or of the order of $10^{49}$ erg are laid out.
Thus, we are dealing with an alternative to an ultra-relativistic fireball, if
it turns out (as follows from observations) that all "long" GRBs are associated
with normal (not peculiar) core-collapse supernovae. The effects of radiation
pressure and the formation of jets as a consequence of even a small amount of
anisotropy in the total radiation field in a (compact) GRB source are examined
in this alternative model. Possible energy release mechanisms acting in regions
smaller or of the order of $10^{8}$ cm in size (a compact model for a GRB) are
discussed. New observational evidence for such compact energy release in the
burst source is considered.


title: Measuring the fading of S0 galaxies using globular clusters

abstract:
  We test the hypothesis that S0 galaxies are the descendants of fading spirals
whose star formation has been shut down, by using the properties of their
globular cluster (GC) systems. We estimate the amount by which the GC specific
frequency (number of GCs per unit V-band luminosity) is enhanced in S0s
relative to spirals. If the transformation hypothesis is correct, and no GCs
are created or destroyed in the process, then this difference provides a
measure of the degree to which the S0's V-band luminosity has faded relative to
that of its spiral progenitor. We also explore whether the degree to which the
GC specific frequency is enhanced in S0s correlates with the colour of the
stellar population, as also predicted by this hypothesis in which galaxies
become redder as they fade. We find that, on average, the GC specific frequency
is a factor ~3 larger for S0s than for spirals, which can be interpreted as
meaning that passively-evolving S0s have faded by about a factor of 3 from
their spiral progenitors. This value fits remarkably well with the predictions
of stellar population synthesis calculations, and the offset between the S0 and
spiral Tully-Fisher relations. We also find that the global colours of S0
galaxies are strongly correlated with their GC specific frequencies: the redder
the stellar population of an S0, the larger its specific frequency, as we might
expect if we are catching different S0s at different stages of passively fading
and reddening. Comparison to the predictions of stellar population synthesis
models show that this explanation works quantitatively as well as
qualitatively. These tests strongly support the hypothesis that S0 galaxies
were once normal spirals, whose star formation was cut off, presumably due to a
change of environment.


title: Is cosmic expansion of the universe accelerating?

abstract:
  Currently available Type Ia distant supernovae observed data seem to support
evidence that the cosmic expansion of the universe is accelerating. This
unexpected result is beyond any standard model of modern cosmology. The new
concept advanced to account for the acceleration is dark energy or quintessence
with negative pressure. Most analyses using this new form of energy describe
the observed data with great accuracy, although there has been no laboratory
confirmation of it. The present work analyzes the consequences of Thomson
scattering on Type Ia supernovae data for two significant reasons; (i) recently
observed data reveal the existence of sufficient amount of ionized baryonic
(hydrogen) dark matter in the intergalactic medium, a necessary ingredient for
Thomson scattering, and (ii) its effects have not been considered previously in
determining distances to the supernovae from their observed distance moduli.
Quantitative results of the present investigation based on observed data and
corrected for Thomson scattering are consistent with the prediction of Hubble
expansion of the universe.
  Subject headings: cosmology: theory - distances and redshifts - supernovae,
Hubble expansion: constituents of universe - missing dark matter


title: Classicality of the primordial perturbations

abstract:
  We show that during inflation, a quantum fluctuation becomes classical at all
orders if it becomes classical at first order. Implications are discussed.


title: Galaxy bimodality versus stellar mass and environment

abstract:
  We analyse a z<0.1 galaxy sample from the Sloan Digital Sky Survey focusing
on the variation of the galaxy colour bimodality with stellar mass and
projected neighbour density Sigma, and on measurements of the galaxy stellar
mass functions. The characteristic mass increases with environmental density
from about 10^10.6 Msun to 10^10.9 Msun (Kroupa IMF, H_0=70) for Sigma in the
range 0.1--10 per Mpc^2. The galaxy population naturally divides into a red and
blue sequence with the locus of the sequences in colour-mass and
colour-concentration index not varying strongly with environment. The fraction
of galaxies on the red sequence is determined in bins of 0.2 in log Sigma and
log mass (12 x 13 bins). The red fraction f_r generally increases continuously
in both Sigma and mass such that there is a unified relation: f_r =
F(Sigma,mass). Two simple functions are proposed which provide good fits to the
data. These data are compared with analogous quantities in semi-analytical
models based on the Millennium N-body simulation: the Bower et al. (2006) and
Croton et al. (2006) models that incorporate AGN feedback. Both models predict
a strong dependence of the red fraction on stellar mass and environment that is
qualitatively similar to the observations. However, a quantitative comparison
shows that the Bower et al. model is a significantly better match; this appears
to be due to the different treatment of feedback in central galaxies.


title:
Comparing Dynamical and Photometric Mass Estimates of Low- and
  High-Redshift Galaxies: Random and Systematic Uncertainties

abstract:
  We determine the importance of redshift-dependent systematic effects in the
determination of stellar masses from broad band spectral energy distributions
(SEDs), using high quality kinematic and photometric data of early-type
galaxies at z~1 and z~0. We find that photometric masses of z~1 galaxies can be
systematically different, by up to a factor of 2, from photometric masses of
z~0 galaxies with the same dynamical mass. The magnitude of this bias depends
on the choice of stellar population synthesis model and the rest-frame
wavelength range used in the fits. The best result, i.e., without significant
bias, is obtained when rest-frame optical SEDs are fitted with models from
Bruzual&Charlot (2003). When the SEDs are extended to the rest-frame near-IR, a
bias is introduced: photometric masses of the z~1 galaxies increase by a factor
of 2 relative to the photometric masses of the z~0 galaxies. When we use the
Maraston (2005) models, the photometric masses of the z~1 galaxies are low
relative to the photometric masses of the z~0 galaxies by a factor of ~1.8.
This offset occurs both for fits based on rest-frame optical SEDs, and fits
based on rest-frame optical+near-IR SEDs. The results indicate that model
uncertainties produce uncertainties as high as a factor of 2.5 in mass
estimates from rest-frame near-IR photometry, independent of uncertainties due
to unknown star formation histories.


title: The Hydrogen Burning Turn-off of RS Ophiuchi 2006

abstract:
  We report a coordinated multi-band photometry of the RS Oph 2006 outburst and
highlight the emission line free y-band photometry that shows a mid-plateau
phase at y ~ 10.2 mag from day 40 to day 75 after the discovery followed by a
sharp drop of the final decline. Such mid-plateau phases are observed in other
two recurrent novae, U Sco and CI Aql, and are interpreted as a bright disk
irradiated by the white dwarf. We have calculated theoretical light curves
based on the optically thick wind theory and have reproduced the observed light
curves including the mid-plateau phase and the final sharp decline. This final
decline is identified with the end of steady hydrogen shell-burning, which
turned out the day ~80. This turnoff date is consistent with the end of a
supersoft X-ray phase observed with Swift. Our model suggests a white dwarf
mass of 1.35 \pm 0.01 M_\sun, which indicates that RS Oph is a progenitor of
Type Ia supernovae. We strongly recommend the y-filter observation of novae to
detect both the presence of a disk and the hydrogen burning turn-off.


title: On the frequency of gravitational waves

abstract:
  We show that there are physically relevant situations where gravitational
waves do not inherit the frequency spectrum of their source but its wavenumber
spectrum.


title:
The Maximum B-mode Polarization of the Cosmic Microwave Background from
  Inhomogeneous Reionization

abstract:
  We compute the B-mode polarization power spectrum of the CMB from an epoch of
inhomogeneous reionization, using a simple model in which HII regions are
represented by ionized spherical bubbles with a log normal distribution of
sizes whose clustering properties are determined by large-scale structure. Both
the global ionization fraction and the characteristic radius of HII regions are
allowed to be free functions of redshift. Models that would produce substantial
contamination to degree scale gravitational wave B-mode measurements have power
that is dominated by the shot noise of the bubbles. Rare bubbles of >100 Mpc at
z>20 can produce signals that in fact exceed the B-modes from gravitational
lensing and are comparable to the maximal allowed signal of gravitational waves
(~0.1uK) while still being consistent with global constraints on the total
optical depth. Even bubbles down to 20 Mpc at z~15, or 40 Mpc at z~10 can be
relevant (0.01uK) once the lensing signal is removed either statistically or
directly. However, currently favored theoretical models that have ionization
bubbles that only grow to such sizes at the very end of a fairly prompt and
late reionization produce signals which are at most at these levels.


title: V1647 Ori: The X-ray Evolution of a Pre-main Sequence Accretion Burst

abstract:
  We present Chandra X-ray Observatory monitoring observations of the recent
accretion outburst displayed by the pre-main sequence (pre-MS) star V1647 Ori.
The X-ray observations were obtained over a period beginning prior to outburst
onset in late 2003 and continuing through its apparent cessation in late 2005,
and demonstrate that the mean flux of the spatially coincident X-ray source
closely tracked the near-infrared luminosity of V1647 Ori throughout its
eruption. We find negligible likelihood that the correspondence between X-ray
and infrared light curves over this period was the result of multiple X-ray
flares unrelated to the accretion burst. The recent Chandra data confirm that
the X-ray spectrum of V1647 Ori hardened during outburst, relative both to its
pre-outburst state and to the X-ray spectra of nearby pre-MS stars in the L1630
cloud. We conclude that the observed changes in the X-ray emission from V1647
Ori over the course of its 2003-2005 eruption were generated by a sudden
increase and subsequent decline in its accretion rate. These results for V1647
Ori indicate that the flux of hard X-ray emission from erupting low-mass,
pre-MS stars, and the duration and intensity of such eruptions, reflect the
degree to which star-disk magnetic fields are reorganized before and during
major accretion events.


title:
Cosmic Evolution of Mass Accretion Rate and Metalicity in Active
  Galactic Nuclei

abstract:
  We present line and continuum measurements for 9818 SDSS type-I active
galactic nuclei (AGNs) with z le 0.75. The data are used to study the four
dimensional space of black hole mass, normalized accretion rate (Ledd),
metalicity and redshift. The main results are: 1. Ledd is smaller for larger
mass black holes at all redshifts. 2. For a given black hole mass Ledd propto
z^gamma or (1+z)^delta where the slope gamma increases with black hole mass.
The mean slope is similar to the star formation rate slope over the same
redshift interval. 3. The FeII/Hb line ratio is significantly correlated with
Ledd. It also shows a weaker negative dependence on redshift. Combined with the
known dependence of metalicity on accretion rate, we suggest that the FeII/Hb
line ratio is a metalicity indicator. 4. Given the measured accretion rates,
the growth times of most AGNs exceed the age of the universe. This suggests
past episodes of faster growth for all those sources. Combined with the FeII/Hb
result, we conclude that the broad emission lines metalicity goes through
cycles and is not a monotonously decreasing function of redshift. 5. FWHM(OIII)
is a poor proxy of sigma_* especially for high Ledd. 6. We define a group of
narrow line type-I AGNs (NLAGN1s) by their luminosity (or mass) dependent Hb
line width. Such objects have Ledd>0.25 and they comprise 8% of the type-I
population. Other interesting results include negative Baldwin relationships
for EW(Hb) and EW(FeII) and a relative increase of the red part of the Hb line
with luminosity.


title:
X-Ray and Optical Flux Ratio Anomalies in Quadruply Lensed Quasars: I.
  Zooming in on Quasar Emission Regions

abstract:
  X-ray and optical observations of quadruply lensed quasars can provide a
microarcsecond probe of the lensed quasar, corresponding to scale sizes of
\~10^2-10^4 gravitational radii of the central black hole. This high angular
resolution is achieved by taking advantage of microlensing by stars in the
lensing galaxy. In this paper we utilize X-ray observations of ten lensed
quasars recorded with the Chandra X-ray Observatory as well as corresponding
optical data obtained with either the Hubble Space Telescope or ground-based
optical telescopes. These are analyzed in a systematic and uniform way with
emphasis on the flux-ratio anomalies that are found relative to the predictions
of smooth lens models. A comparison of the flux ratio anomalies between the
X-ray and optical bands allows us to conclude that the optical emission regions
of the lensed quasars are typically larger than expected from basic thin disk
models by factors of ~3-30.


title: Magnetic Reconnection in Astrophysical Systems

abstract:
  The main subject of my talk is the question: in what kind of astrophysical
systems magnetic reconnection is interesting and/or important? To address this
question, I first put forward three general criteria for selecting the relevant
astrophysical environments. Namely, reconnection should be: fast; energetically
important; and observable. From this, I deduce that the gas density should be
low, so that the plasma is: collisionless; force-free; and optically thin.
Thus, for example, the requirement that reconnection is fast implies that
Petschek's reconnection mechanism must be operating, which is possible,
apparently, only in the collisionless regime. Next, I argue that the force-free
condition implies that the magnetic field be produced in, and anchored by, a
nearby dense massive object, e.g., a star or a disk, strongly stratified by
gravity. I then stress the importance of field-line opening (e.g., by
differential rotation) as a means to form a reconnecting current sheet.
Correspondingly, I suggest the Y-point helmet streamer as a generic
prototypical magnetic configuration relevant to large-scale reconnection in
astrophysics. Finally, I discuss several specific astrophysical systems where
the above criteria are met: stellar coronae, magnetically-interacting
star--disk systems, and magnetized coronae above turbulent accretion disks. In
the Appendix, I apply the ideas put forward in this talk to the solar coronal
heating problem.


title: Constraint on the Post-Newtonian Parameter gamma on Galactic Size Scales

abstract:
  We constrain the post-Newtonian gravity parameter gamma on kiloparsec scales
by comparing the masses of 15 elliptical lensing galaxies from the Sloan Lens
ACS Survey as determined in two independent ways. The first method assumes only
that Newtonian gravity is correct and is independent of gamma, while the second
uses gravitational lensing which depends on gamma. More specifically, we
combine Einstein radii and radial surface-brightness gradient measurements of
the lens galaxies with empirical distributions for the mass concentration and
velocity anisotropy of elliptical galaxies in the local universe to predict
gamma-dependent probability distributions for the lens-galaxy velocity
dispersions. By comparing with observed velocity dispersions, we derive a
maximum-likelihood value of gamma = 0.98 +/- 0.07 (68% confidence). This result
is in excellent agreement with the prediction of general relativity that has
previously been verified to this accuracy only on solar-system length scales.


title:
On a possible regularity connecting physical characteristics of a Solar
  system planet and elements of its orbit

abstract:
  This paper is an attempt to detect correlation between characteristics of a
big planet of the Solar System (such as mass \QTR{it}{m}, radius \QTR{it}{r},
and sidereal period of rotation on its axis \QTR{it}{t}) and elements of its
orbit (such as radius of a big half-axis of the orbit \QTR{it}{R} and sidereal
period \QTR{it}{T} of rotation of the planet on the Sun). The existence of this
correlation can be generally considered a generalization of the third Kepler's
law, which is the logical conclusion of the nebular model of formation of the
big planets of the Solar System. There has been made an attempt to find out if
this correlation is typical of the big planets with a large number of
satellites. The aim of the paper is to search for the stated correlation.


title:
Cyclotron resonance energies at a low X-ray luminosity: A0535+262
  observed with Suzaku

abstract:
  The binary X-ray pulsar A0535+262 was observed with the Suzaku X-ray
observatory, on 2005 September 14 for a net exposure of 22 ksec. The source was
in a declining phase of a minor outburst, exhibiting 3--50 keV luminosity of
about $3.7 \times 10^{35}$ ergs s$^{-1}$ at an assumed distance of 2 kpc. In
spite of the very low source intensity (about 30 mCrab at 20 keV), its electron
cyclotron resonance was detected clearly with the Suzaku Hard X-ray Detector,
in absorption at about 45 keV. The resonance energy is found to be essentially
the same as those measured when the source is almost two orders of magnitude
more luminous. These results are compared with the luminosity-dependent changes
in the cyclotron resonance energy, observed from 4U 0115+63 and X 0331+53.


title: Spectral ageing analysis of the double-double radio galaxy J1453+3308

abstract:
  We present new radio observations at frequencies ranging from 240 to 4860 MHz
of the well-known, double-double radio galaxy (DDRG), J1453+3308, using both
the Giant Metrewave Radio Telescope (GMRT) and the Very Large Array (VLA).
These observations enable us to determine the spectra of the inner and outer
lobes over a large frequency range and demonstrate that while the spectrum of
the outer lobes exhibits significant curvature, that of the inner lobes appears
practically straight. The break frequency, and hence the inferred synchrotron
age of the outer structure, determined from 16$-$arcsec strips transverse to
the source axis, increases with distance from the heads of the lobes. The
maximum spectral ages for the northern and southern lobes are $\sim$47 and 58
Myr respectively. Because of the difference in the lengths of the lobes these
ages imply a mean separation velocity of the heads of the lobes from the
emitting plasma of 0.036c for both the northern and southern lobes. The
synchrotron age of the inner double is about 2 Myr which implies an advance
velocity of $\sim$0.1c, but these values have large uncertainties because the
spectrum is practically straight.


title:
The relation between the optical spectral slope and the luminosity for
  17 Palomar-Green QSOs

abstract:
  Using 7.5-year spectroscopic monitoring data of a sample of 17 Palomar-Green
QSOs (PG QSOs) (z=0.061-0.371), we obtain the optical spectral slope for each
object at all epochs by a power-law fit to the spectra in continuum bands. All
of these 17 PG QSOs exhibit obvious spectral slope variability. Most of the 17
objects show anti-correlation between the spectral slope and the rest-frame
5100$\AA$ continuum flux while five of them exist strong anti-correlation
(correlation coefficient R larger than 0.5). For the ensemble of these 17 PG
QSOs, a strong anti-correlation between the average spectral slope and the
average rest-frame 5100$\AA$ luminosity is found while no correlation is found
between the spectral slope and the Eddington ratio. A median anti-correlation
between spectral slope changes and continuum flux variations is also found
which indicates a hardening of the spectrum during bright phases. Accretion
disk (jet) instability models with other mechanisms associated with changes in
the accretion processes are promising.


title:
The X-ray properties of optically-selected z>0.6 clusters in the ESO
  Distant Cluster Survey

abstract:
  We present XMM-Newton observations of three optically-selected z > 0.6
clusters from the ESO Distant Cluster Survey (EDisCS), comprising the first
results of a planned X-ray survey of the full EDisCS high-redshift sample. The
EDisCS clusters were identified in the Las Campanas Distant Cluster Survey as
surface brightness fluctuations in the optical sky and their masses and galaxy
populations are well described by extensive photometric and spectroscopic
observations. We detect two of the three clusters in the X-ray and place a firm
upper limit on diffuse emission in the third cluster field. We are able to
constrain the X-ray luminosity and temperature of the detected clusters and
estimate their masses. We find the X-ray properties of the detected EDisCS
clusters are similar to those of X-ray-selected clusters of comparable mass and
-- unlike other high-redshift, optically-selected clusters -- are consistent
with the T - sigma and L_x - sigma relations determined from X-ray selected
clusters at low redshift. The X-ray determined mass estimates are generally
consistent with those derived from weak lensing and spectroscopic analyses.
These preliminary results suggest that the novel method of optical selection
used to construct the EDisCS catalog may, like selection by X-ray luminosity,
be well-suited for identification of relaxed, high-redshift clusters whose
intracluster medium is in place and stable by z ~ 0.8.


title:
Polarization in the prompt emission of gamma-ray bursts and their
  afterglows

abstract:
  Synchrotron is considered the dominant emission mechanism in the production
of gamma-ray burst photons in the prompt as well as in the afterglow phase.
Polarization is a characteristic feature of synchrotron and its study can
reveal a wealth of information on the properties of the magnetic field and of
the energy distribution in gamma-ray burst jets. In this paper I will review
the theory and observations of gamma-ray bursts polarization. While the theory
is well established, observations have prove difficult to perform, due to the
weakness of the signal. The discriminating power of polarization observations,
however, cannot be overestimated.


title:
Tempo2, a new pulsar timing package. II: The timing model and precision
  estimates

abstract:
  Tempo2 is a new software package for the analysis of pulsar pulse times of
arrival. In this paper we describe in detail the timing model used by tempo2,
and discuss limitations on the attainable precision. In addition to the
intrinsic slow-down behaviour of the pulsar, tempo2 accounts for the effects of
a binary orbital motion, the secular motion of the pulsar or binary system,
interstellar, Solar system and ionospheric dispersion, observatory motion
(including Earth rotation, precession, nutation, polar motion and orbital
motion), tropospheric propagation delay, and gravitational time dilation due to
binary companions and Solar system bodies. We believe the timing model is
accurate in its description of predictable systematic timing effects to better
than one nanosecond, except in the case of relativistic binary systems where
further theoretical development is needed. The largest remaining sources of
potential error are measurement error, interstellar scattering, Solar system
ephemeris errors, atomic clock instability and gravitational waves.


title:
The Spitzer c2d Survey of Nearby Dense Cores: I: First Direct Detection
  of the Embedded Source in IRAM 04191+1522

abstract:
  We report the first detections of the Class 0 protostellar source IRAM
04191+1522 at wavelengths shortward of 60 microns with the Spitzer Space
Telescope. We see extended emission in the Spitzer images that suggests the
presence of an outflow cavity in the circumstellar envelope. We combine the
Spitzer observations with existing data to form a complete dataset ranging from
3.6 to 1300 microns and use these data to construct radiative transfer models
of the source. We conclude that the internal luminosity of IRAM 04191+1522,
defined to be the sum of the luminosity from the internal sources (a star and a
disk), is L_int = 0.08 +/- 0.04 L_sun, placing it among the lowest luminosity
protostars known. Though it was discovered before the launch of the Spitzer
Space Telescope, IRAM 04191+1522 falls within a new class of Very Low
Luminosity Objects being discovered by Spitzer. Unlike the two other
well-studied objects in this class, which are associated either with weak,
compact outflows or no outflows at all, IRAM 04191+1522 has a well-defined
molecular outflow with properties consistent with those expected based on
relations derived from higher luminosity (L_int > 1 L_sun) protostars. We
discuss the difficulties in understanding IRAM 04191+1522 in the context of the
standard model of star formation, and suggest a possible explanation for the
very low luminosity of this source.