pinecone/core-2020-05-10-deduplication huggingface dataset:
Andromeda IV, a solitary gas-rich dwarf galaxy

Observations are presented of the isolated dwarf irregular galaxy And IV made
with the Hubble Space Telescope Advanced Camera for Surveys and the Giant
Metrewave Radio Telescope in the 21 cm HI line. We determine the galaxy
distance of $7.17\pm0.31$ Mpc using the Tip of Red Giant Branch method. The
galaxy has a total blue absolute magnitude of -12.81 mag, linear Holmberg
diameter of 1.88 kpc and an HI-disk extending to 8.4 times the optical Holmberg
radius. The HI mass-to-blue luminosity ratio for And IV amounts
$12.9~M_{\odot}/L_{\odot}$. From the GMRT data we derive the rotation curve for
the HI and fit it with different mass models. We find that the data are
significantly better fit with an iso-thermal dark matter halo, than by an NFW
halo. We also find that MOND rotation curve provides a very poor fit to the
data. The fact that the iso-thermal dark matter halo provides the best fit to
the data supports models in which star formation feedback results in the
formation of a dark matter core in dwarf galaxies. The total mass-to-blue
luminosity ratio of $162~M_{\odot}/L_{\odot}$ makes And IV among the darkest
dIrr galaxies known. However, its baryonic-to-dark mass ratio
($M_{gas}+M^*)/M_T = 0.11$ is close to the average cosmic baryon fraction,
0.15.Comment: 9 pages, 10 figures, 2 tables, accepted in Astronomische Nachrichte
Optimisation of the Population Monte Carlo algorithm: Application to
  constraining isocurvature models with cosmic microwave background data

We optimise the parameters of the Population Monte Carlo algorithm using
numerical simulations. The optimisation is based on an efficiency statistic
related to the number of samples evaluated prior to convergence, and is applied
to a D-dimensional Gaussian distribution to derive optimal scaling laws for the
algorithm parameters. More complex distributions such as the banana and bimodal
distributions are also studied. We apply these results to a cosmological
parameter estimation problem that uses CMB anisotropy data from the WMAP
nine-year release to constrain a six parameter adiabatic model and a fifteen
parameter admixture model, consisting of correlated adiabatic and isocurvature
perturbations. In the case of the adiabatic model and the admixture model we
find respective degradation factors of three and twenty, relative to the
optimal Gaussian case, due to degeneracies in the underlying parameter space.
The WMAP nine-year data constrain the admixture model to have an isocurvature
fraction of at most $36.3 \pm 2.8$ percent.Comment: 21 pages, 10 figure
Fitting peculiar spectral profiles in He I 10830 \r{A} absorption
  features

The new generation of solar instruments provides better spectral, spatial,
and temporal resolution for a better understanding of the physical processes
that take place on the Sun. Multiple-component profiles are more commonly
observed with these instruments. Particularly, the He I 10830 \r{A} triplet
presents such peculiar spectral profiles, which give information on the
velocity and magnetic fine structure of the upper chromosphere. The purpose of
this investigation is to describe a technique to efficiently fit the two
blended components of the He I 10830 \r{A} triplet, which are commonly observed
when two atmospheric components are located within the same resolution element.
The observations used in this study were taken on 2015 April 17 with the very
fast spectroscopic mode of the GREGOR Infrared Spectrograph (GRIS) attached to
the 1.5-meter GREGOR solar telescope, located at the Observatorio del Teide,
Tenerife, Spain. We apply a double-Lorentzian fitting technique using
Levenberg-Marquardt least-squares minimization. This technique is very simple
and much faster than inversion codes. Line-of-sight Doppler velocities can be
inferred for a whole map of pixels within just a few minutes. Our results show
sub- and supersonic downflow velocities of up to 32 km/s for the fast component
in the vicinity of footpoints of filamentary structures. The slow component
presents velocities close to rest.Comment: 7 pages, 5 color figures, accepted for publication in Astron. Nachr.
  as a part of special edition of the 12th Potsdam Thinksho
Ultraluminous X-ray sources: three exciting years

The extreme extragalactic sources known as Ultraluminous X-ray Sources (ULX)
represent a unique testing environment for compact objects population studies
and the accretion process. Their nature has long been disputed. Their
luminosity, well above the Eddington luminosity for a stellar-mass black hole,
can imply the presence of an intermediate-mass black hole or a stellar black
hole accreting above the Eddington limit. Both these interpretations are
important to understand better the accretion process and the evolution of
massive black holes. The last few years have seen a dramatic improvement of our
knowledge of these sources. In particular, the super-Eddington interpretation
for the bulk of the ULX population has gained a strong consensus. Nonetheless,
exceptions to this general trend do exist, and in particular one ULX was shown
to be a neutron star, and another was shown to be a very likely IMBH candidate.
In this paper, I will review the progress done in the last few years.Comment: 6 pages, 3 figures. Proceedings from the 2015 XMM-Newton Science
  Workshop, Astronomical Notes, in pres
Gravitational Lensing Size Scales for Quasars

We review results from our monitoring observations of several lensed quasars
performed in the optical, UV, and X-ray bands. Modeling of the multi-wavelength
light curves provides constraints on the extent of the optical, UV, and X-ray
emission regions. One of the important results of our analysis is that the
optical sizes as inferred from the microlensing analysis are significantly
larger than those predicted by the theoretical-thin-disk estimate. In a few
cases we also constrain the slope of the size-wavelength relation. Our size
constraints of the soft and hard X-ray emission regions of quasars indicate
that in some objects of our sample the hard X-ray emission region is more
compact than the soft and in others the soft emission region is smaller. This
difference may be the result of the relative strengths of the disk-reflected
(harder and extended) versus corona-direct (softer and compact) components in
the quasars of our sample. Finally, we present the analysis of several strong
microlensing events where we detect an evolution of the relativistic Fe line
profile as the magnification caustic traverses the accretion disk. These
caustic crossings are used to provide constraints on the innermost stable
circular orbit (ISCO) radius and the accretion disk inclination angle of the
black hole in quasar RX J1131-1231.Comment: 6 pages, 6 figures, To appear in Astronomische Nachrichten
  (Astronomical Notes
Accretion disc atmospheres and winds in low-mass X-ray binaries

In the last decade, X-ray spectroscopy has enabled a wealth of discoveries of
photoionised absorbers in X-ray binaries. Studies of such accretion disc
atmospheres and winds are of fundamental importance to understand accretion
processes and possible feedback mechanisms to the environment. In this work, we
review the current observational state and theoretical understanding of
accretion disc atmospheres and winds in low-mass X-ray binaries, focusing on
the wind launching mechanisms and on the dependence on accretion state. We
conclude with issues that deserve particular attention.Comment: 6 pages. Accepted for publication in Astronomical Notes (Proceedings
  of "The Extremes of Black Hole Accretion" workshop, held at ESAC, Madrid, in
  June 2015
The Innermost Extremes of Black Hole Accretion

The inner 20 gravitational radii around the black hole at the centre of
luminous Active Galactic Nuclei and stellar mass Black Hole Binaries are now
being routinely mapped by X-ray spectral-timing techniques. Spectral blurring
and reverberation of the reflection spectrum are key tools in this work. In the
most extreme AGN cases with high black hole spin, when the source appears in a
low state, observations probe the region within 1 gravitational radius of the
event horizon. The location, size and operation of the corona, which generates
the power-law X-ray continuum, are also being revealed.Comment: 6 pages. 12 figures, in press Astronomical Notes (Proc. XMM-Newton
  2015 Science Workshop
Modelling aperiodic X-ray variability in black hole binaries as
  propagating mass accretion rate fluctuations: a short review

Black hole binary systems can emit very bright and rapidly varying X-ray
signals when material from the companion accretes onto the black hole,
liberating huge amounts of gravitational potential energy. Central to this
process of accretion is turbulence. In the propagating mass accretion rate
fluctuations model, turbulence is generated throughout the inner accretion
flow, causing fluctuations in the accretion rate. Fluctuations from the outer
regions propagate towards the black hole, modulating the fluctuations generated
in the inner regions. Here, I present the theoretical motivation behind this
picture before reviewing the array of statistical variability properties
observed in the light curves of black hole binaries that are naturally
explained by the model. I also discuss the remaining challenges for the model,
both in terms of comparison to data and in terms of including more
sophisticated theoretical considerations.Comment: 6 pages, 4 figures, Invited review at the XMM-Newton 2015 Science
  Workshop, The Extremes of Black Hole Accretion, ESAC, Madrid, Spain, 8th -
  10th June 2015, accepted for publication in Astronomische Nachrichte
Spectral components in black hole X-ray binaries

This paper summarises our current understanding of the spectral continuum
components observed in black hole X-ray binaries. The consequences for
theoretical models are discussed with an emphasis on the constraints set by
observations on the nature of the X-ray corona in different spectral states.Comment: 7 pages, 3 figures, invited review at the XMM-Newton 2015 Science
  Workshop, The Extremes of Black Hole Accretion, ESAC, Madrid, Spain, 8th -
  10th June 2015, accepted for publication in Astronomische Nachrichte
Quasi periodic oscillations in black hole binaries

Fast time variability is the most prominent characteristic of accreting
systems and the presence of quasi periodic oscillations (QPOs) is a constant in
all accreting systems, from cataclysmic variables to AGNs, passing through
black hole and neutron star X-ray binaries and through the enigmatic
ultra-luminous X-ray sources. In this paper I will briefly review the current
knowledge of QPOs in black hole X-ray binaries, mainly focussing on their
observed properties, but also mentioning the most important models that have
been proposed to explain the origin of QPOs over the last decades.Comment: 7 pages, 3 figures. Accepted by Astron. Nachrichte
Unwrapping the X-ray Spectra of Active Galactic Nuclei

Active galactic nuclei (AGN) are complex phenomena. At the heart of an AGN is
a relativistic accretion disk around a spinning supermassive black hole (SMBH)
with an X-ray emitting corona and, sometimes, a relativistic jet. On larger
scales, the outer accretion disk and molecular torus act as the reservoirs of
gas for the continuing AGN activity. And on all scales from the black hole
outwards, powerful winds are seen that probably affect the evolution of the
host galaxy as well as regulate the feeding of the AGN itself. In this review
article, we discuss how X-ray spectroscopy can be used to study each of these
components. We highlight how recent measurements of the high-energy cutoff in
the X-ray continuum by NuSTAR are pushing us to conclude that X-ray coronae are
radiatively-compact and have electron temperatures regulated by
electron-positron pair production. We show that the predominance of
rapidly-rotating objects in current surveys of SMBH spin is entirely
unsurprising once one accounts for the observational selection bias resulting
from the spin-dependence of the radiative efficiency. We review recent progress
in our understanding of fast (v~0.1-0.3c), highly-ionized (mainly visible in
FeXXV and FeXXVI lines), high-column density winds that may dominate
quasar-mode galactic feedback. Finally, we end with a brief look forward to the
promise of Astro-H and future X-ray spectropolarimeters.Comment: 7 pages. Accepted for publication in Astronomical Notes (Proceedings
  of "The Extremes of Black Hole Accretion" workshop, held at ESAC, Madrid, in
  June 2015
Accretion disk winds in active galactic nuclei: X-ray observations,
  models, and feedback

Powerful winds driven by active galactic nuclei (AGN) are often invoked to
play a fundamental role in the evolution of both supermassive black holes
(SMBHs) and their host galaxies, quenching star formation and explaining the
tight SMBH-galaxy relations. A strong support of this "quasar mode" feedback
came from the recent X-ray observation of a mildly relativistic accretion disk
wind in a ultraluminous infrared galaxy (ULIRG) and its connection with a
large-scale molecular outflow, providing a direct link between the SMBH and the
gas out of which stars form. Spectroscopic observations, especially in the
X-ray band, show that such accretion disk winds may be common in local AGN and
quasars. However, their origin and characteristics are still not fully
understood. Detailed theoretical models and simulations focused on radiation,
magnetohydrodynamic (MHD) or a combination of these two processes to
investigate the possible acceleration mechanisms and the dynamics of these
winds. Some of these models have been directly compared to X-ray spectra,
providing important insights into the wind physics. However, fundamental
improvements on these studies will come only from the unprecedented energy
resolution and sensitivity of the upcoming X-ray observatories, namely ASTRO-H
(launch date early 2016) and Athena (2028).Comment: Review article accepted for publication in Astronomische Nachrichte
Quasi periodic oscillations in active galactic nuclei

Quasi-periodic oscillations (QPOs) are coherent peaks of variability power
observed in the X-ray power spectra (PSDs) of stellar mass X-ray binaries
(XRBs). A scale invariance of the accretion process implies they should be
present in the active galactic nuclei. The first robust detection was a $\sim
1$ hr periodicity in the Seyfert galaxy RE J1034+396 from a $\sim 90$ ks
XMM-Newton observation, however, subsequent observations failed to detect the
QPO in the $0.3-10.0$ keV band. In this talk we present the recent detection of
the $\sim 1$ hr periodicity in the $1.0-4.0$ keV band of 4 further
low-flux/spectrally-harder observations of RE J1034+396 (see Alston et al
2014). We also present recent work on the discovery of a QPO in the Seyfert
galaxy, MS 22549-3712, which again is only detected in energy bands associated
with the primary power-law continuum emission (Alston et al 2015). We conclude
these features are most likely analogous to the high-frequency QPOs observed in
XRBs. In both sources, we also see evidence for X-ray reverberation at the QPO
frequency, where soft X-ray bands and Iron K$\alpha$ emission lag the primary
X-ray continuum. These time delays may provide another diagnostic for
understanding the underlying QPO mechanism observed in accreting black holes.Comment: Proceedings for The Extremes of Black Hole Accretion, Madrid, 2015.
  To appear in Astronomische Nachrichten, 6 pages, 4 figure
Magneto centrifugal winds from accretion discs around black hole
  binaries

We want to test if self-similar magneto-hydrodynamic (MHD) accretion-ejection
models can explain the observational results for accretion disk winds in BHBs.
In our models, the density at the base of the outflow, from the accretion disk,
is not a free parameter, but is determined by solving the full set of dynamical
MHD equations without neglecting any physical term. Different MHD solutions
were generated for different values of (a) the disk aspect ratio
($\varepsilon$) and (b) the ejection efficiency ($p$). We generated two kinds
of MHD solutions depending on the absence (cold solution) or presence (warm
solution) of heating at the disk surface. The cold MHD solutions are found to
be inadequate to account for winds due to their low ejection efficiency. The
warm solutions can have sufficiently high values of $p (\gtrsim 0.1)$ which is
required to explain the observed physical quantities in the wind. The heating
(required at the disk surface for the warm solutions) could be due to the
illumination which would be more efficient in the Soft state. We found that in
the Hard state a range of ionisation parameter is thermodynamically unstable,
which makes it impossible to have any wind at all, in the Hard state. Our
results would suggest that a thermo-magnetic process is required to explain
winds in BHBs.Comment: Draft contains 6 pages and 6 figures. Accepted for publication in
  Astronomical Notes (AN) as Conference Proceedings of XMM-Newton 2015 Science
  Workshop - The Extremes of Black Hole Accretio
Systematic spectral analysis of GX 339-4: influence of Galactic
  background and reflection models

Black hole X-ray binaries display large outbursts, during which their
properties are strongly variable. We develop a systematic spectral analysis of
the 3-40 keV RXTE/PCA data in order to study the evolution of these systems and
apply it to GX 339-4. Using the low count rate observations, we provide a
precise model of the Galactic background at GX 339-4's location and discuss its
possible impact on the source spectral parameters. At higher fluxes, the use of
a Gaussian line to model the reflection component can lead to the detection of
a high-temperature disk, in particular in the high-hard state. We demonstrate
that this component is an artifact arising from an incomplete modeling of the
reflection spectrum.Comment: 6 pages, 3 figures, Proceeding of the XMM-Newton 2015 Science
  Workshop 'The Extremes of Black Hole Accretion', Accepted for publication in
  Astronomical Note
An Intermediate-Mass Black Hole Candidate in M51?

We present the current results of an investigation into M51 ULX-7, using
archival data from XMM-Newton, Chandra and NuSTAR, and optical and radio data
from HST and VLA. The source has a consistently hard power-law X-ray spectrum
and high short-term variability. This is unusual variability behaviour for a
ULX, as we would expect highly variable ULXs to have soft energy spectra. The
power spectrum features a break at ~1e-3 Hz, from low frequency spectral index
alpha=0.1 to high frequency spectral index alpha=0.8, analogous to the low
frequency break found in power spectra of black holes accreting in the low/hard
state. We do not observe a corresponding high frequency break, however taking
the white noise level as a frequency lower limit of the break, we can calculate
a black hole mass upper limit of 9.12e4 solar masses, assuming that the ULX is
in the low/hard state. While there is no radio detection, we find a flux
density upper limit of 87 micro-Jy/beam. Using the X-ray/radio fundamental
plane, we calculate a black hole mass upper limit of 1.95e5 solar masses.
Therefore, this ULX is consistent with being an IMBH accreting in the low/hard
state.Comment: 6 pages, 4 figures, conference proceedings from the 2015 XMM-Newton
  Science Workshop, to be published in Astronomical Notes (Astronomische
  Nachrichten
Unveiling the X-ray/UV properties of disk winds in active galactic
  nuclei using broad and mini-broad absorption line quasars

We present the results of the uniform analysis of 46 XMM-Newton observations
of six BAL and seven mini-BAL QSOs belonging to the Palomar-Green Quasar
catalogue. Moderate-quality X-ray spectroscopy was performed with the EPIC-pn,
and allowed to characterise the general source spectral shape to be complex,
significantly deviating from a power law emission. A simple power law analysis
in different energy bands strongly suggests absorption to be more significant
than reflection in shaping the spectra. If allowing for the absorbing gas to be
either partially covering the continuum emission source or to be ionised, large
column densities of the order of $10^{22-24}$ cm$^{-2}$ are inferred. When the
statistics was high enough, virtually every source was found to vary in
spectral shape on various time scales, from years to hours. All in all these
observational results are compatible with radiation driven accretion disk winds
shaping the spectra of these intriguing cosmic sources.Comment: 7 pages, 2 figures. Proceedings of the 2015 XMM-Newton workshop: "The
  Extremes of Black Hole Accretion". Accepted for publication in Astronomische
  Nachrichten/Astronomical Note
A New Characterization of the Compton Process in the ULX Spectra

Attempts were made to construct a unified description of the spectra of ULX
(Ultra Luminous X-ray source) objects, including their Power-Law (PL) state and
Disk-like state. Among spectral models proposed to explain either state, the
present work adopts the one which combines multi-color disk (MCD) emission and
its thermal Comptonization (THC). This model was applied to several datasets of
ULXs obtained by Suzaku, XMM-Newton, and Nustar. The model well explains all
the spectra, regardless of the spectral states, in terms of a cool disk (inner
radius temperature of 0.2-0.5 keV) and a cool thick (electron temperature of
1-3 keV, and optical thickness ~10) corona. The fit results can be
characterized by two new parameters. One is Q (defined as the electron
temerature divided by the inner radius temperature) which describes balance
between the Compton cooling and gravitational heating of the coronal electrons,
while the other is F, namely, the covering fraction of the MCD by the corona.
Here, F is calculated from the percentage of the directly-visible disk
luminosity in the total radiation. Then, the PL-state spectra have been found
to show Q~10 and F~0.5, while those of the Disk-like state Q~3 and F~1. Thus,
the two states are clearly separated in terms of Q and F. The obtained results
are employed to argue for their interpretation in terms of high-mass (several
tens to several hundreds solar masses) black holes.Comment: 6 pages, 3 figures. Proceedings of the 2015 XMM-Newton science
  workshop 'The extremes of black hole accretion', Madrid, 2015
  (http://xmm.esac.esa.int/external/xmm_science/workshops/2015_science/).
  Accepted for publication in Astronomische Nachrichte
The coronal parameters of local Seyfert galaxies

One of the open problems for AGN is the nature of the primary X-ray emission:
it is likely due to Comptonization of soft UV photons, but the optical depth
and temperature of the emitting corona were largely unknown before the launch
of the Nuclear Spectroscopic Telescope Array (NuSTAR). It is the first focusing
hard X-ray telescope on orbit, 100 times more sensitive in the 10-79 keV band
compared to previous observatories, enabling the study of AGN at high energies
with high precision. We present and discuss the results on the hot corona
parameters of Active Galactic Nuclei that have been recently measured with
NuSTAR (often in coordination with XMM-Newton, Suzaku or Swift) with
unprecedented accuracy, in a number of local Seyfert galaxies.Comment: 6 pages, 3 figures, accepted for publication on Astronomische
  Nachrichten/Astronomical Notes, proceedings of "The Extremes of Black Hole
  Accretion