pinecone/core-2020-05-10-deduplication huggingface dataset:
Compact radio emission in Ultraluminous X-ray sources

We present results from our studies of radio emission from selected
Ultraluminous X-ray (ULX) sources, using archival Giant Metrewave Radio
Telescope (GMRT) data and new European VLBI Network (EVN) observations. The
GMRT data are used to find possible faint radio emission from ULX sources
located in late-type galaxies in the Chandra Deep Fields. No detections are
found at 235, 325 and 610 MHz, and upper limits on the radio flux densities at
these frequencies are given. The EVN observations target milliarcsecond-scale
structures in three ULXs with known radio counterparts (N4449- X1, N4088-X1,
and N4861-X2). We confirm an earlier identification of the ULX N4449-X1 with a
supernova remnant and obtain the most accurate estimates of its size and age.
We detect compact radio emission for the ULX N4088-X1, which could harbour an
intermediate mass black hole (IMBH) of 10^5 M\odot accreting at a sub-Eddington
rate. We detect a compact radio component in the ULX N4861-X2, with a
brightness temperature > 10^6 K and an indication for possible extended
emission. If the extended structure is confirmed, this ULX could be an HII
region with a diameter of 8.6 pc and surface brightness temperature \geq 10^5
K. The compact radio emission may be coming from a ~ 10^5 M\odot black hole
accreting at 0.1M_Edd.Comment: 5 pages, 6 figures. Accepted for publication in the Astronomische
  Nachrichte
A search for radio counterparts to Chandra ULX candidates

We present a systematic search for radio counterparts to Ultra Luminous X-ray
(ULX) source candidates based on a cross-correlation of the Swartz et al.
(2004) ULX catalogue based on Chandra data and the FIRST radio survey. We find
seven cases of conspiscuous peaks of radio emission that could be associated to
ULX sources. Among these seven ULX radio candidates, three X-ray sources are
located within 5" of the FIRST radio peaks. These three cases are shown and
discussed individually.Comment: 5 pages, 3 figures. Accepted for publication in the Astronomische
  Nachrichten, to appear in the proceedings of the conference "Ultra-Luminous
  X-ray sources and Middle Weight Black Holes" (Madrid, May 24-26, 2010).
  Resubmission corrects the Authors list and the acknowledgement
Exploring the Nature of the Brightest Hyper-luminous X-ray Source

The small subset of hyper-luminous X-ray sources with luminosities in excess
of ~1E41 erg/s are hard to explain without the presence of an intermediate mass
black hole, as significantly super-Eddington accretion and/or very small
beaming angles are required. The recent discovery of HLX-1, the most luminous
object in this class with a record breaking luminosity of ~1E42 erg/s in the
galaxy ESO 243-49, therefore currently provides some of the strongest evidence
for the existence of intermediate mass black holes. HLX-1 is almost an order of
magnitude brighter than the other hyper-luminous sources, and appears to
exhibit X-ray spectral and flux variability similar to Galactic stellar mass
black hole X-ray binaries. In this paper we review the current state of
knowledge on this intriguing source and outline the results of multi-wavelength
studies from radio to ultra-violet wavelengths, including imaging and
spectroscopy of the recently identified optical counterpart obtained with the
Very Large Telescope. These results continue to support an intermediate mass
black hole in excess of 500 MsunComment: 6 pages, 6 figures. Accepted for publication in the Astronomische
  Nachrichten, to appear in the proceedings of the conference "Ultra-Luminous
  X-ray sources and Middle Weight Black Holes" (Madrid, May 24-26, 2010
Remnants of massive metal-poor stars: viable engines for ultra-luminous
  X-ray sources

Massive metal-poor stars might end their life by directly collapsing into
massive (~25-80 Msun) black holes (BHs). We derive the number of massive BHs
(N_BH) that are expected to form per galaxy via this mechanism. We select a
sample of 66 galaxies with X-ray coverage, measurements of the star formation
rate (SFR) and of the metallicity. We find that N_BH correlates with the number
of observed ultra-luminous X-ray sources (ULXs) per galaxy (N_ULX) in this
sample. We discuss the dependence of N_ULX and of N_BH on the SFR and on the
metallicity.Comment: 4 pages, 3 figures, accepted for publication in the Astronomische
  Nachrichten, to appear in the proceedings of the conference "Ultra-luminous
  X-ray sources and Middle Weight Black Holes" (Madrid, May 24-26, 2010
The metallicity of the nebula surrounding the ultra-luminous X-ray
  source NGC 1313 X-2

Recent models of the formation of ultra-luminous X-ray sources (ULXs) predict
that they preferentially form in low-metallicity environments. We look at the
metallicity of the nebula surrounding NGC 1313 X-2, one of the best-studied
ULXs. Simple estimates, based on the extrapolation of the metallicity gradient
within NGC 1313, or on empirical calibrations (relating metallicity to strong
oxygen lines) suggest a quite low metal content (Z ~ 0.1 Zsun). But such
estimates do not account for the remarkably strong X-ray flux irradiating the
nebula. Then, we build photoionization models of the nebula using CLOUDY; using
such models, the constraints on the metallicity weaken substantially, as we
find 0.15 Zsun <= Z <= 0.5 Zsun.Comment: 4 pages. Accepted for publication in the Astronomische Nachrichten,
  to appear in the proceedings of the conference "Ultra-Luminous X-ray sources
  and Middle Weight Black Holes" (Madrid, May 24-26, 2010
The black hole in NGC 1313 X-2

The amount of data available for NGC 1313 X-2 make it a cornerstone for the
study of ultraluminous X-ray sources (ULXs). We modelled the optical and X-ray
data of this ULX with a binary evolution code that takes into account X-ray
irradiation. We restricted the candidate binary system to be either a 50-100
Msun black hole (BH) accreting from a 12-15 Msun main sequence star or a 20
Msun BH with a 12-15 Msun giant donor. If the orbital period of the system is
~6 days, a 20 Msun BH model becomes unlikely and we are left with the only
possibility that the compact accretor in NGC1313 X-2 is a massive BH of 50-100
Msun. We briefly discuss these results within the framework of an alternative
scenario for the formation of ULXs, in which a portion of them may contain BHs
of >~30-40 Msun formed from very massive stars in a low metallicity
environment.Comment: 4 pages, 2 figures. Accepted for publication in the Astronomische
  Nachrichten (Astronomical Notes), to appear in the proceedings of the
  conference "Ultra-Luminous X-ray sources and Middle Weight Black Holes"
  (Madrid, May 24-26, 2010
The Effelsberg-Bonn HI Survey (EBHIS)

The Effelsberg-Bonn HI survey (EBHIS) comprises an all-sky survey north of
Dec = -5 degrees of the Milky Way and the local volume out to a red-shift of z
~ 0.07. Using state of the art Field Programmable Gate Array (FPGA)
spectrometers it is feasible to cover the 100 MHz bandwidth with 16.384
spectral channels. High speed storage of HI spectra allows us to minimize the
degradation by Radio Frequency Interference (RFI) signals. Regular EBHIS survey
observations started during the winter season 2008/2009 after extensive system
evaluation and verification tests. Until today, we surveyed about 8000 square
degrees, focusing during the first all-sky coverage of the Sloan-Digital Sky
Survey (SDSS) area and the northern extension of the Magellanic stream. The
first whole sky coverage will be finished in 2011. Already this first coverage
will reach the same sensitivity level as the Parkes Milky Way (GASS) and
extragalactic surveys (HIPASS). EBHIS data will be calibrated, stray-radiation
corrected and freely accessible for the scientific community via a
web-interface. In this paper we demonstrate the scientific data quality and
explore the expected harvest of this new all-sky survey.Comment: 19 pages, 11 figures, accepted for publication by Astronomical Note
Nonthermal emission from the radio relic of the galaxy cluster A2256

We aim to obtain a consistent description of non-thermal emissions from Abell
2256 and to give a prediction for a gamma-ray emission from this galaxy
cluster. Assuming that a radio relic illuminates a localization of an ongoing
merger, and that both radio and non-thermal part of hard X-ray emission are due
to electron component of cosmic rays filling the relic, we derived from radio
and hard X-ray properties of the relic in A2256 the magnetic field strength and
number densities for relativistic electrons and protons. Due to the
interpretation of the radio relic as a structure formed just where a shock
front is, we discuss a gamma-ray emission at the cluster periphery. The
estimated strength of the magnetic field in the relic is equal to 0.05 \muG,
while the amplitude of the electron number density varies from 3 x 10^{-4} to 3
x 10^{-5} cm^{-3} (respectively for the relic thickness of 50 to 500 kpc). We
got a substantial degree of non-equipartition between cosmic rays and magnetic
field in the relic region, where the CR pressure is approaching that of thermal
gas. Our prediction for LOFAR is a synchrotron flux from the relic region of
the order of \sim 6 Jy at 60MHz and \sim 10 Jy at 30MHz. The lower limit of the
gamma-ray flux from the relic region calculated for a hadronic channel is of
the order of 10^{-12} erg cm^{-2}.Comment: 6 pages, 1 figure, Accepted for publication in A
The short-period low-mass binary system CC Com revisited

In this study we determined precise orbital and physical parameters of the very short-period low-mass contact binary system CC Com. The parameters are obtained by analysis of new CCD data combined with archival spectroscopic data. The physical parameters of the cool and hot components are derived as Mc = 0.717(14) M⊙, Mh = 0.378(8) M⊙, Rc = 0.708(12) R⊙, Rh = 0.530(10) R⊙, Lc = 0.138(12) L⊙, and Lh = 0.085(7) L⊙, respectively, and the distance of the system is estimated as 64(4) pc. The times of minima obtained in this study and with those published before enable us to calculate the mass transfer rate between the components which is 1.6 × 10-8 M⊙ yr-1. Finally, we discuss the possible evolutionary scenario of CC Com.Turkish Scientiﬁc and Research Council (TUBITAK 109T047); TUBITAK National Observatory (TUG); Ege University; Turkish Academy of Sciences (TUBA
On global solar dynamo simulations

Global dynamo simulations solving the equations of magnetohydrodynamics (MHD)
have been a tool of astrophysicists who try to understand the magnetism of the
Sun for several decades now. During recent years many fundamental issues in
dynamo theory have been studied in detail by means of local numerical
simulations that simplify the problem and allow the study of physical effects
in isolation. Global simulations, however, continue to suffer from the age-old
problem of too low spatial resolution, leading to much lower Reynolds numbers
and scale separation than in the Sun. Reproducing the internal rotation of the
Sun, which plays a crucual role in the dynamo process, has also turned out to
be a very difficult problem. In the present paper the current status of global
dynamo simulations of the Sun is reviewed. Emphasis is put on efforts to
understand how the large-scale magnetic fields, i.e. whose length scale is
greater than the scale of turbulence, are generated in the Sun. Some lessons
from mean-field theory and local simulations are reviewed and their possible
implications to the global models are discussed. Possible remedies to some
current issues of solar simulations are put forward.Comment: 8 pages, published versio
An X-shooter survey of star forming regions: Low-mass stars and sub-stellar objects

We present preliminary results of our X-shooter survey in star forming regions. In this contribution we focus on sub-samples of young stellar and sub-stellar objects (YSOs) in the Lupus star forming region and in the TW Hya association. We show that the X-shooter spectra are suitable for conducting several parallel studies such as YSO + disk fundamental parameters, accretion and outflow activity in the very low-mass (VLM) and sub-stellar regimes, as well as magnetic activity in young VLM YSOs, and Li abundance determinations. The capabilities of X-shooter in terms of wide spectral coverage, resolution and limiting magnitudes, allow us to assess simultaneously the accretion/outflow, magnetic activity, and disk diagnostics, from the UV and optical to the near-IR, avoiding ambiguities due to possible YSO variability.\ud
\ud
Based on observations collected at the European Southern Observatory, Chile, under Programmes 084.C-0269 and 085.C-0238
Studying the SN-GRB connection with X-shooter: The GRB 100316D / SN
  2010bh case

During the last ten years, observations of long-duration gamma-ray bursts
brought to the conclusion that at least a fraction of them is associated with
bright supernovae of type Ib/c. In this talk, after a short review on the
previously observed GRB-SN connection cases, we present the recent case of GRB
100316/SN 2010bh. In particular, during the observational campaign of SN
2010bh, a pivotal role was played by VLT/X-shooter, sampling with unique high
quality data the spectral energy distribution of the early evolution phases
from the UV to the K band.Comment: 4 pages, 2 figure. Proceedings of the workshop "The first year with
  X-shooter" October 19-22 2010, Como, Italy. References adde
The Bar and Spiral Structure Legacy (BeSSeL) Survey: Mapping the Milky
  Way with VLBI Astrometry

Astrometric Very Long Baseline Interferometry (VLBI) observations of maser
sources in the Milky Way are used to map the spiral structure of our Galaxy and
to determine fundamental parameters such as the rotation velocity ($\Theta_0$)
and curve and the distance to the Galactic center (R$_0$). Here, we present an
update on our first results, implementing a recent change in the knowledge
about the Solar motion. It seems unavoidable that the IAU recommended values
for R$_0$ and $\Theta_0$ need a substantial revision. In particular the
combination of 8.5 kpc and 220 \kms\, can be ruled out with high confidence.
Combining the maser data with the distance to the Galactic center from stellar
orbits and the proper motion of Sgr\,A* gives best values of R$_0$ = 8.3 $\pm$
0.23 kpc and $\Theta_0$ = 239 or 246 $\pm$ 7 \kms, for Solar motions of V$_
\odot$ = 12.23 and 5.25 \kms, respectively. Finally, we give an outlook to
future observations in the Bar and Spiral Structure Legacy (BeSSeL) Survey.Comment: 6 pages, 3 figures. 'Highlight talk' held at the Meeting of the
  Astronomische Gesellschaft (2010). To be published in Reviews in Modern
  Astronomy, Volume 2
The absorption and emission spectrum of the magnetic Herbig Ae star HD 190073

We determine abundances from the absorption spectrum of the magnetic Herbig Ae star HD 190073 (V1295 Aql). The observations are primarily from HARPS spectra obtained at a single epoch. We accept arguments that the presence of numerous emission lines does not vitiate a classical abundance analysis, though it likely reduces the achievable accuracy. Most abundances are closely solar, but several elements show departures of a factor of two to three, as an earlier study has also shown. We present quantitative measurements of more than 60 emission lines, peak intensities, equivalent widths, and FWHM's. The latter range from over 200 km s –1 (H α , He D 3 ) down to 10–20 km s –1 (forbidden lines). Metallic emission lines have intermediate widths. We eschew modeling, and content ourselves with a presentation of the observations a successful model must explain. Low‐excitation features such as the Na I D‐lines and [O I] appear with He I D 3 , suggesting proximate regions with widely differing  T  e  and  N  e  as found in the solar chromosphere. The [O I] and [Ca II] lines show sharp, violet‐shifted features. Additionally, [Fe II] lines appear tobe weakly present in emission (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim
Spectroscopic variability and magnetic fields of HgMn stars

The discovery of exotic abundances, chemical inhomogeneities, and weak magnetic fields on the surface of late B‐type primaries in spectroscopic binaries has important implications not only for our understanding of the formation mechanisms of stars with Hg and Mn peculiarities themselves, but also for the general understanding of B‐type star formation in binary systems. The origin of the abundance anomalies observed in late B‐type stars with HgMn peculiarity is still poorly understood. The connection between HgMn peculiarity and membership in binary and multiple systems is supported by our observations during the last decade. The important result achieved in our studies of a large sample of HgMn stars is the finding that most HgMn stars exhibit spectral variability of various chemical elements, proving that the presence of an inhomogeneous distribution on the surface of these stars is a rather common characteristic and not a rare phenomenon. Further, in the studied systems, we found that all components are chemically peculiar with different abundance patterns. Generally, He and Si variable Bp stars possess large‐scale organised magnetic fields that in many cases appear to occur essentially in the form of a single large dipole located close to the centre of the star. The presence of magnetic fields in the atmospheres of HgMn stars has been demonstrated in several studies. In addition to the measurements of longitudinal and quadratic magnetic fields, this work also showed evidence for a relative magnetic intensification of Fe II lines produced by different magnetic desaturations induced by different Zeeman‐split components (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim
Angular momentum transport by thermal emission in black hole accretion
  disks

We calculate the amount of angular momentum that thermal photons carry out of
a viscous black hole accretion disc, due to the strong Doppler shift imparted
to them by the high orbital velocity of the radiating disc material. While the
emission of radiation can not drive accretion on its own, we find that it does
result in a loss of specific angular momentum, thereby contributing to an
otherwise viscosity-driven accretion flow. In particular, we show that the
fraction of the angular momentum that is lost to thermal emission at a radius r
in a standard, multi-color disc is ~ 0.4r_s/r, where r_s is the Schwarzschild
radius of the black hole. We briefly highlight the key similarities between
this effect and the closely related Poynting-Robertson effect.Comment: 6 pages, 2 figures; to appear in A
Recent studies of magnetic fields in Herbig Ae/Be stars

New determinations of the mean longitudinal magnetic field for several Herbig Ae/Be stars are presented. The longitudinal magnetic field measurements of MWC 480 reveal the presence of a strong kG field, which was undetected in our previous low‐resolution polarimetric observations with FORS 1. The magnetic field geometries of Herbig Ae/Be stars studied with spectropolarimetric time series can likely be described by centred dipoles with polar magnetic field strengths of several hundred Gauss. A number of Herbig Ae/Be stars with detected magnetic fields were recently observed with X‐shooter in the visible and near‐IR as well as with the high‐resolution near‐IR spectrograph CRIRES. These observations are of great importance to understand the relation between the magnetic field topology and the physics of accretion flow and accretion disk gas emission (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim
Delta Scuti stars in the Praesepe cluster observed by the MOST satellite

The Praesepe cluster contains a number of Delta Sct and Gamma Dor pulsators.
Asteroseismology of cluster stars is simplified by the common distance, age and
stellar abundances. Since asteroseismology requires a large number of known
frequencies, the small pulsation amplitudes of these stars require space
satellite campaigns. The present study utilizes photometric MOST satellite
measurements in order to determine the pulsation frequencies of two evolved (EP
Cnc, BT Cnc) and two main-sequence (BS Cnc, HD 73872) Delta Sct stars in the
Praesepe cluster. The frequency analysis of the 2008 and 2009 data detected up
to 34 frequencies per star with most amplitudes in the submillimag range. In BS
Cnc, two modes showed strong amplitude variability between 2008 and 2009. The
frequencies ranged from 0.76 to 41.7 c/d. After considering the different
evolutionary states and mean stellar densities of these four stars, the
differences and large ranges in frequency remain.Comment: Accepted for publication in Astronomische Nachrichten / Astronomical
  Note
Recent photometry of symbiotic stars - XIII

We present new multicolour (UBVRcIc) photometric observations of classical
symbiotic stars, EG And, Z And, BF Cyg, CH Cyg, CI Cyg, V1329 Cyg, TX CVn, AG
Dra, Draco C1, AG Peg and AX Per, carried out between 2007.1 and 2011.9. The
aim of this paper is to present new data of our monitoring programme, to
describe the main features of their light curves and to point problems for
their future investigation. The data were obtained by the method of the
classical photoelectric and CCD photometry.Comment: 39 pages, 16 figures, 16 tables (tables 2-16 are available also in
  the electronic form
The significance of the Hansen Ideal space frame

Known and unknown properties of Hansen Ideal coordinates are summarized. It is shown that the ideal space frame is a general and necessary component of basic celestial mechanics and astrodynamics, as well as of any theory of motion. A typical consequence is the intimate correlation of the Hansen frame with the Lagrange constraint within the method of the variation of the parameters. The use of observations in the ideal frame may allow conclusions on the intergalactic fundamental coordinate system
Space Astronomy for the mid-21st Century: Robotically Maintained Space
  Telescopes

The historical development of ground based astronomical telescopes leads us
to expect that space-based astronomical telescopes will need to be operational
for many decades. The exchange of scientific instruments in space will be a
prerequisite for the long lasting scientific success of such missions.
Operationally, the possibility to repair or replace key spacecraft components
in space will be mandatory. We argue that these requirements can be fulfilled
with robotic missions and see the development of the required engineering as
the main challenge. Ground based operations, scientifically and technically,
will require a low operational budget of the running costs. These can be
achieved through enhanced autonomy of the spacecraft and mission independent
concepts for the support of the software. This concept can be applied to areas
where the mirror capabilities do not constrain the lifetime of the mission.Comment: 4 pages, accepted in February 2012 for publication in A
Spectroscopic evidence of charge exchange X-ray emission from galaxies

What are the origins of the soft X-ray line emission from non-AGN galaxies?
XMM-Newton RGS spectra of nearby non-AGN galaxies (including starforming ones:
M82, NGC 253, M51, M83, M61, NGC 4631, M94, NGC 2903, and the Antennae
galaxies, as well as the inner bulge of M31) have been analyzed. In particular,
the K{\alpha} triplet of O VII shows that the resonance line is typically
weaker than the forbidden and/or inter-combination lines. This suggests that a
substantial fraction of the emission may not arise directly from optically thin
thermal plasma, as commonly assumed, and may instead originate at its interface
with neutral gas via charge exchange. This latter origin naturally explains the
observed spatial correlation of the emission with various tracers of cool gas
in some of the galaxies. However, alternative scenarios, such as the resonance
scattering by the plasma and the relic photo-ionization by AGNs in the recent
past, cannot be ruled out, at least in some cases, and are being examined. Such
X-ray spectroscopic studies are important to the understanding of the
relationship of the emission to various high-energy feedback processes in
galaxies.Comment: 5 pages, published in Astronomical Notes, for "Charge exchange in the
  Universe" workshop, Paris 201