4,240 research outputs found
Swift J053041.9-665426, a new Be/X-ray binary pulsar in the Large Magellanic Cloud
We observed the newly discovered X-ray source Swift J053041.9-665426 in the
X-ray and optical regime to confirm its proposed nature as a high mass X-ray
binary. We obtained XMM-Newton and Swift X-ray data, along with optical
observations with the ESO Faint Object Spectrograph, to investigate the
spectral and temporal characteristics of Swift J053041.9-665426. The XMM-Newton
data show coherent X-ray pulsations with a period of 28.77521(10) s (1 sigma).
The X-ray spectrum can be modelled by an absorbed power law with photon index
within the range 0.76 to 0.87. The addition of a black body component increases
the quality of the fit but also leads to strong dependences of the photon
index, black-body temperature and absorption column density. We identified the
only optical counterpart within the error circle of XMM-Newton at an angular
distance of ~0.8 arcsec, which is 2MASS J05304215-6654303. We performed optical
spectroscopy from which we classify the companion as a B0-1.5Ve star. The X-ray
pulsations and long-term variability, as well as the properties of the optical
counterpart, confirm that Swift J053041.9-665426 is a new Be/X-ray binary
pulsar in the Large Magellanic Cloud.Comment: 10 pages, 8 figures, accepted for publication in A&
Discovery of a 168.8 s X-ray pulsar transiting in front of its Be companion star in the Large Magellanic Cloud
We report the discovery of LXP169, a new high-mass X-ray binary (XRB) in the
LMC. The optical counterpart has been identified and appears to exhibit an
eclipsing light curve. We performed follow-up observations to clarify the
eclipsing nature of the system. Energy spectra and time series were extracted
from two XMM-Newton observations to search for pulsations, characterise the
spectrum, and measure spectral and timing changes. Long-term X-ray variability
was studied using archival ROSAT data. The XMM positions were used to identify
the optical counterpart. We obtained UV to NIR photometry to characterise the
companion, along with its 4000 d long I-band light curve. We observed LXP169
with Swift at two predicted eclipse times. We found a spin period of 168.8 s
that did not change between two XMM observations. The X-ray spectrum, well
characterised by a power law, was harder when the source was brighter. The
X-ray flux of LXP169 is found to be variable by a factor of at least 10. The
counterpart is highly variable on short and long timescales, and its photometry
is that of an early-type star with a NIR excess. This classifies the source as
a BeXRB pulsar. We observed a transit in the UV, thereby confirming that the
companion star itself is eclipsed. We give an ephemeris for the transit of MJD
56203.877 + N*24.329. We propose and discuss the scenario where the matter
captured from the companion's equatorial disc creates an extended region of
high density around the neutron star (NS), which partially eclipses the
companion as the NS transits in front of it. This is most likely the first time
the compact object in an XRB is observed to eclipse its companion star. LXP169
would be the first eclipsing BeXRB, and a wealth of important information might
be gained from additional observations, such as a measure of the possible Be
disc/orbital plane misalignment, or the mass of the NS.Comment: Updated version of arXiv 1302.4665v1, accepted for publication in
Astronomy and Astrophysics. 11 pages, 8 figures, 3 table
Imaging density disturbances in water with 41.3 attosecond time resolution
We show that the momentum flexibility of inelastic x-ray scattering may be
exploited to invert its loss function, alowing real time imaging of density
disturbances in a medium. We show the disturbance arising from a point source
in liquid water, with a resolution of 41.3 attoseconds (
sec) and 1.27 ( cm). This result is used to
determine the structure of the electron cloud around a photoexcited molecule in
solution, as well as the wake generated in water by a 9 MeV gold ion. We draw
an analogy with pump-probe techniques and suggest that energy-loss scattering
may be applied more generally to the study of attosecond phenomena.Comment: 4 pages, 4 color figure
A new super-soft X-ray source in the Small Magellanic Cloud: Discovery of the first Be/white dwarf system in the SMC?
The Small Magellanic Cloud (SMC) hosts a large number of Be/X-ray binaries,
however no Be/white dwarf system is known so far, although population synthesis
calculations predict that they might be more frequent than Be/neutron star
systems. XMMUJ010147.5-715550 was found as a new faint super-soft X-ray source
(SSS) with a likely Be star optical counterpart. We investigate the nature of
this system and search for further high-absorbed candidates in the SMC. We
analysed the XMM-Newton X-ray spectrum and light curve, optical photometry, and
the I-band OGLE III light curve. The X-ray spectrum is well represented by
black-body and white dwarf atmosphere models with highly model-dependent
temperature between 20 and 100 eV. The likely optical counterpart AzV 281
showed low near infrared emission during X-ray activity, followed by a
brightening in the I-band afterwards. We find further candidates for
high-absorbed SSSs with a blue star as counterpart. We discuss
XMMUJ010147.5-715550 as the first candidate for a Be/white dwarf binary system
in the SMC.Comment: 6 pages, 4 figures, accepted by A&
Angle-dependence of the Hall effect in HgBa2CaCu2O6 thin films
Superconducting compounds of the family Hg-Ba-Ca-Cu-O have been the subject
of intense study since the current record-holder for the highest critical
temperature of a superconductor belongs to this class of materials. Thin films
of the compound with two adjacent copper-oxide layers and a critical
temperature of about 120 K were prepared by a two-step process that consists of
the pulsed-laser deposition of precursor films and the subsequent annealing in
mercury-vapor atmosphere. Like some other high-temperature superconductors,
Hg-Ba-Ca-Cu-O exhibits a specific anomaly of the Hall effect, a double-sign
change of the Hall coefficient close to the superconducting transition. We have
investigated this phenomenon by measurements of the Hall effect at different
angles between the magnetic field direction and the crystallographic c-axis.
The results concerning the upper part of the transition, where the first sign
change occurs, are discussed in terms of the renormalized fluctuation model for
the Hall conductivity, adapted through the field rescaling procedure in order
to take into account the arbitrary orientation of the magnetic field.Comment: to be published in Phys. Rev.
The KATRIN Experiment
The KArlsruhe TRitium Neutrino mass experiment, KATRIN, aims to search for
the mass of the electron neutrino with a sensitivity of 0.2 eV/c^2 (90% C.L.)
and a detection limit of 0.35 eV/c^2 (5 sigma). Both a positive or a negative
result will have far reaching implications for cosmology and the standard model
of particle physics and will give new input for astroparticle physics and
cosmology. The major components of KATRIN are being set up at the Karlsruhe
Institut of Technology in Karlsruhe, Germany, and test measurements of the
individual components have started. Data taking with tritium is scheduled to
start in 2012.Comment: 3 pages, 1 figure, proceedings of the TAUP 2009 International
Conference on Topics in Astroparticle and Underground Physics, to be
published in Journal of Physics, Conference Serie
AGN behind the SMC selected from radio and X-ray surveys
The XMM-Newton survey of the Small Magellanic Cloud (SMC) revealed 3053 X-ray
sources with the majority expected to be active galactic nuclei (AGN) behind
the SMC. However, the high stellar density in this field often does not allow
assigning unique optical counterparts and hinders source classification. On the
other hand, the association of X-ray point sources with radio emission can be
used to select background AGN with high confidence, and to constrain other
object classes like pulsar wind nebula. To classify X-ray and radio sources, we
use clear correlations of X-ray sources found in the XMM-Newton survey with
radio-continuum sources detected with ATCA and MOST. Deep radio-continuum
images were searched for correlations with X-ray sources of the XMM-Newton
SMC-survey point-source catalogue as well as galaxy clusters seen with extended
X-ray emission. Eighty eight discrete radio sources were found in common with
the X-ray point-source catalogue in addition to six correlations with extended
X-ray sources. One source is identified as a Galactic star and eight as
galaxies. Eight radio sources likely originate in AGN that are associated with
clusters of galaxies seen in X-rays. One source is a PWN candidate. We obtain
43 new candidates for background sources located behind the SMC. A total of 24
X-ray sources show jet-like radio structures.Comment: 9 pages, 6 figures, accepted for publication in A&
The XMM-Newton survey of the Small Magellanic Cloud: The X-ray point-source catalogue
Local-Group galaxies provide access to samples of X-ray source populations of
whole galaxies. The XMM-Newton survey of the Small Magellanic Cloud (SMC)
completely covers the bar and eastern wing with a 5.6 deg^2 area in the
(0.2-12.0) keV band. To characterise the X-ray sources in the SMC field, we
created a catalogue of point sources and sources with moderate extent. Sources
with high extent (>40") have been presented in a companion paper. We searched
for point sources in the EPIC images using sliding-box and maximum-likelihood
techniques and classified the sources using hardness ratios, X-ray variability,
and their multi-wavelength properties. The catalogue comprises 3053 unique
X-ray sources with a median position uncertainty of 1.3" down to a flux limit
for point sources of ~10^-14 erg cm^-2 s^-1 in the (0.2-4.5) keV band,
corresponding to 5x10^33 erg s^-1 for sources in the SMC. We discuss
statistical properties, like the spatial distribution, X-ray colour diagrams,
luminosity functions, and time variability. We identified 49 SMC high-mass
X-ray binaries (HMXB), four super-soft X-ray sources (SSS), 34 foreground
stars, and 72 active galactic nuclei (AGN) behind the SMC. In addition, we
found candidates for SMC HMXBs (45) and faint SSSs (8) as well as AGN (2092)
and galaxy clusters (13). We present the most up-to-date catalogue of the X-ray
source population in the SMC field. In particular, the known population of
X-ray binaries is greatly increased. We find that the bright-end slope of the
luminosity function of Be/X-ray binaries significantly deviates from the
expected universal high-mass X-ray binary luminosity function.Comment: 32 pages, 18 figures, accepted for publication in A&A, catalog will
be available at CD
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