203 research outputs found
Cyclotron lines in X-ray pulsars as a probe of relativistic plasmas in superstrong magnetic fields
The systematic search for the presence of cyclotron lines in the spectra of
accreting X-ray pulsars is being carried on with the BeppoSAX satellite since
the beginning of the mission. These highly successful observations allowed the
detection of cyclotron lines in many of the accreting X-ray pulsars observed.
Some correlations between the different measured parameters were found. We
present these correlations and discuss them in the framework of the current
theoretical scenario for the X-ray emission from these sources.Comment: 5 pages, 2 figures, uses aipproc.sty, to appear in Proceeding of
Fifth Compton Symposiu
The pulse phase-dependent spectrum of the anomalous X-ray pulsar 1RXS J170849-400910
We report on the results of a 50ks BeppoSAX observation of 1RXS
J170849-400910, one of the five (plus a candidate) known anomalous X-ray
pulsars. The BeppoSAX data are consistent with a power-law plus blackbody
spectral decomposition, making 1RXS J170849-400910 the fourth source of this
class for which such a spectral decomposition was found. The inferred power-law
slope and blackbody temperature are Gamma~2.6 and kT_BB~0.46keV, respectively.
We found significant energy-dependence of the pulse profile, a remarkable
feature for an AXP. By using the power-law plus blackbody decomposition we
detected a significant variation in at least one spectral parameter, the
power-law photon index, as a function of the pulse phase. This is the first
significant detection of spectral parameter variation in an AXP. The
implications of these results are briefly discussed.Comment: 5 pages. Accepted for publication on ApJ Letters. emulateapj5.sty
macro use
Evaluation of Anti-Hyperlipidemic Activity of Ethanolic Extract of Cassia Fistula Leaf
The present study was designed to perform evaluate antihyperglycemic activity of ethanolic extract of Cassia Fistula leaf. Leaf of cassia fistula was extracted using ethanol as solvent by soxhlet apparatus. The evaluation of antihyperlipidemic activity was done using High Fat Diet induced hyperlipidemia models in Wistar albino rats. The work entitled evaluation of anti-obesity activity of leaf of Cassia fistula was to determine the efficacy and safety in experimental animals. Both aqueous and alcoholic extract of leaf of Cassia Fistula (Linn.) have shown significant reduction in weight of heart and both the kidney as compared to cafeteria diet fed animals confirming their anti-obesity property. The aqueous and alcoholic extract of leaf of Cassia Fistula (Linn.) has shown significant decrease in serum levels of Total-Cholesterol, LDL-Cholesterol, VLDL-Cholesterol and Triglyceride.
Keywords: Antihyperglycemic, cassia fistula, hyperlipidemia, High fat diet, alcoholic extrac
X-RED: A Satellite Mission Concept To Detect Early Universe Gamma Ray Bursts
Gamma ray bursts (GRBs) are the most energetic eruptions known in the
Universe. Instruments such as Compton-GRO/BATSE and the GRB monitor on BeppoSAX
have detected more than 2700 GRBs and, although observational confirmation is
still required, it is now generally accepted that many of these bursts are
associated with the collapse of rapidly spinning massive stars to form black
holes. Consequently, since first generation stars are expected to be very
massive, GRBs are likely to have occurred in significant numbers at early
epochs. X-red is a space mission concept designed to detect these extremely
high redshifted GRBs, in order to probe the nature of the first generation of
stars and hence the time of reionisation of the early Universe. We demonstrate
that the gamma and x-ray luminosities of typical GRBs render them detectable up
to extremely high redshifts (z~10-30), but that current missions such as HETE2
and SWIFT operate outside the observational range for detection of high
redshift GRB afterglows. Therefore, to redress this, we present a complete
mission design from the science case to the mission architecture and payload,
the latter comprising three instruments, namely wide field x-ray cameras to
detect high redshift gamma-rays, an x-ray focussing telescope to determine
accurate coordinates and extract spectra, and an infrared spectrograph to
observe the high redshift optical afterglow. The mission is expected to detect
and identify for the first time GRBs with z > 10, thereby providing constraints
on properties of the first generation of stars and the history of the early
Universe.Comment: 14 pages, 10 figures, spie.cls neede
The ASTRO-H X-ray Observatory
The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly
successful X-ray missions initiated by the Institute of Space and Astronautical
Science (ISAS). ASTRO-H will investigate the physics of the high-energy
universe via a suite of four instruments, covering a very wide energy range,
from 0.3 keV to 600 keV. These instruments include a high-resolution,
high-throughput spectrometer sensitive over 0.3-2 keV with high spectral
resolution of Delta E < 7 eV, enabled by a micro-calorimeter array located in
the focal plane of thin-foil X-ray optics; hard X-ray imaging spectrometers
covering 5-80 keV, located in the focal plane of multilayer-coated, focusing
hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4-12
keV, with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and
a non-focusing Compton-camera type soft gamma-ray detector, sensitive in the
40-600 keV band. The simultaneous broad bandpass, coupled with high spectral
resolution, will enable the pursuit of a wide variety of important science
themes.Comment: 22 pages, 17 figures, Proceedings of the SPIE Astronomical
Instrumentation "Space Telescopes and Instrumentation 2012: Ultraviolet to
Gamma Ray
The Quiescent Intracluster Medium in the Core of the Perseus Cluster
Clusters of galaxies are the most massive gravitationally-bound objects in
the Universe and are still forming. They are thus important probes of
cosmological parameters and a host of astrophysical processes. Knowledge of the
dynamics of the pervasive hot gas, which dominates in mass over stars in a
cluster, is a crucial missing ingredient. It can enable new insights into
mechanical energy injection by the central supermassive black hole and the use
of hydrostatic equilibrium for the determination of cluster masses. X-rays from
the core of the Perseus cluster are emitted by the 50 million K diffuse hot
plasma filling its gravitational potential well. The Active Galactic Nucleus of
the central galaxy NGC1275 is pumping jetted energy into the surrounding
intracluster medium, creating buoyant bubbles filled with relativistic plasma.
These likely induce motions in the intracluster medium and heat the inner gas
preventing runaway radiative cooling; a process known as Active Galactic
Nucleus Feedback. Here we report on Hitomi X-ray observations of the Perseus
cluster core, which reveal a remarkably quiescent atmosphere where the gas has
a line-of-sight velocity dispersion of 164+/-10 km/s in a region 30-60 kpc from
the central nucleus. A gradient in the line-of-sight velocity of 150+/-70 km/s
is found across the 60 kpc image of the cluster core. Turbulent pressure
support in the gas is 4% or less of the thermodynamic pressure, with large
scale shear at most doubling that estimate. We infer that total cluster masses
determined from hydrostatic equilibrium in the central regions need little
correction for turbulent pressure.Comment: 31 pages, 11 Figs, published in Nature July
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