95 research outputs found
ASCA observation of Unusually X-ray Hard Radio Quiet QSO Kaz 102
We have observed a radio-quiet QSO Kaz 102 (z=0.136) with ASCA as a part of
our program of complete spectral characterization of hard X-ray selected AGNs.
We found that Kaz 102 shows unusual spectral properties. A simple power-law
with absorption in our galaxy gave a satisfactory description of the spectrum.
However, it showed a very hard photon index of Gamma=1.0 with no sign of deep
absorption or a prominent spectral feature. We further explored the Compton
reflection with Fe K-alpha line and warm absorber models for hardening the
spectrum. Both gave statistically satisfactory fits. However, the Compton
reflection model requires a very low metal abundance (0.03-0.07 in solar
units).The warm absorber model with no direct component is preferred and gave a
very high ionization parameter xi=200. If this is the case, the values of xi,
warm absorber column density, and variability over about 10 years may suggest
that the warm absorber resides in the broad-line region and crosses the line of
sight to the central X-ray source.Comment: 5 pages, 5 figures. Accepted to Publication of the Astronomical
Society of Japan (Letters
Optical Identification of the ASCA Lynx Deep Survey: An Association of QSOs and a Supercluster at z=1.3?
Results of optical identification of the ASCA Lynx deep survey are presented.
Six X-ray sources are detected in the 2-7 keV band using the SIS in a 20'x20'
field of view with fluxes larger than ~4x10^{-14} erg s-1 cm-2 in the band.
Follow-up optical spectroscopic observations were made, and five out of six
sources are identified with AGNs/QSOs at redshifts of 0.5-1.3. We also identify
two more additional X-ray sources detected in a soft X-ray band with AGNs/QSOs.
It is found that three QSOs identified are located at z~1.3. Two rich clusters
and several groups of galaxies are also placed at the same redshift in the
surveyed field, and projected separations between the QSOs and the clusters are
3-8 Mpc at the redshift.Comment: 15 pages with 3 figures. Accepted to Ap
(R)-ketamine restores anterior insular cortex activity and cognitive deficits in social isolation-reared mice
Yokoyama R., Ago Y., Igarashi H., et al. (R)-ketamine restores anterior insular cortex activity and cognitive deficits in social isolation-reared mice. Molecular Psychiatry , (2024); https://doi.org/10.1038/s41380-024-02419-6.Chronic social isolation increases the risk of mental health problems, including cognitive impairments and depression. While subanesthetic ketamine is considered effective for cognitive impairments in patients with depression, the neural mechanisms underlying its effects are not well understood. Here we identified unique activation of the anterior insular cortex (aIC) as a characteristic feature in brain-wide regions of mice reared in social isolation and treated with (R)-ketamine, a ketamine enantiomer. Using fiber photometry recording on freely moving mice, we found that social isolation attenuates aIC neuronal activation upon social contact and that (R)-ketamine, but not (S)-ketamine, is able to counteracts this reduction. (R)-ketamine facilitated social cognition in social isolation-reared mice during the social memory test. aIC inactivation offset the effect of (R)-ketamine on social memory. Our results suggest that (R)-ketamine has promising potential as an effective intervention for social cognitive deficits by restoring aIC function
Suzaku observations of the hard X-ray variability of MCG-6-30-15: the effects of strong gravity around a Kerr black hole
Suzaku has, for the first time, enabled the hard X-ray variability of the
Seyfert 1 galaxy MCG-6-30-15 to be measured. The variability in the 14-45 keV
band, which is dominated by a strong reflection hump, is quenched relative to
that at a few keV. This directly demonstrates that the whole reflection
spectrum is much less variable than the power-law continuum. The broadband
spectral variability can be decomposed into two components - a highly variable
power-law and constant reflection - as previously inferred from other
observations in the 2-10 keV band. The strong reflection and high iron
abundance give rise to a strong broad iron line, which requires the inner disc
radius to be at about 2 gravitational radii. Our results are consistent with
the predictions of the light bending model which invokes the very strong
gravitational effects expected very close to a rapidly spinning black hole.Comment: accepted for publication in PASJ Suzaku special issu
Thyroid ultrasound findings in a follow-up survey of children from three Japanese prefectures: Aomori, Yamanashi, and Nagasaki
We conducted ultrasound thyroid screening in cohort of 4,365 children aged between 3 to 18 years in three Japanese prefectures (Aomori, Yamanashi, and Nagasaki) using the same procedures as used in the Fukushima Health Survey. Forty-four children had nodules ? 5.1 mm in diameter or cysts ? 20.1 mm in diameter detected at the first screening, and 31 of these children underwent the second follow-up survey. We collected information from thyroid ultrasound examinations and final clinical diagnoses and re-categorized the thyroid findings after the second examination. Twenty children had nodules ? 5.1 mm in diameter or cysts ? 20.1 mm in diameter at the second examination; of these, one child was diagnosed with a thyroid papillary carcinoma and the remaining 19 children were diagnosed with possibly benign nodules such as adenomas, adenomatous nodules, and adenomatous goiters. A further 11 children were re-categorized as "no further examinations were required." Our results suggest that ultrasound thyroid findings in children may change with a relatively short-term passing period, and that thyroid cancer may exist at a very low but certain frequency in the general childhood population
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
Fermi Large Area Telescope Constraints on the Gamma-ray Opacity of the Universe
The Extragalactic Background Light (EBL) includes photons with wavelengths
from ultraviolet to infrared, which are effective at attenuating gamma rays
with energy above ~10 GeV during propagation from sources at cosmological
distances. This results in a redshift- and energy-dependent attenuation of the
gamma-ray flux of extragalactic sources such as blazars and Gamma-Ray Bursts
(GRBs). The Large Area Telescope onboard Fermi detects a sample of gamma-ray
blazars with redshift up to z~3, and GRBs with redshift up to z~4.3. Using
photons above 10 GeV collected by Fermi over more than one year of observations
for these sources, we investigate the effect of gamma-ray flux attenuation by
the EBL. We place upper limits on the gamma-ray opacity of the Universe at
various energies and redshifts, and compare this with predictions from
well-known EBL models. We find that an EBL intensity in the optical-ultraviolet
wavelengths as great as predicted by the "baseline" model of Stecker et al.
(2006) can be ruled out with high confidence.Comment: 42 pages, 12 figures, accepted version (24 Aug.2010) for publication
in ApJ; Contact authors: A. Bouvier, A. Chen, S. Raino, S. Razzaque, A.
Reimer, L.C. Reye
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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