33 research outputs found
The hot interstellar medium in NGC 1399
The first two high signal-to-noise, broad bandpass x-ray spectra of elliptical galaxies were obtained with the Broad Band X-ray Telescope (BBXRT) as part of the December 1990 Astro mission. These observations provided unprecedented information on the thermal and metallicity structure of the hot interstellar media in two ellipticals: NGC 1399, the central galaxy in the Fornax cluster, and NGC 4472, the brightest galaxy in the Virgo cluster. The finalized analysis and interpretation of the approximately 4000 sec of BBXRT data on NGC 1399 is reported
Calibration of the Soft X-ray Telescopes (SXT) Onboard the ASTRO-H Satellite
ASTRO-H is an astrophysics satellite dedicated for non-dispersive X-ray spectroscopic study on selective celestial X-ray sources. Among the onboard instruments there are four Wolter-I X-ray mirrors of their reflectors' figure in conical approximation. Two of the four are soft X-ray mirrors, of which the energy range is from a few hundred eV to 15 keV. The focal point instruments will be a calorimeter (SXS) and a CCD camera (SXI), respectively. The mirrors were in quadrant configuration with photons being reflected consecutively in the primary and secondary stage before landing on the focal plane of 5.6 m away from the interface between the two stages. The reflectors of the mirror are made of heat-formed aluminum substrate of the thickness gauged of 152 m, 229 m, and 305 m of the alloy 5052 H-19, followed by epoxy replication on gold-sputtered smooth Pyrex cylindrical mandrels to acquire the X-ray reflective surface. The epoxy layer is 10 m nominal and surface gold layer of 0.2 m. Improvements on angular response over its predecessors, e.g. Astro-E1/Suzaku mirrors, come from error reduction on the figure, the roundness, and the grazing angle/radius mismatching of the reflecting surface, and tighter specs and mechanical strength on supporting structure to reduce the reflector positioning and the assembly errors. Each soft x-ray telescope (SXT), FM1 or FM2, were integrated from four independent quadrants of mirrors. The stray-light baffles, in quadrant configuration, were mounted onto the integrated mirror. Thermal control units were attached to the perimeter of the integrated mirror to keep the mirror within operating temperature in space. The completed instrument went through a series of optical alignment, thus made the quadrant images confocal and their optical axes in parallel to achieve highest throughput possible. Environmental tests were carried out, and optical quality of the telescopes has been confirmed. The optical and x-ray calibrations also include: angular resolution, effective area in the energy range of ~ 0.4 - 12keV, off-axis response, etc. Some of those are being carried out by our counterpart at JAXA/ISAS, Japan. We report the calibration results of the FM1 and FM2 that were obtained at Goddard Space Flight Center
ASTRO-H Soft X-Ray Telescope (SXT)
ASTRO-H is an astrophysics satellite dedicated for X-ray spectroscopic study non-dispersively and to carry out survey complementally, which will be borne out of US-Japanese collaborative effort. Among the onboard instruments there are four conically approximated Wolter-I X-ray mirrors, among which two of them are soft X-ray mirrors\ of which the energy range is from a few hundred eV to 15 keY, currently being fabricated in the X-ray Optics Lab at Goddard Space Flight Center. The focal point instruments will be a calorimeter (SXS) and a CCD camera (SXI), respectively. The reflectors of the mirror are made of heat-formed aluminum substrate of the thickness gauged of 152 micron, 229 micron, and 305 micron of the alloy 5052 H-19, followed by epoxy replication on gold-sputtered smooth Pyrex cylindrical mandrels to acquire the X-ray reflective surface. The epoxy layer is 10 micron nominal and surface gold layer of 0.2 micron. Improvements on angular response over the Astro-El/Suzaku mirrors come from error reduction on the figure, the roundness, and the grazing angle/radius mismatching of the reflecting surface, and tighter specs and mechanical strength on supporting structure to reduce the reflector positioning and the assembly errors. In this paper, we report the results of calibration of the engineering model of SXT (EM), and project the quality of the flight mirrors
X-ray Properties of the Weak Seyfert 1 Nucleus in NGC 4639
We obtained observations of NGC 4639 with ASCA in order to investigate its
mildly active Seyfert 1 nucleus at hard X-ray energies. Koratkar et al. (1995)
have previously shown that the nucleus is a pointlike source in the ROSAT soft
X-ray band. We detected in the 2-10 keV band a compact central source with a
luminosity of 8.3E+40 erg/s. Comparison of the ASCA data with archival data
taken with the Einstein and ROSAT satellites shows that the nucleus varies on
timescales of months to years. The variability could be intrinsic, or it could
be caused by variable absorption. More rapid variability, on a timescale of
\~10^4 s, may be present in the ASCA data. The spectrum from 0.5 to 10 keV is
well described by a model consisting of a lightly absorbed (N_H = 7.3E+20
cm^-2) power law with a photon index of 1.68. We find no evidence for
significant emission from a thermal plasma; if present, it can account for no
more than 25% of the flux in the 0.5-2.0 keV band. The limited photon
statistics of our data do not allow us to place significant limits on the
presence of iron K emission. (abridged)Comment: To appear in The Astrophysical Journal. LaTex, 18 pages including
embedded figures and table
Precision Fe Kalpha and Fe Kbeta Line Spectroscopy of the Seyfert 1.9 Galaxy NGC 2992 with Suzaku
We present detailed time-averaged X-ray spectroscopy in the 0.5--10 keV band
of the Seyfert~1.9 galaxy NGC 2992 with the Suzaku X-ray Imaging Spectrometers
(XIS). We model the complex continuum in detail. There is an Fe K line emission
complex that we model with broad and narrow lines and we show that the
intensities of the two components are decoupled at a confidence level >3sigma.
The broad Fe K line has an EW of 118 (+32,-61) eV and could originate in an
accretion disk (with inclination angle greater than ~30 degrees). The narrow Fe
Kalpha line has an EW of 163 (+47,-26) eV and is unresolved FWHM <4090 km/s)
and likely originates in distant matter. The absolute flux in the narrow line
implies that the column density out of the line-of-sight could be much higher
than measured in the line-of-sight, and that the mean (historically-averaged)
continuum luminosity responsible for forming the line could be a factor of
several higher than that measured from the data. We also detect the narrow Fe
Kbeta line with a high signal-to-noise ratio and describe a new robust method
to constrain the ionization state of Fe responsible for the Fe Kalpha and Fe
Kbeta lines that does not require any knowledge of possible gravitational and
Doppler energy shifts affecting the line energies. For the distant
line-emitting matter (e.g. the putative obscuring torus) we deduce that the
predominant ionization state is lower than Fe VIII (at 99% confidence),
conservatively taking into account residual calibration uncertainties in the
XIS energy scale and theoretical and experimental uncertainties in the Fe K
fluorescent line energies. From the limits on a possible Compton-reflection
continuum it is likely that the narrow Fe Kalpha and Fe Kbeta lines originate
in a Compton-thin structure.Comment: Abstract is abridged. Accepted for publication in the Suzaku special
issue of PASJ (November 2006). 18 pages, 6 figure
ASCA Observations of "Type 2" LINERs: Evidence for a Stellar Source of Ionization
We present ASCA observations of LINERs without broad H emission in
their optical spectra. The sample of "type 2" LINERs consists of NGC 404, 4111,
4192, 4457, and 4569. We have detected X-ray emission from all the objects
except for NGC 404; among the detected objects are two so-called transition
objects (NGC 4192 and NGC 4569), which have been postulated to be composite
nuclei having both an HII region and a LINER component. The images of NGC 4111
and NGC 4569 in the soft (0.5-2 keV) and hard (2-7 keV) X-ray bands are
extended on scales of several kpc. The X-ray spectra of NGC 4111, NGC 4457 and
NGC 4569 are well fitted by a two-component model that consists of soft thermal
emission with keV and a hard component represented by a power law
(photon index 2) or by thermal bremsstrahlung emission ( several
keV). The extended hard X-rays probably come from discrete sources, while the
soft emission most likely originates from hot gas produced by active star
formation in the host galaxy. We have found no clear evidence for the presence
of active galactic nuclei (AGNs) in the sample. If an AGN component is the
primary ionization source of the optical emission lines, then it must be
heavily obscured with a column density significantly larger than
cm. Alternatively, the optical emission could be ionized by a population
of exceptionally hot stars.Comment: 13 pages, 5 figures, emulateapj.sty, Accepted for publication in the
Astrophysical Journa
Iron K line Variability in the Low-Luminosity AGN NGC 4579
We present results of new ASCA observations of the low-luminosity AGN (LLAGN)
NGC 4579 obtained on 1998 December 18 and 28, and we report on detection of
variability of an iron K emission line. The X-ray luminosities in the 2--10 keV
band for the two observations are nearly identical (LX
2 ergs/s), but they are 35% larger than that measured in
1995 July by Terashima et al. An Fe K emission line is detected at
keV (source rest frame) which is lower than the line energy
keV in the 1995 observation. If we fit the Fe lines with
a blend of two Gaussians centered at 6.39 keV and 6.73 keV, the intensity of
the 6.7 keV line decreases, while the intensity of the 6.4 keV line increases,
within an interval of 3.5 yr. This variability rules out thermal plasmas in the
host galaxy as the origin of the ionized Fe line in this LLAGN. The detection
and variability of the 6.4 keV line indicates that cold matter subtends a large
solid angle viewed from the nucleus and that it is located within pc
from the nucleus. It could be identified with an optically thick standard
accretion disk. If this is the case, a standard accretion disk is present at
the Eddington ratio of . A
broad disk-line profile is not clearly seen and the structure of the innermost
part of accretion disk remains unclear.Comment: 9 pages, 3 figures, To appear in the Astrophyscal Jounal Letter
In-flight Calibration of Hitomi Soft X-ray Spectrometer (3) Effective Area
We present the result of the in-flight calibration of the effective area of
the Soft X-ray Spectrometer (SXS) onboard the Hitomi X-ray satellite using an
observation of the Crab nebula. We corrected for the artifacts when observing
high count rate sources with the X-ray microcalorimeter. We then constructed a
spectrum in the 0.5-20 keV band, which we modeled with a single power-law
continuum attenuated by an interstellar extinction. We evaluated the systematic
uncertainty upon the spectral parameters by various calibration items. In the
2-12 keV band, the SXS result is consistent with the literature values in flux
(2.20 0.08) 10 erg s cm with a 1
statistical uncertainty) but is softer in the power-law index (2.19
0.11). The discrepancy is attributable to the systematic uncertainty of about
6/7% and 2/5% respectively for the flux and the power-law index.
The softer spectrum is affected primarily by the systematic uncertainty of the
Dewar gate valve transmission and the event screening.Comment: 13 pages, 7 figures.PASJ accepte