79 research outputs found
X-Ray and Near-Infrared Spectroscopy of Dim X-Ray Point Sources Constituting the Galactic Ridge X-Ray Emission
We present the results of X-ray and Near-Infrared observations of the Galactic Ridge X-ray Emission (GRXE). We extracted 2,002 X-ray point sources in the Chandra Bulge Field (l =0°.113, b = 1°.424) down to ~10-14.8 ergscm-2s-1 in 2-8 keV band with the longest observation (900 ks) of the GRXE. Based on X-ray brightness and hardness, we classied the X-ray point sources into three groups: A (hard), B (soft and broad spectrum), and C (soft and peaked spectrum). In order to know populations of the X-ray point sources, we carried out NIR imaging and spectroscopy observation. We identied 11% of X-ray point sources with NIR and extracted NIR spectra for some of them. Based on X-ray and NIR properties, we concluded that non-thermal sources in the group A are mostly active galactic nuclei and the thermal sources are mostly white dwarf binaries such as cataclysmic variables (CVs) and Pre-CVs. We concluded that the group B and C sources are X-ray active stars in flare and quiescence, respectively
Near- to mid-infrared spectroscopy of the heavily obscured AGN LEDA 1712304 with AKARI/IRC
Context. Although heavily obscured active galactic nuclei (AGNs) have been
found by many observational studies, the properties of the surrounding dust are
poorly understood. Using AKARI/IRC spectroscopy, we discover a new sample of a
heavily obscured AGN in LEDA 1712304 which shows a deep spectral absorption
feature due to silicate dust. Aims. We study the infrared (IR) spectral
properties of circumnuclear silicate dust in LEDA 1712304. Methods. We perform
IR spectral fitting, considering silicate dust properties such as composition,
porosity, size and crystallinity. Spectral energy distribution (SED) fitting is
also performed to the flux densities in the UV to sub-millimeter range to
investigate the global spectral properties. Results. The best-fit model
indicates 0.1 m-sized porous amorphous olivine (; ) with crystalline pyroxene. The optical
depth is , while the total IR luminosity and stellar
mass are estimated to be and
, respectively. In such low
and ranges, there are few galaxies which show that
large . Conclusions. The silicate dust in the AGN torus of
LEDA 1712304 has properties notably similar to those in other AGNs as a whole,
but slightly different in the wing shape of the absorption profile. The
porosity of the silicate dust suggests dust coagulation or processing in the
circumnuclear environments, while the crystallinity suggests that the silicate
dust is relatively fresh.Comment: 9 pages, 6 figures, accepted for publication in A&
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