357 research outputs found
The diffuse component of the cosmic X-radiation
The A-2 experiment on HEAO-1 is specifically developed to study the diffuse radiation of the entire X-ray sky over a wide bandwidth, covering both the soft X-ray emission from nearby regions of the galaxy and the isotropic hard X-radiation indicative of remote extragalactic origins. A partial conclusion from the experiment is that a hot thermal plasma, on a scale comparable to that of the universe, may be the principal source of hard X-radiation characteristic of the extragalactic sky. Some key features of this background were defined
Stimulated brillouin scattering in liquids
Stimulated Brillouin scattering of intense laser light with build-up of coherent hypersonic waves in liquid
Optical frequency waveguide and transmission system Patent
Optical communication system with gas filled waveguide for laser beam transmissio
Laser machining apparatus Patent
Laser machining device with dielectric functioning as beam waveguide for mechanical and medical application
Optical frequency waveguide Patent
Self-generating optical frequency waveguid
X-ray Spectroscopy of QSOs with Broad Ultraviolet Absorption Lines
For the population of QSOs with broad ultraviolet absorption lines, we are
just beginning to accumulate X-ray observations with enough counts for spectral
analysis at CCD resolution. From a sample of eight QSOs [including four Broad
Absorption Line (BAL) QSOs and three mini-BAL QSOs] with ASCA or Chandra
spectra with more than 200 counts, general patterns are emerging. Their
power-law X-ray continua are typical of normal QSOs with Gamma~2.0, and the
signatures of a significant column density [N_H~(0.1-4)x10^{23} cm^{-2}] of
intrinsic, absorbing gas are clear. Correcting the X-ray spectra for intrinsic
absorption recovers a normal ultraviolet-to-X-ray flux ratio, indicating that
the spectral energy distributions of this population are not inherently
anomalous. In addition, a large fraction of our sample shows significant
evidence for complexity in the absorption. The subset of BAL QSOs with broad
MgII absorption apparently suffers from Compton-thick absorption completely
obscuring the direct continuum in the 2-10 keV X-ray band, complicating any
measurement of their intrinsic X-ray spectral shapes.Comment: 9 pages, 6 figures, uses AASTeX. Accepted to the Astrophysical
Journa
Chandra Observations of the Gravitationally Lensed System 2016+112
An observation of the gravitationally lensed system 2016+112 with the Chandra
X-ray Observatory has resolved a mystery regarding the proposed presence of a
dark matter object in the lens plane of this system. The Chandra ACIS
observation has clearly detected the lensed images of 2016+112 with positions
in good agreement with those reported in the optical and also detects 13
additional X-ray sources within a radius of 3.5 arcmin. Previous X-ray
observations in the direction of 2016+112 with the ROSAT HRI and ASCA SIS have
interpreted the X-ray data as arising from extended emission from a dark
cluster. However, the present Chandra observation can account for all the X-ray
emission as originating from the lensed images and additional point X-ray
sources in the field. Thus cluster parameters based on previous X-ray
observations are unreliable. We estimate an upper limit on the mass-to-light
ratio within a radius of 800 h_(50)^(-1) kpc of M/L_(V) < 190 h_(50)
(M/L_(V))_Sun. The lensed object is quite unusual, with reported narrow
emission lines in the optical that suggest it may be a type-2 quasar (Yamada
et. al. 1999). Our modeling of the X-ray spectrum of the lensed object implies
that the column density of an intrinsic absorber must lie between 3 and 85 x
10^22 cm^-2 (3 sigma confidence level). The 2-10 keV luminosity of the lensed
object, corrected for the lens magnification effect and using the above range
of intrinsic absorption, is 3 x 10^43 - 1.4 x 10^44 erg/s.Comment: 9 pages, includes 2 figures, Accepted for publication in ApJ
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