6,025 research outputs found
The z=5.8 Quasar SDSSp J1044-0125: A Peek at Quasar Evolution?
The newly discovered z=5.8 quasar SDSSp J104433.04-012502.2 was recently
detected in X-rays and found to be extremely X-ray weak. Here we present the
hardness ratio analysis of the XMM-Newton observation. We consider various
models to explain the detection in the soft X-ray band and non-detection in the
hard band, together with its X-ray weakness. We show that the source may have a
steep power-law slope, with an absorber partially covering the continuum. This
may be X-ray evidence to support the argument of Mathur (2000) that narrow line
Seyfert 1 galaxies, which show steep power-law slopes, might be the low
redshift, low luminosity analogues of the high redshift quasars. Heavily
shrouded and steep X-ray spectrum quasars may indeed represent the early stages
of quasar evolution (Mathur 2000, Fabian 1999) and SDSSp J104433.04-012502.2 is
possibly giving us a first glimpse of the physical evolution of quasar
properties.Comment: To appear in A
A Review of Pentaquark Calculations on the Lattice
We review lattice calculations of pentaquarks and discuss issues pertaining
to interpolation fields, distinguishing the signal of pentaquarks from those of
the KN scattering states, chiral symmetry, and ghost state contaminations.Comment: Talk at International Conference on QCD and Hadronic Physics, 8
pages, 3 figure
Working Capital Management of Cement Industry in India - A Comparative Analysis of Selected Units
Not availabl
Chandra Detection of Highest Redshift (z~6) Quasars in X-rays
We report on Chandra observations of three quasars SDSSP J083643+005453,
SDSSP J103027+052455, and SDSSP J130608+035626 at redshifts 5.82, 6.28 and 5.99
respectively. All the three sources are clearly detected in the X-ray band, up
to rest frame energies of ~55 keV. These observations demonstrate the
unprecedented sensitivity of Chandra to detect faint sources in relatively
short exposure times (5.7--8.2 ksec). The broad band X-ray properties of these
highest redshift quasars do not appear to be any different from their lower
redshift cousins. Spectra of the sources could not be determined with only few
counts detected. Observations with XMM-Newton will be able to constrain the
spectral shapes, if they are simple. Determination of complex spectra in a
reasonable amount of time, however, will have to await next generation of X-ray
missions.Comment: Submitted to ApJ Letter
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