16,797 research outputs found
Compton processes in the bright AGN MCG+8-11-11
We present preliminary results on the hard X-ray emission properties of the
Seyfert 1.5 galaxy MCG+8-11-11 as observed by INTEGRAL and SWIFT. All the
INTEGRAL IBIS/ISGRI data available up to October 2009 have been analyzed
together with two SWIFT/XRT snapshot observations performed in August and
October 2009, quasi-simultaneously to INTEGRAL pointed observations of
MCG+8-11-11. No correlation is observed between the hard X-ray flux and the
spectral slope, while the position of the high-energy cut-off is found to have
varied during the INTEGRAL observations. This points to a change in the
temperature of the Comptonising medium from a minimum value of kT = 30-50 keV
to values larger than 100-150 keV. There is no significant detection of Compton
reflection, with a 3 sigma upper limit of R < 0.2, and no line has been
detected at 112 keV, as previously claimed from HEAT observations (112 keV flux
F < 2.4e-4 ph/cm^2/s). The variability behaviour of MCG+8-11-11 is found to be
similar to that shown by IC 4329A, with different temperatures of the electron
plasma for similar flux levels of the source, while other bright Seyfert
galaxies present different variability patterns at hard X-rays, with spectral
changes correlated to flux variations (e.g. NGC 4151).Comment: 6 pages, 4 figures. Accepted for publication on PoS (contribution
PoS(INTEGRAL 2010)077), proceedings of the 8th INTEGRAL Workshop "The
Restless Gamma-ray Universe" (September 2010, Dublin, Ireland
How Postsecondary Education Improves Adult Outcomes for Supplemental Security Income Children with Severe Hearing Impairments
This is a case study of SSI children who apply for postsecondary education at the National Technical Institute of the Deaf (NTID) within the Rochester Institute of Technology. We estimate the likelihood that an SSI child will graduate from NTID relative to other hearing impaired NTID applicants and estimate the influence of graduation from NTID on participation in the SSI adult program and later success in the labor market. To do so we create a unique longitudinal administrative records data set (n=5,638) based on administrative records from NTID linked to Social Security Administration (SSA) microdata. We find that SSI children who graduate from NTID spend less time on the SSI adult program and have higher earnings than those who do not graduate. However, we also find that SSI children who apply to NTID have a greater risk of not graduating than their fellow deaf students who did not participate in the SSI program as children. Our findings suggest that greater effort may be necessary to prepare SSI children for postsecondary education and that the currently SSA-funded youth transition demonstration projects are necessary to explore how such efforts can improve adult outcomes for SSI children with disabilities
Revisiting the Parallax of the Isolated Neutron Star RX J185635-3754 Using HST/ACS Imaging
We have redetermined the parallax and proper motion of the nearby isolated
neutron star RX~J185635-3754. We used eight observations with the high
resolution camera of the HST/ACS taken from 2002 through 2004. We performed the
astrometric fitting using five independent methods, all of which yielded
consistent results. The mean estimate of the distance is 123 (+11, -15) pc (1
sigma), in good agreement with our earlier published determination
The Chandra LETGS high resolution X-ray spectrum of the isolated neutron star RX J1856.5-3754
We present the Chandra LETGS X-ray spectrum of the nearby (~60 pc) neutron
star RX J1856.5-3754. Detailed spectral analysis of the combined X-ray and
optical data rules out the nonmagnetic neutron star atmosphere models with
hydrogen, helium, iron and solar compositions. We also conclude that strongly
magnetized atmosphere models are unable to represent the data. The data can be
explained with a two-component blackbody model. The harder component with
temperature of kT_bb~63 eV and a radius R_bb~2.2 km of the emitting region well
fits the X-ray data and can be interpreted as radiation from a hot region on
the star's surface.Comment: 4 pages, 3 color figures; acceped by A&A Letters;
http://www.xray.mpe.mpg.de/~burwitz/burwitz_refereed.htm
On the mixing property for a class of states of relativistic quantum fields
Let be a factor state on the quasi-local algebra of
observables generated by a relativistic quantum field, which in addition
satisfies certain regularity conditions (satisfied by ground states and the
recently constructed thermal states of the theory). We prove that
there exist space and time translation invariant states, some of which are
arbitrarily close to in the weak* topology, for which the time
evolution is weakly asymptotically abelian
Decoherence and Entanglement Dynamics in Fluctuating Fields
We study pure phase damping of two qubits due to fluctuating fields. As
frequently employed, decoherence is thus described in terms of random unitary
(RU) dynamics, i.e., a convex mixture of unitary transformations. Based on a
separation of the dynamics into an average Hamiltonian and a noise channel, we
are able to analytically determine the evolution of both entanglement and
purity. This enables us to characterize the dynamics in a concurrence-purity
(CP) diagram: we find that RU phase damping dynamics sets constraints on
accessible regions in the CP plane. We show that initial state and dynamics
contribute to final entanglement independently.Comment: 10 pages, 5 figures, added minor changes in order to match published
versio
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