4,936 research outputs found
A search for thermal X-ray signatures in Gamma-Ray Bursts II: The Swift sample
In several gamma-ray bursts (GRBs) excess emission, in addition to the
standard synchrotron afterglow spectrum, has been discovered in the early time
X-ray observations. It has been proposed that this excess comes from black body
emission, which may be related to the shock break-out of a supernova in the
GRBs progenitor star. This hypothesis is supported by the discovery of excess
emission in several GRBs with an associated supernova. Using mock spectra we
show that it is only likely to detect such a component, similar to the one
proposed in GRB 101219B, at low redshift and in low absorption environments. We
also perform a systematic search for black body components in all the GRBs
observed with the Swift satellite and find six bursts (GRB 061021, 061110A,
081109, 090814A, 100621A and 110715A) with possible black body components.
Under the assumption that their excess emission is due to a black body
component we present radii, temperatures and luminosities of the emitting
components. We also show that detection of black body components only is
possible in a fraction of the Swift bursts.Comment: 11 pages, 8 figures, accepted for MNRA
Strong spectral evolution during the prompt emission of GRB 070616
Swift has revealed features in GRB early light curves, such as steep decays
and X-ray flares, whose properties are consistent with an internal origin
though they are far from understood. The steep X-ray decay is often explained
using the curvature effect; however a significant number of GRBs display strong
spectral evolution during this phase, and a new mechanism must be invoked to
explain this. Of particular interest are the longest duration GRBs in which the
early emission can be studied in most detail. Here we present data for GRB
070616, in which the prompt emission shows a complex multipeaked structure,
leading to one of the longest prompt emission durations ever recorded. We take
advantage of extensive coverage of such a long burst by all Swift instruments.
Combining data from Swift and Suzaku we study the evolution of the prompt
emission spectrum, following the temporal variability of the peak energy and
spectral slope.Comment: 4 pages, 2 figures (Fig 1 in colour), contributed talk, submitted to
the proceedings of Gamma Ray Bursts 2007, Santa Fe, New Mexico, November 5-9
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The soft X-ray excess AGN RE J2248-511
We model the spectral energy distribution of the ultrasoft broad-line AGN RE
J2248-511 with Comptonised accretion disc models. These are able to reproduce
the steep optical and ultrasoft X-ray slopes, and the derived black hole mass
is consistent with independent mass estimates. This AGN displays properties of
both broad and narrow line Seyfert 1 galaxies, but we conclude that it is
intrinsically a `normal' Seyfert 1 viewed at high inclination angle.Comment: 4 pages, 1 figure. MG10 Proceeding
Prometheus unbound: A study of the Dallas/Fort Worth Regional Airport
The history of the controversies in the development of the Dallas/Fort Worth Regional Airport is detailed. Present technological and organizational management problems are outlined. Maps and illustrations are included
Oral History Interview: Edward M. Starling
Mr. Starling discusses working in the athletic department at Marshall University (including brief sections on the plane crash and women\u27s athletics), discrimination he faced as an African American, as well as brief sections about his service in World War II and a brief autobiography. This interview is one of a series conducted concerning rural life in West Virginia.https://mds.marshall.edu/oral_history/1509/thumbnail.jp
The Language in Classrooms Program : an evaluation of a whole-school intervention for adolescents with language impairment
Technology and politics: The regional airport experience
The findings of a comparative study of the following six regional airports were presented: Dallas/Fort Worth, Kansas City, Washington, D.C., Montreal, Tampa, and St. Louis. Each case was approached as a unique historical entity, in order to investigate common elements such as: the use of predictive models in planning, the role of symbolism to heighten dramatic effects, the roles of community and professional elites, and design flexibility. Some of the factors considered were: site selection, consolidation of airline service, accessibility, land availability and cost, safety, nuisance, and pollution constraints, economic growth, expectation of regional growth, the demand forecasting conundrum, and design decisions. The hypotheses developed include the following: the effect of political, social, and economic conflicts, the stress on large capacity and dramatic, high-technology design, projections of rapid growth to explain the need for large capital outlays
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