3,477 research outputs found
Blueshift Without Blueshift: Red Hole Gamma-Ray Burst Models Explain the Peak energy Distribution
Gamma-ray bursts are still a puzzle. In particular, the central engine, the
total energy and the very narrow distribution of peak energies challenge model
builders. We consider here an extreme model of gamma-ray bursts based on highly
red- and blue-shifted positron annihilation radiation. The burst emerges from
inside the red hole created by the complete gravitational collapse of the GRB
progenitor.Comment: To appear in Proc of the 10th Annual October Astrophysics Conference
in Maryland: Cosmic Explosions, 4 Pages, LaTe
Young Collapsed Supernova Remnants: Similarities and Differences in Neutron Stars, Black Holes, and More Exotic Objects
Type Ia supernovae are thought to explode completely, leaving no condensed
remnant, only an expanding shell. Other types of supernovae are thought to
involve core collapse and are expected to leave a condensed remnant, which
could be either a neutron star or a black hole, or just possibly, something
more exotic, such as a quark orstrange star, a naked singularity, a frozen
star, a wormhole or a red hole. It has proven surprisingly difficult to
determine which type of condensed remnant has been formed in those cases where
the diagnostic highly regular pulsar signature of a neutron star is absent. We
consider possible observational differences between the two standard
candidates, as well as the more speculative alternatives.
We classify condensed remnants according to whether they do or do not possess
three major features: 1)a hard surface, 2)an event horizon, and 3)a
singularity. Black holes and neutron stars differ on all three criteria. Some
of the less frequently considered alternatives are "intermediate," in the sense
that they possess some of the traits of a black hole and some of the traits of
a neutron star. This possibility makes distinguishing the various possibilities
even more difficult.Comment: 4 pages, submitted to conference proceedings "Young Supernova
Remnants" Eds. Stephen S. Holt and Una Hwan
Constraining Post_Newtonian Parameters With Gravitational Waves
We re-express gravitational wave results in terms of post-Newtonian
parameters. Using these expressions, and some simplifying assumptions, we
compute that in a favorable case, i.e. a ten solar-mass black hole spiraling in
to a 10^6 solar-mass black hole, LISA observations will be able to constrain at
the 10% level or better a single combination of post-post-Newtonian parameters
one order higher than those already constrained by solar system evidence. This
significant constraint will be possible even if the signal-to-noise level is so
low that the signal can only be found by matched filtering, and hence only
deviations between alternate signal interpretations of order one half cycle or
more can be detected.Comment: 8 pages, abbreviated version to be submitted to conference
proceedings Twentieth Texas Symposium on Relativistic Astrophysics, Eds. J.
Craig Wheeler and Hugo Marte
Dual Accretion Disks in Alternate Gravity Theories
The interior of gravitationally collapsed objects in alternate theories of
gravity in which event horizons and singularities do not occur in strong field
gravity were generically investigated. These objects, called red holes, were
found to contain dynamic configurations of matter, radiation and spacetime
similar to inside out accretion disks well inside the photon orbit.
Applications to astrophysical phenomena are briefly described.Comment: 4 pages, to appear in "Accretion Processes in Astrophysical Systems",
Proc.of the 8th Annual Astrophysics Conference in Maryland, S. S. Holt & T.
Kallman (eds.
Strategy, policies, and programs for economic growth and social progress in the Dominican Republic: with reference to rural development
Validation and assimilation of Seasat altimeter wave heights using the WAM wave model
The mutual consistency of the Seasat global data sets of scatterometer winds and altimeter wave heights is investigated for the complete Seasat period using the third-generation wave model WAM. The wave model was driven by surface (1000 hPa) wind and surface stress fields constructed by the Goddard Laboratory for Atmospheres (GLA) by assimilation of the scatterometer winds in an atmospheric model. For the 10-day period September 7?17 the intercomparison was extended to two further scatterometer wind fields: a 1000-hPa assimilated wind field from the European Centre for Medium-Range Weather Forecasts and a subjectively analyzed 19.5-m-height surface wind field from the Jet Propulsion Laboratory. On the global average, the modeled and observed wave heights agree reasonably well. Regional differences, however, can be large and sometimes exceed 40%. The errors are attributed mainly to deficiencies in the forcing wind fields. Low wind speeds are found to be overestimated and high wind speeds underestimated by the Seasat scatterometer algorithm. The friction velocities of the GLA model are found to be significantly underestimated in the high-wind belt of the southern hemisphere. The analysis demonstrates the diagnostic advantages of applying a wave model for the quality assessment of satellite wind and wave data. A preliminary wave data assimilation scheme is presented in which the wave field is updated without changing the forcing wind field. A considerable improvement of the computed wave field is achieved, particularly in regions in which the wave energy is dominated by swell. However, a more general assimilation scheme including modifications of the wind field is needed to upgrade wind sea forecasts
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