26,189 research outputs found
Exact solution of a quantum forced time-dependent harmonic oscillator
The Schrodinger equation is used to exactly evaluate the propagator, wave function, energy expectation values, uncertainty values, and coherent state for a harmonic oscillator with a time dependent frequency and an external driving time dependent force. These quantities represent the solution of the classical equation of motion for the time dependent harmonic oscillator
Broad band time-resolved E_{p,i}--L_{iso} correlation in GRBs
We report results of a systematic study of the broad band (2--2000 keV) time
resolved prompt emission spectra of a sample of gamma-ray bursts (GRBs)
detected with both Wide Field Cameras on board the \sax\ satellite and the
\batse\ experiment on board CGRO. In this first paper, we study the
time-resolved dependence of the intrinsic peak energy of the
spectrum on the corresponding isotropic bolometric luminosity .
The -- relation or the equivalent relation between
and the bolometric released energy , derived using the time
averaged spectra of long GRBs with known redshift, is well established, but its
physical origin is still a subject of discussion. In addition, some authors
maintain that these relations are the result of instrumental selection effects.
We find that not only a relation between the measured peak energy and the
corresponding energy flux, but also a strong versus
correlation are found within each burst and merging together the time resolved
data points from different GRBs. We do not expect significant instrumental
selection effects that can affect the obtained results, apart from the fact
that the GRBs in our sample are sufficiently bright to perform a time-resolved
spectroscopy and that they have known redshift. If the fundamental physical
process that gives rise to the GRB phenomenon does not depend on its
brightness, we conclude that the found versus
correlation within each GRB is intrinsic to the emission process, and that the
correlations discovered by Amati et al. and Yonetoku et al. are likely not the
result of selection effects. We also discuss the properties of the correlations
found.Comment: 27 pages,4 tables, 7 figure, accepted for publication in The
Astrophysical Journa
Genera of curves on a very general surface in
In this paper we consider the question of determining the geometric genera of
irreducible curves lying on a very general surface of degree at least 5
in (the cases are well known).
We introduce the set of all non-negative integers which are not
realized as geometric genera of irreducible curves on . We prove that
is finite and, in particular, that . The set
is the union of finitely many disjoint and separated integer
intervals. The first of them, according to a theorem of Xu, is . We show that the next one is for all .Comment: 16 page
New BeppoSAX-WFC results on superbursts
Presently seven superbursters have been identified representing 10% of the
total Galactic X-ray burster population. Four superbursters were discovered
with the Wide Field Cameras (WFCs) on BeppoSAX and three with the All-Sky
Monitor and Proportional Counter Array on RXTE. We discuss the properties of
superbursters as derived from WFC observations. There are two interesting
conclusions. First, the average recurrence time of superbursts among X-ray
bursters that are more luminous than 10% of the Eddington limit is 1.5 yr per
object. Second, superbursters systematically have higher alpha values and
shorter ordinary bursts than most bursters that have not exhibited superbursts,
indicating a higher level of stable thermonuclear helium burning. Theory
predicts hitherto undetected superbursts from the most luminous neutron stars.
We investigate the prospects for finding these in GX~17+2.Comment: Submitted in January 2004 for the Proceedings of the meeting 'X-Ray
Timing 2003: Rossi and Beyond', eds. P. Kaaret, F. K. Lamb, & J. H. Swank
(Melville, NY: American Institute of Physics
The BeppoSAX WFC X-ray source catalogue
We present the catalogue of X-ray sources detected by the two Wide Field
Cameras (WFCs) in complete observations on board BeppoSAX during its 6 years of
operational lifetime, between April 1996 and April 2002. The BeppoSAX WFCs were
coded mask instruments sensitive in the 2-28 keV energy band with a 40x40
square degree fields of view, pointing in opposite directions and
perpendicularly to the BeppoSAX Narrow Field Instruments (NFI). The WFCs were
usually operated simultaneously to NFI observations, each lasting up to several
days. WFCs observed thus the entire sky several times with a typical
sensitivity of 2 to 10 mCrab. A systematic analysis of all WFC observations in
the BeppoSAX archive has been carried out using the latest post-mission release
of the WFC analysis software and calibrations. The catalogue includes 253
distinct sources, obtained from a total sample of 8253 WFC detections. We
describe the basic statistical properties of the sample and present a six-year
history of two celestial calibration X-ray sources.Comment: 15 pages, 11 figures, Catalogue, Accepted for publication on A&
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