811 research outputs found
The Spectrum and Dips of RE 0751+14: A joint evaluation of ROSAT and ASCA Archival Data
Using archival ASCA and ROSAT observations of RE 0751+14, X-ray energy
spectra, pulse profiles and the results of pulse timing analysis are presented.
The energy spectra are well-fitted by a blackbody model at low energy and a
Raymond-Smith model at high energy, together with a partial covering absorber.
A fluorescence emission line at 6.4 keV with an equivalent width eV
was resolved for the first time.Comment: To appear on Astrophysics and Space Science, vol 259, pages 191-203,
January 199
First results of observations of transient pulsar SAXJ2103.5+4545 with the INTEGRAL observatory
We present preliminary results of observations of X-ray pulsar SAX
J2103.5+4545 with INTEGRAL observatory in Dec 2002. Maps of this sky region in
energy bands 3-10, 15-40, 40-100 and 100-200 keV are presented. The source is
significantly detected up to energies of keV. The hard X-ray flux in
the 15-100 energy band is variable, that could be connected with the orbital
phase of the binary system. We roughly reconstructed the source spectrum using
its comparison to that of Crab nebula. It is shown that the parameters of the
source spectrum in 18-150 keV energy range are compatible with that obtained
earlier by RXTE observatoryComment: 5 pages, 4 figures, accepted for publication in the Astronomy Letter
Post-Glitch RXTE-PCA Observations of the Vela Pulsar
We report the results of analysis of observations of the Vela Pulsar by PCA
on RXTE. Our data consists of two parts. The first part contains observations
at 1, 4, and 9 days after the glitch in 1996 and has 27000 sec. total exposure
time. The second part of observations were performed three months after this
glitch and have a total exposure time of 93000 sec. We found pulsations in both
sets. The observed spectrum is a power-law with no apparent change in flux or
count rate. The theoretical expectations of increase in flux due to internal
heating after a glitch are smaller than the uncertainty of the observations.Comment: 6 pages, 5 figures in 9 ps/eps files. Accepted for publication in A&A
Main Journa
The Timing Noise of PSR 0823+26, PSR 1706-16, PSR 1749-28, PSR 2021+51 and The Anomalous Braking Indices
We have investigated the stability of the pulse frequency second derivatives
() of PSR 0823+26, PSR 1706-16, PSR 1749-28, PSR 2021+51 which show
significant quadratic trends in their pulse frequency histories in order to
determine whether the observed second derivatives are secular or they arise as
part of noise processes. We have used TOA data extending to more than three
decades which are the longest time spans ever taken into account in pulse
timing analyses. We investigated the stability of pulse frequency second
derivative in the framework of low resolution noise power spectra (Deeter 1984)
estimated from the residuals of pulse frequency and TOA data. We have found
that the terms of these sources arise from the red torque noise in
the fluctuations of pulse frequency derivatives which may originate from the
external torques from the magnetosphere of pulsar
Differences between the Two Anomalous X-Ray Pulsars: Variations in the Spin Down Rate of 1E 1048.1-5937 and An Extended Interval of Quiet Spin Down in 1E 2259+586
We analysed the RXTE archival data of 1E 1048.1-5937 covering a time span of
more than one year. The spin down rate of this source decreases by 30 percent
during the observation. We could not resolve the X-ray flux variations because
of contamination by Eta Carinae. We find that the level of pulse frequency
fluctuations of 1E 1048.1-5937 is consistent with typical noise levels of
accretion powered pulsars. Recent RXTE observations of 1E 2259+586 have shown a
constant spin down with a very low upper limit on timing noise. We used the
RXTE archival X-ray observations of 1E 2259+586 to show that the intrinsic
X-ray luminosity times series is also stable, with an rms fractional variation
of less than 15 percent. The source could have been in a quiet phase of
accretion with a constant X-ray luminosity and spin down rate.Comment: MNRAS in pres
Pulsar Braking Indices, Glitches and Energy Dissipation In Neutron Stars
Almost all pulsars with anomalous positive measurements
(corresponding to anomalous braking indices in the range 5100), including
all the pulsars with observed large glitches (
10) as well as post glitch or interglitch measurements
obey the scaling between and glitch parameters originally noted
in the Vela pulsar. Negative second derivative values can be understood in
terms of glitches that were missed or remained unresolved. We discuss the
glitch rates and a priori probabilities of positive and negative braking
indices according to the model developed for the Vela pulsar. This behavior
supports the universal occurrence of a nonlinear dynamical coupling between the
neutron star crust and an interior superfluid component. The implied lower
limit to dynamical energy dissipation in a neutron star with spindown rate
is . Thermal
luminosities and surface temperatures due to dynamical energy dissipation are
estimated for old neutron stars which are spinning down as rotating magnetic
dipoles beyond the pulsar death line.Comment: Accepted for publication in MNRA
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