730 research outputs found
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
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
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
Viscous timescale in high mass X-ray binaries
Context: Low mass X-ray binaries were found to have very low frequency breaks
in their power density spectra below which the power density spectra are nearly
in white noise structure and at higher frequencies they approximately follow
the law.
Aims: In 2005, Gilfanov and Arefiev studied X-ray variability of persistent
LMXBs in the Hz frequency range and
To determine whether high mass X-ray binary power density spectra have
similar properties and the findings for low mass X-ray binaries are also valid
for high mass binaries, we analyzed the time series of high mass X-ray binary
sources produced by All Sky Monitor of Rossi X-ray Timing Explorer.
Method: We obtained the power density spectra of the high mass X-ray binaries
using the cosine transform of autocorrelation function.
Results: We identified break frequencies for seven sources, namely OAO
1657-415, SS 433, Vela X-1, SMC X-1, 4U 1700-377, GX 301-2, and LMC X-1. The
normalized break frequencies with respect to the orbital frequency
() for sources OAO 1657-415, SS 433, SMC X-1 and LMC X-1
are consistent with those of Roche lobe overflow systems. The other high mass
X-ray binary systems, Vela X-1, GX 301-2, and 4U 1700-377, however, have larger
break frequency ratios, , which are indicative of short
viscous times. These are all wind-accreting sources and the stellar winds in
the systems allow the formation of only short radius discs.
Consequently, we qualitatively distinguished the Roche lobe overflow binaries
from the wind accreting system by comparing their normalized break frequencies.Comment: 9 pages, 5 figures, accepted by A&
ROTSE observations of the young cluster IC 348
CCD observations of stars in the young cluster IC 348 were obtained from 2004
August to 2005 January with a 0.45 m ROTSEIIId robotic reflecting telescope at
the Turkish National Observatory site, Bakirlitepe, Turkey. The timing analysis
of selected stars whose X-Ray counterpart were detected by Chandra X-Ray
Observatory were studied. The time series of stars were searched for rotational
periodicity by using different period search methods. 35 stars were found to be
periodic with periods ranging from 0.74 to 32.3 days. Eighteen of the 35
periodic stars were new detections. Four of the new detections were CTTSs and
the others were WTTSs and G type (or unknown spectral class) stars. In this
study, we confirmed the stability of rotation periods of TTauri stars. The
periods obtained by Cohen et al. and us were different by 1%. We also confirmed
the 3.24 h pulsation period of H254 which is a delta Scuti type star as noted
by Ripepi et al. but the other periods detected by them were not found. We
examined correlation between X-ray luminosity and rotational period of our
sample of TTSs. There is a decline in the rotational period with X-ray
luminosity for late type TTSs.Comment: 15 pages, 14 figures, accepted for publication in Astronomical
Journa
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