2008A&A...486..293B


Query : 2008A&A...486..293B

2008A&A...486..293B - Astronomy and Astrophysics, volume 486, 293-302 (2008/7-4)

INTEGRAL observations of the variability of OAO1657-415.

BARNSTEDT J., STAUBERT R., SANTANGELO A., FERRIGNO C., HORNS D., KLOCHKOV D., KRETSCHMAR P., KREYKENBOHM I., SEGRETO A. and WILMS J.

Abstract (from CDS):

The Galactic Plane Scan (GPS) was one of the core observation programmes of the INTEGRAL satellite. The highly variable accreting pulsar OAO1657-415 was frequently observed within the GPS. We investigate the spectral and timing properties of OAO1657-415 and their variability on short and long time scales in the energy range 6-160 keV. Using standard extraction tools and custom software for extracting INTEGRAL data we analysed energy-resolved light curves with a time resolution of one second - mainly data of the ISGRI instrument. We also analysed phase-averaged broad band spectra - including JEM-X spectra - and pulse-phase resolved spectra of ISGRI. During the time covered by the INTEGRAL observations, the pulse period evolution shows an initial spin-down, which is followed by an equally strong spin-up. In combining our results with historical pulse period measurements (correcting them for orbital variation) and with stretches of continuous observations by BATSE, we find that the long-term period evolution is characterised by a long-term spin-up overlayed by sets of relative spin-down/spin-up episodes, which appear to repeat quasi-periodically on a 4.8yr time scale. We measure an updated local ephemeris and confirm the previously determined orbital period with an improved accuracy. The spectra clearly change with pulse phase. The spectrum measured during the main peak of the pulse profile is particularly hard. We do not find any evidence of a cyclotron line, wether in the phase-averaged spectrum or in phase-resolved spectra.

Abstract Copyright:

Journal keyword(s): X-rays: binaries - pulsars: individual: OAO1657-415

Simbad objects: 7

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Number of rows : 7
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 V* V635 Cas HXB 01 18 31.9704955824 +63 44 33.072603144 17.05 16.64 15.19 14.34 13.22 B0.2Ve 746 0
2 V* GP Vel HXB 09 02 06.8608812864 -40 33 16.899168060 6.85 7.37 6.87 6.31 6.05 B0.5Ia 1505 0
3 V* V779 Cen HXB 11 21 15.0920532528 -60 37 25.630264596   14.4 12.27     O9III/Veq 1101 0
4 V* BP Cru HXB 12 26 37.5605188992 -62 46 13.261044684   12.482 10.803 10.304   B1Ia+ 689 0
5 V* HZ Her LXB 16 57 49.8110126616 +35 20 32.486555472 11.90 14.89 13.63 13.88   B3/6ep 2081 0
6 NAME OAO 1657-41 HXB 17 00 48.884 -41 39 21.46           Ofpe/WN9 248 0
7 V* V2116 Oph Sy* 17 32 02.1532435416 -24 44 44.129169096   20.78 18.4     M6IIIe 692 1

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