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An EXOSAT detection of the transient X-ray pulsar GRO J1008-57
- Source :
- Astrophysical Journal, Part 1. 437(2)
- Publication Year :
- 1994
- Publisher :
- United States: NASA Center for Aerospace Information (CASI), 1994.
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Abstract
- The hard X-ray transient, GRO J1008-57, was discovered during a bright outburst in 1993 July by the Burst and Transient Source Experiment (BATSE) instrument on board the Compton Gamme-Ray Observatory (CGRO). There are no published reports of previous emission from this 93.6 sec X-ray pulsar. Recent optical results have suggested a Be star as the companion. A search of the EXOSAT archives shows that an ME observation centered on the star HD 88661 includes GRO J1008-57 within the field of view. The characteristics of the medium-energy detection including a hard spectrum and pulsed emission at 91.36 sec (with chance probability of 3 x 10(exp -4)) indicates that EXOSAT detected GRO J1008-57 rather than the field star. The estimated flux is 2.4 x 10(exp -11) ergs/cm sq/sec for a luminosity of 1.1 x 10(exp 34) (D/2 kpc)(exp 2) ergs/sec. The X-ray spectrum is hard (photon index approximately equals 1.2) and highly absorbed (N(sub H) approximately equals 0.7 x 10(exp 22)). The detection of this transient suggests that there is a pulse shape dependence on luminosity, a spectral shape independent of luminosity, a large period derivative of P-dot/P = 2.3 x 10(exp -3)/yr, and a dynamic range of at least 100 in L(sub chi). We discuss GRO J1008-57 data in the context of wind-accretion models for this new member of the Be class of X-ray binaries.
- Subjects :
- Astrophysics
Subjects
Details
- Language :
- English
- ISSN :
- 0004637X
- Volume :
- 437
- Issue :
- 2
- Database :
- NASA Technical Reports
- Journal :
- Astrophysical Journal, Part 1
- Publication Type :
- Report
- Accession number :
- edsnas.19950043750
- Document Type :
- Report
- Full Text :
- https://doi.org/10.1086/175044