ar X iv : a st ro - p h / 04 06 68 3 v 1 3 0 Ju n 20 04 1
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چکیده
We present observations of the High Mass X-ray Binary GX 301−2 taken during the Galactic Plane Scan (GPS) with INTEGRAL following our RXTE observations (Kreykenbohm et al., 2004). The optical companion of GX 301−2 is the B1Ia+ hyper-giant Wray 977 with a luminosity of 1.3 × 10 6 L ⊙ and a mass of ∼48 M ⊙ making the system one of the most massive X-ray binaries known. The system was observed 24 times during the GPS thus covering many orbital phases including the pre-periastron flare. The source is clearly detected in all INTEGRAL instruments in most pointings. The derived X-ray light curves show strong variability on all timescales. Depending on the orbital phase of the pointings, the luminosity changes by factor of more than 10 during the pre-periastron flare compared to other pointings. Furthermore, broad band spectra using all instruments available on INTEGRAL are compared with data taken by the RXTE instruments PCA and HEXTE (using the same data as in Kreykenbohm et al., 2004). 1. WRAY 977 AND GX 301−2 GX 301−2 consists of a 1.4 M ⊙ neutron star orbiting the early B-emission line star Wray 977. The neutron star is an accreting X-ray pulsar with a rota-tional period of∼685 s and a magnetic field strength of ∼4 × 10 12 G (derived from the measurement of a cyclotron line at ∼35 keV, Kreykenbohm et al., 2004). While Parkes et al. (1980) classify Wray 977 as a B2 Iae supergiant, Kaper et al. (1995) reclassify it as a B1 Ia+ hypergiant, derive a distance of d = 5.3 kpc, opposed to ∼1.8 kpc, and a higher lower mass limit of ∼48 M ⊙. The latter authors also estimate a mass-loss via wind (v ∞ = 400 km s −1) of
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تاریخ انتشار 2004