Discovery of type I X-ray bursts from the low-mass X-ray binary 4U 1708 – 40 |
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| Authors: | S. Migliari,T. Di Salvo,T. Belloni,M. van der Klis,R. P. Fender,S. Campana,C. Kouveliotou,M. Mé ndez, W. H. G. Lewin |
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| Affiliation: | Astronomical Institute 'Anton Pannekoek' University of Amsterdam and Centre for High-Energy Astrophysics, Kruislaan 403, 1098 SJ, Amsterdam, the Netherlands;INAF–Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate (LC), Italy;NASA Marshall Space Flight Center, SD50, Huntsville, AL 35812, USA;Universities Space Research Association/NSSTC, SD-50, Huntsville, AL 35805, USA;SRON, National Institute for Space Research, Sorbonnelaan 2, 3584 CA, Utrecht, the Netherlands;Center for Space Research and Department of Physics, Massachusetts Institute of Technology, 70 Vassar Street, Cambridge, MA 02139-4307, USA |
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| Abstract: | We report the discovery of type I X-ray bursts from the low-mass X-ray binary 4U 1708 − 40 during the 100-ks observation performed by BeppoSAX on 1999 August 15–16. Six X-ray bursts have been observed. The unabsorbed 2–10 keV fluxes of the bursts range from ∼3 to 9 × 10−10 erg cm−2 s−1 . A correlation between peak flux and fluence of the bursts is found, in agreement with the behaviour observed in other similar sources. There is a trend of the burst flux to increase with the time interval from the previous burst. From the value of the persistent flux we infer a mass accretion rate , which may correspond to the mixed hydrogen/helium burning regime triggered by thermally unstable hydrogen. We have also analysed a BeppoSAX observation performed on 2001 August 22 and previous RXTE observations of 4U 1708 − 40 , where no bursts have been observed; we find persistent fluxes of more than a factor of 7 higher than the persistent flux observed during the BeppoSAX observation showing X-ray bursts. |
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| Keywords: | accretion, accretion discs stars: individual: 4U 1708 − 40 stars: neutron X-rays: bursts X-rays: general |
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