Discovery of type-I X-ray bursts from the low-mass X-ray binary 4U 1708-40
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 ~ (3-9)x10^(-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 Mdot~7x10^(-11) Msun/yr, that 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 found persistent fluxes of more than a factor of 7 higher than the persistent flux observed during the BeppoSAX observation showing X-ray bursts.
Cite
@article{arxiv.astro-ph/0303136,
title = {Discovery of type-I X-ray bursts from the low-mass X-ray binary 4U 1708-40},
author = {S. Migliari and T. Di Salvo and T. Belloni and M. van der Klis and R. P. Fender and S. Campana and C. Kouveliotou and M. Méndez and W. H. G. Lewin},
journal= {arXiv preprint arXiv:astro-ph/0303136},
year = {2009}
}
Comments
accepted for publication in MNRAS