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.

arXiv commentaccepted for publication in MNRAS

References in corpus (4)

• Nearly Coherent Oscillations in Type I X-Ray Bursts from KS 1731-260
• The Broad Band Spectrum of MXB 1728-34 Observed by BeppoSAX
• An Atlas of Burst Oscillations and Spectral Properties in 4U 1728-34
• The Effect of the Mass Accretion Rate on the Burst Oscillations in 4U 1728-34

Cited by in corpus (8)

• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• Six new candidate ultracompact X-ray binaries
• The Multi-INstrument Burst ARchive (MINBAR)
• Analysing the atolls: X-ray spectral transitions of accreting neutron stars
• Magnetically-Dominated Accretion Flows (MDAFs) and Jet Production in the Low/Hard STate
• Chandra Observations of the Faintest Low-Mass X-ray Binaries
• The Galactic LMXB Population and the Galactic Centre Region
• A thin diffuse component of the Galactic Ridge X-ray emission and heating of the interstellar medium contributed by the radiation of Galactic X-ray binaries