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Two-phase X-ray burst from GX 3+1 observed by INTEGRAL

Abstract : We present an analysis of an anomalously long X-ray burst from the low-mass X-ray binary system GX~3+1 observed by INTEGRAL on August 31, 2004. The burst is characterized by two distinct phases: an initial short spike of 6 s followed by an extended decay phase lasting more than 2000 s. Due to its uncommon duration this burst appears as intermediate between the normal type I X-ray bursts and the long superbursts. We see emission up to 30 keV energy during the first 5 s of the outburst where the bolometric burst peak luminosity approaches the Eddington limit. Indications of a radius expansion episode during the peak phase are thus not overruled. A time-resolved two-component spectral analysis of the total emission reveals similar results as a black-body modeling of the net burst emission. From the burst light curve and the derived burst parameters we conclude that we observed a type I X-ray burst of an unusual character. We discuss three alternative schemes to explain this peculiar X-ray burst: 1) unstable burning of a hydrogen/helium layer involving an unusually large amount of hydrogen, 2) pure helium ignition at an unusually large depth, but this seems unlikely in the present case, and 3) limited carbon burning at an unusually shallow depth triggered by unstable helium ignition.
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http://hal.in2p3.fr/in2p3-00025506
Contributor : Simone Lantz <>
Submitted on : Thursday, January 26, 2006 - 5:35:16 PM
Last modification on : Wednesday, September 23, 2020 - 4:39:57 AM

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J. Chenevez, M. Falanga, S. Brandt, R. Farinelli, F. Frontera, et al.. Two-phase X-ray burst from GX 3+1 observed by INTEGRAL. Astronomy and Astrophysics - A&A, EDP Sciences, 2006, 449, pp.L5-L8. ⟨10.1051/0004-6361:200600016⟩. ⟨in2p3-00025506⟩

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