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Type-I X-ray bursts from XTE J1739-285

ATel #622; S. Brandt (DNSC, Denmark), E. Kuulkers (ESA/ESAC, Spain), A. Bazzano (IASF/INAF, Rome), T. J.-L. Courvoisier (ISDC, Geneva), A. Domingo (LAEFF, Madrid), K. Ebisawa (NASA/GSFC, USA), N. Gehrels (NASA/GSFC, USA), P. Kretschmar (ESA/ESAC, Spain), R. Krivonos (IKI/RSDC, Moscow), N. Lund (DNSC, Denmark), C. Markwardt (NASA/GSFC, USA), N. Mowlavi (ISDC, Geneva), T. Oosterbroek (ESA/ESTEC, Netherlands), A. Orr (ESA/ESTEC, Netherlands), A. Paizis (ISDC, Geneva / IASF, Milano), J.-P. Roques (CESR, Toulouse), S. E. Shaw (Southampton, UK/ ISDC, Geneva), R. Wijnands (UvA, Netherlands)
on 8 Oct 2005; 22:36 UT
Credential Certification: Erik Kuulkers (ekuulker@rssd.esa.int)

Subjects: X-ray, Binary, Black Hole, Neutron Star, Transient

Referred to by ATel #: 734, 777, 784

During the Galactic Bulge Monitoring and Galactic Centre Scan observations performed with INTEGRAL, two X-ray flares coming from XTE J1739-285 were observed with the X-ray monitor JEM-X (3-25 keV). The events started on UT Sep 30, 2005 11:51:21 and UT Oct 04 2005 17:49:41, respectively, and reached a net-peak flux of ~500 mCrab. The flares had a rise-time of 2-3 seconds, followed by an exponential-like decay with an e-folding time of 10-15 seconds in the 3-25 keV band. The duration of the events are shorter at higher X-ray energies, indicating softening of the X-ray spectrum during the decay. These characteristics are typical of type-I X-ray bursts. The observations strongly suggest that XTE J1739-285 harbors a neutron star, and not a black hole as previously suggested based on the spectral evolution of the source (ATel #615).