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Astron. Astrophys. 357, L41-L44 (2000)

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Letter to the Editor

An X-ray burst with strong photospheric radius expansion observed from the source 4U1724-307 in Terzan 2

S.V. Molkov 1,2, S.A. Grebenev 1,2 and A.A. Lutovinov 1

1 Space Research Institute, Russian Academy of Sciences, Profsoyuznaya 84/32, 117810 Moscow, Russia
2 Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Strasse 1, 85740 Garching, Germany

Received 30 November 1999 / Accepted 19 April 2000


We present results of the RXTE observations of an extremely intense X-ray burst detected from the source 4U1724-307 in the globular cluster Terzan 2. The burst profile was complex consisting of two precursors and a long primary peak. During the first (strong) precursor the source luminosity, [FORMULA], was comparable with that measured in the main event. The structure of the profile, its dependence on energy and observed spectral evolution indicated strong photospheric expansion of a neutron star. The effective temperature and radius of the photosphere were estimated from the black body model at different stages of expansion, their correlations and specific features of the profile were analyzed and discussed.

Key words: stars: neutron – Galaxy: globular clusters: individual: Terzan 2 – X-rays: bursts – X-rays: stars

Send offprint requests to: S.V. Molkov (msv@hea.iki.rssi.ru)

© European Southern Observatory (ESO) 2000

Online publication: June 5, 2000