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Astron. Astrophys. 358, L71-L74 (2000)

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Letter to the Editor

Discovery of 1RXS J171824.2-402934 as an X-ray burster

R.G. Kaptein 1, J.J.M. in 't Zand 1, E. Kuulkers 1,2, F. Verbunt 2, J. Heise 1 and R. Cornelisse 1,2

1 Space Research Organization Netherlands, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
2 Utrecht University, Astronomical Institute, P.O. Box 80000, 3508 TA Utrecht, The Netherlands

Received 20 April 2000 / Accepted 23 May 2000


We report the first-time detection of a type-I X-ray burst from a position that is consistent with that of 1RXS J171824.2-402934. The detection was made on Sep 23, 1996, with the Wide Field Cameras on board the BeppoSAX satellite. The burst had a peak intensity of 1.3 Crab units in 2 to 28 keV and is relatively long (at least 3.5 min). Analysis of the burst gives clear evidence for photospheric radius expansion. Assuming the peak luminosity to be close to the Eddington limit, standard burst parameters and taking into account gravitational redshift effects, the distance to the source is approximately 6.5 kpc. No other bursts from this source have been observed during the rest of the WFC observations. The detection of a type-I burst implies that 1RXS J171824.2-402934 in all likelihood is a low-mass X-ray binary where the compact object is a neutron star.

Key words: stars: individual: 1RXS J171824.2 – 402934 – stars: neutron – X-rays: bursts

Send offprint requests to: R.G.Kaptein (ronaldk@sron.nl)

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© European Southern Observatory (ESO) 2000

Online publication: June 20, 2000