Letter to the Editor

Discovery of the neutron star nature of SLX 1737-282

¹ Astronomical Institute, Utrecht University, PO Box 80000, 3508 TA Utrecht, The Netherlands
² SRON National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
³ Dept. of Astronomy, University of Maryland, College Park, MD 20742, USA
⁴ NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771, USA
⁵ Istituto di Astrofisica Spaziale e Fysica Cosmica (CNR), Area Ricerca Roma Tor Vergata, Via del Fosso , 00133 Roma, Italy

Received: 1 April 2002
Accepted: 23 April 2002

Abstract

SLX 1737-282 is a persistent moderately bright X-ray source 12 from the Galactic center. X-ray observations with the Wide Field Cameras on BeppoSAX have for the first time revealed the true nature of SLX 1737-282: a 15 min long thermonuclear flash was detected exposing the source as a neutron star in a binary system. The flash was Eddington-limited constraining the distance to between 5 and 8 kpc. We analyze BeppoSAX, ROSAT, and RXTE data on SLX 1737-282. The persistent 0.5–200 keV luminosity is close to or less than 1% of the Eddington limit which implies a rarely-seen circumstance for thermonuclear flash activity.