Simultaneous radio and X-ray observations of the low-mass X-ray binary GX 13+1

• Published in: arXiv.org
• Main Authors: Homan, Jeroen, Wijnands, Rudy, Rupen, Michael P, Fender, Rob, Hjellming, Robert M, Tiziana di Salvo, Michiel van der Klis
• Format: Paper
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 02.09.2003
• Subjects: Binary stars; Flux density; Neutron flux; Neutron stars; Quasars; Radio; Radio observation; X ray binaries; X ray spectra; X ray stars; X-rays
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.0309042

We present the results of two simultaneous X-ray/radio observations of the low-mass X-ray binary GX 13+1, performed in July/August 1999 with the Rossi X-ray Timing Explorer and the Very Large Array. In X-rays the source was observed in two distinct spectral states; a soft state, which had a corresponding 6 cm flux density of ~0.25 mJy, and a hard state, which was much brighter at 1.3-7.2 mJy. For the radio bright observation we measured a delay between changes in the X-ray spectral hardness and the radio brightness of ~40 minutes, similar to what has been found in the micro-quasar GRS 1915+105. We compare our results with those of GRS 1915+105 and the atoll/Z-type neutron star X-ray binaries. Although it has some properties that do not match with either atoll or Z sources, GX 13+1 seems more similar to the Z sources.