BeppoSAX study of the X-ray binary XB1832-330 located in the globular cluster NGC6652

¹ Astrophysics Division, Space Science Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
² Osservatorio Astronomico di Roma, via Frascati 33, Monteporzio Catone, 00040 Roma, Italy
³ Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, via Gobetti 101, 40129 Bologna, Italy

Corresponding author: A. N. Parmar, aparmar@astro.estec.esa.nl

Received: 22 August 2001
Accepted: 18 October 2001

Abstract

Results of a 2001 March 17-20 BeppoSAX observation of the X-ray binary XB1832-330 located in the globular cluster NGC6652 are presented. In contrast to the majority of luminous globular cluster X-ray sources, the (0.1-200 keV) BeppoSAX spectrum cannot be fit with a disk-blackbody and comptt Comptonization model, unless partial covering is included. This confirms the ASCA detection of partial covering by Mukai & Smale ([CITE]). The best-fit spectral parameters are similar to those of the globular cluster sources with orbital periods of <1 hr, implying that XB1832-330 is also an ultra-compact system. A plausible optical candidate to XB1832-330has recently been discovered by Heinke et al. ([CITE]) which shows evidence for possible 0.92, 2.22, or 4.44 hr periodicities. We find no evidence for any 2-10 keV periodic modulation at any of these periods with a 2σ upper limit to the semi-amplitude of any sinusoid of ≲1.5% .