Swift monitoring of the massive X-ray binary SAX J0635.2+0533
Abstract
SAX J0635.2+0533 is a binary pulsar with a very short pulsation period (P = 33.8 ms) and a high long-term spin down (Ṗ> 3.8 × 10-13 s s-1), which suggests a rotation-powered (instead of an accretion-powered) nature for this source. While it was discovered at a flux level around 10-11 erg cm-2 s-1, between 2003 and 2004, this source was detected with XMM-Newton at an average flux of about 10-13 erg cm-2 s-1; moreover, the flux varied by over one order of magnitude on timescales of a few days, sometimes decreasing to below 3 × 10-14 erg cm-2 s-1. Since both the rotation-powered and the accretion-powered scenarios have difficulties to explain these properties, the nature of SAX J0635.2+0533 is still unclear. Here we report on our recent long-term monitoring campaign on SAX J0635.2+0533 carried out with Swift, and on a systematic reanalysis of all the RXTE observations performed between 1999 and 2001. We found that during this time interval, the source remained almost always active at a flux level above 10-12 erg cm-2 s-1.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 2017
- DOI:
- 10.1051/0004-6361/201730887
- arXiv:
- arXiv:1705.03230
- Bibcode:
- 2017A&A...602A.114L
- Keywords:
-
- stars: individual: SAX J0635+0533;
- X-rays: binaries;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 8 pages, 6 figures, 2 tables. Accepted for publication in Astronomy &