Volume 527, March 2011
|Number of page(s)||5|
|Section||Stellar structure and evolution|
|Published online||18 January 2011|
Finding a 24-day orbital period for the X-ray binary 1A 1118-616
Institut für Astronomie und Astrophysik, Abteilung Astronomie, Universität
2 NASA-Goddard Space Flight Center, Astrophysics Science Division, Code 661, Greenbelt, MD 20771, USA
3 Center for Space Science and Technology (CRESST), University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
4 Dr. Karl Remeis-Sternwarte and Erlangen Center for Astroparticle Physics, Universität Erlangen-Nürnberg, Sternwartstr. 7, 96049 Bamberg, Germany
5 Center for Astrophysics and Space Sciences (CASS), University of California San Diego, La Jolla, CA 92093-0424, USA
Received: 10 September 2010
Accepted: 2 November 2010
We report the first determination of the binary period and orbital ephemeris of the Be X-ray binary containing the pulsar 1A 1118-616 (35 years after the discovery of the source). The orbital period is found to be Porb = 24.0 ± 0.4days. The source was observed by RXTE during its last large X-ray outburst in January 2009, which peaked at MJD 54845.4, by taking short observations every few days, covering an elapsed time comparable to the orbital period. Using the phase connection technique, pulse arrival time delays could be measured and an orbital solution determined. The data are consistent with a circular orbit and the time of 90 degrees longitude was found to be Tπ/2 = MJD 54845.37(10), which is coincident with that of the peak X-ray flux.
Key words: binaries: general / stars: neutron / X-rays: general / X-rays: binaries / X-rays: individuals: 1A 1118-616 / ephemerides
© ESO, 2011
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