2003/10/04 by W. Pietsch, B. J. Mochejska, Z. Misanovic +3 · 1 citation
Engineering · Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Binary number #Binary star #Compact star #Eclipse #Ephemeris #Light curve #Luminosity #Mass ratio #Mechanics and Biomechanics Studies #Neutron star #Orbital inclination #Orbital period #Physics #Roche lobe #Satellite #Stars #X-ray binary #astro-ph
paper · pdf · doi:10.1051/0004-6361:20034081
published as Astron.Astrophys. 413 (2004) 879-887 · 9 pages including 6 figures, A&A accepted
arxiv created 2003/10/04 · openalex publication_date 2004/01/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The eclipsing X-ray binary M 33 X-7 was in the field of view during several observations of our XMM-Newton M 33 survey and in the archival Chandra observation 1730 which cover a large part of the 3.45 d orbital period. We detect emission of M 33 X-7 during eclipse and a soft X-ray spectrum of the source out of eclipse that can best be described by bremsstrahlung or disk blackbody models. No significant regular pulsations of the source in the range 0.25–1000 s were found. The average source luminosity out of eclipse is 5 1037 (0.5–4.5 keV). In a special analysis of DIRECT observations we identify as optical counterpart a B0I to O7I star of 18.89 mag in V which shows the ellipsoidal heating light curve of a high mass X-ray binary with the M 33 X-7 binary period. The location of the X-ray eclipse and the optical minima allow us to determine an improved binary period and ephemeris of mid-eclipse as HJD . The mass of the compact object derived from orbital parameters and the optical companion mass, the lack of pulsations, and the X-ray spectrum of M 33 X-7 may indicate that the compact object in the system is a black hole. M 33 X-7 would be the first detected eclipsing high mass black hole X-ray binary.