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Time variability of the X-ray sources in M33The results of a variability study of the X-ray sources detected by the Einstein Observatory in the galaxy M33 are reported. Two of the 15 known sources are variable above the 99.73 percent confidence level. The light curve of one of these sources, M33 X-7, exhibits a variability pattern of high and low states, suggesting an eclipsing binary X-ray source. Such a finding would be the first identification of a close accreting binary system with an X-ray source in an external galaxy other than the Magellanic Clouds. The data suggest a binary period of 1.7857 day and an eclipse duration of about 0.4 day. The nuclear source M33 X-8 varies only in the softest part of the spectrum. The observations suggest a rapid variability and show a rapid flare with a rise time shorter than three days together with longer timescale variability.
Document ID
19890035317
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Peres, G.
(Osservatorio Astronomico Palermo, Italy)
Reale, F.
(Palermo Osservatorio Astronomico, Italy)
Collura, A.
(CNR Istituto per le Applicazioni Interdisciplinari della Fisica, Palermo, Italy)
Fabbiano, G.
(Harvard-Smithsonian Center for Astrophysics Cambridge, MA, United States)
Date Acquired
August 14, 2013
Publication Date
January 1, 1989
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 336
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
89A22688
Funding Number(s)
CONTRACT_GRANT: NAS8-30751
Distribution Limits
Public
Copyright
Other

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