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On the Nature of the Bright Short-Period X-Ray Source in the Circinus Galaxy FieldThe spectrum and light curve of the bright X-ray source CG X-1 in the field of the Circinus galaxy are reexamined. Previous analyses have concluded that the source is an accreting black hole of mass > or approx. 50 solar masses although it has been noted that the light curve resembles that of an AM Herculis system. Here we show that the short period and an assumed main-sequence companion constrain the mass of the companion to less than 1 solar mass. Furthermore, a possible eclipse seen during one of the Chandra observations and a subsequent XMM-Newton observation constrain the mass of the compact object to less than 60 solar masses. If such a system lies in the Circinus galaxy, then the accreting object must either radiate anisotropically or strongly violate the Eddington limit. Even if the emission is beamed, then the companion star that intercepts this flux during eclipse will be driven out of thermal equilibrium and evaporate within approx. 10(exp 3) yr. We find that the observations cannot rule out an AM Herculis system in the Milky Way and that such a system can account for the variations seen in the light curve.
Document ID
20040071009
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Weisskopf, Martin C.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Wu, Kinwah
(University Coll. London, United Kingdom)
Tennant, Allyn F.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Swartz, Douglas A.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Ghosh, Kajal K.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Date Acquired
August 21, 2013
Publication Date
April 10, 2004
Publication Information
Publication: The Astrophysical Journal
Volume: 605
Subject Category
Astronomy
Distribution Limits
Public
Copyright
Other

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