Optical identification of the transient supersoft X-ray source RX J0527.8-6954, in the LMC

Abstract

Context. Close binary supersoft X-ray sources (CBSS) are binary systems that contain a white dwarf with stable nuclear burning on its surface. These sources, first discovered in the Magellanic Clouds, have high accretion rates and near-Eddington luminosities (10^37 - 10^38 erg/s) with high temperatures (T = 2 - 7 x 10^5 K). Aims. The total number of known objects in the MC is still small and, in our galaxy, even smaller. We observed the field of the unidentified transient supersoft X-ray source RX J0527.8-6954 in order to identify its optical counterpart. Methods. The observation was made with the IFU-GMOS on the Gemini South telescope with the purpose of identifying stars with possible He II or Balmer emission or else of observing nebular extended jets or ionization cones, features that may be expected in CBSS. Results. The X-ray source is identified with a B5e V star that is associated with subarcsecond extended Halpha emission, possibly bipolar. Conclusions. If the primary star is a white dwarf, as suggested by the supersoft X-ray spectrum, the expected orbital period exceeds 21 h; therefore, we believe that the 9.4 h period found so far is not associated to this system.

4 pages, 4 figures, A&A, in press

References in corpus (3)

• Detection of a Rare Supersoft Outburst Event during a Suzaku Observation of 1E0102.2-7219
• Supersoft X-ray Sources. Basic Parameters
• Transient jets in V617 Sagittarii

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• Swift J004427.3-734801- a probable Be/white dwarf system in the Small Magellanic Cloud
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• Supersoft X-ray sources identified with Be binaries in the Magellanic Clouds
• Multiwavelength modeling the SED of Luminous Supersoft X-ray Sources in Large Magellanic Cloud and Small Magellanic Cloud