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Searching for X-ray Binaries in the LMC: The Optical Counterparts of CAL 9 and CAL E

Published online by Cambridge University Press:  12 April 2016

Paul C. Schmidtke  and
Anne P. Cowley
Paul C. Schmidtke
Affiliation:
Department of Physics and Astronomy, Arizona State University, Tempe, AZ 85287-1504, USA
Anne P. Cowley
Affiliation:
Department of Physics and Astronomy, Arizona State University, Tempe, AZ 85287-1504, USA

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To better define the global properties of X-ray binaries in the Large Magellanic Cloud, a program of optical identification has been initiated, combining improved X-ray positions from ROSAT with photometry and spectroscopy obtained at CTIO. This initiative is an extension of work by Cowley et al. (1984) and Crampton et al. (1985), who attempted to identify the optical counterparts of “CAL” X-ray point sources found in the Einstein IPC survey of the LMC conducted by Columbia Astrophysical Laboratory (Long et al. 1981). A key element in our investigation of the remaining unidentified sources is the use of significantly more accurate coordinates (typically ±5″ from ROSAT HRI data versus ±30″ for the older IPC positions), thereby greatly reducing the number of stars needing examination. Likely candidates are selected using multicolor photometry (by location in color–color plots or through variability) prior to spectroscopic observing. Although the identifications for CAL 9 and CAL E were reasonably secure (in particular the latter since it had an Einstein HRI position, see Crampton et al.), these sources have been re-observed to test our procedures and to verify the previous results.

Type
HST, IUE, & Rosat Observations
Information
International Astronomical Union Colloquium , Volume 135: Complementary Approaches to Double and Multiple Star Research , 1992 , pp. 386 - 388
Copyright
Copyright © Astronomical Society of the Pacific 1992

References

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