No optical pulses from the Geminga candidate

Creators: Kulkarni, Shrinivas R.; Djorgovski, S.

Abstract

We have conducted several optical studies of a 21 mag star suggested to be the optical counterpart of the pulsed x-ray source IE 0630 + 178 and the γ-ray source 2CG 195 + 04 (Geminga). We report the absence of significant optical pulsed emission over the entire period range claimed from the analysis of high-energy data. We also find no significant variability on time scales from tens of minutes to a few months. We suggest that the true optical counterpart of the x-ray source is either one of the two fainter stars in the x-ray source error box or an as yet undetected fainter star. In either case, IE 0630 + 178 is a unique x-ray source because its ratio of L_x (0.2-2.0 keV)/L_v (3000-7000 Å) is at least 1100, which is characteristic of galactic-bulge x-ray sources. However, its absolute magnitude is at least about M_v ~ 20 and not M_v ~ 3 mag, typical of the bulge sources.

Additional Information

© 1986 American Astronomical Society. Provided by the NASA Astrophysics Data System. Received: 26 July 1985; revised 6 September 1985. Based in part on research done at Lick Observatory, University of California. Dan Werthimer was principally responsible for the design and fabrication of the shutter-controller mechanism. We are much indebted to him for this and also gratefully acknowledge him for the loan of his synthesizer and help in observations. H. Spinrad made generous contributions of observing time at Lick. We would like to thank C. Heiles for discussion about the data analysis and J. Arons for stimulating conversations on theoretical issues. The "phased"-image observations required many changes at Lick. We are grateful to the staff of Lick for their cooperation and help, and in particular to R. Stone, K. Baker, W. Earthman, J. Morey, C. Clark, and B. Alcott. We thank A. Klemola for his help with astrometry. A major portion of the data reductions were done with vista, a software package developed by R. Stover, T. Lauer, and D. Temdrup of the Lick Observatory. This work was supported in part by NSF Grants Nos. AST 82-12058 and AST 84-16863 and a University of California Regents Fellowship to S.D.

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