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Astron. Astrophys. 329, L53-L56 (1998)

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1. Introduction

The last two years have witnessed the first detections of extra-solar planets. Following the discovery of a planet near 51 Peg by Mayor & Queloz (1995) and similar results for 47 UMa, 70 Vir and HD 114762, the discovery of 3 new cases was announced by Butler et al. (1997). Among these stars is [FORMULA]  Cnc (HR 3522, HD 75732). [FORMULA]  Cnc is a solar-type star with spectral class G8V, slightly metal-rich, at a distance of 12.5 pc. Its age inferred from CaII H and K fluxes is 5 Gyr (Baliunas et al. 1997). According to Butler et al. (1997), the planet near [FORMULA]  Cnc has a period of 14.65 days implying a semi major axis of 0.11 AU. The inferred mass is [FORMULA]. This is one of the 51 Pegasi-like "hot Jupiter" planets. The Doppler velocity of the primary also exhibits a long term trend consistent with a second, as yet unconfirmed companion ([FORMULA] yr, [FORMULA]). [FORMULA]  Cnc is also a resolved double star with an M5 dwarf companion (HD 75732B, [FORMULA]) at a distance of approximately 1150 AU from the primary.

In 1983 IRAS detected infrared excess from several main-sequence stars, e.g. Vega, [FORMULA]  Pic, Formalhaut. This excess was attributed to a disk of dust around the star, which was later confirmed dramatically in the case of [FORMULA]  Pic by the observation of scattered light from the disk. Subsequent analysis of the IRAS data base showed that this phenomenon was widely spread among main-sequence stars (Aumann et al. 1984 , Aumann 1985). The detection of planets around other main sequence stars raised the question whether planets and Vega-like disks can exist together. Unfortunately, the star [FORMULA]  Cnc was not on any target list for ISO. We therefore applied for discretionary time which was subsequently granted. ISOPHOT measurements were obtained only a few days before the star disappeared from ISO's visibility zone.

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© European Southern Observatory (ESO) 1998

Online publication: December 16, 1997