Detection of 6-cm radio-continuum emission from an EB (β-Lyrae type) variable star - HIP 68718

Abstract

We report the 6-cm radio-continuum detection of a previously unknown radio star, HIP 68718, identified by the Hipparcos satellite as an EB or β-Lyrae type optical variable. Only five prior radio detections of this type are reported in the literature. The radio source (VLA J140402-002145) was detected at the 6σ level, with an associated <1arcsec position error. The radio-optical separation is 0.2arcsec and is well within the position errors. A ROSAT X-ray source (RXJ 1404.0-0021) is located 4.5 arcsec from the radio position. Based on the component spectral types (F5V + G5V), 1.52 d period, variations in the peak of the light curve and the X-ray and 6-cm radio luminosities, we conclude the star is a candidate RS CVn. The binary is in a near-contact phase based on the asymmetric light curve (O'Connell effect). Evidence of two faint possible companion objects was also found in the J- and K-band Two-Micron All-Sky Survey images.