A VLA Radio Continuum Survey of Active Late-Type Giants in Binary Systems: Preliminary Results

Abstract

We have made a sensitive survey at 6 cm of “active” G and K giants in binary systems, including the so-called Long-Period RS CVn stars. The systems observed have orbital periods in the range of ~10 to more than 100 days, and are judged to be “active” on the basis of their pronounced chromospheric and transition region emission lines and (where available) strong X-ray emission compared to single giants of similar spectral type. Our results to date show that strong radio continuum emission at centimeter wavelengths is a common but not universal property of this class of stars. On the basis of our VLA data and those obtained in a recent, less sensitive survey by Mutel and Lestrade, we discuss possible correlations between radio luminosity and other properties, such as X-ray luminosity, rotational period, and type of companion. Binary systems detected for the first time as radio continuum sources include 12 Cam (KO III + ?; P_orb = 80^d.2), HD 185510 (KO III-IV + sdB; P_rot = 25^d), 29 Dra (K0-2 III + wd; P_rot = 31^d), and FF Aqr (G8 III-IV + sdB; P_orb = 9^ḍ21). Sensitive upper limits are presented for five other systems including the closest Long Period RS CVn binary, α Aur (G6 III + F9 III; P_orb - 104^d).