The Mysterious IR Excesses in RS CVn Binaries
First Author:
Marco Matranga
Email: mmatranga AT cfa.harvard.edu
Harvard-Smithsonian Center for Astrophysics
60 Garden St, MS-70
Cambridge, 02138, MA (USA)
Coauthors:
Drake, Jeremy, Harvard-Smithsonian Center for Astrophysics
Marengo, Massimo, Harvard-Smithsonian Center for Astrophysics
Kashyap, Vinay, Harvard-Smithsonian Center for Astrophysics
Abstract
One of the most remarkable properties sometimes attributed to RS CVn binaries is evidence of infrared excess, which is thought related to the presence of circumstellar matter. The existence of this non-stellar component in the flux distribution of such a class of object has been the subject of considerable controversy. Within current scenarios explaining IR excess around late type stars, RS CVn should not have any: they represent a significantly older population than the ~ 400 Myr dusty disk lifetime, with typical ages of 1 Gyr or more. Moreover, they have not undergone any evolutionary period during which substantial mass loss is expected. If the IR excesses in close binary stars are real, they are caused either by long-lived dusty disks, an unexpected episode of significant mass loss at the subgiant Hertzsprung gap phase, or mass loss through stellar winds and coronal mass ejections at rates much higher than currently assumed. However, incorrect assessment of the binary photospheric SED might also be to blame. Here we present the results of a Spitzer investigation into the putative IR excesses of 9 RS CVn systems, and a discussion of the results in the context of these competing scenarios.
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