2002/09/30 by Noam Soker, Joel H. Kastner · 5 citations
Physics and Astronomy · Social Sciences · #Astronomy and Astrophysical Research #Educational Leadership and Practices #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/375686
published as Astrophys.J. 592 (2003) 498-503 · ApJ, Accepted; revised version of astro-ph/0209236
arxiv created 2003/04/06 · openalex publication_date 2003/07/18 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We investigate the consequences of magnetic flares on the surface of asymptotic giant branch (AGB) and similar stars. In contrast to the solar wind, in the winds of AGB stars the gas cooling time is much shorter than the outflow time. As a result, we predict that energetic flaring will not inhibit, and may even enhance, dust formation around AGB stars. If magnetic flares do occur around such stars, we expect some AGB stars to exhibit X-ray emission; indeed certain systems including AGB stars, such as Mira, have been detected in X-rays. However, in these cases, it is difficult to distinguish between potential AGB star X-ray emission and, e.g., X-ray emission from the vicinity of a binary companion. Analysis of an archival ROSAT X-ray spectrum of the Mira system suggests an intrinsic X-ray luminosity 2x1029 erg/sec and temperature 107 K. These modeling results suggest that magnetic activity, either on the AGB star (Mira A) or on its nearby companion (Mira B), is the source of the X-rays, but do not rule out the possibility that the X-rays are generated by an accretion disk around Mira B.