TY - JOUR
T1 - Magnetic flares on asymptotic giant branch stars
AU - Soker, Noam
AU - Kastner, Joel H.
N1 - Copyright:
Copyright 2015 Elsevier B.V., All rights reserved.
PY - 2003/7/20
Y1 - 2003/7/20
N2 - 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 ROSATX-ray spectrum of the Mira system suggests an intrinsic X-ray luminosity ∼2 × 1029 ergs s-1 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.
AB - 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 ROSATX-ray spectrum of the Mira system suggests an intrinsic X-ray luminosity ∼2 × 1029 ergs s-1 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.
KW - Stars: AGB and post-AGB
KW - Stars: magnetic fields
KW - Stars: mass loss stars: winds, outflows
KW - X-rays: stars
UR - http://www.scopus.com/inward/record.url?scp=0042834378&partnerID=8YFLogxK
U2 - 10.1086/375686
DO - 10.1086/375686
M3 - 文章
AN - SCOPUS:0042834378
VL - 592
SP - 498
EP - 503
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 1 I
ER -