Constraining the X-ray luminosities of asymptotic giant branch stars: TX Camelopardalis and T Cassiopeia

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Title: Constraining the X-ray luminosities of asymptotic giant branch stars: TX Camelopardalis and T Cassiopeia
Author: Kastner, Joel; Soker, Noam
Abstract: To probe the magnetic activity levels of asymptotic giant branch (AGB) stars, we used XMM-Newton to search for X-ray emission from two well-studied objects, TX Cam and T Cas. The former star displays polarized maser emission, indicating magnetic field strengths of B ~ 5 G, and the latter is one of the nearest known AGB stars. Neither star was detected by XMM-Newton. We use the upper limits on EPIC (CCD detector) count rates to constrain the X-ray luminosities of these stars and derive Lx<10^31 ergs s^-1 (<103^0 ergs s^-1) for an assumed X-ray emission temperature Tx= 3 x10^6 K (10^7 K). These limits represent <~10% (<~1%) of the X-ray luminosity expected under models in which AGB magnetic fields are global and potentially play an important role in collimating and/or launching AGB winds. We suggest, instead, that the B field strengths inferred from maser observations are representative of localized magnetic clouds (Refer to PDF file for exact formulas).
Description: Also archived in: arXiv: astro-ph/0403063 v1 2 Mar 2004
Record URI: http://hdl.handle.net/1850/1839
Date: 2004-06-20

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