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).

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Also archived in: arXiv: astro-ph/0403063 v1 2 Mar 2004 The authors thank John Houck and the anonymous referee for helpful suggestions concerning this paper. We acknowledge support for this research provided by NASA/GSFC XMM-Newton General Observer grant NAG5–13158 to RIT. N.S. acknowledges support from the Israel Science Foundation.ISSN:1538-4365 Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in February 2014.

Document Type


Department, Program, or Center

Chester F. Carlson Center for Imaging Science (COS)


RIT – Main Campus