Abstract

We present the results of XMM-Newton X-ray observations of the Mira AB binary system, which consists of a pulsating, asymptotic giant branch primary and nearby (~0.6′′ separation) secondary of uncertain nature. The EPIC CCD (MOS and pn) X-ray spectra of Mira AB are relatively soft, peaking at ~1 keV, with only very weak emission at energies >3 keV; lines of Ne ix, Ne x, and O viii are apparent. Spectral modeling indicates a characteristic temperature TX ~10^7 K and intrinsic luminosity LX ~5×10^29 erg s^−1, and suggests enhanced abundances of O and, possibly, Ne and Si in the X-ray-emitting plasma. Overall, the X-ray spectrum and luminosity of the Mira AB system more closely resemble those of late-type, pre-main sequence stars or late-type, magnetically active main sequence stars than those of accreting white dwarfs. We conclude that Mira B is most likely a late-type, magnetically active, main-sequence dwarf, and that X-rays from the Mira AB system arise either from magnetospheric accretion of wind material from Mira A onto Mira B, or from coronal activity associated with Mira B itself, as a consequence of accretion-driven spin-up. One (or both) of these mechanisms also could be responsible for the recently discovered, point-like X-ray sources within planetary nebulae (Refer to PDF file for exact formulas).

Publication Date

12-1-2004

Comments

Also archived in: arXiv :astro-ph/0408329 v2 27 Aug 2004 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. We thank Falk Herwig and Norbert Schulz for useful comments and suggestions.ISSN:1538-4365 Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in February 2014.

Document Type

Article

Department, Program, or Center

Chester F. Carlson Center for Imaging Science (COS)

Campus

RIT – Main Campus

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