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).
Department, Program, or Center
Chester F. Carlson Center for Imaging Science (COS)
Joel H. Kastner and Noam Soker 2004 ApJ 616 1188 https://doi.org/10.1086/424921
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