RX J0515.6+0105: An AM Her System with an 8 Hour Period?

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Session 116 -- Globular Clusters and Compact Objects
Oral presentation, Thursday, 12, 1995, 10:00am - 11:30am

[116.04] RX J0515.6+0105: An AM Her System with an 8 Hour Period?

A.W.Shafter, K.A.Misselt (SDSU), K.Reinsch, K.Beuermann, V.Burwitz (G\"ottingen), D.A.H.Buckley (SAAO), A.D.Schwope (Potsdam)

We report multiwavelength observations of the optical counterpart of the ROSAT\/ X-ray source RX J0515.6+0105. Optical photometric data spanning $\sim$1~yr reveal eclipse features that are deep, total, and variable in profile. The eclipse timings give an orbital ephemeris of JD$_{\sun}$ = 2449087.8173(3) + 0.3326120(7) E, with considerable phase jitter caused by the variable eclipse profiles. The system is characterized by a soft thermal spectrum ($kT_{bb} \simeq33$~eV), strong He~II $\lambda 4686$ emission, large-amplitude radial velocity variations consistent with emission from an accretion stream, and, most significantly, significant circular polarization. The optical light curve is characterized by a strong and asymmetric brightness modulation at twice the orbital frequency, and by quasi-periodic oscillations with a characteristic time scale of 6 -- 15 min. Spectroscopic observations suggest the possibility of cyclotron features near 8500~\AA~and 5900~\AA. These wavelengths are roughly consistent with those expected for the second and third harmonics of cyclotron radiation originating from an $\sim$61~MG field. Taken together, these characteristics strongly suggest that RX J0515.6+0105 is a magnetic cataclysmic variable, most likely an AM~Herculis system in which the accretion column/stream is eclipsed. However, the possibility that the white dwarf rotates asynchronously, and that RX J0515.6+0105 is a DQ~Her system, has not yet been ruled out unequivocally.

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