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Time-resolved spectroscopy of CSS160603:162117+441254

ATel #9141; John Thorstensen (Dartmouth)
on 11 Jun 2016; 09:37 UT
Credential Certification: J. R. Thorstensen (john.thorstensen@dartmouth.edu)

Subjects: Optical, Binary, Cataclysmic Variable, Star, Variables

Referred to by ATel #: 9167

I obtained a full orbit of time-resolved spectroscopy of CSS160603:162117+441254 (ATel #9112, #9113, #9122, #9132, #9138), using the 2.4m Hiltner telescope at MDM and the modular spectrograph. The spectral resolution was 3.5 Angstroms from 4300 to 7600 Angstroms, and the exposures were mostly 5 minutes. In addition to broad emission emission lines (ATel #9122), the spectrum shows a strong contribution from a K-type secondary star. A fit to the radial velocities of the secondary, with the period fixed at 0.207852 d (ATel #9112), gave a semi-amplitude K2 = 271 +- 3 km/s, while the broad emission yielded K1 = 115 +- 6 km/s. The emission lines showed a strong rotational disturbance in eclipse, indicating that it originates in a rapidly-rotating disk. Assuming that the velocity amplitudes faithfully trace the center-of-mass velocities of the binary components, the masses of the compact object and donor star are roughly 0.9 and 0.4 solar masses respectively. The compact object is therefore almost certainly a white dwarf, and the system is confirmed to be a cataclysmic variable, as previous authors have suggested.