FAR-ULTRAVIOLET SPECTROSCOPY OF THE NOVA-LIKE VARIABLE KQ MONOCEROTIS: A NEW SW SEXTANTIS STAR?
Aaron Wolfe, Edward M. Sion, Howard E. Bond
2013
Astronomical Journal
New optical spectra obtained with the SMARTS 1.5m telescope and archival IUE far-ultraviolet spectra of the nova-like variable KQ Mon are discussed. The optical spectra reveal Balmer lines in absorption as well as He I absorption superposed on a blue continuum. The 2011 optical spectrum is similar to the KPNO 2.1m IIDS spectrum we obtained 33 years earlier, except that the Balmer and He I absorption is stronger in 2011. Far-ultraviolet IUE spectra reveal deep absorption lines due to C II, Si
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... , Si IV, C IV, and He II, but no P Cygni profiles indicative of wind outflow. We present the results of the first synthetic spectral analysis of the IUE archival spectra of KQ Mon with realistic optically thick, steady-state, viscous accretion-disk models with vertical structure and high-gravity photosphere models. We find that the photosphere of the white dwarf (WD) contributes very little FUV flux to the spectrum and is overwhelmed by the accretion light of a steady disk. Disk models corresponding to a WD mass of 0.6 Msun, with an accretion rate of order 10^-9 Msun/yr and disk inclinations between 60 and 75 deg, yield distances from the normalization in the range of 144 to 165 pc. KQ Mon is discussed with respect to other nova-like variables. Its spectroscopic similarity to the FUV spectra of three definite SW Sex stars suggests that it is likely a member of the SW Sex class and lends support to the possibility that the WD is magnetic.
doi:10.1088/0004-6256/145/6/168
fatcat:jiqtfqhdwvg6fgnhvo4347nz2q