V418 Ser: A Sub-Period Minimum CV With Hydrogen
ATel #6287; P. Garnavich, C. Littlefield (Notre Dame), D. Terndrup and S. Adams (Ohio State)
on 3 Jul 2014; 16:43 UT
Credential Certification: Peter Garnavich (pgarnavi@gmail.com)
Subjects: Optical, Cataclysmic Variable
We obtained spectra of the cataclysmic variable V418 Ser,
which was recently found by the VSNET collaboration
(Kato et al. 2004, PASJ, 56, 1) to have an orbit
shorter than the period minimum for hydrogen-rich
CVs (Littlefield, VSNET-alert 17321; de Miguel, VSNET-alert 17322).
The spectrum was taken with the Large Binocular
Telescope (LBT) and MODS spectrograph on 2014 June 30,
and covers wavelengths from 320 nm to 1 micron. The
spectrum shows doubled peaked emission lines characteristic
of a quiescent accretion disk. Hydrogen is clearly present
indicating that this is not an AM CVn star, but the
Helium to Hydrogen ratio is large when compared with long
period CVs.
Overall the spectrum is very similar to the short period
system SBS 1108+574 (CSS 120422:111127+571239; Littlefield
et al. 2013, AJ, 145, 145; Carter et al. 2013, MNRAS, 431, 372)
making V418 Ser a new member of a small but growing number of
sub-period minimum binaries accreting some hydrogen.