A New Sub-Period-Minimum CV with Partial Hydrogen Depletion and Evidence of Spiral Disk Structure
Abstract
We present time-resolved spectroscopy and photometry of CSS 120422:111127+571239 (= SBS1108+574), a recently discovered SU UMa-type dwarf nova whose 55-minute orbital period is well below the CV period minimum of ~78 minutes. In contrast with most other known CVs, its spectrum features He I emission of comparable strength to the Balmer lines, implying a hydrogen abundance less than 0.1 of long period CVs---but still at least 10 times higher than than in AM CVn stars. Together, the short orbital period and remarkable helium-to-hydrogen ratio suggest that mass transfer in "CSS 1204" began near the end of the donor star's main-sequence lifetime, meaning that the system is probably an AM CVn progenitor as described by Podsiadlowski, Han, and Rappaport (2003). Moreover, a Doppler tomogram of the Halpha line reveals two distinct regions of enhanced emission. While one is the result of the stream-disk impact, the other is probably attributable to spiral disk structure generated when material in the outer disk achieves a 2:1 orbital resonance with respect to the donor.
Cite
@article{arxiv.1301.7480,
title = {A New Sub-Period-Minimum CV with Partial Hydrogen Depletion and Evidence of Spiral Disk Structure},
author = {C. Littlefield and P. Garnavich and A. Applegate and K. Magno and R. Pogge and J. Irwin and G. H. Marion and J. Vinko and R. P. Kirshner},
journal= {arXiv preprint arXiv:1301.7480},
year = {2015}
}
Comments
11 figures