2013/01/31 by C. Littlefield, Colin Littlefield, P. Garnavich +12
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Star Formation Studies #Balmer series #Cataclysmic variable star #Dwarf nova #Emission spectrum #Gamma-ray bursts and supernovae #Hydrogen #Intermediate polar #Orbital period #Photometry (optics) #Physics #Spectral line #Spiral galaxy #Stars #White dwarf #astro-ph.SR
paper · pdf · doi:10.1088/0004-6256/145/6/145
11 figures
arxiv created 2013/01/31 · openalex publication_date 2013/04/19 · arxiv updated 2015/06/12 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
We present time-resolved spectroscopy and photometry of CSS 120422:111127+571239 (=SBS 1108+574), a recently discovered SU UMa-type dwarf nova whose 55 minute orbital period is well below the cataclysmic variable (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 that in AM CVn stars. Together, the short orbital period and remarkable helium-to-hydrogen ratio suggest that mass transfer in CSS 120422 began near the end of the donor star's main-sequence lifetime, meaning that this CV is a strong candidate progenitor of an AM CVn system as described by Podsiadlowski et al. Moreover, a Doppler tomogram of the Hα 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.