2002/06/25 by J. R. Thorstensen, W. H. Fenton, William H. Fenton +7 · 2 citations
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Cataclysmic variable star #Dwarf nova #Gamma-ray bursts and supernovae #Orbital period #Photometry (optics) #Physics #Stars #Stellar, planetary, and galactic studies #White dwarf #astro-ph
paper · pdf · doi:10.1086/342513
11 pages, 3 postscript figures, 1 jpeg greyscale figure. Accepted for publication in PASP
arxiv created 2002/06/25 · openalex publication_date 2002/09/24 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present spectroscopy and time‐series photometry of the dwarf nova QZ Ser. The spectrum shows a rich absorption‐line spectrum of type K 4 ± 2. K‐type secondary stars are generally seen in dwarf novae with orbital periods P orb ∼ 6 hr, but in QZ Ser the absorption radial velocities show an obvious modulation [semiamplitude 207(5) km s -1 ] at P orb = 119.752(2) minutes, much shorter than typical for such a relatively warm and prominent secondary spectrum. The Hα emission‐line velocity is modulated at the same period and roughly opposite phase. Time‐series photometry shows flickering superposed on a modulation with two humps per orbit, consistent with ellipsoidal variation of the secondary's light. QZ Ser is a second example of a relatively short period dwarf nova with a surprisingly warm secondary. Model calculations suggest that the secondary is strongly enhanced in helium and had already undergone significant nuclear evolution when mass transfer began. Several sodium absorption features in the secondary spectrum are unusually strong, which may indicate that the present‐day surface was the site of CNO‐cycle hydrogen burning in the past.