Browsing by Subject "accreting white-dwarfs"

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Self-Shielding Of Soft X-Rays In Type Ia Supernova Progenitors
(2013-01) Wheeler, J. Craig; Pooley, David; Wheeler, J. Craig
There are insufficient super-soft (similar to 0.1 keV) X-ray sources in either spiral or elliptical galaxies to account for the rate of explosion of Type Ia supernovae (SNe Ia) in either the single-degenerate or the double-degenerate scenarios. We quantify the amount of circumstellar matter that would be required to suppress the soft X-ray flux by yielding a column density in excess of 10(23) cm(-2). We summarize evidence that appropriate quantities of matter are extant in SNe Ia and in recurrent novae that may be supernova precursors. The obscuring matter is likely to have a large, but not complete, covering factor and to be substantially non-spherically symmetric. Assuming that much of the absorbed X-ray flux is re-radiated as blackbody radiation in the UV, we estimate that less than or similar to 100 sources might be detectable in the Galaxy Evolution Explorer All-sky Survey.
Type Iax Supernovae: A New Class Of Stellar Explosion
(2013-04) Foley, Ryan J.; Challis, Peter J.; Chornock, Ryan; Ganeshalingam, Mohan; Li, W.; Marion, G. H.; Morrell, Nidia I.; Pignata, G.; Stritzinger, Maximillian D.; Silverman, Jeffrey M.; Wang, X.; Anderson, J. P.; Filippenko, Alexei V.; Freedman, W. L.; Hamuy, Mario; Jha, Saurabh W.; Kirshner, Robert P.; McCully, C.; Persson, S. E.; Phillips, Mark M.; Reichart, D. E.; Soderberg, Alicia M.; Silverman, Jeffrey M.
We describe observed properties of the Type Iax class of supernovae (SNe Iax), consisting of SNe observationally similar to its prototypical member, SN 2002cx. The class currently has 25 members, and we present optical photometry and/ or optical spectroscopy for most of them. SNe Iax are spectroscopically similar to SNe Ia, but have lower maximum-light velocities (2000 less than or similar to broken vertical bar v broken vertical bar less than or similar to 8000 km s(-1)), typically lower peak magnitudes (-14.2 >= M-V,M-peak greater than or similar to -18.9 mag), and most have hot photospheres. Relative to SNe Ia, SNe Iax have low luminosities for their light-curve shape. There is a correlation between luminosity and light-curve shape, similar to that of SNe Ia, but offset from that of SNe Ia and with larger scatter. Despite a host-galaxy morphology distribution that is highly skewed to late-type galaxies without any SNe Iax discovered in elliptical galaxies, there are several indications that the progenitor stars are white dwarfs (WDs): evidence of C/ O burning in their maximum-light spectra, low (typically similar to 0.5 M-circle dot) ejecta masses, strong Fe lines in their late-time spectra, a lack of X-ray detections, and deep limits on massive stars and star formation at the SN sites. However, two SNe Iax show strong He lines in their spectra. The progenitor system and explosion model that best fits all of the data is a binary system of a C/ O WD that accretes matter from a He star and has a deflagration. At least some of the time, this explosion will not disrupt the WD. The small number of SNe in this class prohibit a detailed analysis of the homogeneity and heterogeneity of the entire class. We estimate that in a given volume there are 31(-13)(+17) SNe Iax for every 100 SNe Ia, and for every 1M(circle dot) of iron generated by SNe Ia at z = 0, SNe Iax generate similar to 0.036M(circle dot). Being the largest class of peculiar SNe, thousands of SNe Iax will be discovered by LSST. Future detailed observations of SNe Iax should further our understanding of both their progenitor systems and explosions as well as those of SNe Ia.