Starrfield is requesting 1 summer month in 2013 to work full time on studies of the outburst of V445 Pup. He will assist in the data analysis and the preparation of the observation paper on the HST data on V445 Pup. He will also continue his modeling of the outburst of V445 Pup but will now use MESA (Paxton, B., et al. 2011, ApJS, 192, 3) instead of his own code, NOVA. He will continue his studies of the accretion of helium rich material (Starrfield, S., et al. 2010, in BAAS, Vol. 42, Abstracts Nu. 215, 416.28) onto white dwarfs of various initial masses and luminosities. His preliminary studies using the proposed conditions of Kato (Kato, M.,& Hachisu, I. 2003, ApJ, 598, L107; Kato, M., et al. 2008, ApJ, 684, 1366) did not reproduce the observations of V445 Pup. In some cases, he found explosions that resembled Supernova Ia explosions. He halted his study because the nuclear reaction network in NOVA does not include Nuclear Statistical Equilibrium at high temperatures which is required for some of the simulations that NOVA produced. He is switching to MESA because it includes the latest nuclear reaction rate libraries, Nuclear Statistical Equilibrium, pulsation, diffusion, and rotation and NOVA does not. Of necessity, he will evolve a broad range in white dwarf mass, white dwarf luminosity, and vary the composition of the accreting material from helium-rich to helium-rich with small amounts of hydrogen. The small amount of hydrogen should cause the thermonuclear runaway to occur earlier with a smaller amount of accreted material and, thereby, less degenerate. He will also use the probable composition attributed to a hydrogen-deficient carbon star as proposed in the latest studies of V445 Pup (Woudt, P. A., Steeghs, D., Karovska, M., et al. 2009, ApJ, 706, 738). His calculations will be guided by the results from our HST Cycle 20 observations.
V445 Puppis underwent a powerful outburst in 2000 and is the first, and still the only helium nova event that has been observed. The outburst itself has been interpreted as a helium shell flash on the surface of an accreting massive white dwarf close to the Chandrasekhar limit, making V445 Puppis a potential Type Ia progenitor via the helium-rich donor channel. We were awarded 4 orbits of HST/WFC3 observations (2 orbits in Cycle 20 and 2 orbits in Cycle 22) of the expanding bipolar shell of the helium nova V445 Puppis (science PI Danny Steeghs, University of Warwick, UK, Budget PI M. Karovska,from the Smithsonian Astrophysical Observatory, USA). There are two US-based Co-Is on this project, M. Karovska from SAO and S.Starrfield from Arizona State University.
|Effective start/end date||5/1/13 → 2/28/18|
- National Aeronautics Space Administration (NASA): $51,867.00