Hydrodynamic Studies Of The Explosions Of Rs Oph, U Sco, And T Pyx And The Progenitors Of Sn Ia

We have begun new studies of the evolution of Thermonuclear Runaways in the accreted envelopes of white dwarfs (WD). Here we focus on the outbursts of the Recurrent Novae (RNe) RS Oph (2006), U Sco(2010), and T Pyx(2011). All 3 RNe (and their analogs) have been proposed as SN Ia progenitors. While the mass of the WD is unknown, it is thought to be close in mass to the Chandrasekhar Limit (except for T Pyx). U Sco explodes about every 10 years and the ejected material from the WD is helium rich while T Pyx just exploded and the ejecta abundances are, as yet, unknown. One important question is the secular evolution of the WD. Do the repeated outbursts cause the WD to gain or lose mass? If it is gaining mass, it could eventually reach the Chandrasekhar Limit and become a supernova or even a SN Ia if it can hide the hydrogen and helium in the system. We will report on our latest studies of TNRs using a variety of initial WD luminosities and mass accretion rates onto the WD (0.7, 1.0, 1.35 and 1.38 solar masses). We use our 1-D hydro code, NOVA, that now includes the Hix and Thielemann nuclear reaction network, the Iliadis reaction rate library, the Timmes equation of state, OPAL opacities, and new convection. We will report on the amount of ejected mass, ejection velocities, evolution time to explode, and the chemical composition of the ejecta.

We gratefully acknowledge partial support from the DOE, NASA, and NSF for these studies.