ACP Seminar (Astronomy - Cosmology - Particle Physics)

Speaker: Samuel Jones (Keele U)
Title: Evolution of electron capture supernova progenitors: new models, improved nuclear physics and hydrodynamic mixing uncertainties
Date (JST): Tue, Nov 05, 2013, 16:00 - 17:00
Place: Seminar Room A
Related File: 1055.pdf
Abstract: I will present new stellar models in the transition mass range from super-AGB star to massive star (8-12 solar masses). This mass range corresponds to the most massive AGB stars and the most numerous massive stars. It is host to a variety of supernova progenitors and is therefore very important for galactic chemical evolution and stellar population studies. Our models suggest that a propagating neon-oxygen burning shell is common to both the most massive electron capture supernova (EC-SN) progenitors and the lowest mass iron-core collapse supernova (FeCCSN) progenitors. Of our models that ignite neon burning off-centre, a 9.5 Mo model will evolve to an FeCCSN after the neon-burning shell propagates to the centre, as in previous studies. The neon-burning shell in the 8.8 Mo model, however, fails to reach the centre as the URCA process and an extended (0.6 Mo) region of low Ye (0.48) in the outer part of the core begin to dominate the late evolution; the model evolves to an EC-SN. This is the first study to follow the most massive EC-SN progenitors to collapse, representing an evolutionary path to EC-SN in addition to that from S-AGB stars undergoing thermal pulses. I will also present the results of an 8.75 Mo super-AGB model for which we have calculated the entire thermal pulse phase until electron captures by neon begin at its centre. I will discuss the uncertainties affecting our understanding of stars in this transition mass range and present our latest results in an attempt to address some of these uncertainties, including new detailed electron-capture and beta-decay rates for SD-shell nuclei.
Remarks: Please note that the date and time of seminar has been changed to *Tuesday, November 5 at 16:00* due to the evacuation drill of Kashiwa campus on November 7.