Tuesday, July 16, 2013

1307.3555 (Jeffrey M. Silverman et al.)

SN 2000cx and SN 2013bh: Extremely Rare, Nearly Twin Type Ia Supernovae    [PDF]

Jeffrey M. Silverman, Jozsef Vinko, Mansi M. Kasliwal, Ori D. Fox, Yi Cao, Joel Johansson, Daniel A. Perley, David Tal, J. Craig Wheeler, Rahman Amanullah, Iair Arcavi, Joshua S. Bloom, Avishay Gal-Yam, Ariel Goobar, Shrinivas R. Kulkarni, Russ Laher, William H. Lee, G. H. Marion, Peter E. Nugent, Isaac Shivvers
The Type Ia supernova (SN Ia) SN 2000cx was one of the most peculiar transients ever discovered. While its rise to maximum brightness was typical for a SN Ia, its decline was slower, causing standard light curve fitting algorithms to fail; its spectra indicated a high photospheric temperature. Thirteen years later SN 2013bh (aka iPTF13abc), the first near identical twin of SN 2000cx, was discovered. We obtained optical and near-IR photometry and low-resolution optical spectroscopy of this object from discovery until about 1 month past r-band maximum brightness. The spectra of both objects indicate the presence of iron-group elements (Co II, Ni II, Fe II, Fe III, and high-velocity features [HVFs] of Ti II), intermediate-mass elements (Si II, Si III, and S II), in addition to separate normal velocity features (~12000 km/s) and HVFs (~24000 km/s) of Ca II. Persistent absorption from Fe III and Si III, along with the colour evolution, imply relatively high blackbody temperatures for SNe 2013bh and 2000cx (~12000 K). Both objects lack narrow Na I D absorption and exploded in the outskirts of their host galaxies, indicating that the SN environment was relatively free of interstellar or circumstellar material. This hints that the progenitors of these objects likely came from a relatively old and low-metallicity stellar population and possibly from the merger of two degenerate objects. Models of SN 2000cx, which seem to be directly applicable to SN 2013bh, imply the production of up to ~1 M_Sun of Ni-56 and, in order to explain the HVFs of Ca II, (4.3-5.5)e-3 M_Sun of fast-moving Ca ejecta (which can be explained by primordial material alone).
View original: http://arxiv.org/abs/1307.3555

No comments:

Post a Comment