We investigate a new empirical fitting method for the optical light curves of Type Ia supernovae (SNe Ia) that is able to estimate the first-light time of SNe Ia, even when they are not discovered extremely early. With an improved ability to estimate the time of first light for SNe Ia, we compute the rise times for a sample of 56 wellobserved SNe Ia. We find rise times ranging from 10.5 to 20.5 days, with a mean of 16.0 days, and confirm that the rise time is generally correlated with the decline rate Δm15 (B), but with large scatter. The rise time could be an additional parameter to help classify SN Ia subtypes.
Bibliographical noteFunding Information:
We thank Isaac Shivvers and Melissa L Graham for useful discussions and suggestions, as well as the staffs of the observatories where data were obtained. We thank the anonymous referee for useful discussions, and an anonymous statistics expert for pointing out that Equation (1) is mathematically similar to the generalized Pareto distribution in statistics. We also thank Brad E Tucker for providing data for the three Kepler SNeIa published by Olling et al. (2015). A.V.F.ʼs supernova group at UC Berkeley is grateful for financial assistance from NSF grant AST-1211916, the TABASGO Foundation, the Christopher R Redlich Fund, and the Miller Institute for Basic Research in Science (U.C. Berkeley). The work of A.V.F. was completed in part at the Aspen Center for Physics, which is supported by NSF grant PHY-1607611; he thanks the Center for its hospitality during the neutron stars workshop in 2017 June and July. Research at Lick Observatory is partially supported by a generous gift from Google.
- methods: data analysis
- supernovae: general