Diversity in extinction laws of Type Ia supernovae measured between 0.2 and 2 μm
Abstract
We present ultraviolet (UV) observations of six nearby Type Ia supernovae (SNe Ia) obtained with the Hubble Space Telescope, three of which were also observed in the near-IR (NIR) with Wide-Field Camera 3. UV observations with the Swift satellite, as well as ground-based optical and NIR data provide complementary information. The combined data set covers the wavelength range 0.2-2 μm. By also including archival data of SN 2014J, we analyse a sample spanning observed colour excesses up to E(B - V) = 1.4 mag. We study the wavelength-dependent extinction of each individual SN and find a diversity of reddening laws when characterized by the total-to-selective extinction RV. In particular, we note that for the two SNe with E(B - V) ≳ 1 mag, for which the colour excess is dominated by dust extinction, we find RV = 1.4 ± 0.1 and RV = 2.8 ± 0.1. Adding UV photometry reduces the uncertainty of fitted RV by ∼50 per cent allowing us to also measure RV of individual low-extinction objects which point to a similar diversity, currently not accounted for in the analyses when SNe Ia are used for studying the expansion history of the Universe.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- November 2015
- DOI:
- 10.1093/mnras/stv1505
- arXiv:
- arXiv:1504.02101
- Bibcode:
- 2015MNRAS.453.3300A
- Keywords:
-
- circumstellar matter;
- supernovae: general;
- supernovae: individual: SNe 2012cg;
- supernovae: individual: 2012cu;
- dust;
- extinction;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 31 pages, 28 figures, accepted for publication in MNRAS