A spectroscopic look at the gravitationally lensed type Ia SN 2016geu at z=0.409
arXiv:1708.05534 · doi:10.1093/mnras/stx2624
Abstract
The spectacular success of type Ia supernovae (SNe Ia) in SN-cosmology is based on the assumption that their photometric and spectroscopic properties are invariant with redshift. However, this fundamental assumption needs to be tested with observations of high-z SNe Ia. To date, the majority of SNe Ia observed at moderate to large redshifts (0.4 < z < 1.0) are faint, and the resultant analyses are based on observations with modest signal-to-noise ratios that impart a degree of ambiguity in their determined properties. In rare cases however, the Universe offers a helping hand: to date a few SNe Ia have been observed that have had their luminosities magnified by intervening galaxies and galaxy clusters acting as gravitational lenses. In this paper we present long-slit spectroscopy of the lensed SNe Ia 2016geu, which occurred at a redshift of z=0.409, and was magnified by a factor of ~55 by a galaxy located at z=0.216. We compared our spectra, which were obtained a couple weeks to a couple months past peak light, with the spectroscopic properties of well-observed, nearby SNe Ia, finding that SN 2016geu's properties are commensurate with those of SNe Ia in the local universe. Based primarily on the velocity and strength of the Si II 6355 absorption feature, we find that SN 2016geu can be classified as a high-velocity, high-velocity gradient and "core-normal" SN Ia. The strength of various features (measured though their pseudo-equivalent widths) argue against SN 2016geu being a faint, broad-lined, cool or shallow-silicon SN Ia. We conclude that the spectroscopic properties of SN 2016geu imply that it is a normal SN Ia, and when taking previous results by other authors into consideration, there is very little, if any, evolution in the observational properties of SNe Ia up to z~0.4. [Abridged]
12 pages, 5 figures, 4 tables. Submitted to MNRAS. Comments welcomed
References in corpus (14)
- Supernova Constraints and Systematic Uncertainties from the First 3 Years of the Supernova Legacy Survey
- Multiple Images of a Highly Magnified Supernova Formed by an Early-Type Cluster Galaxy Lens
- Improved Distances to Type Ia Supernovae with Two Spectroscopic Subclasses
- The Spectroscopic Diversity of Type Ia Supernovae
- Optical and Near-Infrared Observations of the Highly Reddened, Rapidly Expanding Type Ia Supernova 2006X in M100
- The rise of SN2014J in the nearby galaxy M82
- The Rise and Fall of Type Ia Supernova Light Curves in the SDSS-II Supernova Survey
- SNLS Spectroscopy: Testing for Evolution in Type Ia Supernovae
- Early Observations and Analysis of the Type Ia SN 2014J in M82
- Quantitative comparison between Type Ia supernova spectra at low and high redshifts: A case study
- Comparative Direct Analysis of Type Ia Supernova Spectra. IV. Postmaximum
- Distances with <4% Precision from Type Ia Supernovae in Young Star-Forming Environments
- A Trio of GRB-SNe: GRB 120729A, GRB 130215A / SN 2013ez and GRB 130831A / SN 2013fu
- Testing for redshift evolution of Type Ia supernovae using the strongly lensed PS1-10afx at