Extraordinary Magnification of the Ordinary Type Ia Supernova PS1-10afx

TL;DR

This paper suggests that the extraordinary brightness of the supernova PS1-10afx is due to gravitational lensing by a black hole or dark matter halo, not an intrinsically luminous event, challenging existing supernova luminosity relations.

Contribution

It proposes that the supernova's brightness is magnified by gravitational lensing, highlighting the need to consider external magnification in supernova observations.

Findings

Spectra fit normal Type Ia supernova templates

Observed flux is ~30 times brighter than expected

Lensing likely caused by a black hole or dark matter halo

Abstract

Recently, Chornock and co-workers announced the Pan-STARRS discovery of a transient source reaching an apparent peak luminosity of ~4x10^44 erg s^-1. We show that the spectra of this transient source are well fit by normal Type Ia supernova (SNIa) templates. The multi-band colors and light-curve shapes are also consistent with normal SNeIa at the spectroscopically determined redshift of z=1.3883; however, the observed flux is a constant factor of ~30 times too bright in each band over time as compared to the templates. At minimum, this shows that the peak luminosities inferred from the light-curve widths of some SNeIa will deviate significantly from the established, empirical relation used by cosmologists. We argue on physical grounds that the observed fluxes do not reflect an intrinsically luminous SNIa, but rather PS1-10afx is a normal SNIa whose flux has been magnified by an external source. The only known astrophysical source capable of such magnification is a gravitational lens. Given the lack of obvious lens candidates, such as galaxy clusters, in the vicinity, we further argue that the lens is a supermassive black hole or a comparatively low-mass dark matter halo. In this case, the lens continues to magnify the underlying host galaxy light. If confirmed, this discovery could impact a broad range of topics including cosmology, gamma-ray bursts, and dark matter halos.