Displaying the Heterogeneity of the SN 2002cx-like Subclass of Type Ia Supernovae with Observations of the Pan-STARRS-1 Discovered SN2009ku

TL;DR

SN2009ku, a Type Ia supernova from Pan-STARRS-1, exhibits unique properties with higher luminosity and low ejecta velocity, challenging the perceived homogeneity of the SN2002cx-like subclass and revealing its diversity.

Contribution

This paper presents the first detailed observation of SN2009ku, demonstrating the heterogeneity within the SN2002cx-like class of Type Ia supernovae.

Findings

SN2009ku is brighter than other SN2002cx-like supernovae.

SN2009ku has low ejecta velocity (~2000 km/s) at 18 days post-maximum.

SN2009ku's properties challenge the idea of homogeneity in the subclass.

Abstract

SN2009ku, discovered by Pan-STARRS-1, is a Type Ia supernova (SNIa), and a member of the distinct SN2002cx-like class of SNeIa. Its light curves are similar to the prototypical SN2002cx, but are slightly broader and have a later rise to maximum in g. SN2009ku is brighter (~0.6 mag) than other SN2002cx-like objects, peaking at M_V = -18.4 mag - which is still significantly fainter than typical SNeIa. SN2009ku, which had an ejecta velocity of ~2000 kms^-1 at 18 days after maximum brightness is spectroscopically most similar to SN2008ha, which also had extremely low-velocity ejecta. However, SN2008ha had an exceedingly low luminosity, peaking at M_V = -14.2 mag, ~4 mag fainter than SN2009ku. The contrast of high luminosity and low ejecta velocity for SN2009ku is contrary to an emerging trend seen for the SN2002cx class. SN2009ku is a counter-example of a previously held belief that the class was more homogeneous than typical SNeIa, indicating that the class has a diverse progenitor population and/or complicated explosion physics. As the first example of a member of this class of objects from the new generation of transient surveys, SN2009ku is an indication of the potential for these surveys to find rare and interesting objects.