A Search for Type Ia Supernovae in Globular Clusters

Abstract

In globular clusters the density is such that stellar interactions are commonplace. It is therefore expected that Type Ia supernovae explosions would occur within them at a high
rate, however no Type Ia supernova has ever been observed in a globular cluster to date. We therefore carried out a search of records in the Open Supernova Catalog from the
Zwicky Transient Facility (ZTF) survey to compile a list of Type Ia supernovae recorded there, with their respective coordinates, from 08/04/2018 to 20/11/2021. The survey has a limiting latitude value of −27◦, which was in turn set as a limit for the project. A further limiting distance of 125 Mpc was also set, within which HyperLEDA extragalactic database was used to compile a sample of bright galaxies. A check was carried out to ensure both supernovae and galaxies were within the imposed limits with a final 307 supernovae and 56,903 galaxies and, using the Globular Cluster Luminosity Factor (GCLF) methodology from Jord´an et al. (2007), a figure of 31,679 visible globular clusters was estimated. PanSTARRS and the Hubble Space Telescope (HST) imaging was used to view the supernova coordinates before and after the supernova event, with an image of the supernova also included from ZTF archives. No definite supernova was seen to occur in a globular cluster, but there were noted instances of correspondence between 3 supernovae and 3 potential Ultra Compact Dwarfs (UCDs) or compact Elliptical galaxies (cEs). The figures found from the project provided a supernova rate for the volume of 1.47 × 10−5 yr−1 Mpc−3 and an upper limit on the globular cluster supernova rate of 2.52 × 10−12 yr−1M−1⊙ . We feel that this is not yet a strong limit due to the small number of globular clusters
surveyed, but are confident that it forms a sound basis for rapid increase in the following years using the Large Synoptic Survey Telescope (LSST).