A Survey for Fast Transients in the Fornax Cluster of Galaxies

TL;DR

This survey of 23 galaxies in the Fornax cluster searched for fast transient events brighter than novae but fainter than supernovae, finding none but identifying several variable stars and setting upper limits on event rates.

Contribution

It provides the first systematic search for fast transients in the Fornax cluster and establishes upper limits on their occurrence rates.

Findings

No fast transients detected down to M_B=-9.3 mag.

Discovered five new foreground variable stars.

Set constraints on the rate of fast transient events.

Abstract

The luminosity gap between novae (M_R < -10) and supernovae (M_R > -14) is well known since the pioneering research of Zwicky and Hubble. Nearby galaxy clusters and concentrations offer an excellent opportunity to search for explosions brighter than classical novae and fainter than supernovae. Here, we present the results of a B-band survey of 23 member galaxies of the Fornax cluster, performed at the Las Campanas 2.5-m Irene duPont telescope. Observations with a cadence of 32 minutes discovered no genuine fast transient to a limiting absolute magnitude of M_B=-9.3 mag. We provide a detailed assessment of the transient detection efficiency and the resulting upper limits on the event rate as function of peak magnitude. Further, we discuss the discoveries of five previously unknown foreground variables which we identified as two flare stars, two W Uma type eclipsing binaries and a candidate delta Scuti/SX Phe star.