Gaia transient detection efficiency: hunting for nuclear transients

TL;DR

This paper evaluates Gaia's ability to detect nuclear transients like supernovae and tidal disruption events, predicting detection rates and identifying optimal conditions for discovery.

Contribution

It provides a simulation-based analysis of Gaia's transient detection efficiency, focusing on nuclear transients and estimating annual discovery rates.

Findings

Gaia can identify transients as new sources with 0.1-0.5 arcsec offset.

No significant loss of supernovae detection near galaxy nuclei.

Expected to discover about 1300 supernovae and 20 TDEs annually at magnitude 19.

Abstract

We present a study of the detectability of transient events associated with galaxies for the Gaia European Space Agency astrometric mission. We simulated the on-board detections, and on-ground processing for a mock galaxy catalogue to establish the properties required for the discovery of transient events by Gaia, specifically tidal disruption events (TDEs) and supernovae (SNe). Transients may either be discovered by the on-board detection of a new source or by the brightening of a previously known source. We show that Gaia transients can be identified as new detections on-board for offsets from the host galaxy nucleus of 0.1--0.5,arcsec, depending on magnitude and scanning angle. The Gaia detection system shows no significant loss of SNe at close radial distances to the nucleus. We used the detection efficiencies to predict the number of transients events discovered by Gaia. For a limiting magnitude of 19, we expect around 1300 SNe per year: 65% SN Ia, 28% SN II and 7% SN Ibc, and ~20 TDEs per year.