Fermi-LAT results on Galactic Plane gamma-ray Transient Sources

TL;DR

This paper reports on Fermi-LAT gamma-ray transient detections in the Galactic plane, highlighting the search for and multiwavelength follow-up of transient sources, including unidentified gamma-ray flares.

Contribution

It introduces a systematic search method for gamma-ray transients using Fermi-LAT data and presents multiwavelength follow-up results for unidentified Galactic plane flares.

Findings

Detection of gamma-ray transients near the Galactic plane

Identification of counterparts through multiwavelength observations

Evidence for a possible new class of Galactic gamma-ray transients

Abstract

The Large Area Telescope on the Fermi gamma-ray Space Telescope provides unprecedented sensitivity for all-sky monitoring of gamma-ray activity. It has detected a few Galactic sources, including 2 gamma-ray binaries and a microquasar. In addition, it is an adequate telescope to detect other transient sources. The observatory scans the entire sky every three hours and allows a general search for flaring activity on daily timescales. This search is conducted automatically as part of the ground processing of the data and allows a fast response to transient events, typically less than a day. Most of the outbursts detected are spatially associated with known blazars, but in several cases during the first years of observations, gamma-ray flares occurring near the Galactic plane did not reveal any initially compelling counterparts. This prompted follow-up observations in X-ray, optical, and radio to attempt to identify the origin of the emission and probe the possible existence of a class of transient gamma-ray sources in the Galaxy. Here we report on these LAT events and the results of the multiwavelength counterpart searches.