Time domain astronomy with Swift and Fermi

Abstract

Swift and Fermi are unveiling an unexpectedly rich tapestry of behavior in the transient γ−ray sky. Sources which were already known to be transient − such as pulsars, gamma-ray bursts, and blazars − have been studied in ever-increasing detail. For example, Fermi/LAT has detected 117 pulsars of which 56 are new. Many of them are only seen so far in γ−rays. In the last 5 years the Crab Nebula, long taken to be a standard candle, has been observed to flare dramatically. A long monitoring campaign on Sgr A∗ with Swift has shown multiple flares on time scales of tens of days. Other sources not usually associated with high-energy emission − e.g., novae and flare stars − are proving to be interesting at γ−ray energies. Discoveries have been made of spectacular transient emission from tidal disruption events and supernova shock breakout. We present an overview of recent γ−ray and hard X-ray observations and discuss their impact on high-energy astrophysics.

Keywords: Black hole physics; radiation mechanisms: non-thermal; Stars: activity; Gamma-ray burst: general; Stars: neutron, novae; Galaxies: star formation