Multi-Wavelength & Time-Domain Astronomy

A close binary in which a white dwarf accretes matter from a companion through a disk, producing recurrent outbursts as the disk brightens — the dwarf novae and related variables of the time-domain sky.

A thermonuclear runaway on the surface of a white dwarf that is accreting matter from a companion star. Unlike a supernova, the white dwarf survives, and the outburst can recur.

The inspiral and merger of two compact objects — black holes or neutron stars — radiating a chirp of gravitational waves. Since 2015 these have been heard routinely; neutron-star mergers also shine as kilonovae.

The catastrophic collapse of the core of a massive star, which rebounds into an explosion and leaves a neutron star or black hole. Most of the energy escapes as neutrinos — first detected from SN 1987A — making these among the earliest multi-messenger sources.

Stars whose brightness changes irregularly through eruptions and flares — from the giant eruptions of luminous blue variables to the flares of young and magnetically-active stars.

Millisecond flashes of radio waves from far across the universe, immensely energetic for their brevity. At least some come from magnetars; most are one-off, though a few repeat. Their dispersion probes the matter between the galaxies.

The most luminous electromagnetic events in the universe — brief, intense flashes of gamma rays. Long bursts come from the collapse of massive stars; short bursts from the mergers of neutron stars. Each is followed by a fading multi-wavelength afterglow.

An exceptionally energetic core-collapse explosion of a very massive star, releasing far more kinetic energy than an ordinary supernova. Hypernovae from rapidly-rotating collapsars are thought to power the long gamma-ray bursts.

The optical and infrared glow that follows the merger of two neutron stars, powered by the radioactive decay of the heavy elements forged in the merger. The 2017 event GW170817, seen in gravitational waves and light, was the landmark of multi-messenger astronomy.

Sudden, intense bursts of gamma and X-rays from magnetars — neutron stars with the strongest magnetic fields known. Their giant flares are so bright they can be detected across the galaxy, and are now linked to some fast radio bursts.

The flare produced when a star wanders too close to a supermassive black hole and is torn apart by tides, some of its debris blazing as it falls in. TDEs light up otherwise-quiet galactic nuclei for months.

The thermonuclear detonation of a white dwarf that has been pushed over a critical mass. Their remarkably uniform peak brightness makes them the standard candles that measured the accelerating expansion of the universe.