The Most Energetic Transients: Tidal Disruptions of High-Mass Stars

TL;DR

This paper introduces a new class of extremely energetic nuclear transients, Gaia18cdj, likely caused by tidal disruptions of high-mass stars by supermassive black holes, offering insights into SMBH populations at high redshifts.

Contribution

It identifies and characterizes the most energetic transients, proposing a tidal disruption origin involving high-mass stars and supermassive black holes, expanding understanding of nuclear transient phenomena.

Findings

Gaia18cdj is the most energetic transient discovered.

ENTo are at least twice as energetic as other transients.

ENTo are consistent with tidal disruptions of high-mass stars by SMBHs.

Abstract

We present the class of extreme nuclear transients (ENTs), including the most energetic single transient yet discovered, Gaia18cdj. Each ENT is coincident with its host-galaxy nucleus and exhibits a smooth ($<$$10$% excess variability), luminous ($2\times$$10^{45}$ to $7\times$$10^{45}$ erg s$^{-1}$), and long-lived ($>$$150$ days) flare. ENTs are extremely rare ($\geq$$1$$\times$$10^{-3}$ Gpc$^{-3}$ yr$^{-1}$) compared to any other known class of transients. They are at least twice as energetic ($0.5\times10^{53}$ to $2.5\times10^{53}$ erg) as any other known transient, ruling out supernova origins. Instead, the high peak luminosities, long flare timescales, and immense radiated energies of the ENTs are most consistent with the tidal disruption of high-mass ($\gtrsim$$3$ M$_{\odot}$) stars by massive ($\gtrsim$$10^8$ M$_{\odot}$) supermassive black holes (SMBHs). ENTs will be visible to high redshifts ($z\sim4$ to $6$) in upcoming surveys, providing an avenue to study the high-mass end of the SMBH mass distribution, complementing recent studies of actively accreting SMBHs at high redshifts with the James Webb Space Telescope.