Now You See It, Now You Don't: The Disappearing Central Engine of the Quasar J1011+5442

TL;DR

This paper reports the discovery of a changing-look quasar that dramatically dims over less than a decade, likely due to a sudden drop in accretion rate onto its supermassive black hole, challenging existing models of quasar variability.

Contribution

It presents the first detailed observation of a quasar undergoing a rapid transition in brightness and emission lines, supporting the hypothesis of abrupt accretion rate changes as the cause.

Findings

The quasar's continuum luminosity drops by a factor of >9.8 within 9.7 years.

Broad H-alpha emission line luminosity decreases by a factor of 55.

The transition occurs within approximately 500 days in the rest frame.

Abstract

We report the discovery of a new "changing-look" quasar, SDSS J101152.98+544206.4, through repeat spectroscopy from the Time Domain Spectroscopic Survey. This is an addition to a small but growing set of quasars whose blue continua and broad optical emission lines have been observed to decline by a large factor on a time scale of approximately a decade. The 5100 Angstrom monochromatic continuum luminosity of this quasar drops by a factor of > 9.8 in a rest-frame time interval of < 9.7 years, while the broad H-alpha luminosity drops by a factor of 55 in the same amount of time. The width of the broad H-alpha line increases in the dim state such that the black hole mass derived from the appropriate single-epoch scaling relation agrees between the two epochs within a factor of 3. The fluxes of the narrow emission lines do not appear to change between epochs. The light curve obtained by the Catalina Sky Survey suggests that the transition occurs within a rest-frame time interval of approximately 500 days. We examine three possible mechanisms for this transition suggested in the recent literature. An abrupt change in the reddening towards the central engine is disfavored by the substantial difference between the timescale to obscure the central engine and the observed timescale of the transition. A decaying tidal disruption flare is consistent with the decay rate of the light curve but not with the prolonged bright state preceding the decay, nor can this scenario provide the power required by the luminosities of the emission lines. An abrupt drop in the accretion rate onto the supermassive black hole appears to be the most plausible explanation for the rapid dimming.