"Spoon-feeding" an AGN

TL;DR

This paper presents evidence of periodic partial tidal disruptions of a star by a black hole, suggesting a new mechanism of black hole feeding through recurring mild stellar stripping.

Contribution

It introduces the first observed case of periodic partial tidal disruptions, demonstrating a novel 'spoon-feeding' process for black hole accretion.

Findings

Observed recurring flare from galaxy IC 3599 over 9.5 years

Modeled light curves and spectra consistent with partial tidal stripping

First evidence of a star on a highly eccentric orbit being mildly disrupted repeatedly

Abstract

Tidal disruption events (TDEs) occur when a star, passing too close to a massive black hole, is ripped apart by tidal forces. A less dramatic event occurs if the star orbits just outside the tidal radius, resulting in a mild stripping of mass. Thus, if a star orbits a central black hole on one of these bound eccentric orbits, weaker outbursts will occur recurring every orbital period. Thanks to five Swift observations, we observed a recent flare from the close by (92 Mpc) galaxy IC 3599, where a possible TDE was already observed in December 1990 during the Rosat All-Sky Survey. By light curve modeling and spectral fitting, we account for all these events as the non-disruptive tidal stripping of a single star into a 9.5 yr highly eccentric bound orbit. This is the first example of periodic partial tidal disruptions, possibly spoon-feeding the central black hole.