Article,
The Sudden Death of the Nearest Quasar
The Astrophysical Journal Letters, 724 (1): L30 (2010)
Abstract
Galaxy formation is significantly modulated by energy
output from supermassive black holes at the centers of
galaxies which grow in highly efficient luminous quasar
phases. The timescale on which black holes transition
into and out of such phases is, however, unknown. We
present the first measurement of the shutdown timescale
for an individual quasar using X-ray observations of
the nearby galaxy IC 2497, which hosted a luminous
quasar no more than 70,000 years ago that is still seen
as a light echo in "Hanny's Voorwerp," but whose
present-day radiative output is lower by at least two,
and more likely by over four, orders of magnitude. This
extremely rapid shutdown provides new insight into the
physics of accretion in supermassive black holes and
may signal a transition of the accretion disk to a
radiatively inefficient state.
