Title: Probing an Intermediate Mass Black Hole
Proposal ID: 0120259
Subject category: Extragalactic Object
Principal investigator: Dean
Institute: University of Southampton
Abstract
NGC4395 is an exceptional and fascinating object and the least luminous Seyfert galaxy known. It radiates a
power law continuum that extends from the classical X-ray band well into the gamma-ray domain. The emission
is unusually variable in time; exhibiting X-ray flares on time scales of hours or less. This object clearly
contains an AGN at its core, but whether it is a Seyfert 1 or 2 still remains in some doubt. The detection
of high energy photons (>10 keV) with BATSE, further underline the exceptionality of this source as strong
high energy emission is not expected from such low luminosity an extremely low mass (10^4 to 10^5 solar
mass) AGN . We propose to use the full diagnostic power of a 100 ks second broadband INTEGRAL observation to
clarify the situation about this object and in particular to define the true nature of this high energy
source. Furthermore, the imaging capability of INTEGRAL will be used to unambiguously identify origin of the
gamma-ray emission in the field of NGC 4395. Through the study of the shape of the continuum emission and
analysis of the temporal characteristics we intend reliably distinguish between the competing possibilities
of an ADAF configuration and "normal" AGN accretion onto a low mass black hole. We also intend to measure
the intrinsic high-energy emission spectrum of the central engine, better understand the nature of the
nearby gas and dust, and hope to provide a meaningful constraint on the mass of the central black hole.