Title: INTEGRAL Observations of a 2.22 MeV Source Candidate
Proposal ID: 0120036
Subject category: Compact Object
Principal investigator: McConnell
Institute: University of New Hampshire
Abstract
Neutron capture processes can be expected in any situation where neutrons are accelerated to high energies
and rapidly thermalized in a sufficiently dense medium. Solar flare spectra, for example, are often
dominated by the presence of very strong narow line emission at 2.2 MeV, resulting from neutron capture on
hydrogen. These observations indicate the importance of neutron capture measurements as a tracer of
energetic particle interactions. This provides a strong motivation to search for observable emission in
other (non-solar) astrophysical sources, where compact binary systems or stelllar flares represent potential
sites of measurable 2.2 MeV emission.
A previous analysis of data from the COMPTEL experiment on
CGRO led to the first all-sky map of 2.2 MeV line emission. The map was nearly featureless, with only one
significant point-like feature. This source (GRO J0332-87) has been tentatively associated with the unusual
white dwarf object RE 0317-853. It has further been speculated that the 2.2 MeV emission may result from
some type of flaring proces near the surface of a white dwarf.
Here we propose an observation of the 2.2
MeV point-source candidate by the IBIS/SPI instruments on INTEGRAL. The purpose of this observation will be
three-fold: 1) to provide an independent confirmation of the COMPTEL source; 2) to further define the
characteristics of the source (energy spectrum, location); and 3) to test for source variability.
Observations with INTEGRAL will take advantage of the unique capabilities of SPI for acquiring high
sensitivity data with both high energy and angular resolution. In addition, observations with JME-X and
IBIS will permit a sensitive search for energetic sources that might be related to the observed COMPTEL
source, irrespective of the results from SPI.