TITLE AND SHORT ABSTRACT   DUE JULY 1, 1994

Title: 	 A SYSTEMATIC SEARCH FOR MEV EMISSION FROM GALACTIC 
	 BLACK HOLE CANDIDATES
     

Author(s):  M. McConnell, D. Forrest, J. Ryan 
             (University of New Hampshire) 
            W. Collmar, V. Schoenfelder, H. Steinle. A. Strong
             (Max-Planck Institut fur Extraterrische Physik) 
            R. van Dijk, W. Hermsen
             (SRON-Leiden)
            K. Bennett, R. Much
             (Astrophysics Division, ESTEC)

Abstract (1/2 page max, 80 words/line):

The COMPTEL instrument on CGRO has surveyed the entire sky in the
energy range of 0.75-30 MeV.  These data provide the opportunity to
perform a systematic search for MeV emission from galactic black hole
candidates.  The COMPTEL team has previously reported on the positive
detection of both Cygnus X-1 and GRO J0422+32 at energies up to 2 MeV
(and even higher for Cygnus X-1).  In the case of GRO J0422+32, there
is some evidence for a hardening of the spectrum near 1 MeV, but no
such evidence in the case of Cygnus X-1 (contrary to some earlier
pre-CGRO observations).  Although these sources appear to be dominated
by thermal emission, the spectrum of Cygnus X-1 as measured by COMPTEL
suggests the need to re-evaluate the standard Sunyaev-Titarchuk
Comptonization model as an acceptable explanation for the observed
spectrum.  The observation of other black hole systems at these
energies may provide further clues towards a better understanding of
these objects.  Not only would such data help to further our
understanding of the thermal component of the emission, but
observations at these energies would also constrain the extent of any
non-thermal emission.  Towards this end, we are using the available
COMPTEL data to search for MeV emissions from all known galactic black
hole candidates.  Here we report on the status of this search.



Poster or Oral presentation preferred?  Poster

Contact person:
   Name:     Dr. Mark McConnell
   Address:  Space Science Center, Morse Hall	
             University of New Hampshire	
             Durham, NH  03824 USA
   Phone:    (603) 862-2047
   FAX:      (603) 862-4685
   email:    mmcconnell@unh.edu


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