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                              G C N E W S
                             * Newsflash *

            - The Newsletter for Galactic Center Research -

gcnews@mpifr-bonn.mpg.de             http://www.mpifr-bonn.mpg.de/gcnews
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Vol. 8, No. 14                                              Jul 14, 1998


Recently submitted papers:
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1) A Model of the EGRET Source at the Galactic Center:         
   Inverse Compton Scattering Within Sgr A East and its Halo (Melia et al., ApJ)

2) BeppoSAX observations of a new X-ray burster in the Galactic Center
   region, possibly coincident with a recurrent transient 
   (Sidoli et al., A&AL)

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Email    : melia@spacetime.physics.Arizona.EDU
Title    : A Model of the EGRET Source at the Galactic Center:,         
           Inverse Compton Scattering Within Sgr A East and its Halo
Author(s): Fulvio Melia(1,3,4),    Farhad Yusef-Zadeh(2)   and 
           Marco Fatuzzo(1)
Institute: (1) Physics Department, The University of Arizona, Tucson, 
           AZ 85721   (2) Department of Physics and Astronomy, 
           Northwestern   University, Evanston, IL 60208  
           (3) Steward Observatory, The University of Arizona, Tucson, 
           AZ    85721   (4) Presidential Young Investigator.
Paper    : ApJ, in press
EPrint   : astro-ph/9806324

Abstract:
Continuum low-frequency radio observations of the Galactic Center
reveal the presence of two prominent radio sources, Sgr A East and its
surrounding Halo, containing non-thermal particle distributions with
power-law indices ~ 2.5-3.3 and ~ 2.4, respectively.  The central 1-2
pc region is also a source of intense (stellar) UV and
(dust-reprocessed) far-IR radiation that bathes these extended
synchrotron-emitting structures.  A recent detection of gamma -rays
(2EGJ1746-2852) from within ~ 1^o of the Galactic Center by EGRET
onboard the Compton GRO shows that the emission from this environment
extends to very high energies.  We suggest that inverse Compton
scatterings between the power-law electrons inferred from the radio
properties of Sgr A East and its Halo, and the UV and IR photons from
the nucleus, may account for the possibly diffuse gamma -ray source as
well.  We show that both particle distributions may be contributing to
the gamma -ray emission, though their relevant strength depends on the
actual physical properties (such as the magnetic field intensity) in
each source. If this picture is correct, the high-energy source at the
Galactic Center is extended over several arcminutes, which can be
tested with the next generation of gamma -ray and hard X-ray missions.
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Email    : sidoli@ifctr.mi.cnr.it
Title    : BeppoSAX observations of a new X-ray burster in the    
           Galactic Center region, possibly coincident with a recurrent 
           transient.
Author(s): L. Sidoli(1, 2), S. Mereghetti(1), G.L. Israel(3, 4),  
           G. Cusumano(5), L. Chiappetti(1), A. Treves(6)
Institute: (1)    Istituto di Fisica Cosmica del C.N.R., Via Bassini 
           15, I-20133 Milano,   Italy;, e-mail: (sidoli, sandro, 
           lucio)@ifctr.mi.cnr.it  (2) Dipartimento di Fisica, 
           Universit`a di Milano, Via Celoria 16, I-20133   Milano, 
           Italy   (3)  Osservatorio Astronomico di Roma, Via 
           dell'Osservatorio 2,   I-00040 Monteporzio Catone (Roma),    
           Italy;, e-mail: israel@coma.mporzio.astro.it  
           (4) Affiliated to I.C.R.A.   (5)  Istituto di Fisica Cosmica 
           ed Applicazioni all'Informatica del C.N.R.,    Via La Malfa 
           153, I-90146 Palermo,    Italy;, e-mail: 
           cusumano@ifcai.pa.cnr.it    (6) Universit`a di Milano, 
           sede di Como, Via Lucini 3, I-22100   Como, Italy;, e-mail: 
           treves@astmiu.uni.mi.astro.it
Paper    : to appear in A&A Letters, Aug 1998
EPrint   : astro-ph/9807054

Abstract:
We report BeppoSAX NFI observations of the   X-ray 
source SAX J1747.0-2853 recently discovered in the 
region of the Galactic Center.  
The presence of type I X-ray bursts indicates that this 
source, positionally coincident with the transient GX 0.2-0.2 
observed in 1976, is a neutron star accreting from a  
low mass companion.
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			       Edited by
Angela Cotera                                Heino Falcke
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