Abstract
view Abstract Citations (17) References (28) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS SMM Observations of Gamma-Ray Transients. III. A Search for a Broadened, Redshifted Positron Annihilation Line from the Direction of the Galactic Center Harris, Michael J. ; Share, Gerald H. ; Leising, Mark D. Abstract We have searched for 1980-1988 Solar Maximum Mission gamma-ray spectrometer data for transient emission on timescales from hours to approximately 12 days of broad gamma-ray lines at energies approximately 400 keV, which were reported by the High Energy Astronomy Observatory (HEAO) 1 and SIGMA experiments from two sources lying toward the Galactic center. The lines have been interpreted as the product of the annihilation of positrons in pair plasmas surrounding the black hole candidate 1E 1740.7-2942 and the X-ray binary 1H 1822-371. Our results from a combined exposure of approximately 1.5 x 107s provide no convincing evidence for transient emission of this line on any timescale between approximately 9 hr and approximately 1 yr. Our 3 sigma upper limits on the line flux during approximately 12 day intervals are characteristically 4.8 x 10-3 photon/sq cm/s, while for approximately 1 day intervals our 3 sigma upper limits are characteristically 4.9 x 10-3 photon/sq cm/s. These results imply a duty cycle of less than 1.3% for the transient line measured from 1H 1822-371 during a approximately 3 week interval in 1977 by HEAO 1, and a duty cycle of less than or = 0.8% for the transient line detected in 1990 and 1992 from 1E 1740.7-2942 on approximately 1 day timescales by SIGMA. Publication: The Astrophysical Journal Pub Date: September 1994 DOI: 10.1086/174627 Bibcode: 1994ApJ...433...87H Keywords: Emission Spectra; Gamma Ray Astronomy; Gamma Ray Spectra; Line Spectra; Positron Annihilation; Space Plasmas; Spaceborne Astronomy; X Ray Binaries; Astronomical Spectroscopy; Black Holes (Astronomy); Gamma Ray Spectrometers; Solar Maximum Mission; Astronomy; GALAXY: CENTER; GAMMA RAYS: OBSERVATIONS full text sources ADS | data products SIMBAD (3) Related Materials (2) Part 1: 1993ApJ...416..601H Part 2: 1994ApJ...420..649H
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