NTRS - NASA Technical Reports Server

Back to Results
Discovery of a Nonblazar Gamma-Ray Transient Source Near the Galactic Plane: GRO J1838-04We report the discovery of a remarkable gamma-ray transient source near the Galactic plane, GRO J1838-04. This source was serendipitously discovered by EGRET in 1995 June with a peak intensity of approx. (4 +/- 1) x 10(exp -6) photons/sq cm s (for photon energies larger than 100 MeV) and a 5.9 sigma significance. At that time, GRO J1838-04 was the second brightest gamma-ray source in the sky. A subsequent EGRET pointing in 1995 late September detected the source at a flux smaller than its peak value by a factor of approx. 7. We determine that no radio-loud spectrally flat blazar is within the error box of GRO J1838-04. We discuss the origin of the gamma-ray transient source and show that interpretations in terms of active galactic nuclei or isolated pulsars are highly problematic. GRO J1838-04 provides strong evidence for the existence of a new class of variable gamma-ray sources.
Document ID
Document Type
Reprint (Version printed in journal)
Tavani, M. (Columbia Univ. New York, NY United States)
Oliversen, Ronald
Date Acquired
August 20, 2013
Publication Date
May 1, 2001
Publication Information
Publication: The New X-Ray/Gamma-Ray Pulsars
Subject Category
Space Radiation
Funding Number(s)
Distribution Limits