Is the EGRET Source 3EG J1621+8203 the Radio Galaxy NGC 6251?

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https://iopscience.iop.org/article/10.1086/340999

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https://doi.org/10.1086/340999
 http://hdl.handle.net/11603/19617

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UMBC Physics Department
UMBC Center for Space Sciences and Technology (CSST) / Center for Research and Exploration in Space Sciences & Technology II (CRSST II)
UMBC Joint Center for Earth Systems Technology (JCET)

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2002-04-03

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journal articles preprints
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R. Mukherjee, J. Halpern, N. Mirabal and E. V. Gotthelf, Is the EGRET Source 3EG J1621+8203 the Radio Galaxy NGC 6251?, ApJ 574 693 (2002), doi: https://doi.org/10.1086/340999

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© 2002. The American Astronomical Society. All rights reserved.

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Abstract

We discuss the nature of the unidentified EGRET source 3EG J1621+8203. In an effort to identify the gamma-ray source, we have examined X-ray images of the field from ROSAT PSPC, ROSAT HRI, and ASCA GIS. Of the several faint X-ray point sources in the error circle of 3EG J1621+8203, most are stars or faint radio sources, unlikely to be counterparts to the EGRET source. The most notable object in the gamma-ray error box is the bright FR I radio galaxy NGC 6251. If 3EG J1621+8203 corresponds to NGC 6251, then it would be the second radio galaxy to be detected in high-energy gamma rays after Cen A, which provided the first clear evidence of the detection above 100 MeV of an active galactic nucleus (AGN) with a large-inclination jet. If the detection of more radio galaxies by EGRET has been limited by its threshold sensitivity, there exists the exciting possibility that new high-energy gamma-ray instruments, with much higher sensitivity, will detect a larger number of radio galaxies in the future.