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A search for a counterpart of the unidentified gamma-ray source 3EG J2020+4017 (2CG078+2)

Martin C. Weisskopf·Douglas A. Swartz·Alberto Carraminana·Luis Carrasco·David L. Kaplan·Werner Becker·Ronald F. Elsner·Gottfried Kanbach·Stephen L. O'Dell·Allyn F. Tennant
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Abstract

We report observations with the Chandra X-ray Observatory of a field in the gamma$-Cygni supernova remnant (SNR78.2+2.1) centered on the cataloged location of the unidentified, bright gamma-ray source 3EG J2020+4017. In this search for an X-ray counterpart to the gamma-ray source, we detected 30 X-ray sources. Of these, we found 17 strong-candidate counterparts in optical (visible through near-infrared) cataloged and an additional 3 through our optical observations. Based upon colors and (for several objects) optical spectra, nearly all the optically identified objects appear to be reddened main-sequence stars. None of the X-ray sources with an optical counterpart is a plausible X-ray counterpart to 3EG J2020+4017 --if that gamma-ray source is a spin-powered pulsar. Many of the 10 X-ray sources lacking optical counterparts are likely (extragalactic) active galactic nuclei, based upon the sky density of such sources. Although one of the 10 optically unidentified X-ray sources could be the gamma-ray source, there is no auxiliary evidence supporting such an identification.

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Martin C. Weisskopf, Douglas A. Swartz, Alberto Carraminana, Luis Carrasco, David L. Kaplan, Werner Becker, Ronald F. Elsner, Gottfried Kanbach, Stephen L. O'Dell, Allyn F. Tennant. 2006-06-23. A search for a counterpart of the unidentified gamma-ray source 3EG J2020+4017 (2CG078+2). https://doi.org/10.1086/508339

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