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e-EVN detection of the candidate radio counterpart of a gamma-ray source

Submitter: Alfonso Trejo and Zsolt Paragi
Description: On the 25th of June 2008 the e-EVN observed the candidate radio
counterpart to a mysterious variable gamma-ray source detected
by AGILE in the Cygnus region. The origin of many of these variable
gamma-ray sources is unknown. Finding counterparts at other wavelengths
may help to reveal their nature.

It was proposed that the recently detected variable gamma-ray source
in Cygnus might be in fact related to 3EG J2020+4017, a long-time
unidentified object first discovered by the EGRET satellite. There is
only one hard X-ray source known in the region, for which accurate
coordinates were measured by INTEGRAL and especially SWIFT. This allowed
a search in the radio regime and indeed a source was detected by the VLA,
in positional agreement with the X-ray source and an IR object known
as 2MASX J20183871+4041003. All this multi-wavelength information supports
the idea of an obscured accreting object for 3EG J2020+4017, likely an AGN at
z<0.1, but X-ray binary nature is still a possibility.

Both of these interpretations require that the radio source is compact on
milliarcsecond scales. Indeed a compact, partially resolved source is
detected in the e-EVN observations, which provide superior resolution
compared to the other instruments. The figure shows the optical image
with a prominent supernova remnant in the middle. The circles show
95% confidence levels in position for the gamma- and X--ray detections,
the + indicates the IR/VLA position, and the inset shows the e-EVN
image. Further observations in all wavelengths are required to fully
establish or reject the relationship of these sources.

For more details about the e-EVN observations see the
Telegram #1597
Large scale colour figure courtesy of Gloria Dubner.
Copyright: JIVE
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