Optical and X-ray Observations of IGR J20187+4041 in the Error Circle of the Variable AGILE Source in Cygnus
ATel #1498; J. P. Halpern (Columbia U.)
on 29 Apr 2008; 23:52 UT
Credential Certification: Jules Halpern (email@example.com)
Subjects: Optical, X-ray, AGN
With regard to the galaxy 2MASX J20183871+4041003 that was mentioned
by Longo et al. (ATel #1492) in connection with a variable AGILE source,
I note that this galaxy was first identified
with the INTEGRAL source IGR J2018+4043 (=IGR J20187+4041)
by Kennea et al. (ATel #788) and
Bykov et al. (2006, ApJ, 649, L21) using the Swift XRT.
(See also Ajello et al., ATel #1497). While these authors
noted the proximity of the unidentified EGRET source 3EG J2020+4017, the
galaxy is actually outside the EGRET error box. The claim by Bykov et al.
that 2MASX J20183871+404100 has blazar-like characteristics, which was
repeated by Iyudin et al. (2007, A&A, 468, 919), is not based on any physical
property of the galaxy. In particular, it does not host a compact radio
source, and other defining blazar signatures such as polarized
optical continuum and high-amplitude variability have not been reported.
The hypothesis that 2MASX J20183871+4041003 is a blazar because of
its association with 3EG J2020+4017 is circular. While the variable
AGILE source may or may not be identical to 3EG J2020+4017, a relationship
of the AGILE source to 2MASX J20183871+4041003 is problematic for similar
I obtained an I-band image of 2MASX J20183871+4041003 on the MDM 2.4m
telescope (see link below) on 2006 June 29. Despite partly cloudy
conditions and Galactic extinction AI~4,
a bulge and disk are clearly resolved, indicating
that it is probably a nearby (z<0.1) Seyfert galaxy.
In contrast, blazars are normally found in elliptical galaxies.
In particular, this bright galaxy cannot be at z=1.5+/-0.2 as concluded by
Iyudin et al. (2007). Optical and/or IR spectra are needed
to determine the classification and redshift of 2MASX J20183871+4041003.
A new Swift XRT observation of IGR J20187+4041 was obtained on 2008
April 29. In 1880 s of quicklook data I measure a count rate of
0.026+/-0.004 s^-1 from 2MASX J20183871+404100, consistent with
0.021+/-0.002 s^-1 measured by Bykov et al. in 2006 March. Thus,
there is no X-ray evidence of current blazar activity from this source.