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ATEL # 1497; M. Ajello, J. Greiner, G. Kanbach (all MPE Garching) N. Gehrels (GSFC)
on 29 Apr 2008; 21:47 UT
Password Certification: J. Greiner (firstname.lastname@example.org)
Subjects: X-ray, Gamma Ray, AGN, Binaries, Pulsars, Quasars
Referred to by ATEL #: 1498
We report on the presence of a Swift/BAT (15-55 keV) source in the error box of the AGILE source (Longo et al. 2008, ATEL #1492) located at l = 78.01 deg, b = 2.19 deg. In the ongoing BAT all-sky survey a source is detected at RA(J2000) = 304.650, Decl.(J2000)= +40.700 (3 arcmin error radius at 90% CL) which is positionally coincident with the INTEGRAL source IGR J20187+4041 (Bykov et al. 2006, ApJ 649, 21). The BAT source is located 30 arcmin away from the AGILE position, so well within the AGILE/GRID error circle.
Two Swift/XRT observations were carried out in April 2006 for ~2ks each (see also Kennea et al. 2006, ATEL #788). In both observations, a faint source is detected inside the BAT error circle at RA = 20:18:38.5 Decl. = +40:41:00 (error of 4.8 arcsec) which is positionally consistent with 2MASX J20183871+4041003 (Bykov et al. 2006). A joint fit to the XRT-BAT spectrum with an absorbed power-law shows that the source is absorbed by a column density of (12.4 ± 8.0) * 1022H-atom/cm2. The photon index is 1.6(±0.2).
The BAT lightcurve, from Jan. 2005 to Mar. 2007, is consistent with being constant. The XRT observations show moderate variability (given the low S/N ratio) of a factor less than 2. While Iyudin et al. (2007, A&A, 468, 919) suggest a blazar nature of the BAT/XRT/2MASX source, the BAT spectrum is also consistent with other interpretations, for instance an absorbed Seyfert or an absorbed HMXB. Given the moderate variability seen in BAT and XRT, the association of this BAT/XRT/2MASX source with the AGILE object remains open.