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XMM-Newton Observations of the Variable AGILE Source in Cygnus Following its Re-brightening in May 2008

ATel #1595; D. Pandel, P. Kaaret, C. C. Lang (University of Iowa)
on 1 Jul 2008; 17:08 UT
Credential Certification: Dirk Pandel (dirk-pandel@uiowa.edu)

Subjects: Ultra-Violet, X-ray, Gamma Ray, >GeV, Transient, Variables

Referred to by ATel #: 1623

Following the re-brightening of the variable AGILE gamma-ray source in the Cygnus region beginning on 2008-05-22 (ATel #1547; ATel #1492), the source region was observed with XMM-Newton on 2008-06-01 8:19 UT for 8.7 ksec. XMM-Newton was pointed at the source position reported in ATel #1547 (Galactic coordinates l=77.9 deg, b=2.6 deg, error radius 0.5 deg). Here we report on the X-ray sources detected in the XMM-Newton field of view (radius 0.24 deg). More recently, the AGILE team reported a possible re-brightening of the source beginning on 2008-06-20 and also the detection of a gamma-ray point source from integrating several months of data (ATel #1585). The field of view for the XMM-Newton observation is outside the error circles for both of the newly reported source positions. We note, however, that the positions of the May transient (ATel #1547) and the June transient (ATel #1585) are inconsistent with each other.

We detect 5 X-ray sources in the XMM-Newton field of view. The following tables show the J2000 source positions, the position error radius in arcseconds, the flux in the 0.5-10 keV energy range, the hardness ratio HR for the 0.5-2 keV and 2-10 keV energy ranges, and the hydrogen column density N_H and photon index for a spectral fit with an absorbed power law model. Uncertainties are given at the 90% confidence level.

No.      R.A.         Decl.     Error radius
1 20:18:38.40 +40:40:58.4 2.7"
2 20:18:49.92 +40:28:23.5 3.4"
3 20:17:34.32 +40:31:42.2 3.2"
4 20:18:45.12 +40:37:26.0 3.4"
5 20:18:21.84 +40:23:46.3 3.6"
No.  Flux (ergs/cm^2/s)   HR     N_H (cm^-2)      Photon index
1 4.3(±0.8)*10^-12 1.0 8(+6/-3)*10^22 1.2(+0.9/-0.7)
2 3.1(±1.3)*10^-14 -0.9 4(+5/-2)*10^21 5.4(+3.4/-2.3)
3 2.4(±1.5)*10^-13 0.8 <4*10^22 <3.5
4 6.2(±3.1)*10^-14 -0.2 5(+5/-2)*10^21 3.4(+2.6/-1.0)
5 2.2(±2.0)*10^-14 -0.4 <9*10^21 3.3(+8/-1.8)

Source #1 is coincident with the Swift/XRT source reported in ATel #788, the Swift/BAT source reported in ATel #1497, the radio point source reported in ATel #1518, and the hard X-ray source IGR J20187+4041 (Bykov et al. 2006, ApJ 649, 21). The X-ray flux and the spectral fit parameters are consistent with those from the Swift/XRT observation (ATel #788). No X-ray flux variability is apparent between the Swift/XRT and XMM-Newton observations or during the XMM-Newton observation.

Source #2 is coincident with the ROSAT PSPC source 2RXP J201849.9+402819. Sources #2 and #5 are within the field of view of the Optical Monitor which was operated with the UVW1 filter, but only source #2 was detected with a UV flux of 6.9(±0.3)*10^-16 ergs/cm^2/s/A at 291 nm.