Swift follow-up observations of an AGILE detected gamma-ray flare of the quasar S5 0836+710 (4C 71.07)

ATel #8229; S. Vercellone, P. Romano (INAF/IASF Palermo), C. M. Raiteri (INAF/OA Torino), I. Donnarumma (INAF/IAPS), C. Pittori (ASDC and INAF/OA Roma), F. Verrecchia (ASDC and INAF/OA Roma)
on 30 Oct 2015; 15:01 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Stefano Vercellone (stefano@ifc.inaf.it)

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On 2015 October 29, following a report of a gamma-ray flare detected by AGILE (Bulgarelli et al., ATel #8223) from the high-redshift (z=2.172) flat-spectrum radio quasar (FSRQ) S5 0836+710 (4C 71.07), we triggered a Swift Target of Opportunity monitoring.

We report the preliminary results of the first Swift observation, starting on 2015-10-30 (MJD 57325.053097).

The XRT/PC spectrum (2936 s), is fitted with an absorbed power law, with two absorbing components (NHGAL=2.8E20 cm-2; Kalberla et al. 2005; and one free NH=3.1E20 cm-2) and a photon index = 1.25 (-0.11, +0.12). The average unabsorbed flux is 5.0E-11 erg/cm2/s (0.3-10 keV).

The UVOT observed the field simultaneously with the XRT in the following optical and UV filters. The preliminary observed magnitudes in the Vega system are:

MJD Filter Magnitude

57325.0612+/-0.0005 V 16.64+/-0.09 (stat) +/-0.01 (sys)

57325.0905+/-0.0345 B 16.88+/-0.04 (stat) +/-0.02 (sys)

57325.0895+/-0.0345 U 16.06+/-0.04 (stat) +/-0.02 (sys)

57325.0881+/-0.0350 W1 16.71+/-0.05 (stat) +/-0.03 (sys)

57325.0717+/-0.0100 M2 17.40+/-0.05 (stat) +/-0.03 (sys)

57325.0921+/-0.0351 W2 17.65+/-0.07 (stat) +/-0.03 (sys)

The magnitudes are not corrected for Galactic extinction.

Our group has been regularly monitoring S5 0836+710 with Swift since October 2014 in collaboration with the GASP-WEBT. Previously, we triggered a Swift ToO (Vercellone et al., ATel #7898) following a gamma-ray flare detected by Fermi (Ciprini et al., ATel #7870). Based on both the XRT and UVOT data, we note a moderate increase in flux in both energy ranges with respect to the follow-up of the previous flare.

We warmly thank N. Gehrels, the Science Planners, and the Observatory Duty Scientists for having scheduled these observations.