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Swift-XRT follow-up of FSRQ GB6 J1700+6830

ATEL # 1991; Matteo Perri (ASI Science Data Center); Sara Cutini and Dario Gasparrini (ASI Science Data Center) for the Fermi Large Area Telescope Collaboration
on 27 Mar 2009; 22:04 UT
Distributed as an Instant Email Notice (Request for Observations)
Password Certification: Paolo Giommi (

Subjects: X-ray, Gamma Ray, Request for Observations, AGN, Quasars

Following the Fermi-LAT detection of new gamma-ray blazar GB6 J1700+6830 (z=0.301) on March 23rd 2009 (Gasparrini et al., ATEL #1986), Swift performed a ToO observation on March 26th and 27th.

SWIFT-XRT observations started on 2009-03-26 at 13:18:01 UT and ended on 2009-03-27 at 03:49:14 UT. Data were taken in Photon Counting mode for a total exposure of 3.8 ksec. The source is well detected by XRT matching the GB6 position. The 0.3-10 keV average count rate is about 4.9E-2 counts/s. The time-integrated XRT spectrum in the 0.3-10 keV range can be fitted by an absorbed power law model with a column density consistent with the Galactic one in the direction of the source (N_H=4.6E20 cm-2, Kalberla et al. 2005) and a photon index Gamma = 1.6 +/- 0.3. The observed 0.3-10 keV flux is (2.1 +/- 0.5)E-12 erg cm-2 s-1. All the quoted errors are at the 90% confidence level.

Compared to the previous ROSAT observations of GB6 J1700+6830, in which the observed 0.1-2.4 keV flux was about 1.7E-13 erg cm-2 s-1 (Voges et al. 2000), the XRT flux is about four times higher. This enhanced X-ray flux strengthens the case that the LAT detected source was a blazar. Further multi-frequency observations of GB6 J1700+6830 are encouraged.

The Fermi-LAT contact person is Sara Cutini ( We thank Neil Gehrels and the Swift science operations team for approving and scheduling this rapid Target of Opportunity observation.

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R. E. Rutledge , Editor
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