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Fermi LAT detection of a flaring, new GeV source near the Galactic plane: J0109+6134

ATEL # 2414; J. Vandenbroucke (Stanford/KIPAC), A. B. Hill (LAOG), on behalf of the Fermi Large Area Telescope Collaboration
on 3 Feb 2010; 7:54 UT
Distributed as an Instant Email Notice (Request for Observations)
Password Certification: Justin Vandenbroucke (

Subjects: Gamma Ray, Request for Observations, Transients
Referred to by ATEL #: 2416, 2420, 2421, 2428, 2429, 2433

The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed an increasing gamma-ray flux from a source ~1 degree from the Galactic plane. Preliminary analysis indicates that, over the two-week period ending February 1, 2010, the source had a gamma-ray flux of (0.5 +/- 0.06) x 10^-6 photons / cm^2 / s, with a photon index of 2.4 +/- 0.1. The preliminary flux estimate for the one-day period February 1, 2010 UTC is (0.8 +/- 0.3) x 10^-6 photons / cm^2 / s, with a photon index of 2.2 +/- 0.2. Fluxes are above 100 MeV. Uncertainties are statistical only. The position estimate from the two-week analysis is RA = 17.459 deg, Dec = 61.568 deg (L = 125.121 deg, B = -1.226 deg), with a 95% error circle radius of 0.088 deg. Several possible counterparts lie within the error circle. In particular, the radio source VCS2 J0109+6133 (RA = 01 09 46.34439, Dec: +61 33 30.4557, J2000, Fomalont, E. B. et al., 2003, AJ, 126:2562-2566) is 0.012 deg from the best fit position estimate. This is a new GeV source: the nearest source in the first-year Fermi LAT catalog ( ) is 1FGL J0131.2+6121, an unassociated source 2.57 deg offset from the flaring source. Multi-wavelength observations are requested to identify the source and in particular to determine whether it is Galactic or extragalactic. Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. For this source the Fermi LAT contact person is J. Vandenbroucke ( The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.

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