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Fermi-LAT detection of ongoing gamma-ray activity from the new gamma-ray source Fermi J1654-1055 (PMN J1632-1052)

ATel #8721; D. Kocevski (GSFC/NASA), M. Ajello (Clemson University), S. Buson (GSFC/NASA), R. Buehler (DESY/Zeuthen), M. Giomi (DESY/Zeuthen) on behalf of the Fermi Large Area Telescope Collaboration
on 22 Feb 2016; 03:46 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Daniel Kocevski (dankocevski@gmail.com)

Subjects: Gamma Ray, >GeV, AGN, Blazar, Transient

Referred to by ATel #: 8735, 8743, 8773

During the week between February 8 and 15, 2016, the Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, observed gamma-ray activity from a new transient source, Fermi J1654-1055. The significance of the source detection in the 100-800 MeV and 800 MeV to 300 GeV energy ranges for the entire LAT exposure from February 8 to February 15, 2016 is approximately 6.5 sigma and 8.7 sigma, respectively. The preliminary best-fit location of the gamma-ray source is RA = 248.19 deg, Dec = -10.93 deg, J2000, with 95% confidence error radius of 0.12 degrees (statistical errors only). A preliminary spectral analysis of the source indicates that the source brightened in gamma rays to a flux (100 MeV < E < 800 MeV) of (2.63 +/- 0.65) x10^-7 ph cm^-2 s^-1, with a spectral index of 2.2 +/- 0.3 (errors are statistical only). The closest 3FGL source is 3FGL J1630.2-1052, located 0.6 deg away from our best-fit position and outside its 95% confidence. A search of the NASA Extragalactic Database (NED) within the 95% containment radius reveals a bright flat-spectrum radio source, PMN J1632-1052, with coordinates RA = 248.20900 deg, Dec = -10.87578 deg (J2000, Condon et al. 1998, AJ, 115, 1693), at an angular distance of approximately 0.05 degrees from the LAT localization. PMN J1632-1052 is coincident with a Wide-field Infrared Survey Explorer (WISE) source (WISE J163250.09-105231.8) whose infrared colors ([3.4]-[4.6]=1.08 and [4.6]-[12]=2.65) are consistent with those of blazars (Massaro et al. 2011, ApJL, 740, 48) and fall in between the region occupied by flat spectrum radio quasars and BL Lacs. Because Fermi provides all-sky coverage, regular gamma-ray monitoring of this source will continue. A Swift ToO has been requested to better determine the source classification. Multi-wavelength observations during the ongoing activity of this source are strongly encouraged. The Fermi LAT contact person for Fermi J1654-1055 is Daniel Kocevski (e-mail: daniel.kocevski@nasa.gov). The transient was identified by the 'Fermi All-sky Variability Analysis' (FAVA) that searches the entire sky for high-energy transients on weekly time scales (Ackermann et al. 2013, ApJ, 771, 57). The FAVA source report for Fermi J1654-1055 can be found at the link below. 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.

FAVA source report for Fermi J1654-1055