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Fermi LAT detection of bright gamma-ray activity related to the M-class solar flare of January 23 2012

ATel #3886; Y. T. Tanaka (ISAS/JAXA), N. Omodei (Stanford U.), N. Giglietto (INFN-Bari), H. Takahashi (Hiroshima U.), D. J. Thompson (NASA-GSFC), S. Ciprini (ASDC-INAF), P. R. den Hartog (Stanford U.), on behalf of the Fermi Large Area Telescope Collaboration
on 25 Jan 2012; 05:00 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Nicola Omodei (nicola.omodei@gmail.com)

Subjects: Gamma Ray, >GeV, The Sun

The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, detected on January 23, 2012 increased gamma-ray flux from a source at R.A.=304.3 deg, Dec.=-19.6 deg, J2000, positionally consistent with the Sun. This detection is likely associated with M9-class solar flare around 03:59 UT on January 23, 2012 where a fast coronal mass ejection appears associated to this flare. Preliminary analysis indicates that gamma-ray emission from the Sun was detected between 00:00 UT and 18:37 UT with a measured flux of F(>100 MeV)=(13.4+/-0.8)x10^-6 photons cm^-2 s^-1 (statistical error only). On shorter time scales, significant gamma-ray emission above 100 MeV is also detected between 00:00 UT and 6:00 UT with a flux of (6+/-1)x10^-6 photons cm^-2 s^-1; between 06:00 UT and 09:00 UT with a with a flux of (24+/-3)x10^-6 photons cm^-2 s^-1 and between 09:00 UT and 12:00 UT with a flux of (23+/-5)x10^-6 photons cm^-2 s^-1. This suggests temporally extended gamma-ray emission. During the brightest peak, the measured gamma-ray flux above 100 MeV was a factor of about 50 greater than the flux of the solar disk for the quiet Sun, Abdo et al. (2011, ApJ, 734, 116). Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of the Sun will continue. For this detection, the Fermi LAT contact person is Nicola Omodei (nicola.omodei@gmail.com). 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.