TITLE: GCN CIRCULAR NUMBER: 14258 SUBJECT: GBM trigger 383712005 (GRB 130228A?) : Possible high-energy photon emission in Fermi/LAT data DATE: 13/03/05 18:55:53 GMT FROM: Weikang Zheng at U.of Michigan WeiKang Zheng (UC Berkeley) and Carl Akerlof (Umich), report on behalf of the ROTSE collaboration (the authors are not affiliated with the Fermi Collaboration), We report the possible high-energy photon emission in Fermi/LAT data correlated with GBM trigger 383712005 (02:40:02 UT on Feb. 28, 2013, probably GRB 130228A) as a follow-up of a routine search in GBM trigger catalogs using our LAT data processing pipeline. The GBM trigger location (RA = 265.830, Dec = 55.930) was about 24 degree from the LAT boresight, and the zenith angle was about 45 degrees. A standard matched filter technique analysis (Akerlof et al. 2010, 2011, 2013, Zheng et al. 2012a,b), which uses a duration data of 47.5s after the trigger, did not reveal confident signal in LAT data. However, if extending the duration to 150s, the matched filter analysis gives a weight value of 10.53, not high enough to claim a firm detection compared to standard case, but is clearly higher than background. This kind of delayed LAT high energy photon emission is quite common in GRB. The new GRB location estimated by the matched filter technique is Ra = 255.46, Dec = 55.02 with uncertainty ~0.5 degree, this is ~6 degrees away from the GBM trigger location. ~7 photons above 100 MeV were detected within 150s, with the highest energy of ~692 MeV at 133s after the burst. A maximum likelihood analysis focusing on the new GRB location gives a TS value of 31.0 over the same time window of 150s after the trigger. This supports the above finding from matched filter analysis. The photon information can be found in the following link including the skymap: http://www.rotse.net/LAT/GBMTriggers/383712005/383712005_res.html