Fermi LAT detection of gamma-ray re-brightening of blazar PKS1510-089

The Large Area Telescope (LAT), one of two instruments on the Fermi Gamma-ray Space Telescope (formerly GLAST, launched June 11, 2008), has observed, since April 25th, 2009, a flare from a gamma-ray source positionally consistent with the blazar PKS 1510-089 (RA 15h12m50.5329s, Dec -09d05m59.828s, redshift 0.360 and already known as an EGRET gamma-ray source, 3EG J1512-0849). Preliminary analysis indicates that on 25th April the source was in a high state with a gamma-ray flux (E>100MeV) of 6.5+/-0.7e-6 cm^-2 s^-1 (statistical only) in the daily time scale and it reached a value of 8.2+/-1.9e-6 cm^-2 s^-1 (statistical only) in the 6-hours interval starting at 06 00 UT of the same day.