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HST observation of the Crab Nebula following the September 2010 gamma-ray flare

ATel #2903; P. Caraveo (IASF/INAF Milano), A. De Luca (IUSS, Pavia), R. Mignani (Mssl, UK), D. Salvetti (IASF/INAF Milano), G. F. Bignami (IUSS, Pavia), M. Tavani (IASF/INAF Roma), E. Costa (IASF/INAF Roma), A. Pellizzoni (IASF/INAF Cagliari) on behalf of the AGILE TEAM, R. Buehler (SLAC/KIPAC), F. D'Ammando (INAF-IASF Palermo), E. Hays (NASA/GSFC) on behalf of the Fermi Large Area Telescope Collaboration, A. Tennant (NASA/MSFC), M. C. Weisskopf (NASA/MSFC), D. Horns (Univ. Hamburg)
on 4 Oct 2010; 11:42 UT
Credential Certification: Andrea De Luca (deluca@iasf-milano.inaf.it)

Subjects: Optical, Neutron Star, Pulsar

Following the discovery by AGILE (ATel #2855) and the confirmation by Fermi/LAT (ATel #2861) of enhanced gamma-ray emission from the Crab Nebula region in the time interval from Sept.18 to Sept.22, 2010, we have been granted a Hubble Space Telescope observation in the frame of the Director Discretionary time (program 12381).

The observation, 2000 sec. long, centered on the Crab pulsar was performed by the ACS instrument (field of view 200 x 200 arcsec) equipped with filter F550M on Oct.2nd, 02:44 UT. (A previous attempt on Sept 29 failed, owing to a star acquisition problem).

Comparing the current Crab Nebula image with the extensive database available in the HST public archive, we notice an increased emission about 3 arcsec East of the pulsar. A Chandra exposure, taken a few days before the HST one, reported a brightening from the same region (ATel #2882). Also, the wisps north-west of the pulsar appear bright, with a remarkable sinuous feature between Wisp 1A and Wisp 2, as named in Hester et al. 1995 (ApJ, 448, 240).

We thank the HST director for the effort done to perform this DD observation.

The data are available in the HST public archive.

HST/ACS image of the Crab (2010 Oct. 2)