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ATEL # 2882; A. Tennant (NASA/MSFC), P. Caraveo (INAF-IASF Milano), E. Costa (INAF-IASF Roma), Y. Evangelista (INAF-IASF Roma), C. Ferrigno (ISDC Data Centre for Astrophysics, University of Geneva ), C. Heinke (U. of Alberta, Canada), D. Horns (Institut für Experimentalphysik, Univ. Hamburg) A. Pellizzoni (INAF-Osserv. Cagliari), M. Tavani (INAF-IASF Roma), M.C. Weisskopf (NASA/MSFC).
on 28 Sep 2010; 20:16 UT
Password Certification: Martin C.Weisskopf (email@example.com)
Subjects: X-ray, Neutron Stars, Pulsars, Supernova Remnants
Referred to by ATEL #: 2903, 2994, 3058
Following the detection by AGILE (ATel #2855) of enhanced gamma-ray emission from a source positionally consistent with the Crab Nebula, and subsequently confirmed by Fermi/LAT (ATel #2861), we requested and performed a ToO Chandra/ACIS-S3 observation (ObsID 13139). We observed for 5ks using a custom window and a 0.2s frame time. Under these conditions, all of the Nebula, except the 2 arc-second region surrounding the pulsar, is observed with Chandra resolution. The pulsar itself is missing from the image due to the high degree of pileup.
We see nothing especially unusual in this image when compared to the over 35 previous Chandra images that show the Nebula in sufficient detail. It is worth noting that the enhancement, or bright knot, of the “jet” about 6-arcseconds south-east of the pulsar, now appears to extend down to about 3 arcsec from the pulsar. A similar extension was seen in Chandra ObsId 2001 (2001-Jan-31). However, the statistics of these two observations limit our ability to make detailed comparisons. To the extent that this feature is new, or that it has been observed before, it is unclear if it is related to the gamma-ray event.
We also note, although not related to the gamma-ray flare, that the large-scale structure of the X-ray jet to the south-east (scales of an arc-minute or more) has changed significantly from what it was several years ago. The jet clearly exhibits the same "firehose-instability-like" structure as seen in Vela.
We thank the CXC and its director, Harvey Tananbaum, for making this observation possible and on on such short notice. The data are available in the Chandra public archive.