{
  "bibcode": "2009GCN..8881....1C",
  "body": "ICSP VLF observation of the signatures of SGR/AXP 1E1547.0-5408 bursts\n\nSandip K. Chakrabarti (S. N. Bose Centre and ICSP), Sushanta K. Mondal (ICSP),\nSudipta Sasmal (ICSP) and Debashis Bhowmick (ICSP)\n\n\nA number of recent satellite observations have reported the outbursts of\nanomalous X-Ray Soft gamma repeater AXP 1E1547.0-5408 which reportedly \nstarted from January 22nd, 2009 (GCN #8833, 8835, 8837, 8838). We looked at\nthe ionospheric data of Indian Centre for Space Physics (ICSP) obtained by\nreceiving Very Low Frequency (VLF) signal from the VTX station at 18.2KHz \nfor the 22nd of January (IST), 2009 (21st Jan. 18:30 UT to 22nd Jan. 18:30 \nUT) using a Gyrator-II receiver. We found statistically significant \nsignatures of short bursts which either suddenly amplified the signal \nor suddenly attenuated the signal. Each event lasted for a few seconds \nas the recombination time is usually longer than the burst duration. We\nobserve 30 significant signatures out of which 9 were not reported by \nothers and these events mostly took pace in late 21st January, 2009 (UT)\nbefore other satellite results were reported. However, the timings of the\nremaining 21 events match with the satellite observations. A list and the\nlight curves of all the major events seen by us in the 22nd January (IST) \ncan be found in http://www.bose.res.in/~chakraba/axpsgr.html.\n\nSince both the amplifications and the attenuations were seen, often one\nafter the other, each event could tell us about the energy spectrum in \neach burst as the upper ionosphere would be primarily affected by \nsoft-X-rays and the lower ionosphere would be primarily affected by the\nhard-X-rays. The highly tangential source illumination of the ionosphere \nas seen from ICSP (22d34m N, 88d21m E) was probably advantageous. \nWe encourage other VLF observers to look into such signatures and \nparticularly the latitude dependence.",
  "circularId": 8881,
  "createdOn": 1233759264000,
  "email": "chakraba@bose.res.in",
  "subject": "ICSP VLF observation of the signatures of SGR/AXP 1E1547.0-5408 bursts",
  "submitter": "Sandip K. Chakrabarti at S.N. Bose Nat. Centre for Basic Sci  <chakraba@bose.res.in>"
}