TITLE: GCN CIRCULAR NUMBER: 8900 SUBJECT: Detailed lightcurves of ICSP VLF Observation of SGR/AXP 1E1547.0-5408 DATE: 09/02/11 05:01:57 GMT FROM: Sandip K. Chakrabarti at S.N. Bose Nat. Centre for Basic Sci. ICSP VLF observation of SGR/AXP 1E1547.0-5408 bursts on 22nd January, 2009 Sandip K. Chakrabarti (S. N. Bose Centre and ICSP), Sushanta K. Mondal (ICSP), Sudipta Sasmal (ICSP) and D. Bhowmick (ICSP) In a previous GCN (#8881) we reported that we were able to identify signatures of unusual activities in the ionosphere based on VLF data averaged over 10 points (5 seconds). After correcting the time stamps and using non-averaged data we are now in a position to claim that numerous ionospheric activities (fast rise and slow decay light curves over 10-20 seconds or more) have been observed on 22nd January, many of which match the activities reported in previous GCNs from FERMI/INTEGRAL/SUZAKU/RHESSI and other teams (e.g., GCNs 8833, 8835, 8837, 8838). Due to intrinsic problem of directional insensitivity and recombination time in lower ionosphe we found two problems (a) Begining of new activity before the earlier one decayed causing display of 'non-ideal' shape change, (b) influence of other active sources could be present. Interesting cases where many activities happened in close succession (as reported mainly by SUZAKU and HESSI) have been separated and they can be found in four PDF files (one2two.pdf, two2three.pdf, 426to533.pdf and eight2nine.pdf). Unlike one or two cases in our previous circular #8881 (based on smoothed data) attenuation events were not found when original data was used. These files are in http://www.bose.res.in/~chakraba/axpsgr2.html. In order to understand the response of the ionosphere by X-ray/gamma-ray activities better, we urge other VLF observers to report if they obtained any such effects. They must check if the object was over their sky during the active period. Prof. Sandip K. Chakrabarti Senior Professor and Head, Astrophysics and Cosmology S.N. Bose National Centre for Basic Sciences JD Block, Salt Lake, Kolkata 700098 INDIA Tel: 23355706 and In Charge, Academic Affairs Indian Centre for Space Physics Chalantika 43, Garia Station Road, Kolkata 700084 INDIA M: 9903120700 Tel: 24366003/24622153 -- Open WebMail Project (http://openwebmail.org)