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GCN Circular 8900

Detailed lightcurves of ICSP VLF Observation of SGR/AXP 1E1547.0-5408
2009-02-11T05:01:57Z (15 years ago)
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

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
In Charge, Academic Affairs
Indian Centre for Space Physics
Chalantika 43, Garia Station Road,
Kolkata 700084 INDIA
M: 9903120700
Tel: 24366003/24622153
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