TITLE:   GCN CIRCULAR
NUMBER:  9649
SUBJECT: GRB 090709A: confirmation of the periodicity in the SPI-ACS data
DATE:    09/07/10 12:15:28 GMT
FROM:    Diego Gotz at CEA  <diego.gotz@cea.fr>

D. Gotz (CEA-Saclay), S. Mereghetti (IASF-Milano), A. von Kienlin (MPE  
Garching), M. Beck (ISDC Versoix)  report:

The Swift GRB 090709A (Morris at al., GCN 9625) is clearly detected  
also in the data of Anticoincidence System (ACS) of the spectrometer  
SPI on board INTEGRAL. SPI-ACS consists on 91 BGO detectors that are  
sensitive to photons above 100 keV, and their light curves are  
continuously stored in 50 ms bins. No directional or spectral  
information is available. The light curve of GRB 090709A  can be found  
here

http://ibas.iasf-milano.inaf.it/090709Alc.jpg

The ~8 s periodicity reported by Markwardt et al. (GCN 9645) in the  
Siwft/BAT data and by Golenetskii et al. (GCN 9647) in Konus-Wind data  
is clearly detected also in the SPI-ACS data. A periodogram over the  
entire burst duration can be found here

http://ibas.iasf-milano.inaf.it/090709A.jpg

By fitting the peak of the periodogram using a gaussian function one  
obtains a best period of 8.11 s. A light curve folded to the best  
period can be fond here

http://ibas.iasf-milano.inaf.it/090709A_folded.jpg


This message can be cited.