Vela X-1 in highly active hard X-ray state
ATel #1782; P. Soffitta, E. Costa, E. Del Monte, I. Donnarumma, Y. Evangelista, M. Feroci, I. Lapshov, F. Lazzarotto, L. Pacciani, M. Rapisarda, A. Argan, A. Trois , M. Tavani, G. Piano, G. Pucella, F. D'Ammando, V. Vittorini (INAF/IASF Roma), A. Bulgarelli, F. Gianotti, M. Trifoglio, G. Di Cocco, C. Labanti, F. Fuschino, M. Marisaldi, M. Galli, (INAF/IASF Bologna), A. Chen, S. Vercellone, A. Giuliani, S. Mereghetti, F. Perotti, P. Caraveo (INAF/IASF Milano), A. Pellizzoni (OAC/INAF Cagliari), G. Barbiellini, F. Longo, E. Vallazza (INFN Trieste), P. Picozza, A. Morselli (INFN Roma-2), M. Prest (Universita` dell'Insubria), P. Lipari, D. Zanello (INFN Roma-1), A. Rappoldi (INFN Pavia) and C. Pittori, F. Verrecchia, P. Santolamazza, B. Preger, P. Giommi (ASDC) and L. Salotti (ASI)
on 15 Oct 2008; 14:54 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Marco Feroci (marco.feroci@iasf-roma.inaf.it)
Subjects: X-ray, Request for Observations, Binary, Neutron Star, Transient
The current pointing of the AGILE mission at (l,b)=(256,-20), started on 10th October
2008, includes the Vela region. In particular, Vela X-1 lies at approximately 25 degrees
off-axis. Between MJD 54750 and 54752 (October 11-13) this source was detected by
SuperAGILE with a flux varying in the range 250 mCrab - 1 Crab in 20-60 keV.
Starting on MJD 54752.5 the flux showed a large and intense flare lasting approximately
12 hours and peaking at 2.3 Crab (AGILE orbit - 90 minutes - average), with a rise
time of about 7 hours. After the flare, the source flux averaged again at about 500 mCrab
for one day and at MJD 54753.8 (October 14) started a new flare that is currently
ongoing. In its brightest periods, the 283.5-s spin pulsation of the source was directly
visible on the raw light curve of the SuperAGILE experiment. During this period of large
activity the source also exhibited intense activity on short time scale. A short flare
occurred today, 15th October 2008, at 05:49 UT and lasted about 100 s, during which
the source average flux was about 4 Crabs.
The AGILE pointing to the Vela region is planned to end on 17th October 2008, 12 UT.
The SuperAGILE orbital light curve of Vela X-1 may be found at the AGILE Science Data
Center website: http://agile.asdc.asi.it/news.html.
