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ATEL # 2238; Y. Evangelista, E. Del Monte, M. Feroci, L. Pacciani, E. Costa, I. Donnarumma, I. Lapshov, F. Lazzarotto, M. Rapisarda, P. Soffitta, A. Argan, A. Trois , M. Tavani, G. Piano, G. Pucella, F. D'Ammando, S. Sabatini, E. Striani, 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, A. Giuliani, S. Mereghetti, F. Perotti, P. Caraveo (INAF/IASF Milano), A. Pellizzoni, M. Pilia (OAC/INAF Cagliari), S. Vercellone (INAF/IASF Palermo), G. Barbiellini, F. Longo, E. Moretti, 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, P. Giommi (ASDC) and L. Salotti (ASI)
on 9 Oct 2009; 22:05 UT
Distributed as an Instant Email Notice (Request for Observations)
Password Certification: Marco Feroci (firstname.lastname@example.org)
Subjects: X-ray, Request for Observations, Binaries, Neutron Stars, Transients
On 9 October 2009 02:57:43 UT SuperAGILE detected a type I X-ray burst from a sky position consistent with the accreting millisecond pulsar HETE J1900.1-2455. The burst was significantly detected only at energies below 28 keV, as typical of type I X-ray bursts in SuperAGILE, due to their soft energy spectrum. The burst profile is double-peaked, with a total duration of about 13 s, similar to previous bursts from this source (e.g., Suzuki et al. PASJ 2007 or Falanga et al. A&A 2008). Using the data in the energy range 17-25 keV, we measure an average burst flux of 1.3e-8 erg/cm2/s (under the assumption of a Crab-like energy spectrum). The latest notified X-ray burst from this source was on April 2009 (Watts et al., ATel #2004). The persistent emission from HETE J1900.1-2455 is currently detected by SuperAGILE at an average flux level of about 50 mCrab (20-60 keV), on daily integrations.
The source localization by SuperAGILE is composed by two one-dimensional projections. One of the two projections of the detected burst position is unambiguously consistent with the position of HETE J1900.1-2455. The other 1D image shows a potential ambiguity due to a secondary peak, possibly due to a statistical fluctuation. In the hypothesis of a source identification with this secondary peak, the burst localization would be (RA,Dec) =(294.3635, -23.7796), with an error radius of 6 arcmin. This position corresponds to Galactic coordinates (l,b)=(15.845,-20.260) and it has no known source counterpart yet.
We however consider the association with HETE J1900.1-2455 more likely.