van der Horst, A. J. and Connaughton, V. and Kouveliotou, C. and Göğüş, E. and Kaneko, Y. and Wachter, S. and Briggs, M. S. and Granot, J. and Ramirez-Ruiz, E. and Woods, P. M. and Aptekar, R. L. and Barthelmy, S. D. and Cummings, J. R. and Finger, M. H. and Frederiks, D. D. and Gehrels, N. and Gelino, C. R. and Gelino, D. M. and Golenetskii, S. and Hurley, K. and Krimm, H. A. and Mazets, E. P. and McEnery, J. E. and Meegan, C. A. and Oleynik, P. P. and Palmer, D. M. and Pal'shin, V. D. and Pe'er, A. and Svinkin, D. and Ulanov, M. V. and van der Klis, M. and von Kienlin, A. and Watts, A. L. and Wilson-Hodge, C. A. (2010) Discovery of a New Soft Gamma Repeater: SGR J0418 + 5729. Astrophysical Journal Letters, 711 (1). L1-L6. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20100401-113302388
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On 2009 June 5, the Gamma-ray Burst Monitor (GBM) onboard the Fermi Gamma-ray Space Telescope triggered on two short and relatively dim bursts with spectral properties similar to soft gamma repeater (SGR) bursts. Independent localizations of the bursts by triangulation with the Konus-RF and with the Swift satellite confirmed their origin from the same, previously unknown, source. The subsequent discovery of X-ray pulsations with the Rossi X-ray Timing Explorer confirmed the magnetar nature of the new source, SGR J0418 + 5729. We describe here the Fermi/GBM observations, the discovery and the localization of this new SGR, and our infrared and Chandra X-ray observations. We also present a detailed temporal and spectral study of the two GBM bursts. SGR J0418 + 5729 is the second source discovered in the same region of the sky in the last year, the other one being SGR J0501 + 4516. Both sources lie in the direction of the galactic anti-center and presumably at the nearby distance of ~2 kpc (assuming they reside in the Perseus arm of our Galaxy). The near-threshold GBM detection of bursts from SGR J0418 + 5729 suggests that there may be more such "dim" SGRs throughout our Galaxy, possibly exceeding the population of "bright" SGRs. Finally, using sample statistics, we conclude that the number of observable active magnetars in our Galaxy at any given time is ≲10, in agreement with our earlier estimates.
|Additional Information:||© 2010 American Astronomical Society. Issue 1 (2010 March 1): received 2009 November 25; accepted for publication 2010 January 8; published 2010 February 10. This publication is part of the GBM/Magnetar Key Project (NASA grant NNH07ZDA001-GLAST; PI: C. Kouveliotou). Chandra observations were carried out under Observation ID 10168, part of the proposal "ToO Observations of SGRs" (NASA grant GO9-0065Z; PI: C. Kouveliotou). We used data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. We thank T. Jarrett (IPAC/Caltech) for use of his WIRC data reduction software. The Konus-RF experiment is supported by a Russian Space Agency contract and RFBR grant 09-02-12080-ofi_m. A.J.v.d.H. was supported by an appointment to the NASA Postdoctoral Program at the MSFC, administered by Oak Ridge Associated Universities through a contract with NASA. Y.K. and E.G. acknowledge EU FP6 Transfer of Knowledge Project "Astrophysics of Neutron Stars" (MTKD-CT-2006-042722). J.G. gratefully acknowledges a Royal Society Wolfson Research Merit Award. K.H. is grateful for support under the Swift Guest Investigator program, NASA grant NNX09AO97G.|
|Subject Keywords:||pulsars: individual (SGR J0418+5729, SGR J0418+5729, SGR J0418+5729, SGR J0418+5729, SGR J0418+5729); stars: neutron; X-rays: bursts|
|Classification Code:||PACS: 98.70.Rz; 97.60.Jd; 95.30.Ky; 98.35.Ln.|
|Official Citation:||A. J. van der Horst et al 2010 ApJ 711 L1 doi: 10.1088/2041-8205/711/1/L1|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||05 Apr 2010 20:29|
|Last Modified:||26 Dec 2012 11:56|
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