The Progenitor Mass of the Magnetar SGR1900+14

Creators: Davies, Ben; Figer, Don F.; Kudritzki, Rolf-Peter; Trombley, Christine; Kouveliotou, Chryssa; Wachter, Stefanie

Abstract

Magnetars are young neutron stars with extreme magnetic fields (B ≳ 10^(14)-10^(15) G). How these fields relate to the properties of their progenitor stars is not yet clearly established. However, from the few objects associated with young clusters it has been possible to estimate the initial masses of the progenitors, with results indicating that a very massive progenitor star (M_(prog) > 40 M_⊙) is required to produce a magnetar. Here, we present adaptive-optics assisted Keck/NIRC2 imaging and Keck/NIRSPEC spectroscopy of the cluster associated with the magnetar SGR 1900+14, and report that the initial progenitor star mass of the magnetar was a factor of 2 lower than this limit, M_(prog) = 17 ± 2 M_⊙. Our result presents a strong challenge to the concept that magnetars can only result from very massive progenitors. Instead, we favor a mechanism which is dependent on more than just initial stellar mass for the production of these extreme magnetic fields, such as the "fossil-field" model or a process involving close binary evolution.

Additional Information

© 2009 The American Astronomical Society. Received 2009 September 3; accepted 2009 October 28; published 2009 November 25. We thank Jim Hinton and John Eldridge for useful discussion, and the anonymous referee for helpful comments and suggestions. This work makes use of the UKIDSS survey; the UKIDSS project is defined in Lawrence et al. (2007). UKIDSS uses the UKIRT Wide Field Camera (WFCAM; Casali et al. 2007) and a photometric system described in Hewett et al. (2006). The pipeline processing and science archive are described in Hambly et al. (2008). The material in this work is supported by NASA under award NNG 05-GC37G, through the Long-term Space Astrophysics program. This research was performed in the Rochester Imaging Detector Laboratory with support from a NYSTAR Faculty Development Program grant. Part of the data presented here were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. This research has made use of the IDL software package and the GSFC IDL library.

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