Model X-ray spectra of magnetic neutron stars with hydrogen atmospheres

A. M. Bykov1, A. M. Krassilchtchikov1, Yu. A. Uvarov1, H. Bloemen2, F. Bocchino3, G. M. Dubner4, E. B. Giacani4, G. G. Pavlov5
1DTA, Ioffe Physical-Technical Institute, St.Petersburg 194021, Russia
2SRON - Netherlands Institute for Space Research, 3584 CA Utrecht, The Netherlands
3INAF - Osservatorio Astronomico "G.S. Vaiana", 90134 Palermo, Italy
4IAFE - Instituto de Astronomia y Fisica del Espacio, Buenos Aires, Argentina
5Astron. & Astrophys., Penn State, 508B Davey Lab, University Park, PA 16802, USA

The nature of the extended hard X-ray source XMMU J061804.3+222732 and its surroundings is investigated using XMM-Newton, Chandra, and Spitzer observations. This source is located in an interaction region of the IC 443 supernova remnant with a neighboring molecular cloud. The X-ray emission consists of a number of bright clumps embedded in an extended structured non-thermal X-ray nebula larger than 30" in size. Some clumps show evidence for line emission at about 1.9 keV and about 3.7 keV at the 99% confidence level. Large-scale diffuse radio emission of IC 443 passes over the source region, with an enhancement near the source. An IR source of about 14" × 7" size is prominent in the 24 mum, 70 mum, and 2.2 mum bands, adjacent to a putative Si K-shell X-ray line emission region. The observed IR/X-ray morphology and spectra are consistent with those expected for J/C-type shocks of different velocities driven by fragmented supernova ejecta colliding with the dense medium of a molecular cloud. The IR emission of the source detected by Spitzer can be attributed to both continuum emission from an HII region created by the ejecta fragment and line emission excited by shocks. This source region in IC 443 may be an example of a rather numerous population of hard X-ray/IR sources created by supernova explosions in the dense environment of star-forming regions. Alternative Galactic and extragalactic interpretations of the observed source are also discussed.


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