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Durham University

Department of Physics

Staff profile

Publication details for Prof David Alexander

Mori, K., Hailey, C.J., Krivonos, R., Hong, J., Ponti, G., Bauer, F., Perez, K., Nynka, M., Zhang, S., Tomsick, J.A., Alexander, D.M., Baganoff, F.K., Barret, D., Barrière, N., Boggs, S.E., Canipe, A.M., Christensen, F.E., Craig, W.W., Forster, K., Giommi, P., Grefenstette, B.W., Grindlay, J.E., Harrison, F.A., Hornstrup, A., Kitaguchi, T., Koglin, J.E., Luu, V., Madsen, K.K., Mao, P.H., Miyasaka, H., Perri, M., Pivovaroff, M.J., Puccetti, S., Rana, V., Stern, D., Westergaard, N.J., Zhang, W.W. & Zoglauer, A. (2015). NuSTAR Hard X-Ray Survey of the Galactic Center Region I: Hard X-Ray Morphology and Spectroscopy of the Diffuse Emission. The Astrophysical Journal 814(2): 94.

Author(s) from Durham

Abstract

We present the first sub-arcminute images of the Galactic Center above 10 keV, obtained with NuSTAR. NuSTAR resolves the hard X-ray source IGR J17456–2901 into non-thermal X-ray filaments, molecular clouds, point sources, and a previously unknown central component of hard X-ray emission (CHXE). NuSTAR detects four non-thermal X-ray filaments, extending the detection of their power-law spectra with Γ ~ 1.3–2.3 up to ~50 keV. A morphological and spectral study of the filaments suggests that their origin may be heterogeneous, where previous studies suggested a common origin in young pulsar wind nebulae (PWNe). NuSTAR detects non-thermal X-ray continuum emission spatially correlated with the 6.4 keV Fe Kα fluorescence line emission associated with two Sgr A molecular clouds: MC1 and the Bridge. Broadband X-ray spectral analysis with a Monte-Carlo based X-ray reflection model self-consistently determined their intrinsic column density (~1023 cm−2), primary X-ray spectra (power-laws with Γ ~ 2) and set a lower limit of the X-ray luminosity of Sgr A* flare illuminating the Sgr A clouds to LX gsim 1038 erg s−1. Above ~20 keV, hard X-ray emission in the central 10 pc region around Sgr A* consists of the candidate PWN G359.95–0.04 and the CHXE, possibly resulting from an unresolved population of massive CVs with white dwarf masses MWD ~ 0.9 M⊙. Spectral energy distribution analysis suggests that G359.95–0.04 is likely the hard X-ray counterpart of the ultra-high gamma-ray source HESS J1745–290, strongly favoring a leptonic origin of the GC TeV emission.