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On the Fe K absorption - accretion state connection in the Galactic Centre neutron star X-ray binary AX J1745.6-2901

Ponti, G. and Bianchi, S. and Muñoz-Darias, T. and De Marco, B. and Dwelly, T. and Fender, R. P. and Nandra, K. and Rea, N. and Mori, K. and Haggard, D. and Heinke, C. O. and Degenaar, N. and Aramaki, T. and Clavel, M. and Goldwurm, A. and Hailey, C. J. and Israel, G. L. and Morris, M. R. and Rushton, A. and Terrier, R. (2015) On the Fe K absorption - accretion state connection in the Galactic Centre neutron star X-ray binary AX J1745.6-2901. Monthly Notices of the Royal Astronomical Society, 446 (2). pp. 1536-1550. ISSN 0035-8711. doi:10.1093/mnras/stu1853.

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AX J1745.6-2901 is a high-inclination (eclipsing) neutron star low-mass X-ray binary (LMXB) located less than ∼1.5 arcmin from Sgr A⋆. Ongoing monitoring campaigns have targeted Sgr A⋆ frequently and these observations also cover AX J1745.6-2901. We present here an X-ray analysis of AX J1745.6-2901 using a large data set of 38 XMM–Newton observations, including 11 which caught AX J1745.6-2901 in outburst. Fe K absorption is clearly seen when AX J1745.6-2901 is in the soft state, but disappears during the hard state. The variability of these absorption features does not appear to be due to changes in the ionizing continuum. The small Kα/Kβ ratio of the equivalent widths of the Fe xxv and Fe xxvi lines suggests that the column densities and turbulent velocities of the absorbing ionized plasma are in excess of NH ≃ 10^(23) cm^(−2) and vturb ≳ 500 km s^(−1). These findings strongly support a connection between the wind (Fe K absorber) and the accretion state of the binary. These results reveal strong similarities between AX J1745.6-2901 and the eclipsing neutron star LMXB, EXO 0748-676, as well as with high-inclination black hole binaries, where winds (traced by the same Fe K absorption features) are observed only during the accretion-disc-dominated soft states, and disappear during the hard states characterized by jet emission.

Item Type:Article
Related URLs:
URLURL TypeDescription
Ponti, G.0000-0003-0293-3608
Bianchi, S.0000-0002-4622-4240
Nandra, K.0000-0002-7150-9192
Rea, N.0000-0003-2177-6388
Mori, K.0000-0002-9709-5389
Haggard, D.0000-0001-6803-2138
Heinke, C. O.0000-0003-3944-6109
Clavel, M.0000-0003-0724-2742
Morris, M. R.0000-0002-6753-2066
Additional Information:© 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2014 September 4. Received 2014 September 4. In original form 2014 July 10. First published online November 21, 2014. The authors wish to thank Jan-Uwe Ness, Ignacio de la Calle and the rest of the XMM–Newton scheduling team for the enormous support that made the new XMM–Newton observations possible. GP and TMD acknowledge support via an EU Marie Curie Intra-European fellowship under contract no. FP-PEOPLE-2012-IEF-331095 and FP-PEOPLE-2011-IEF-301355, respectively. The GC XMM–Newton monitoring project is partially supported by the Bundesministerium fur Wirtschaft und Technologie/Deutsches Zentrum fur Luft-und Raumfahrt (BMWI/DLR, FKZ 50 OR 1408) and the Max Planck Society. This project was funded in part by European Research Council Advanced Grant 267697 ‘4πsky:Extreme Astrophysics with Revolutionary Radio Telescopes’. DH acknowledges support from Chandra X-ray Observatory (CXO) Award Number GO3-14121X, operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-03060, and also by NASA Swift grant NNX14AC30G. CH is supported by an NSERC Discovery Grant, and an Ingenuity New Faculty Award. ND is supported by NASA through Hubble Postdoctoral Fellowship grant number HST-HF-51287.01-A from the Space Telescope Science Institute. The scientific results reported in this article are based on observations obtained with XMM–Newton, Swift and NuSTAR.
Funding AgencyGrant Number
Marie Curie FellowshipFP-PEOPLE-2012-IEF-331095
Marie Curie FellowshipFP-PEOPLE-2011-IEF-301355
Bundesministerium fur Wirtschaft und Technologie (BMWI)FKZ 50
Bundesministerium fur Wirtschaft und Technologie (BMWI)FKZ 1408
Max Planck SocietyUNSPECIFIED
European Research Council (ERC)267697
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Deutsches Zentrum fur Luft-und RaumfahrtUNSPECIFIED
Issue or Number:2
Record Number:CaltechAUTHORS:20150824-162639408
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ID Code:59865
Deposited By: Joy Painter
Deposited On:25 Aug 2015 01:22
Last Modified:10 Nov 2021 22:26

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