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Demonstrating the likely neutron star nature of five M31 globular cluster sources with Swift-NuSTAR spectroscopy

Maccarone, Thomas J. and Yukita, Mihoko and Hornschemeier, Ann and Lehmer, Bret D. and Antoniou, Vallia and Ptak, Andrew and Wik, Daniel R. and Zezas, Andreas and Boyd, Padi and Kennea, Jamie and Page, Kim L. and Eracleous, Mike and Williams, Benjamin F. and Boggs, Steven E. and Christensen, Finn E. and Craig, William W. and Hailey, Charles J. and Harrison, Fiona A. and Stern, Daniel and Zhang, William W. (2016) Demonstrating the likely neutron star nature of five M31 globular cluster sources with Swift-NuSTAR spectroscopy. Monthly Notices of the Royal Astronomical Society, 458 (4). pp. 3633-3643. ISSN 0035-8711. doi:10.1093/mnras/stw530.

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We present the results of a joint Swift-NuSTAR spectroscopy campaign on M31. We focus on the five brightest globular cluster X-ray sources in our fields. Two of these had previously been argued to be black hole candidates on the basis of apparent hard-state spectra at luminosities above those for which neutron stars are in hard states. We show that these two sources are likely to be Z-sources (i.e. low magnetic field neutron stars accreting near their Eddington limits), or perhaps bright atoll sources (low magnetic field neutron stars which are just a bit fainter than this level) on the basis of simultaneous Swift and NuSTAR spectra which cover a broader range of energies. These new observations reveal spectral curvature above 6-8 keV that would be hard to detect without the broader energy coverage the NuSTAR data provide relative to Chandra and XMM-Newton. We show that the other three sources are also likely to be bright neutron star X-ray binaries, rather than black hole X-ray binaries. We discuss why it should already have been realized that it was unlikely that these objects were black holes on the basis of their being persistent sources, and we re-examine past work which suggested that tidal capture products would be persistently bright X-ray emitters. We discuss how this problem is likely due to neglecting disk winds in older work that predict which systems will be persistent and which will be transient.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Maccarone, Thomas J.0000-0003-0976-4755
Yukita, Mihoko0000-0001-6366-3459
Hornschemeier, Ann0000-0001-8667-2681
Lehmer, Bret D.0000-0003-2192-3296
Antoniou, Vallia0000-0001-7539-1593
Ptak, Andrew0000-0001-5655-1440
Wik, Daniel R.0000-0001-8952-676X
Zezas, Andreas0000-0001-8952-676X
Kennea, Jamie0000-0002-6745-4790
Page, Kim L.0000-0001-5624-2613
Eracleous, Mike0000-0002-3719-940X
Williams, Benjamin F.0000-0002-7502-0597
Boggs, Steven E.0000-0001-9567-4224
Christensen, Finn E.0000-0001-5679-1946
Harrison, Fiona A.0000-0003-2992-8024
Stern, Daniel0000-0003-2686-9241
Zhang, William W.0000-0002-1426-9698
Additional Information:© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2016 March 1. Received 2016 March 1. In original form 2015 September 21. First published online March 7, 2016. TJM thanks Christian Knigge for an illuminating talk at ‘The Physics of Cataclysmic and Compact Binaries’, and Helena Uthas, Joe Patterson, Christian Knigge and Jeno Sokoloski for having organized the meeting. He also thanks Joey Neilsen, Chris Done, and Maria Diaz Trigo for useful discussions about disc winds. AZ acknowledges funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2103)/ ERC Grant Agreement no. 617001.
Group:NuSTAR, Space Radiation Laboratory
Funding AgencyGrant Number
European Research Council (ERC)617001
Subject Keywords:globular clusters: general galaxies: individual: M 31 X-rays: binaries
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Space Radiation Laboratory2016-16
Issue or Number:4
Record Number:CaltechAUTHORS:20160318-084747231
Persistent URL:
Official Citation:Thomas J. Maccarone, Mihoko Yukita, Ann Hornschemeier, Bret D. Lehmer, Vallia Antoniou, Andrew Ptak, Daniel R. Wik, Andreas Zezas, Padi Boyd, Jamie Kennea, Kim L. Page, Mike Eracleous, Benjamin F. Williams, Steven E. Boggs, Finn E. Christensen, William W. Craig, Charles J. Hailey, Fiona A. Harrison, Daniel Stern, and William W. Zhang Demonstrating the likely neutron star nature of five M31 globular cluster sources with Swift-NuSTAR spectroscopy MNRAS (June 01, 2016) Vol. 458 3633-3643 doi:10.1093/mnras/stw530 first published online March 7, 2016
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:65472
Deposited By: Melissa Ray
Deposited On:18 Mar 2016 16:52
Last Modified:10 Nov 2021 23:46

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