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An in-depth study of a neutron star accreting at low Eddington rate: On the possibility of a truncated disk and an outflow

Degenaar, N. and Pinto, C. and Miller, J. M. and Wijnands, R. and Altamirano, D. and Paerels, F. and Fabian, A. C. and Chakrabarty, D. (2017) An in-depth study of a neutron star accreting at low Eddington rate: On the possibility of a truncated disk and an outflow. Monthly Notices of the Royal Astronomical Society, 464 (1). pp. 398-409. ISSN 0035-8711. doi:10.1093/mnras/stw2355.

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Due to observational challenges, our knowledge of low-level accretion flows around neutron stars is limited. We present NuSTAR, Swift and Chandraobservations of the low-mass X-ray binary IGR J17062-6143, which has been persistently accreting at ≃0.1 per cent of the Eddington limit since 2006. Our simultaneous NuSTAR/Swift observations show that the 0.5–79 keV spectrum can be described by a combination of a power law with a photon index of Γ ≃ 2, a blackbody with a temperature of kT_(bb) ≃ 0.5 keV (presumably arising from the neutron star surface) and disc reflection. Modelling the reflection spectrum suggests that the inner accretion disc was located at R_(in) ≳ 100 GM/c^2 (≳225 km) from the neutron star. The apparent truncation may be due to evaporation of the inner disc into a radiatively-inefficient accretion flow, or due to the pressure of the neutron star magnetic field. Our Chandra gratings data reveal possible narrow emission lines near 1 keV that can be modelled as reflection or collisionally ionized gas, and possible low-energy absorption features that could point to the presence of an outflow. We consider a scenario in which this neutron star has been able to sustain its low accretion rate through magnetic inhibition of the accretion flow, which gives some constraints on its magnetic field strength and spin period. In this configuration, IGR J17062-6143 could exhibit a strong radio jet as well as a (propeller-driven) wind-like outflow.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Pinto, C.0000-0003-2532-7379
Altamirano, D.0000-0002-3422-0074
Fabian, A. C.0000-0002-9378-4072
Chakrabarty, D.0000-0001-8804-8946
Additional Information:© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2016 September 14. Received 2016 September 12; in original form 2016 August 16. Published: 15 September 2016. ND is supported by an NWO Vidi grant and an EU Marie Curie Intra-European fellowship (contract no. FP-PEOPLE-2013-IEF- 627148). ND acknowledges valuable discussions with Anne Lohfink, Victor Doroshenko, and Caroline D’Angelo. CP and ACF are supported by ERC Advanced Grant Feedback 340442. JMM acknowledges support from the Chandra guest observer program. DA acknowledges support from the Royal Society. RW is supported by an NWO Top grant, module 1. We thank the referee for useful comments. This work is based on data from the NuSTAR mission, a project led by California Institute of Technology, managed by the Jet Propulsion Laboratory, and funded by NASA. We thank Neil Gehrels and the Swift duty scientists for rapid scheduling of observations and acknowledge the use of the Swift public data archive.
Subject Keywords:accretion, accretion discs – stars: individual: (IGR J17062-6143) – stars: neutron – pulsars: general –X-rays: binaries – X-rays: bursts
Issue or Number:1
Record Number:CaltechAUTHORS:20160919-103607188
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Official Citation:N. Degenaar, C. Pinto, J. M. Miller, R. Wijnands, D. Altamirano, F. Paerels, A. C. Fabian, D. Chakrabarty; An in-depth study of a neutron star accreting at low Eddington rate: on the possibility of a truncated disc and an outflow, Monthly Notices of the Royal Astronomical Society, Volume 464, Issue 1, 1 January 2017, Pages 398–409,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:70425
Deposited By: Joy Painter
Deposited On:19 Sep 2016 17:52
Last Modified:11 Nov 2021 04:29

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