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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

An in-depth study of a neutron star accreting at low Eddington rate: On the possibility of a truncated disk and an outflow
An in-depth study of a neutron star accreting at low Eddington rate: On the possibility of a truncated disk and an outflow
Due to observational challenges, our knowledge of low-level accretion flows around neutron stars is limited. We present NuSTAR, Swift and Chandra observations 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 ? ? 2, a blackbody with a temperature of kTbb ? 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 Rin ? 100?GM/c2 (?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.
0035-8711
398-409
Degenaar, N.
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Pinto, C.
3331e9ac-b6c6-4967-af51-3bbce228c1c4
Miller, J.M.
078305f0-03c7-4982-95ff-a92bc2f75b54
Wijnands, R.
382893ee-0e03-45e3-9321-db8b9fc74914
Altamirano, D.
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Paerels, F.
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Fabian, A.C.
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Chakrabarty, D.
f70eba21-20cc-4f7f-87b3-ccd8716ddea1
Degenaar, N.
54149051-d74e-4e43-a7cd-501ec4023511
Pinto, C.
3331e9ac-b6c6-4967-af51-3bbce228c1c4
Miller, J.M.
078305f0-03c7-4982-95ff-a92bc2f75b54
Wijnands, R.
382893ee-0e03-45e3-9321-db8b9fc74914
Altamirano, D.
d5ccdb09-0b71-4303-9538-05b467be075b
Paerels, F.
a60020f7-e623-442b-a2d5-c1cf4a957d69
Fabian, A.C.
0c353376-f159-4129-b03e-d3993c0c5406
Chakrabarty, D.
f70eba21-20cc-4f7f-87b3-ccd8716ddea1

Degenaar, N., Pinto, C., Miller, J.M., Wijnands, R., Altamirano, D., Paerels, F., 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), 398-409. (doi:10.1093/mnras/stw2355).

Record type: Article

Abstract

Due to observational challenges, our knowledge of low-level accretion flows around neutron stars is limited. We present NuSTAR, Swift and Chandra observations 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 ? ? 2, a blackbody with a temperature of kTbb ? 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 Rin ? 100?GM/c2 (?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.

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Accepted/In Press date: 14 September 2016
e-pub ahead of print date: 15 September 2016
Published date: 1 January 2017
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 401480
URI: http://eprints.soton.ac.uk/id/eprint/401480
ISSN: 0035-8711
PURE UUID: 595dc6ca-db01-4bb8-8bc7-51a921b8f0ba
ORCID for D. Altamirano: ORCID iD orcid.org/0000-0002-3422-0074

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Date deposited: 17 Oct 2016 15:28
Last modified: 26 Nov 2021 03:02

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Contributors

Author: N. Degenaar
Author: C. Pinto
Author: J.M. Miller
Author: R. Wijnands
Author: D. Altamirano ORCID iD
Author: F. Paerels
Author: A.C. Fabian
Author: D. Chakrabarty

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