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Resolved atomic lines reveal outflows in two ultraluminous X-ray sources

Resolved atomic lines reveal outflows in two ultraluminous X-ray sources
Resolved atomic lines reveal outflows in two ultraluminous X-ray sources
Ultraluminous X-ray sources are extragalactic, off-nucleus, point sources in galaxies, and have X-ray luminosities in excess of 3 × 1039 ergs per second. They are thought to be powered by accretion onto a compact object. Possible explanations include accretion onto neutron stars with strong magnetic fields, onto stellar-mass black holes (of up to 20 solar masses) at or in excess of the classical Eddington limit, or onto intermediate-mass black holes (103-105 solar masses). The lack of sufficient energy resolution in previous analyses has prevented an unambiguous identification of any emission or absorption lines in the X-ray band, thereby precluding a detailed analysis of the accretion flow. Here we report the presence of X-ray emission lines arising from highly ionized iron, oxygen and neon with a cumulative significance in excess of five standard deviations, together with blueshifted (about 0.2 times light velocity) absorption lines of similar significance, in the high-resolution X-ray spectra of the ultraluminous X-ray sources NGC 1313 X-1 and NGC 5408 X-1. The blueshifted absorption lines must occur in a fast-outflowing gas, whereas the emission lines originate in slow-moving gas around the source. We conclude that the compact object in each source is surrounded by powerful winds with an outflow velocity of about 0.2 times that of light, as predicted by models of accreting supermassive black holes and hyper-accreting stellar-mass black holes.
0028-0836
64-67
Pinto, Ciro
9d6e45cf-4900-42c4-8ca0-134c0af99af2
Middleton, Matthew
f91b89d9-fd2e-42ec-aa99-1249f08a52ad
Fabian, A.C.
0c353376-f159-4129-b03e-d3993c0c5406
Pinto, Ciro
9d6e45cf-4900-42c4-8ca0-134c0af99af2
Middleton, Matthew
f91b89d9-fd2e-42ec-aa99-1249f08a52ad
Fabian, A.C.
0c353376-f159-4129-b03e-d3993c0c5406

Pinto, Ciro, Middleton, Matthew and Fabian, A.C. (2016) Resolved atomic lines reveal outflows in two ultraluminous X-ray sources. Nature, 533 (7601), 64-67. (doi:10.1038/nature17417).

Record type: Letter

Abstract

Ultraluminous X-ray sources are extragalactic, off-nucleus, point sources in galaxies, and have X-ray luminosities in excess of 3 × 1039 ergs per second. They are thought to be powered by accretion onto a compact object. Possible explanations include accretion onto neutron stars with strong magnetic fields, onto stellar-mass black holes (of up to 20 solar masses) at or in excess of the classical Eddington limit, or onto intermediate-mass black holes (103-105 solar masses). The lack of sufficient energy resolution in previous analyses has prevented an unambiguous identification of any emission or absorption lines in the X-ray band, thereby precluding a detailed analysis of the accretion flow. Here we report the presence of X-ray emission lines arising from highly ionized iron, oxygen and neon with a cumulative significance in excess of five standard deviations, together with blueshifted (about 0.2 times light velocity) absorption lines of similar significance, in the high-resolution X-ray spectra of the ultraluminous X-ray sources NGC 1313 X-1 and NGC 5408 X-1. The blueshifted absorption lines must occur in a fast-outflowing gas, whereas the emission lines originate in slow-moving gas around the source. We conclude that the compact object in each source is surrounded by powerful winds with an outflow velocity of about 0.2 times that of light, as predicted by models of accreting supermassive black holes and hyper-accreting stellar-mass black holes.

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More information

Accepted/In Press date: 4 February 2016
e-pub ahead of print date: 27 April 2016
Published date: May 2016
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 411907
URI: http://eprints.soton.ac.uk/id/eprint/411907
ISSN: 0028-0836
PURE UUID: e0de650e-96f9-4151-be80-6c23d2ee8d8f

Catalogue record

Date deposited: 29 Jun 2017 16:31
Last modified: 06 Aug 2018 16:31

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