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New insights on accretion in supergiant fast X-ray transients from XMM-Newton and INTEGRAL observations of IGR J17544-2619

New insights on accretion in supergiant fast X-ray transients from XMM-Newton and INTEGRAL observations of IGR J17544-2619
New insights on accretion in supergiant fast X-ray transients from XMM-Newton and INTEGRAL observations of IGR J17544-2619
XMM–Newton observations of the supergiant fast X-ray transient IGR J17544?2619 are reported and placed in the context of an analysis of archival INTEGRAL/IBIS data that provide a refined estimate of the orbital period at 4.9272?±?0.0004?d. A complete outburst history across the INTEGRAL mission is reported. Although the new XMM–Newton observations (each lasting ?15 ks) targeted the peak flux in the phase-folded hard X-ray light curve of IGR J17544?2619, no bright outbursts were observed, the source spending the majority of the exposure at intermediate luminosities of the order of several 1033?erg?s?1 (0.5–10 keV) and displaying only low level flickering activity. For the final portion of the exposure, the luminosity of IGR J17544?2619 dropped to ?4?×?1032?erg?s?1 (0.5–10 keV), comparable with the lowest luminosities ever detected from this source, despite the observations being taken near to periastron. We consider the possible orbital geometry of IGR J17544?2619 and the implications for the nature of the mass transfer and accretion mechanisms for both IGR J17544?2619 and the supergiant fast X-ray transients (SFXTs) population. We conclude that accretion under the ‘quasi-spherical accretion’ model provides a good description of the behaviour of IGR J17544?2619 and suggests an additional mechanism for generating outbursts based upon the mass accumulation rate in the hot shell (atmosphere) that forms around the neutron star under the quasi-spherical formulation. Hence, we hope to aid in explaining the varied outburst behaviours observed across the SFXT population with a consistent underlying physical model.
0035-8711
2175-2185
Drave, S. P.
af90315d-37c4-451f-a7d8-2ef0e8e22722
Bird, A. J.
045ee141-4720-46fd-a412-5aa848a91b32
Sidoli, L.
2207422d-1a4d-448c-8c0b-8f0c2bf78a18
Sguera, V.
371bb568-7e56-496e-a624-dba6de79d9e1
Bazzano, A.
8eef0c6e-1a5f-4bcd-a034-9a5c3b29104d
Hill, A. B.
b1007941-b5b1-47cd-8476-7c6b9c57f347
Goossens, M. E.
235aceb1-f527-4f2a-8f5e-8b680936c062
Drave, S. P.
af90315d-37c4-451f-a7d8-2ef0e8e22722
Bird, A. J.
045ee141-4720-46fd-a412-5aa848a91b32
Sidoli, L.
2207422d-1a4d-448c-8c0b-8f0c2bf78a18
Sguera, V.
371bb568-7e56-496e-a624-dba6de79d9e1
Bazzano, A.
8eef0c6e-1a5f-4bcd-a034-9a5c3b29104d
Hill, A. B.
b1007941-b5b1-47cd-8476-7c6b9c57f347
Goossens, M. E.
235aceb1-f527-4f2a-8f5e-8b680936c062

Drave, S. P., Bird, A. J., Sidoli, L., Sguera, V., Bazzano, A., Hill, A. B. and Goossens, M. E. (2014) New insights on accretion in supergiant fast X-ray transients from XMM-Newton and INTEGRAL observations of IGR J17544-2619. Monthly Notices of the Royal Astronomical Society, 439 (2), 2175-2185. (doi:10.1093/mnras/stu110).

Record type: Article

Abstract

XMM–Newton observations of the supergiant fast X-ray transient IGR J17544?2619 are reported and placed in the context of an analysis of archival INTEGRAL/IBIS data that provide a refined estimate of the orbital period at 4.9272?±?0.0004?d. A complete outburst history across the INTEGRAL mission is reported. Although the new XMM–Newton observations (each lasting ?15 ks) targeted the peak flux in the phase-folded hard X-ray light curve of IGR J17544?2619, no bright outbursts were observed, the source spending the majority of the exposure at intermediate luminosities of the order of several 1033?erg?s?1 (0.5–10 keV) and displaying only low level flickering activity. For the final portion of the exposure, the luminosity of IGR J17544?2619 dropped to ?4?×?1032?erg?s?1 (0.5–10 keV), comparable with the lowest luminosities ever detected from this source, despite the observations being taken near to periastron. We consider the possible orbital geometry of IGR J17544?2619 and the implications for the nature of the mass transfer and accretion mechanisms for both IGR J17544?2619 and the supergiant fast X-ray transients (SFXTs) population. We conclude that accretion under the ‘quasi-spherical accretion’ model provides a good description of the behaviour of IGR J17544?2619 and suggests an additional mechanism for generating outbursts based upon the mass accumulation rate in the hot shell (atmosphere) that forms around the neutron star under the quasi-spherical formulation. Hence, we hope to aid in explaining the varied outburst behaviours observed across the SFXT population with a consistent underlying physical model.

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e-pub ahead of print date: February 2014
Published date: 1 April 2014
Organisations: Physics & Astronomy

Identifiers

Local EPrints ID: 369402
URI: http://eprints.soton.ac.uk/id/eprint/369402
ISSN: 0035-8711
PURE UUID: 9c10a029-643f-4bf0-a5a8-b19b0f92e4e6
ORCID for A. J. Bird: ORCID iD orcid.org/0000-0002-6888-8937
ORCID for A. B. Hill: ORCID iD orcid.org/0000-0003-3470-4834

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Date deposited: 25 Sep 2014 11:58
Last modified: 21 Nov 2021 02:54

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Contributors

Author: S. P. Drave
Author: A. J. Bird ORCID iD
Author: L. Sidoli
Author: V. Sguera
Author: A. Bazzano
Author: A. B. Hill ORCID iD
Author: M. E. Goossens

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