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Observations of the ultra-compact x-Ray binary 4U 1543-624 in outburst with NICER, INTEGRAL, Swift, and ATCA

Observations of the ultra-compact x-Ray binary 4U 1543-624 in outburst with NICER, INTEGRAL, Swift, and ATCA
Observations of the ultra-compact x-Ray binary 4U 1543-624 in outburst with NICER, INTEGRAL, Swift, and ATCA

We report on X-ray and radio observations of the ultra-compact X-ray binary 4U 1543-624 taken in August 2017 during an enhanced accretion episode. We obtained Neutron Star Interior Composition Explorer (NICER) monitoring of the source over a ∼10 day period during which target-of-opportunity observations were also conducted with Swift, INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL), and the Australia Telescope Compact Array. Emission lines were measured in the NICER X-ray spectrum at ∼0.64 keV and ∼6.4 keV that correspond to O and Fe, respectively. By modeling these line components, we are able to track changes in the accretion disk throughout this period. The innermost accretion flow appears to move inwards from hundreds of gravitational radii (R g = GM/c 2) at the beginning of the outburst to <8.7 R g at peak intensity. We do not detect the source in radio, but are able to place a 3σ upper limit on the flux density at 27 μJy beam-1. Comparing the radio and X-ray luminosities, we find that the source lies significantly away from the range typical of black holes in the - plane, suggesting a neutron star primary. This adds to the evidence that neutron stars (NSs) do not follow a single track in the - plane, limiting its use in distinguishing between different classes of NSs based on radio and X-ray observations alone.

accretion, accretion disks, stars: neutron
0004-637X
Ludlam, R. M.
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Shishkovsky, L.
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Bult, P. M.
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Miller, J. M.
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Zoghbi, A.
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Strohmayer, T. E.
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Reynolds, M.
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Natalucci, L.
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Miller-Jones, J. C.A.
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Jaisawal, G. K.
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Guillot, S.
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Gendreau, K. C.
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García, J. A.
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Fiocchi, M.
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Fabian, A. C.
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Chakrabarty, D.
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Cackett, E. M.
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Bahramian, A.
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Arzoumanian, Z.
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Altamirano, D.
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Ludlam, R. M.
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Shishkovsky, L.
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Bult, P. M.
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Miller, J. M.
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Zoghbi, A.
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Strohmayer, T. E.
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Reynolds, M.
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Natalucci, L.
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Miller-Jones, J. C.A.
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Jaisawal, G. K.
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Guillot, S.
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Gendreau, K. C.
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García, J. A.
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Fiocchi, M.
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Fabian, A. C.
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Chakrabarty, D.
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Cackett, E. M.
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Bahramian, A.
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Arzoumanian, Z.
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Altamirano, D.
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Ludlam, R. M., Shishkovsky, L., Bult, P. M., Miller, J. M., Zoghbi, A., Strohmayer, T. E., Reynolds, M., Natalucci, L., Miller-Jones, J. C.A., Jaisawal, G. K., Guillot, S., Gendreau, K. C., García, J. A., Fiocchi, M., Fabian, A. C., Chakrabarty, D., Cackett, E. M., Bahramian, A., Arzoumanian, Z. and Altamirano, D. (2019) Observations of the ultra-compact x-Ray binary 4U 1543-624 in outburst with NICER, INTEGRAL, Swift, and ATCA. Astrophysical Journal, 883 (1), [39]. (doi:10.3847/1538-4357/ab3806).

Record type: Article

Abstract

We report on X-ray and radio observations of the ultra-compact X-ray binary 4U 1543-624 taken in August 2017 during an enhanced accretion episode. We obtained Neutron Star Interior Composition Explorer (NICER) monitoring of the source over a ∼10 day period during which target-of-opportunity observations were also conducted with Swift, INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL), and the Australia Telescope Compact Array. Emission lines were measured in the NICER X-ray spectrum at ∼0.64 keV and ∼6.4 keV that correspond to O and Fe, respectively. By modeling these line components, we are able to track changes in the accretion disk throughout this period. The innermost accretion flow appears to move inwards from hundreds of gravitational radii (R g = GM/c 2) at the beginning of the outburst to <8.7 R g at peak intensity. We do not detect the source in radio, but are able to place a 3σ upper limit on the flux density at 27 μJy beam-1. Comparing the radio and X-ray luminosities, we find that the source lies significantly away from the range typical of black holes in the - plane, suggesting a neutron star primary. This adds to the evidence that neutron stars (NSs) do not follow a single track in the - plane, limiting its use in distinguishing between different classes of NSs based on radio and X-ray observations alone.

Text
Observations of the ultra-compact x-ray binary 4u 1543-624 in outburst with nicer, integral, swift, and atca - Accepted Manuscript
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Accepted/In Press date: 31 July 2019
e-pub ahead of print date: 18 September 2019
Published date: 20 September 2019
Additional Information: arXiv is AM
Keywords: accretion, accretion disks, stars: neutron

Identifiers

Local EPrints ID: 435353
URI: http://eprints.soton.ac.uk/id/eprint/435353
ISSN: 0004-637X
PURE UUID: 524d4fc6-ad67-40ab-bd6f-a3f95fbe3aed
ORCID for D. Altamirano: ORCID iD orcid.org/0000-0002-3422-0074

Catalogue record

Date deposited: 31 Oct 2019 17:30
Last modified: 26 Nov 2021 03:02

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Contributors

Author: R. M. Ludlam
Author: L. Shishkovsky
Author: P. M. Bult
Author: J. M. Miller
Author: A. Zoghbi
Author: T. E. Strohmayer
Author: M. Reynolds
Author: L. Natalucci
Author: J. C.A. Miller-Jones
Author: G. K. Jaisawal
Author: S. Guillot
Author: K. C. Gendreau
Author: J. A. García
Author: M. Fiocchi
Author: A. C. Fabian
Author: D. Chakrabarty
Author: E. M. Cackett
Author: A. Bahramian
Author: Z. Arzoumanian
Author: D. Altamirano ORCID iD

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