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An ultracompact X-ray binary in the globular cluster NGC 1851

An ultracompact X-ray binary in the globular cluster NGC 1851
An ultracompact X-ray binary in the globular cluster NGC 1851
We present far-ultraviolet photometry obtained with the Hubble Space Telescope of the low-mass X-ray binary 4U 0513-40 in the globular cluster NGC 1851. Our observations reveal a clear, roughly sinusoidal periodic signal with P sime 17 minutes and amplitude 3%-10%. The signal appears fully coherent and can be modeled as a simple reprocessing effect associated with the changing projected area presented by the irradiated face of a white dwarf donor star in the system. All of these properties suggest that the signal we have detected is orbital in nature, thus confirming 4U 0513-40 as an ultracompact X-ray binary (UCXB). All four confirmed UCXBs in globular clusters have orbital periods below 30 minutes, whereas almost all UCXBs in the Galactic field have orbital periods longer than this. This suggests that dynamical formation processes dominate UCXB production in clusters, producing a different orbital period distribution than observed among field UCXBs. Based on the likely system parameters, we show that 4U 0513-40 should be a strong gravitational wave source and may be detectable by Laser Interferometer Space Antenna over the course of a multiyear mission.
binaries: close, globular clusters: individual: ngc 1851, stars: individual: 4U 0513-40, ultraviolet: stars
0004-637X
1113-1118
Zurek, D.R.
4745ee98-520b-4e26-a05a-113c0c563b97
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Maccarone, T.J.
5d8ee27f-a174-424c-b3b7-a6739bfeea50
Dieball, A.
5f595453-aa6b-4067-a3e1-026867fb9f7a
Long, K.S.
91417b3d-d408-475a-8907-eec131e17c66
Zurek, D.R.
4745ee98-520b-4e26-a05a-113c0c563b97
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Maccarone, T.J.
5d8ee27f-a174-424c-b3b7-a6739bfeea50
Dieball, A.
5f595453-aa6b-4067-a3e1-026867fb9f7a
Long, K.S.
91417b3d-d408-475a-8907-eec131e17c66

Zurek, D.R., Knigge, C., Maccarone, T.J., Dieball, A. and Long, K.S. (2009) An ultracompact X-ray binary in the globular cluster NGC 1851. The Astrophysical Journal, 699 (2), 1113-1118. (doi:10.1088/0004-637X/699/2/1113).

Record type: Article

Abstract

We present far-ultraviolet photometry obtained with the Hubble Space Telescope of the low-mass X-ray binary 4U 0513-40 in the globular cluster NGC 1851. Our observations reveal a clear, roughly sinusoidal periodic signal with P sime 17 minutes and amplitude 3%-10%. The signal appears fully coherent and can be modeled as a simple reprocessing effect associated with the changing projected area presented by the irradiated face of a white dwarf donor star in the system. All of these properties suggest that the signal we have detected is orbital in nature, thus confirming 4U 0513-40 as an ultracompact X-ray binary (UCXB). All four confirmed UCXBs in globular clusters have orbital periods below 30 minutes, whereas almost all UCXBs in the Galactic field have orbital periods longer than this. This suggests that dynamical formation processes dominate UCXB production in clusters, producing a different orbital period distribution than observed among field UCXBs. Based on the likely system parameters, we show that 4U 0513-40 should be a strong gravitational wave source and may be detectable by Laser Interferometer Space Antenna over the course of a multiyear mission.

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More information

Published date: 18 June 2009
Keywords: binaries: close, globular clusters: individual: ngc 1851, stars: individual: 4U 0513-40, ultraviolet: stars

Identifiers

Local EPrints ID: 79529
URI: http://eprints.soton.ac.uk/id/eprint/79529
ISSN: 0004-637X
PURE UUID: 20384538-962a-45a8-941a-bf4b0308d4d3

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Date deposited: 17 Mar 2010
Last modified: 14 Mar 2024 00:31

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Contributors

Author: D.R. Zurek
Author: C. Knigge
Author: T.J. Maccarone
Author: A. Dieball
Author: K.S. Long

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