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Very long-term optical variability of high-mass X-ray binaries in the Small Magellanic Cloud

Very long-term optical variability of high-mass X-ray binaries in the Small Magellanic Cloud
Very long-term optical variability of high-mass X-ray binaries in the Small Magellanic Cloud
We have studied the very long-term temporal properties of the optical emission from Be X-ray binaries (BeX) in the Small Magellanic Cloud over a ~ 16yr baseline, using light curves from the MACHO and OGLE databases. All the BeX in our sample display superorbital variations, many of them quasi-periodic on timescales of ~ 200-3000 d. These long-term variations are believed to be related to the formation and depletion of the circumstellar disc around the Be star and we compare and contrast their behaviour with that of the LMC's prototypical BeX, A0538-66. The great majority of sources show a correlation of outburst amplitude with brightness (the opposite to that seen in A0538-66) although the amplitudes are mostly small (< 0.1 mag). We suggest this is an orbital inclination effect. In addition, we have also detected many of their optical orbital periodicities, visible as a series of precisely regular outbursts. Furthermore, the amplitude of these periodic outbursts can vary through the long-term superorbital cycle, and we discuss mechanisms which can produce this effect, as well as examining an apparent correlation between these periodicities. As a by-product of this variation survey we have compiled a list of all the reported SMC BeX orbital and superorbital periodicities at optical and X-ray wavelengths.
stars, emission-line, Be, magellanic clouds, X-rays, binaries
0035-8711
1600-1622
Rajoelimanana, A.F.
d4ba3ebb-4a84-44d8-9d69-223be7e8a61e
Charles, P.A.
0429b380-0754-4dc1-8def-885c7fa6a086
Udalski, A.
a7d3b194-1531-47cd-a634-abe3b8b067b0
Rajoelimanana, A.F.
d4ba3ebb-4a84-44d8-9d69-223be7e8a61e
Charles, P.A.
0429b380-0754-4dc1-8def-885c7fa6a086
Udalski, A.
a7d3b194-1531-47cd-a634-abe3b8b067b0

Rajoelimanana, A.F., Charles, P.A. and Udalski, A. (2011) Very long-term optical variability of high-mass X-ray binaries in the Small Magellanic Cloud. Monthly Notices of the Royal Astronomical Society, 413 (3), 1600-1622. (doi:10.1111/j.1365-2966.2011.18243.x).

Record type: Article

Abstract

We have studied the very long-term temporal properties of the optical emission from Be X-ray binaries (BeX) in the Small Magellanic Cloud over a ~ 16yr baseline, using light curves from the MACHO and OGLE databases. All the BeX in our sample display superorbital variations, many of them quasi-periodic on timescales of ~ 200-3000 d. These long-term variations are believed to be related to the formation and depletion of the circumstellar disc around the Be star and we compare and contrast their behaviour with that of the LMC's prototypical BeX, A0538-66. The great majority of sources show a correlation of outburst amplitude with brightness (the opposite to that seen in A0538-66) although the amplitudes are mostly small (< 0.1 mag). We suggest this is an orbital inclination effect. In addition, we have also detected many of their optical orbital periodicities, visible as a series of precisely regular outbursts. Furthermore, the amplitude of these periodic outbursts can vary through the long-term superorbital cycle, and we discuss mechanisms which can produce this effect, as well as examining an apparent correlation between these periodicities. As a by-product of this variation survey we have compiled a list of all the reported SMC BeX orbital and superorbital periodicities at optical and X-ray wavelengths.

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More information

e-pub ahead of print date: 4 March 2011
Published date: May 2011
Keywords: stars, emission-line, Be, magellanic clouds, X-rays, binaries
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 339322
URI: http://eprints.soton.ac.uk/id/eprint/339322
ISSN: 0035-8711
PURE UUID: 3393f56a-61b1-4eed-8137-6e8bcda7d0ed

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Date deposited: 28 May 2012 14:26
Last modified: 16 Jul 2019 22:02

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Contributors

Author: A.F. Rajoelimanana
Author: P.A. Charles
Author: A. Udalski

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