Optical spectroscopy and Doppler tomography of Cygnus X-2

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dc.contributor.authorElebert, Patrick
dc.contributor.authorCallanan, Paul J.
dc.contributor.authorTorres, M. A. P.
dc.contributor.authorGarcia, M. R.
dc.contributor.funderScience Foundation Ireland
dc.contributor.funderNational Aeronautics and Space Administration
dc.date.accessioned2017-11-07T09:38:56Z
dc.date.available2017-11-07T09:38:56Z
dc.date.issued2009
dc.description.abstractWe present phase resolved optical spectroscopy and Doppler tomography of V1341 Cygni, the optical counterpart to the neutron star low-mass X-ray binary (LMXB) Cygnus X-2 (Cyg X-2). We derive a radial velocity (RV) curve for the secondary star, finding a projected RV semi-amplitude of K(2) = 79 +/- 3 km s(-1), leading to a mass function of 0.51 +/- 0.06 M(circle dot), similar to 30 per cent lower than the previous estimate. We tentatively attribute the lower value of K(2) (compared to that obtained by other authors) to variations in the X-ray irradiation of the secondary star at different epochs of observations. The limited phase coverage and/or longer timebase of previous observations may also contribute to the difference in K(2). Our value for the mass function implies a primary mass of 1.5 +/- 0.3 M(circle dot), somewhat lower than previous dynamical estimates, but consistent with the value found by analysis of type-I X-ray bursts from this system. Our Doppler tomography of the broad He II lambda 4686 line reveals that most of the emission from this line is produced on the irradiated face of the donor star, with little emission from the accretion disc. In contrast, the Doppler tomogram of the N III lambda 4640.64 Bowen blend line shows bright emission from near the gas stream/accretion disc impact region, with fainter emission from the gas stream and secondary star. This is the first LMXB for which the Bowen blend is dominated by emission from the gas stream/accretion disc impact region, without comparable emission from the secondary star. This has implications for the interpretation of Bowen blend Doppler tomograms of other LMXBs for which the ephemeris may not be accurately known.en
dc.description.sponsorshipNASA (NAS8-03060)en
dc.description.statusPeer revieweden
dc.description.versionPublished Versionen
dc.format.mimetypeapplication/pdfen
dc.identifier.citationElebert, P., Callanan, P. J., Torres, M. A. P. and Garcia, M. R. (2009) 'Optical spectroscopy and Doppler tomography of Cygnus X-2', Monthly Notices of the Royal Astronomical Society, 395(4), pp. 2029-2038. doi: 10.1111/j.1365-2966.2009.14685.xen
dc.identifier.doi10.1111/j.1365-2966.2009.14685.x
dc.identifier.endpage2038
dc.identifier.issn0035-8711
dc.identifier.issued4
dc.identifier.journaltitleMonthly Notices of the Royal Astronomical Societyen
dc.identifier.startpage2029
dc.identifier.urihttps://hdl.handle.net/10468/4970
dc.identifier.volume395
dc.language.isoenen
dc.publisherOxford University Pressen
dc.relation.urihttps://academic.oup.com/mnras/article-lookup/doi/10.1111/j.1365-2966.2009.14685.x
dc.rights© 2009, the Authors. Journal compilation © 2009, RASen
dc.subjectAccretionen
dc.subjectAccretion discsen
dc.subjectStarsen
dc.subjectIndividualen
dc.subjectCygnus X-2en
dc.subjectV1341 Cygnien
dc.subjectStarsen
dc.subjectNeutronen
dc.subjectX-raysen
dc.subjectBinariesen
dc.titleOptical spectroscopy and Doppler tomography of Cygnus X-2en
dc.typeArticle (peer-reviewed)en
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