Optical spectroscopy and photometry of SAX J1808.4-3658 in outburst

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dc.contributor.authorElebert, Patrick
dc.contributor.authorReynolds, M. T.
dc.contributor.authorCallanan, Paul J.
dc.contributor.authorHurley, Daniel Jason
dc.contributor.authorRamsay, G.
dc.contributor.authorLewis, F.
dc.contributor.authorRussell, D. M.
dc.contributor.authorNord, B.
dc.contributor.authorKane, S. R.
dc.contributor.authorDePoy, D. L.
dc.contributor.authorHakala, P.
dc.contributor.funderDill Faulkes Educational Trust
dc.contributor.funderScience Foundation Ireland
dc.contributor.funderFermilab
dc.contributor.funderLas Cumbres Observatory
dc.contributor.funderEuropean Southern Observatory
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 photometry of V4580 Sagittarii, the optical counterpart to the accretion powered millisecond pulsar SAX J1808.4-3658, obtained during the 2008 September/October outburst. Doppler tomography of the NIII lambda 4640.64 Bowen blend emission line reveals a focused spot of emission at a location consistent with the secondary star. The velocity of this emission occurs at 324 +/- 15 km s(-1); applying a 'K-correction', we find the velocity of the secondary star projected on to the line of sight to be 370 +/- 40 km s-1. Based on existing pulse timing measurements, this constrains the mass ratio of the system to be 0.044(-0.004)(+0.005), and the mass function for the pulsar to be 0.44(-0.13)(+0.16)M(circle dot). Combining this mass function with various inclination estimates from other authors, we find no evidence to suggest that the neutron star in SAX J1808.4-3658 is more massive than the canonical value of 1.4M(circle dot). Our optical light curves exhibit a possible superhump modulation, expected for a system with such a low mass ratio. The equivalent width of the CaII H and K interstellar absorption lines suggest that the distance to the source is similar to 2.5 kpc. This is consistent with previous distance estimates based on type-IX-ray bursts which assume cosmic abundances of hydrogen, but lower than more recent estimates which assume helium-rich bursts.en
dc.description.sponsorshipEuropean Southern Observatory (DDT 281, D-5060, 281. D-5061); Fermilab (DE-AC02-07CH11359);Las Cumbres Observatory ( Faulkes Telescope Project )en
dc.description.statusPeer revieweden
dc.description.versionPublished Versionen
dc.format.mimetypeapplication/pdfen
dc.identifier.citationElebert, P., Reynolds, M. T., Callanan, P. J., Hurley, D. J., Ramsay, G., Lewis, F., Russell, D. M., Nord, B., Kane, S. R., DePoy, D. L. and Hakala, P. (2009) 'Optical spectroscopy and photometry of SAX J1808.4−3658 in outburst', Monthly Notices of the Royal Astronomical Society, 395(2), pp. 884-894. doi: 10.1111/j.1365-2966.2009.14562.xen
dc.identifier.doi10.1111/j.1365-2966.2009.14562.x
dc.identifier.endpage894
dc.identifier.issn0035-8711
dc.identifier.issn1365-2966
dc.identifier.issued2
dc.identifier.journaltitleMonthly Notices of the Royal Astronomical Societyen
dc.identifier.startpage884
dc.identifier.urihttps://hdl.handle.net/10468/4971
dc.identifier.volume395
dc.language.isoenen
dc.publisherOxford University Pressen
dc.relation.urihttps://academic.oup.com/mnras/article-lookup/doi/10.1111/j.1365-2966.2009.14562.x
dc.rights© 2009, the Authors. Journal compilation © 2009, RASen
dc.subjectAccretionen
dc.subjectAccretion discsen
dc.subjectBinariesen
dc.subjectCloseen
dc.subjectStarsen
dc.subjectIndividualen
dc.subjectV4580 Sagittariien
dc.subjectStarsen
dc.subjectNeutronen
dc.subjectPulsarsen
dc.subjectIndividualen
dc.subjectSAX J1808.4-3658en
dc.subjectX-raysen
dc.subjectBinariesen
dc.titleOptical spectroscopy and photometry of SAX J1808.4-3658 in outbursten
dc.typeArticle (peer-reviewed)en
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