The nature of the companion star in Circinus X-1
|dc.identifier.citation||Johnston, H. and Soria, R. and Gibson, J. 2016. The nature of the companion star in Circinus X-1. Monthly Notices of the Royal Astronomical Society. 456 (1): pp. 347-355.|
© 2015 The Authors. We present optical spectra and images of the X-ray binary Circinus X-1. The optical light curve of Cir X-1 is strongly variable, changing in brightness by 1.2 mag in the space of four days. The shape of the light curve is consistent with that seen in the 1980s, when the X-ray and radio counterparts of the source were at least ten times as bright as they are currently. We detect strong, variable H a emission lines, consisting of multiple components which vary with orbital phase. We estimate the extinction to the source from the strength of the diffuse interstellar bands and the Balmer decrement; the two methods give AV = 7.6 ± 0.6mag and AV > 9.1 mag, respectively. The optical light curve can be modelled as arising from irradiation of the companion star by the central X-ray source, where a low-temperature star fills its Roche lobe in an orbit of moderate eccentricity (e ~ 0.4). We suggest that the companion star is overluminous and underdense, due to the impact of the supernova which occurred less than 5000 yr ago.
|dc.publisher||Oxford University Press|
|dc.title||The nature of the companion star in Circinus X-1|
|dcterms.source.title||Monthly Notices of the Royal Astronomical Society|
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
|curtin.department||Department of Physics and Astronomy|