Echoes from the companion star in Sco X-1期刊界 All Journals 搜尽天下杂志传播学术成果专业期刊搜索期刊信息化学术搜索

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Echoes from the companion star in Sco X-1

Authors:	T Muñoz-Darias I G Martínez-Pais J Casares V S Dhillon T R Marsh R Cornelisse D Steeghs P A Charles

Institution:	Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain;Departamento de Astrofica, University de La Laguna, E-38206 La Laguna, Tenerife, Spain;Department of Physics &Astronomy, University of Sheffield, Sheffield S3 7RH;Department of Physics, University of Warwick, Coventry CV4 7AL;Harvard–Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA;South Africa Astronomical Observatory, PO Box 9, Observatory 7935, South Africa;University of Southampton, Southampton SOB17 1BJ

Abstract:	We present simultaneous X-ray ( RXTE ) and optical (ULTRACAM) narrow-band (Bowen blend/He ii and nearby continuum) observations of Sco X-1 at 2–10 Hz time resolution. We find that the Bowen/He ii emission lags the X-ray light curves with a light traveltime of s which is consistent with reprocessing in the companion star. The echo from the donor is detected at orbital phase ～0.5 when Sco X-1 is at the top of the flaring branch (FB). Evidence of echoes is also seen at the bottom of the FB but with time-lags of 5–10 s which are consistent with reprocessing in an accretion disc with a radial temperature profile. We discuss the implication of our results for the orbital parameters of Sco X-1.

Keywords:	accretion accretion discs binaries: close stars: individual: Sco X-1 X-rays: binaries