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Appendix A: Details of the spectral data reduction and measurements

The initial reduction of all Ondřejov and DAO spectra (bias subtraction, flat-fielding, creation of 1-D spectra, and wavelength calibration) was carried out in IRAF. For Elodie and Hermes spectra, dedicated reduction pipelines were used, combined with some IDL routines in the case of Elodie. See Baranne et al. (1996) and Raskin et al. (2011) for detailed descriptions of the Elodie and Hermes spectrographs. Rectification, removal of residual cosmics and flaws and RV measurements of all spectra were carried out with the program SPEFO (Horn et al. 1996; Škoda 1996), namely the latest version 2.63 developed by Mr. J. Krpata. SPEFO displays direct and flipped traces of the line profiles superimposed on the computer screen that the user can slide to achieve a precise overlapping of the parts of the profile of whose RV one wants to measure. Using a selection of stronger unblended lines of the cool component 2 (see Table A.1) covering the red spectral region (available for all spectra), we measured RVs of all of them to obtain a mean RV for all spectra. We also measured a selection of good telluric lines and used them for an additional fine correction of the RV zero point of

each spectrogram (Horn et al. 1996). Moreover, we measured the RVs of the steep wings of the Hα emission line and of the two absorption cores of Hα. We point out that although some broad and shallow lines of component 1 are seen in the spectra, their direct RV measurement is impossible because of numerous blends with the lines of component 2.

Appendix B: Details on the photometric data reductions

Since we used photometry from various sources and photometric systems, both all-sky and differential, relative to several different comparison stars, we attempted to arrive at some homogenisation and standardisation. Special effort was made to derive improved all-sky values for the comparison stars used, employing carefully standardised UBV observations secured at Hvar over several decades of systematic observations. The adopted values are collected in Table B.1, together with the number of all-sky observations and the rms errors of one observation. They were added to the respective magnitude differences to obtain directly comparable standard UBV magnitudes for all stations. To illustrate the accuracy, with which various data sets were transformed to the standard system, we give (in Table B.2) mean differential UBV values for the check stars used. They were derived relatively to the Hvar values for the comparison stars HD 58187 and HD 61341.

Below, we provide some details of the individual data sets and their reductions.

• Station 01 – Hvar: these differential observations have been secured by HB and PZ relative to HD 58187 (the check star HD 59059 being observed as frequently as the variable) and carefully transformed to the standard UBV system via non-linear transformation formulæ using the HEC22 reduction program – see Harmanec et al. (1994) and Harmanec & Horn (1998) for the observational strategy and data reduction³. All observations were reduced with the latest HEC22 rel.17 program, which allows the time variation of linear extinction coefficients to be modelled in the course of observing nights.

• Station 11 – South African Astronomical Observatory (SAAO): these differential UBV observations were obtained by PZ with the 0.50 m reflector relative to HD 61341 (SAO 115750 being used as the check star) and also transformed to the standard Johnson system with the help of HEC22.

• Station 37 – La Palma: these all-sky seven-colour (7-C) observations were secured in the Geneva photometric system using the two-channel aperture photometer P7-2000 (Raskin et al. 2004) mounted on the 1.20 m Belgian Mercator reflector at the Observatorio de los Muchachos at La Palma.

• Station 61 – Hipparcos: these all-sky observations were reduced to the standard V magnitude via the transformation formulæ derived by Harmanec (1998) to verify that no secular light changes in the system were observed. However, for the light-curve solution in PHOEBE, we consider the Hipparcos transmission curve for the H_p magnitude.

• Station 93 – ASAS3 V photometry: we extracted these all-sky observations from the ASAS3 public archive (Pojmanski 2002), using the data for diaphragm 1, having on average the lowest rms errors. We omitted all observations of grade D and observations having rms errors larger than 004. We also omitted a strongly deviating observation at HJD 2 452 662.6863.

© ESO, 2015