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Appendix A: Details of the reduction and transformation of photometric data

Comments on individual data sets:

Station 19: Abastumani 0.48 m reflector These observations are on an instrumental UBV system and suffer from an unusually large scatter. Moreover, the last night (HJD 2 441 154) seems to deviate from the general light curve quite a lot. In addition, the times of the inflection inside the light minimum differ notably for different passbands for this particular night. Since we now have at our disposal numerous observations covering a similar period of time, we excluded these definitely lower-quality data from our analyses.

Station 42: Dyer A very limited set of instrumental UBV observations from three nights only.

Station 70: Mojon de Trigo The data for the night HJD 2 444 083 in Table I of Giménez & Costa (1980) are not presented in an increasing order which looks a bit confusing, but there is no actual misprint in the table, as kindly communicated to us by Dr. Alvaro Giménez. The data are on an instrumental system.

Station 71: Vatican According to O’Connell (1977), these data were transformed to the standard Johnson system using observations of several UBV standards. In addition, the extinction was derived and appropriate corrections were applied. We note that there is an obvious misprint in the first observation, obtained on HJD 2 439 712.3492, at the U colour: It should read –0641 instead of the tabulated value of –0941.

Station 72: University of Victoria 0.30 m These are data on an instrumental UBV system. No extinction corrections were applied.

Station 74: Abastumani 0.33 m This is the largest homogeneous set of photoelectric observations of Y Cyg, covering the period from 1950 to 1957. The data were obtained without any filter and the check star used, HD 197 419, is listed under the name V568 Cyg in the General Catalogue of Variable Stars. There is a misprint in the last page of Table 1 of Magalashvili & Kumsishvili (1959): the first Julian date is HJD 2 435 663 (continuation from the previous page), not 2 435 659 as given in the Table. The data are of a good quality, with the exception of the following deviating observations which we omitted from our analysis: HJD 2 434 209.316, all three observations from 2434897, 2 434 949.298, 2 435 635.408, .423, 2 435 647.365, 2 436 071.339, and .342.

Station 75: Tübingen 0.40 m A limited set of instrumental BV observations.

Station 76: Hoher List These early blue and yellow observations are on an instrumental system. They were secured relative to a red comparison star HD 198 692.

Station 77: IUE Fine Error Sensor These observations, transformed to Johnson V by Stickland et al. (1992), come from two tracking stations. They have larger scatter than most of the photoelectric observations secured on the Earth, but their time distribution ensures a relatively uniform, although not dense coverage of the light curve. There is one deviating point at HJD 2 448 040.442 that we omitted from the analyses.

© ESO, 2014