BV Ic Photoelectric Observations of 16 Double-Mode Classical Cepheids

We performed photoelectric observations of double-mode Cepheids between March 10, 1999 and April 22, 2004 (JD 2451248–2453118) with the 0.76-m reflector of the South African Astronomical Observatory (SAAO), equipped with a pulse-counting photoelectric photometer. It is a cooled unit that employs a Hamamatsu photomultiplier in conjunction with BV Ic filters of the Kron–Cousins photometric system (Cousins, 1976). A description of the observing techniques can be found in Berdnikov and Turner (2004). Observational uncertainties are close to 0.01 mag in all bands. We have obtained a total of 2902 measurements for 16 double-mode Cepheids, listed in the Table. The phases of the observations were calculated with the elements from GCVS (Samus et al., 2017) for BE Pup and U TrA; from Antipin (1997) for V458 Sct; from Berdnikov (1992) for AX Vel; and from ASAS-3 (Pojmanski, 2002) for the other stars. The star BE Pup was identified as a double-mode Cepheid by Hacke and Richert (1990); the GCVS considers it a doubtful CWB star. For all the listed Cepheids, with the exception of V1048 Cen, the period in the Table is that of the fundamental mode. V1048 Cen pulsates in the first and second overtones, and the period in the Table is that of the first overtone.