Further Observations of Magellanic Cloud Cepheids

Abstract

Two-colour light-curves have been obtained, mostly by photoelectric photometry, for 13 SMC and 7 LMC cepheids, with periods in the range 1.24 to 6.69 days. The following P–L and P–C relations were found: |$LMC: \langle V \rangle = 17.58 - 3.072 \,\text{log} P$| |$\langle B \rangle -\langle V \rangle = 0.49 + 0.191 \,\text{log} \,P$| |$\text{SMC:} \langle V \rangle = 17.73 - 2.879 \,\text{log} \,P$| |$\langle B \rangle - \langle V \rangle = 0.26 + 0.306 \,\text{log} \,P$| The 25 SMC, 18 LMC and 13 galactic cepheids for which the appropriate data are available also obey, to within observational error, the Sandage relation |$\langle V \rangle = a-3.609 \,\text{log} P + 2.52 (\langle B \rangle - \langle V \rangle)$| where a = – 2.33 for the galactic cepheids, 17.03 for the SMC, and 16.40 for the LMC. This implies moduli for 18.73 for the LMC and 19.36 for the S.M. C. Reddening has been estimated from the colours of field B-stars, mostly faint. We found 0.02 for the SMC and 0.05 for the LMC. With this reddening the SMC cepheids are in the mean about 0.1 mag bluer than those in the Galaxy, as opposed to the 0.2 found previously. Some implications of the above results are briefly discussed.