SIMBAD references

The Vanderbilt Unviersity 16-inch APT was used to collect BV observations of the long period Cepheid S Vul. A period of 68.385 days was found from these observations. Comparison of these data with all the previous photoelectric observaitosn indicates a period decrease over 28 years of about 0.41 days. Cepheid evolution models were used to find the location of S Vul in an M_V B-V instability strip from which an M_V of -6.41 was determined.