Galactic clusters with associated Cepheid variables. I - NGC 6087 and S Normae

Abstract

view Abstract Citations (49) References (38) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Galactic clusters with associated Cepheid variables. I. NGC 6087 and S Normae. Turner, D. G. Abstract New photoelectric UBV photometry is presented for stars in NGC 6087, the cluster containing the 9.75-day period Cepheid S Normae. The data are used with published photoelectric observations for cluster stars to redetermine the cluster reddening and distance by means of a careful application of the ZAMS fitting technique. The derived distance modulus, V(0)-M(v) = 9.78 + or - 0.03 (internal error), + or - 0.13 (total estimated uncertainty), is shown to be in very good agreement with the cluster distance modulus obtained from Walraven photometry and from the analysis of Stroemgren and H-beta photometry for cluster stars. However, the hydrogen-line data are found to produce more accurate and precise results if evolutionary corrections are ignored and replaced by due consideration of the cosmic scatter in H-beta distance moduli introduced by the effects of stellar rotation. The excellent agreement of the various distance estimates for NGC 6087 presented in this study results from the demonstrably identical zero points shared by the various luminosity calibrations used in the analysis. Internal consistency of this type has tended to be disregarded in some recent analyses of the Cepheid calibration clusters. Publication: The Astronomical Journal Pub Date: July 1986 DOI: 10.1086/114141 Bibcode: 1986AJ.....92..111T Keywords: Cepheid Variables; Star Clusters; Stellar Spectrophotometry; Ubv Spectra; Astronomical Catalogs; H Beta Line; Interstellar Extinction; Stellar Rotation; Astrophysics full text sources ADS | data products SIMBAD (50) GCPD (1) Related Materials (6) Part 2: 1992AJ....104.1132T Part 3: 1992AJ....104.1865T Part 4: 1994AJ....107.1796T Part 5: 1997AJ....113.2104T Part 6: 1998AJ....115.1958T Part 7: 2008MNRAS.388..444T