Independent Distance Determinations to Milky Way Cepheids in Open Clusters and Associations.II.CF CAS in NGC 7790

Abstract

view Abstract Citations (11) References (48) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Independent Distance Determinations to Milky Way Cepheids in Open Clusters and Associations.II.CF CAS in NGC 7790 Matthews, Jaymie M. ; Gieren, Wolfgang P. ; Mermilliod, Jean-Claude ; Welch, Douglas L. Abstract Containing three Cepheids and an eclipsing binary, the open cluster NGC 7790 has the potential to be a Rosetta Stone for refining the zero point of the extragalactic distance scale. Unfortunately, ZAMS fitting of this relatively sparse, heavily reddened cluster is fraught with difficulty, and even modern determinations of its distance modulus based on comparable data and techniques differ by over 0.3 mag. To provide an independent calibration of the distance to NGC 7790, we have performed a surface brightness analysis of the Cepheid CF Cas (P≃4.88 days), which is widely believed to be a member of the cluster. For this analysis, we use new high-quality radial-velocity data obtained with the DAO Radial Velocity Spectrometer, as well as archival velocities and photometry. Our new measurements increase the available set of published RV data for CF Cas by over a third. We derive the distance and radius of CF Cas to be 3130±160 pc and 40.6±2.0Rsun, respectively. This radius is consistent with fundamental-mode pulsation for a Cepheid of this period, removing a possible ambiguity in mode identification which could bias a period-luminosity calibration incorporating CF Cas. We go on to estimate the absolute magnitude (<MV> ≃ -3.05±0.10 mag) and effective temperature (log Teff ≃ 3.74±0.02) of CF Cas, although we caution that these values are sensitive to the assumed reddening (unlike our surface-brightness distance and radius). Evolutionary and Wesselink relations yield very similar values for the mass of CF Cas, near 5 Msun. Publication: The Astronomical Journal Pub Date: November 1995 DOI: 10.1086/117689 Bibcode: 1995AJ....110.2280M Keywords: OPEN CLUSTERS AND ASSOCIATIONS: NGC 7790; CEPHEIDS; BINARIES: ECLIPSING full text sources ADS | data products SIMBAD (6) Related Materials (2) Part 1: 1994AJ....107.2093G Part 3: 1996AJ....111.2059G