Characteristics of the Variable Star P Cygni Determined From Cluster Membership

Volume 29 number 2 (2001)

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David G. Turner
Saint Mary’s University Halifax, Nova Scotia, B3H 3C3 Canada
Gary Welch
Saint Mary’s University Halifax, Nova Scotia, B3H 3C3 Canada
Marianne Graham
Saint Mary’s University Halifax, Nova Scotia, B3H 3C3 Canada
David Fairweather
Saint Mary’s University Halifax, Nova Scotia, B3H 3C3 Canada
Andrew Horsford
Typex Business Centre Newcastle-Upon-Tyne United Kingdom
Michael Seymour
Queen’s University Kingston, Ontario, K7L 3N6 Canada
Walter Feibelman
Goddard Space Flight Center Laboratory for Astronomy and Solar Physics Code 681 Greenbelt, MD 20771

Abstract

Empirical information on the luminosity, reddening, age, and mass of the variable B2 Oe supergiant P Cygni is derived from its assumed membership in the sparse anonymous cluster on which it is projected, as well as its association with the spatially adjacent cluster IC 4996, which forms a double cluster with the P Cyg cluster. Evidence for the high luminosity of P Cyg is confirmed by its derived absolute magnitude of M(v) = -8.46 +/-0.03, which translates to log (L/L(solar)) = 5.54 +/-0.02 for an effective temperature consistent with the star's derived space reddening (E(B-V)=0.53 +/-0.02). More surprising is an age for the associated clusters of 6 (+/-1.5) x 10^6 years, corresponding to a turnoff point mass of 25.1 (+/-5.5 solar mass). By inference, P Cygni, as a post main-sequence object, should have a mass of no more than ~23-25 solar mass.