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Composite Spectra, Paper XXI: 14 Serpentis
Author(s) -
Griffin R. E. M.,
Griffin R. F.
Publication year - 2017
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.201713309
Subject(s) - physics , astrophysics , stars , spectral line , radius , stellar classification , diagram , giant star , star (game theory) , red giant , astronomy , mathematics , statistics , computer security , computer science
We separate the component spectra of the composite‐spectrum binary 14 Serpentis, derive a precise double‐lined (SB2) orbit for the system, and investigate the physical properties and evolutionary states of its component stars. The 260‐day binary is comprised of an early‐K giant plus a late‐Am star that is rotating at ∼60–70 km s −1 . We find that the system has a mass ratio ( M 1 / M 2 ) of 1.14 ± 0.01, and that the cool star is ∼1.7 times as bright as its hot companion in V , though ∼2.5 times brighter bolometrically. We derive individual masses and logarithmic luminosities of the cool star and the hotter one as 2.05 and 1.8 M ⊙ , and 1.57 and 1.18 log L ⊙ , respectively, with corresponding uncertainties close to 0.1 M ⊙ and 0.07 log L ⊙ . Fitting evolutionary tracks to the H–R diagram positions of the two stars suggests that the cool primary is part‐way up the red‐giant branch and that the system has been evolving for more than 10 9 years; the absence of Li from its spectrum may support the latter statement. The hotter, less massive companion appears to have left the zero‐age main sequence, which accords with the log g <4.0 indicated by comparisons with synthetic spectra, though its radius is currently only 2.5 R ⊙ .