The mass of the classical Cepheid S Muscae

被引:14
作者
BohmVitense, E
Evans, NR
Carpenter, K
BeckWinchatz, B
Robinson, R
机构
[1] HARVARD SMITHSONIAN CTR ASTROPHYS,CAMBRIDGE,MA 02138
[2] YORK UNIV,DEPT PHYS & ASTRON,N YORK,ON M3J 1P3,CANADA
[3] NASA,GODDARD SPACE FLIGHT CTR,ASTRON & SOLAR PHYS LAB,GREENBELT,MD 20771
[4] COMP SCI CORP,GREENBELT,MD 20771
关键词
binaries; visual; Cepheids; stars; evolution; fundamental parameters; individual (S Muscae); stars interiors;
D O I
10.1086/303725
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
A good determination of the mass-luminosity relation for evolved stars on blue loops can determine the degree of excess mixing in the interiors of their main-sequence companions. In this study we determine the dynamical mass of the Cepheid binary S Muscae. This can be combined with its known luminosity and be fitted on evolutionary tracks to determine the amount of mixing in the main-sequence progenitor. Using the Goddard High Resolution Spectrograph on the Hubble Space Telescope we have measured the orbital radial velocity changes for the companion of the Cepheid S Mus. Spectra taken at minimum and maximum orbital velocities were cross-correlated. The velocity difference was measured to be 30.6+/-0.4 km s(-1). The difference for the orbital velocities of the Cepheid for the same phases was determined to be 26.9 km s(-1)+/-0.4 km s(-1). This gives a velocity ratio of 1.14+/-0.02, which gives us the mass ratio for the companions. Adding possible centering errors of the target in the entrance apertures the error limit would be increased to +/-0.06. The derived spectral types of the companion S Mus B range from B3 V to B5 V depending on the criterion used to determine it, with an average spectral type B3.8 V. Using the average spectral type and the main-sequence mass-spectral type relation from Andersen & Harmanec we find for S Mus B a mass of 5.2+/-0.2 M.. With the newly determined mass ratio the mass for the Cepheid S Mus A comes out to be 5.9(-0.6)(+0.7) M.. Taking the mass of 5.9 M. at face value and adopting the absolute visual magnitude of M(upsilon)=-4.29 (log L/L.=3.62) for the Cepheid S Mus this indicates mixing in its main-sequence progenitor slightly in excess of the one assumed for the Maeder and Meynet evolutionary tracks. The present uncertainties in mass and luminosity prevent, however, a firm conclusion about the exact degree of mixing.
引用
收藏
页码:916 / 925
页数:10
相关论文
共 52 条
[1]   ACCURATE MASSES AND RADII OF NORMAL STARS [J].
ANDERSEN, J .
ASTRONOMY AND ASTROPHYSICS REVIEW, 1991, 3 (02) :91-126
[2]   FREQUENCY-PERIOD DISTRIBUTIONS OF CEPHEID VARIABLES IN GALAXIES IN LOCAL GROUP [J].
BECKER, SA ;
IBEN, I ;
TUGGLE, RS .
ASTROPHYSICAL JOURNAL, 1977, 218 (03) :633-653
[3]   THE EVOLUTION OF INTERMEDIATE-MASS STARS FROM THE ZERO-AGE MAIN-SEQUENCE TO THE BASE OF THE ASYMPTOTIC GIANT BRANCH AS A FUNCTION OF MASS AND COMPOSITION [J].
BECKER, SA .
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 1981, 45 (03) :475-505
[4]   CNO ABUNDANCES IN CEPHEIDS AND SUPER-GIANTS - THEORETICAL IMPLICATIONS [J].
BECKER, SA ;
COX, AN .
ASTROPHYSICAL JOURNAL, 1982, 260 (02) :707-715
[5]  
BERTELLI G, 1986, ASTRON ASTROPHYS SUP, V66, P191
[6]   BLUE COMPANIONS OF CEPHEIDS [J].
BOHMVITENSE, E ;
PROFFITT, C .
ASTROPHYSICAL JOURNAL, 1985, 296 (01) :175-184
[7]   THE 2 PERIOD-LUMINOSITY RELATIONS FOR POPULATION-I CEPHEIDS [J].
BOHMVITENSE, E .
ASTRONOMICAL JOURNAL, 1994, 107 (02) :673-678
[8]   THE CEPHEID MASS PROBLEM AND CEPHEID BINARIES [J].
BOHMVITENSE, E .
ASTROPHYSICAL JOURNAL, 1986, 303 (01) :262-272
[9]   THE DYNAMICAL MASS OF S-MUSCAE [J].
BOHMVITENSE, E ;
CLARK, M ;
COTTRELL, PL ;
WALLERSTEIN, G .
ASTRONOMICAL JOURNAL, 1990, 99 (01) :353-372
[10]   THE EFFECTIVE TEMPERATURE SCALE [J].
BOHMVITENSE, E .
ANNUAL REVIEW OF ASTRONOMY AND ASTROPHYSICS, 1981, 19 :295-317