EDP Sciences
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Volume 415, Number 1, February III 2004
Page(s) 289 - 297
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20034614

A&A 415, 289-297 (2004)
DOI: 10.1051/0004-6361:20034614

An improved ephemeris and physical elements of ER Vul

P. Harmanec1, 2, H. Bozic3, K. Thanjavur4, R. M. Robb4, D. Ruzdjak3 and D. Sudar3

1  Astronomical Institute of the Charles University, V Holesovickách 2, 180 00 Praha 8, Czech Republic
2  Astronomical Institute, Academy of Sciences of the Czech Republic, 251 65 Ondrejov, Czech Republic
    e-mail: hec@sunstel.asu.cas.cz
3  Hvar Observatory, Faculty of Geodesy, Zagreb University, Kaciceva 26, 10000 Zagreb, Croatia
    e-mail: hbozic,rdomagoj,dsudar@geof.hr
4  Department of Physics and Astronomy, University of Victoria, Victoria, BC, Canada, V8W 3P6
    e-mail: karun@uvastro.phys.uvic.ca; robb@uvic.ca

(Received 30 April 2003 / Accepted 14 October 2003 )

New photoelectric and $BV\!RI$ observations, secured during August-November of 2002 at two observatories distant in local time are analyzed together with two earlier photometric data sets and all available radial velocities to derive the most accurate ephemeris of the binary and to set limits on its basic physical elements. These observations were obtained as a support for a high-dispersion spectroscopic study, results of which will be published separately. It was found that radial velocities and photometric observations spanning 53 years can be reconciled with the linear ephemeris $T_{\rm prim.min.}={\rm HJD}\,2\,440\,182.25628(46)\!+\!0\,\fd698095113(29)\times E$, where the rms errors of the last digits are given in brackets. Masses of the stars are 1.02  $M_{\odot}$ and 0.97  $M_{\odot}$ and the binary separation is 4.170  $R_{\odot}$. There is still a large uncertainty in the stellar radii. We also report the discovery of rapid light variations on a time scale of hours seen in the U band light curve and offer a few thoughts on the future investigation of this binary.

Key words: stars: binaries: close -- stars: binaries: eclipsing -- stars: binaries: spectroscopic -- stars: fundamental parameters -- stars: individual: ER Vul

Offprint request: P. Harmanec, hec@sunstel.asu.cas.cz

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