Astron. Astrophys. Suppl. Ser. 139, 57-62

A rediscussion on the eclipsing binary YY Canis Minoris

P. Vivekananda Rao - M.B.K. Sarma - K.D. Abhyankar

Send offprint request: P. Vivekananda Rao,
e-mail: pvr@ouastr.ernet.in

Centre for Advanced Study in Astronomy, Osmania University, Hyderabad 500 007, India

Received November 19, 1998; accepted April 29, 1999

Abstract:

We have reanalysed the UBV light curves of [2, Abhyankar (1962b)] using the 1993 version of Wilson-Devinney computer programme with a view to derive a consistent solution in all the three passbands and to answer the discordant opinions on the general picture of YY CMi. Initially, a preliminary unspotted solution was obtained and a photometric mass ratio was derived. From the present analysis, we obtained a mass ratio of q=0.89 which differs from the mass ratio of 0.8 derived by [7, Giuricin & Mardirossian (1981)] and 0.65 derived by [2, Abhyankar (1962b)] but agrees with the value of 0.885 derived by [18, Niarchos et al. (1998)]. Finally, the light curves were modelled by introducing a spot on the cooler secondary component to represent the observed light curve asymmetries. Assuming the mass of the primary component to be $1.56\ m_\odot$(F1V), the absolute elements of YY CMi are found to be $m_{\rm c}=1.39\ m_\odot$, $R_{\rm h}=2.52\ R_\odot$, $R_{\rm c}=2.38\ R_\odot$, ${\rm Log}\ L_{\rm h}=1.13\ L_\odot$, ${\rm Log}\ L_{\rm c}=0.86\ L_\odot$, ${\rm Log}\ g_{\rm h}=3.83$ and ${\rm Log} g_{\rm c}=3.83$. The primary and secondary components are found to be slightly overluminous and bigger in size when compared to stars of the same mass. In the H-R diagram ($\log\ T_{\rm e}$ versus $\log\ L$,ZAMS), both the components are above but near the ZAMS suggesting that both of them have left the main sequence and have come into contact. Our results essentially agree with those of [18, Niarchos et al. (1998)] based on V passband only.

Key words: stars: YY CMi -- stars: binaries: eclipsing -- stars: fundamental parameters