J/A+AS/133/7 J/A+AS/133/7 V photometry of YY CMi P G Niarchos L Mantegazza E Poretti V Manimanis Astron. Astrophys. Suppl. Ser. 133 7 1998 1998A&AS..133....7N Binaries, eclipsing Photometry binaries: eclipsing stars: individual (YY Cmi) stars: spots New V photoelectric observations of the eclipsing system YY CMi, obtained at La Silla, Chile, and Merate Observatory, Italy, are presented. New times of minima and ephemeris based on our observations are also given. The V light curve was analysed by using the WD code to derive the geometrical and physical parameters of the system. Since no spectroscopic mass ratio is available, the q-search method was applied to yield the preliminary range of the mass ratio in order to search for the final solution. First the unspotted solution was carried out by using the unperturbed parts of the light curve and applying the DC program of the WD code. The solution was performed by assuming contact (mode 3) and semi-detached (mode 4) configuration, since no classification of the system is possible from the shape of the light curve. The solution in mode 4 does not lead to an acceptable model, since the secondary was found to be slightly overcontact. Therefore the contact solution was finally adopted. Moreover the light curve peculiarities (MaxII fainter than MaxI and excess of light around the phase 0.32) were explained by assuming a cool and a hot spot on the surface of the secondary (cooler) component. The degree of contact is very small (f=~3%) and the thermal contact is poor (T_1_-T_2_)=~650K. These results together with the high photometric mass ratio q=~0.89 indicate that YY CMi is very probably a system at the beginning or the end of the contact phase.

YY CMiHD 6711008 06 38.5+01 55 46 HD 6692508 05 47.7+02 09 54

HJD Heliocentric Julian date d {DELTA}V V magnitude difference respect with HD 66925 mag table1.texLaTeX version of table.dat Patricia Bauer CDS 1998May15Ennio Poretti <poretti@merate.mi.astro.it> J_A+AS_133_7.xml