We present optical B and V band photometry of GP Com - an ultracompact binary consisting of an accreting white dwarf and helium secondary component. Our data set contains 7.7 hours observations in V band with the 2.0m telescope and 2.9 hours simultaneous observations in B and V bands with the 1.5m telescope of the Rozhen National Astronomical Obsevatory, Bulgaria. The observations cover of about 13 orbital periods. We find an orbital modulation with amplitude 0.04-0.05 mag in B and V bands. Adopting that it is due to a bright spot, we estimate its temperature 19700 \pm 3000 K. We estimate mass accretion rate onto the white dwarf of about 2.10^{-12} M_sun/yr, consistent with the predicted rate for a cool donor. The data are available on Zenodo: zenodo.org/records/18768211.
@article{arxiv.2604.21440,
title = {BV photometry of the ultracompact binary star GP Com},
author = {R. Zamanov and L. Dankova and M. Minev and D. Boneva and K. Yankova},
journal= {arXiv preprint arXiv:2604.21440},
year = {2026}
}
Comments
published in C. R. Acad. Bulg. Sci., 79, 285-293 (2026)