Photometric analysis and evolutionary stages of the contact binary V2790
  Ori
  A photometric analysis and evolutionary stages of the contact binary
V2790~Ori is presented. The $BVR_\mathrm{C}$ observations were carried out at
the Thai National Observatory. The photometric light curves were fitted to
provide fundamental parameters, required to use in the analysis of evolutionary
stages of the binary. The results show that V2790~Ori is a W-type contact
system with a mass ratio of $q$~=~2.932. The orbital period increase is found
at a rate of $\mathrm{d}P\slash \mathrm{d}t~=~$1.03$\times10^{-7}~$d~yr$^{-1}$.
It implies that a rate of mass transfer from the secondary component to the
primary one is $\mathrm{d}m_2\slash
\mathrm{d}t~=~$6.31$\times10^{-8}~M_{\odot}$~yr$^{-1}$. Furthermore, we find
that from the detached phase to the contact phase, mass of the evolved
secondary component has been lost 1.188$\pm$0.110~$\mathrm{M}_{\odot}$, i.e.,
mass lost by the system of 0.789$\pm$0.073~$\mathrm{M}_{\odot}$ and mass
transfer to the primary of 0.399$\pm$0.037~$\mathrm{M}_{\odot}$. Since the time
of the first overflow, the angular momentum loss is found to be 72.2~$\%$ of
$J_\mathrm{FOF}$, causing the orbit and Roche surface to shrink until the
present time.
