# Multi-color photometric investigation of the totally eclipsing binary NO Cam

## TL;DR

This study presents multi-color photometric analysis of NO Cam, revealing it as an overcontact binary with ongoing period increase and potential tertiary component influence, providing insights into its structure and evolution.

## Contribution

First detailed period variation analysis of NO Cam, indicating mass transfer and possible third body effects, enhancing understanding of W UMa binary formation.

## Key findings

- NO Cam is an A-subtype overcontact binary with 55.5% contact degree.
- The orbital period is increasing at 1.46×10^{-9} days/year.
- Evidence suggests a tertiary companion influencing the system's dynamics.

## Abstract

Multi-color photometric light curves of NO Cam in $V$ $R_C$ and $I_C$ bands are obtained and analyzed simultaneously using the Wilson-Devinney (W-D) program. The solutions suggest that NO Cam is an A-subtype overcontact binary with its mass ratio to be $q = 0.439$ and a contact degree of $f = 55.5\,\%$. The small temperature difference ($\Delta T = 44K$) between its two components indicates that the system is under thermal contact. The high orbital inclination ($i = 84.5^{\circ}$) strengthens our confidence in the parameters determined from the light curves. All available times of minimum light are collected and period variations are analyzed for the first time. The $O - C$ curve reveals that its period is increasing continuously at a rate of $dP/dt=+1.46\times{10^{-9}}$, which can be explained by mass transfer from the less massive component to the more massive one. After the upward parabolic variation is subtracted, the residuals suggest that there may be a cyclic variation with a period of 2.23 years and an amplitude of $A_3 = 0.00153$ days, which may due to the light-travel time effect (LTTE) arising from the gravitational influence of a close-in tertiary component. The close-in companion reveals that early dynamic interaction among triple system may have played very important role in the formation of the W UMa type binaries.