# Photometric and Spectroscopic Observations of the Algol Type Binary V Triangle

## TL;DR

This study presents detailed photometric and spectroscopic analysis of the Algol-type binary V Tri, revealing its semi-detached configuration, period decrease due to mass transfer, and updated stellar parameters.

## Contribution

It provides the first comprehensive analysis combining light and radial velocity curves for V Tri, clarifying its classification as an EA type system and updating its orbital and stellar parameters.

## Key findings

- Orbital period is 0.58520481 days and decreasing.
- V Tri is a semi-detached Algol-type binary with mass transfer.
- Derived stellar masses, radii, and luminosities for both components.

## Abstract

Time-series, multi-color photometry and high-resolution spectra of the short period eclipsing binary V Tri were obtained by observations. The completely covered light and radial velocity curves of the binary system are presented. All times of light minima derived from both photoelectric and CCD photometry were used to calculate the orbital period and new ephemerides of the eclipsing system. The analysis of $O-C$ diagram reveals that the orbital period is $0.58520481\ days$, decreasing at a rate of $dP/dt=-7.80\times10^{-8} d\ yr^{-1} $. The mass transfer between the two components and the light time-travel effect due to a third body could be used to explain the period decrease. However, a semidetached configuration with the less-mass component filling and the primary nearly filling each of their Roche lobes was derived from the synthesis of the light and radial velocity curves by using the 2015 version of the Wilson-Devinney code. We consider the period decrease to be the nonconservative mass transfer from the secondary component to the primary and the mass loss of the system, which was thought to be an EB type while it should be an EA type (semi-detached Algol-type) from our study. The masses, radii and luminosities of the primary and secondary are $1.60\pm0.07 M_\odot$, $1.64\pm0.02 R_\odot$, $14.14\pm0.73 L_\odot$ and $0.74\pm0.02 M_\odot$, $1.23\pm0.02 R_\odot$, $1.65\pm0.05 L_\odot$, respectively.