# Orbital variations and outbursts of the unusual variable star V1129 Centauri

## TL;DR

V1129 Centauri exhibits rare annual outbursts and orbital variations dominated by ellipsoidal effects, suggesting it is a dwarf nova with an unusually bright early-type donor star that masks typical cataclysmic variable features.

## Contribution

This study provides the first detailed light curve analysis of V1129 Centauri, revealing its orbital characteristics and proposing it as a dwarf nova with an atypically luminous donor star.

## Key findings

- Orbital period of 21h 26m identified.
- Outbursts occur roughly once a year, lasting about 40 days.
- The system's properties can be explained by dwarf nova models with a bright early-type donor.

## Abstract

The variable star V1129 Cen is classified in the GCVS as being of $\beta$ Lyr type. Unusual for such stars, it exhibits outbursts roughly once a year, lasting for $\sim$40 days. For this reason, a relationship to the dwarf novae has been suspected. Here, for the first time a detailed analysis of the light curve of the system is presented. Based on observations with high time resolution obtained at the Observat\'orio do Pico dos Dias and on the long term ASAS light curve the orbital variations of the system are studied. They are dominated by ellipsoidal variations and partial eclipses of a probably slightly evolved F2 star in a binary with an orbital period of $21^{\rm h}$ $26^{\rm m}$. Comparison with the characteristics of dwarf novae show that the observational properties of V1129 Cen can be explained if it is just another dwarf novae, albeit with an unusually bright and early type mass donor which outshines the accretion disk and the mass gainer to a degree that many normal photometric and spectroscopic hallmarks of cataclysmic variables remain undetected.