Variable stars in the field of intermediate-age open cluster NGC 559

TL;DR

This study conducts the first long-term photometric survey of NGC 559, discovering 70 variable stars, analyzing their properties, and classifying their types, including cluster members and field stars, over three years.

Contribution

It provides the first comprehensive variability catalog of NGC 559, identifying and classifying 70 new variable stars and analyzing their physical parameters using light curve modeling.

Findings

70 variable stars discovered, 67 are periodic

30 variables are cluster members, 37 are field stars

Multiple types of variables identified, including eclipsing binaries and pulsators

Abstract

This work presents the first long-term photometric variability survey of the intermediate-age open cluster NGC 559. Time-series V band photometric observations on 40 nights taken over more than three years with three different telescopes are analyzed to search for variable stars in the cluster. We investigate the data for the periodicity analysis and reveal 70 variable stars including 67 periodic variables in the target field, all of them are newly discovered. The membership analysis of the periodic variables reveal that 30 of them belong to the cluster and remaining 37 are identified as field variables. Out of the 67 periodic variables, 48 are short-period (P<1 day) variables and 19 are long-period (P>1 day) variables. The variable stars have periodicity between 3 hours to 41 days and their brightness ranges from V = 10.9 to 19.3 mag. The periodic variables belonging to the cluster are then classified into different variability types on the basis of observational properties such as shape of the light curves, periods, amplitudes, as well as their positions in the Hertzsprung-Russell (H-R) diagram. As a result, we identify one Algol type eclipsing binary, one possible blue straggler star, 3 slowly pulsating B type stars, 5 rotational variables, 11 non-pulsating variables, 2 FKCOM variables and remaining 7 are characterized as miscellaneous variables. We also identify three Eclipsing Binary stars (EBs) belonging to the field star population. The PHOEBE package is used to analyse the light curve of all four EBs in order to determine the parameters of the binary systems such as masses, temperatures and radii.