Investigating stellar variability in the open cluster region NGC 381

We study variable stars in the field of the open cluster NGC 381 using photometric data observed over 27 nights and identify a total of 57 variable stars out of which five are member stars. The variable stars are classified based on their periods, amplitudes, light curve shapes, and locations in the H-R diagram. We found a rich variety of variable stars in the cluster. We identified a total of 10 eclipsing binaries out of which 2 are Algol type (EA) while 8 are W UMa type (EW) binaries. The estimated ages of these EW binaries are greater than 0.6 Gyr which is in agreement with the formation time constraint of > 0.6 Gyr on short-period eclipsing binaries. The estimation of the physical parameters of the three EW type binaries is done using PHOEBE model-fitting software. The pulsating variable stars include one each from {\delta} Scuti and {\gamma} Dor variability class. We determined the pulsation modes of pulsating variables with the help of the FAMIAS package. We obtained 15 rotational variables stars comprising four dwarf stars identified on the basis log(g) versus log(Tef f ) diagram. These dwarf stars are found to have generally larger periods than the remaining rotational variables.Comment: The paper is accepted for publication in The Astronomical Journal (AJ). It contains 6 tables and 14 figure

The statistical analysis of the dynamical evolution of the open clusters

We present the dynamical evolution of ten open clusters which were part of our previous studies. These clusters include both young and intermediate-age open clusters with ages ranging from 25$\pm$19 Myr to 1.78$\pm$0.20 Gyr. The total mass of these clusters ranges from 356.18$\pm$142.90 to 1811.75$\pm$901.03 M$_{\odot}$. The Galactocentric distances to the clusters are in the range of 8.91$\pm$0.02 to 11.74$\pm$0.18 kpc. The study is based on the ground-based UBVRI data supplemented by the astrometric data from the Gaia archive. We studied the minimum spanning tree of the member stars for these clusters. The mass segregation in these clusters was quantified by mass segregation ratios calculated from the mean edge length obtained through the minimum spanning tree. The clusters NGC 2360, NGC 1960, IC 1442, King 21, and SAI 35 have ${\Gamma}_{MSR}$ to be 1.65$\pm$0.18, 1.94$\pm$0.22, 2.21$\pm$0.20, 1.84$\pm$0.23, and 1.96$\pm$0.25, respectively which indicate moderate mass segregation in these clusters. The remaining five clusters are found to exhibit weak or no mass segregation. We used the ratio of half mass radius to the tidal radius i.e. R$_{h}$/R$_{t}$ to investigate the effect of the tidal interactions on the cluster structure and dynamics. The ratios of half mass radii to tidal radii are found to be positively correlated with the Galactocentric distances with a linear slope of 0.06$\pm$0.01 having linear regression coefficient r-square = 0.93 for the clusters.Comment: 9 pages, 3 figures, 2 table

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

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 3 yr with three different telescopes are analysed 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 reveals 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 d) variables and 19 are long-period (P > 1 d) variables. The variable stars have periodicity between 3 h to 41 d 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 1 Algol type eclipsing binary, 1 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

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

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 3 yr with three different telescopes are analysed 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 reveals 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 d) variables and 19 are long-period (P > 1 d) variables. The variable stars have periodicity between 3 h to 41 d 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 1 Algol type eclipsing binary, 1 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