Photometric analysis of variable stars in intermediate-age open clusters

การวิเคราะห์ทางโฟโตเมตรีของดาวแปรแสงในกระจุกดาวเปิดอายุปานกลาง

Name: Nareemas Chehlaeh

LCSH: Astrophysics

Classification :.DDC: 523.01

LCSH: Stars

Abstract: This study present the results of an analysis of photometric time-series observations for open clusters NGC 2126 and NGC 1528. CCD images of NGC 2126 were acquired at the Mount Lemmon Optical Astronomy Observatory (LOAO) in Arizona and the Thai National Observatory (TNO) during the years 2004, 2013 and 2015. CCD images of NGC 1528 were observed at the Beersel Hills Observatory (BHO), Beersel, Belgium during the year 2003 and 2007. The main purpose is to search for new variable stars and to study the light curves of binary systems as well as the oscillation spectra of pulsating stars in these clusters. NGC 2126 is an intermediate-age open cluster which has a population of stars inside the δ Scuti instability strip. Eleven variable stars are reported here including eight pulsating stars and three eclipsing binary stars, one of which is an eclipsing binary star with a pulsating component (V551 Aur). A period analysis was performed for all of them. Our four epochs of light minimum along with others compiled from the literature were used to revise the orbital period of V551 Aur. The Wilson-Devinney technique was used to analyze its light curves and to determine a new set of the system’s parameters. A frequency analysis of the eclipse-subtracted light curve was also performed. An accurate value of a single pulsation period Ppul = 0.129649 d which is in near 1:9 resonance to the orbital period was found. By excluding high proper motion stars within the range |µ| > 30 mas/ yr, This study found the average proper motion of the cluster µα cos δ = 0.36±0.20 mas/yr and µδ = -2.21±0.23 mas/yr. These values are close to zero, therefore the cluster members cannot be well distinguished from the background stars. We determined the accurate value of the high proper motion star LHS 1809 as 115.7, -823.7 mas/yr. A frequency analysis of the eclipse-subtracted light curve was also performed. From a theoretical isochrone fitting in the colour-magnitude diagram, we estimated the physical parameters of the clusters including the age, metallicity, and distance modulus. We found that the shape of the colour-magnitude diagram of NGC 2126 at the turn-off point is well reproduced with an isochrone of log(t) of 9.1±0.1 yr, metallicity of 0.019, E(B − V ) = 0.27±0.01 mag and (m−M)0 = 10.80±0.05 mag. For NGC 1528, the shape of the colour-magnitude diagram at the turn-off point is well reproduced with an isochrone of log(t) of 8.50±0.05 yr and a metallicity of 0.019. E(B −V ) = 0.25±0.01 mag and (m−M)0 = 9.85±0.05 mag. CCD times of the light minimum in B and V bands of the eclipsing binary AO Ser were obtained using the telescope at Beersel Hills Observatory and spectroscopic data using HERMES high-resolution spectrograph. The new light and radial velocity curves of AO Ser were simultaneously analyzed using the Wilson-Devinney technique. A semi-detached configuration of the system is confirmed. An accurate mass ratio from the binary radial velocity orbit and absolute physical properties, effective temperatures, radii and a surface gravity of components are determined.

Chiang Mai University Library

Address: Chiang Mai

Email: cmulibref@cmu.ac.th

Name: David Mkrtchian

Role: Chairman

Name: Siramas Komonjinda

Role: Member

Name: Suwicha Wannawichian

Role: Member

Name: Siriporn Chaisri

Role: Member

Name: Duangmanee Wongratanaphisan

Role: Member

Created: 2018

Modified: 2020-01-10

Issued: 2020-01-10

วิทยานิพนธ์/Thesis

application/pdf

Th 523.01 N225P

eng

DegreeName: Doctor of Philosophy

Level: Doctoral Degree

Descipline: Physics

Grantor: Chiang Mai University

©copyrights Chiang Mai University

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