International Astronomy and Astrophysics Research Journal

Photometric Analysis for Searching Variable Stars in the Field of the Northern Open Cluster NGC 1960

Gireesh Chandra Joshi *

Department of Physics, Government Degree College, Kanvaghati, Kotdwar, Uttarakhand, India.

*Author to whom correspondence should be addressed.

---

Abstract

The aim of the present work is to extract and analyses the light curves of the stars in the field of the cluster, NGC 1960. The photometric calibration is performed by a comprehensive method of secondary standard transformation alongwith differential photometry using two comparison stars per candidate variable star. The resultant light curves for each potential variable star are displayed and their period are analyzed by two different methods. The period and classification of the 18 discovered short periodic type variable stars of NGC 1960 are discussed, which consist of four known variable stars and fourteen new variable stars. Among the eighteen detected variables of NGC 1960, one as \(\gamma\) - Dor, one as RR Lyre, two as EB, two as Ellipsoidal, two as hybrid (\(\delta\) \(\mathit{Scuti}\) - \(\gamma\) - \(\mathit{Dor}\)), two as LADS, two as rotational and six as irregular or miscellaneous type variable stars. In the case of NGC 1960, the 12 selected comparison stars appear to be likely candidate for long periodic variability, and four stars may be possible candidate for standard stars. The variation in brightness of the other twenty comparison stars is non-pulsating with an irregular pattern. Mean proper motions of the core region of NGC1960 are \(\bar{\mu}\)_{\(\mathit{x}\)} = 0:314\(\pm\) 0:026 \(\mathit{mas/yr}\) and \(\bar{\mu}\)_{\(\mathit{y}\)} = -2.333 \(\pm\) 0.037 \(\mathit{mas/yr}\) in the R.A. and DEC. directions, respectively.Membership analysis of variable stars is performed using their distance, kinematic probability and location in ( \(\mathit{U - B}\) ) vs ( \(\mathit{B - V}\) ) TCD. C-M diagrams were constructed to confirm the evolutionary state of the new variable stars.

Keywords: Astronomical reduction - NGC 1960, stellar variability

---

---

---

References

Luo YP, Zhang XB, Deng LC, Han ZW. Discovery of 14 new slowly pulsating b stars in the open cluster NGC 7654, ApJ Letters. 2012;746:L7.

Dupret MA, Grigahcene A, Garrido R, Gabriel M, Scuflaire R. Theoretical instability strips for Scuti and Doradus syars, A&A. 2004;414(2):L17.

Sharma S, Pandey AK, Ogura K, Mito H, Tarusawa K, Sagar R. Wide-field CCD photometry around nine open clusters. The Astronomical Journal. 2006;132(4):1669.

Cantat-Gaudin T, Anders F. Clusters and mirages: Cataloguing stellar aggregates in the Milky Way. Astronomy Astrophysics. 2020;633:A99.

Joshi, Gireesh C, Tyagi RK. Statistical analysis for precise estimation of Structural Properties of NGC 1960, Mathematical Sciences Int Research Journal. 2015;4:384.

Barkhatova KA, Zokharova PE, Shaskina LP, Oreknova LK. Some Kinematic parameters of open cluster systems, Astron. Zh., 1985;62:854.

Conrad C, Scholz RD, Kharchenko NV, Piskunov AE, R¨oser S, Schilbach E, De Jong RS, Schnurr O, Steinmetz M, Grebel EK, Zwitter T. A RAVE investigation on Galactic open clusters-II. Open cluster pairs, groups and complexes. Astronomy & Astrophysics. 2017;600:A106.

Hasan P, Kilambi GC, Hasan SN. Near Infrared Photometry of the Young star clusters NGC 1960, NGC 2453 and NGC 2384, Bull. Astr. Soc. India. 2005;33:151.

Jeffries RD, Naylor T, Mayne NJ, Bell CPM, Littlefair SP. A lithium depletion boundary age of 22 Myr for NGC 1960, MNRAS. 2013;434(3):2438.

Johnson HL, Morgan WW. Fundamental stellar photometry for standards of spectral type on the Revised System of the Yerkes Spectral Atlas, Astrophysical Journal. 1953;117:313.

Kharchenko NV, Piskunov AE, Roeser S, Schilbach E, Schola RD. Astrophysical supplements to the ASCC-2.5 II. Membership probabilities in 520 Galactic open cluster sky areas, Astron. Nachr., 2004;325:740.

Nilakshi, Sagar R, Pandey AK, Mohan V. A study of spacial structure of galactic open star clusters, A&A. 2002;383:153.

Sanner J, Altmann M, Brunzendorf J, Geffert M. Photometric and kinematic studies of open star clusters. II. NGC 1960 (M 36) and NGC 2194, A&A. 2000;357:471.

Sharma S, Pandey AK, Ogura K, Aoki T, Pandey K, Sandhu TS, Sager R. Mass functions and photometric binaries in nine open clusters, AJ. 2008;135:1934.

Delgado AJ, Alfaro EJ, Garrido R, Garcia- Pelayo JM. Search for B-Type variables stars in open clusters, Information Bullatine on Variable Stars(IBVS). 1984;2603:1.

Smith R, Jeffries RD. Dust discs around intermediate-mass and Sun-like stars in the 16 Myr old NGC 1960 open cluster. Monthly Notices of the Royal Astronomical Society. 2012;420(4):2884-98.

Joshi YC, Joshi S, Kumar B, Mondal S, Balona LA. MNRAS. 2012;419:2379.

Landolt AU. AJ. 1992;104:340.

Stetson PB. DAOPHOT: A computer program for crowded-field stellar photometry. Publications of the Astronomical Society of the Pacific. 1987 Mar 1;99(613):191.

Stetson PB. In ASP conf. Ser. vol. 25, Astronomical Data Analysis Software and System, I. Astron. Soc. Pac., ed. Warrall D. M., and Biemesderfer C., Barnes J., San Francisco. 1992;297.

Joshi, Gireesh C. Dynamic Properties and Search of Variable Stars: NGC 1960, In: Mishra, G.C. editor. National Conference on Innovative Research in Chemical, Physical, Mathematical Sciences, Applied Statistics and Environment Dynamics (CPMSED-2015), Krishi Sanskriti Publications (New Delhi) ISBN: 978-93- 85822-07-0. 2015;22-27.

Sariya DP, Lata S, Yadav RK. Variable stars in the globular cluster NGC 4590 (M68). New Astronomy. 2014 Feb 1;27:56-62.

Wood PR, Sebo KM. On the pulsation mode of Mira variables: evidence from the Large Magellanic Cloud. Monthly Notices of the Royal Astronomical Society. 1996;282(3):958-64.

Lata S, Yadav RK, Pandey AK, Richichi A, Eswaraiah C, Kumar B, Kappelmann N, Sharma S. Main-sequence variable stars in Young open cluster NGC 1893, MNRAS. 2014;442(1):273.

Lomb N. Least-squares frequency analysis of unequally spaced data, AP&SS0. 1976;39(2):447

Scargle JD. Studies in astronomical time series analysis. II-Statistical aspects of spectral analysis of unevenly spaced data. Astrophysical Journal, Part 1, vol. 263, Dec. 15, 1982, p. 835-853. 1982;263:835-53.

Kov´acs G, Zucker S, Mazeh T. A box-fitting algorithm in the search for periodic transits. Astronomy Astrophysics. 2002;391(1):369-77.

Plavchan P, Jura M, Kirkpatrick JD, Cutri RM, Gallagher SC. Near-infrared variability in the 2MASS calibration fields: A search for planetary transit candidates. The Astrophysical Journal Supplement Series. 2008;175(1):191.

Ransom SM, Eikenberry SS, Middleditch J. Fourier techniques for very long astrophysical time-series analysis. The Astronomical Journal. 2002 Sep 1;124(3):1788.

Meurers J. Ein Stern-Aggregat im M 36. Mit 7 Textabbildungen. Zeitschrift f ¨ ur Astrophysik. 1958;44:203.

Chian BT, Zhu GL. An Investigation on the Proper- Motions of the Open Clusters NGC1960 NGC6530 and NGC7380. Shanghai Observatory Annals. 1966;26:63.

Joshi YC, Maurya J, John AA, Panchal A, Joshi S, Kumar B. Photometric, kinematic, and variability study in the young open cluster NGC 1960. Monthly Notices of the Royal Astronomical Society. 2020;492(3):3602-21.

Gaia collaboration et al., A&A. 2016;595:A2.

Gaia collaboration et al., A&A. 2021;649:A1

Joshi GC. Implication of Phase-folded Diagrams for Validation of the Nature of Stellar Variability I: the case of NGC 6866. Bulgarian Astronomical Journal. 2022;37(01).

Hanson MM, ZAMS O Stars, (Boulder-Munich II: Properties of Hot, Luminous Stars, Edited by Ian) ASP Conference Series. 1998;131-1.

Balona LA, Guzik JA, Uytterhoeven K, Smith JC, Tenenbaum P, Twicken JD. The Kepler view of Doradus stars. Monthly Notices of the Royal Astronomical Society. 2011;415(4):3531-8.

Clement CM, Muzzin A, Dufton Q, Ponnampalam T, Wang J, Burford J, Richardson A, Rosebery T, Rowe J, Hogg HS. Variable stars in Galactic globular clusters. The Astronomical Journal. 2001;122(5):2587.

Luo YP. Variable stars in the open cluster NGC 2141, RAA. 2015;15(5):733.

Catelan M, Pritzl BJ, Smith HA. The rr lyrae period-luminosity relation. i. theoretical calibration. The Astrophysical Journal Supplement Series. 2004;154(2):633.

Balona LA, Baran AS, Daszy´nska-Daszkiewicz J, De Cat P. Analysis of Kepler B stars: rotational modulation and Maia variables. Monthly Notices of the Royal Astronomical Society. 2015;451(2):1445-59.

Samus' NN, Kazarovets EV, Durlevich OV, Kireeva NN, Pastukhova EN. General catalogue of variable stars: Version GCVS 5.1. Astronomy Reports. 2017;61:80-8.

Hartman JD, Gaudi BS, Holman MJ, McLeod BA, Stanek KZ, Barranco JA, Pinsonneault MH, Kalirai JS, Deep MMT Transit Survey of the Open Cluster M37. II. Variable Stars., The Astrophysical Journal. 2008;675:1254.

Michel E, Dupret MA, Reese D, et al., What CoroT tells us about -Scuti stars-Existence of a regular pattern and seismic indicates to characterize stars, EPJ Web Conferences. 2017;160:03001.