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Eclipsing Binaries’ Minima Monitoring From Ccd Photometry

Eclipsing Binaries’ Minima Monitoring From Ccd Photometry

Eclipsing Binaries’ Minima Monitoring From Ccd Photometry

The Eclipsing Binaries’ Minima Monitoring Project (BIMA project) is a long-term observational program that focuses on a CCD photometric observations, specifically in the mid-eclipse timing or also known as time of minimum (ToM). This project aims to improve our understanding on eclipsing binaries either the nature of the systems or their evoution. Our basic goals are to obtain data of eclipsing binaries through CCD photometry, to determine the ToM for each system, to identify the period change in the eclipsing binaries, to build the O-C (Observed minus Calculated) diagram and give the analysis for each system, to explore the utilization of asinh magnitude system (or luptitude), and to build an open- database containing complete informations of the ToMs, periods, ephemerides, the light curves data, and the O-C diagrams of those selected eclipsing binaries. This project was initiated at Bosscha Observatory, Indonesia, in June 2012 and open for collaboration since. On December 2012, the National Astronomical Research Institute of Thailand (NARIT) has joined and become the main partner of the project. This project is conducted on the basis of multisite monitoring observations. There are three observing sites for this project: Bosscha Observatory in Indonesia, Thai National Observatory in Thailand, and Cerro Tololo Inter- American Observatory in Chile. A 0.2 m (f/10) Schmidt-Cassegrain telescope installed at Gunma Astronomical ObservatoryInstitut Teknologi Bandung Remote Telescope System (GAOITB RTS) house in Indonesia and equipped with a SBIG ST Series CCD and Bessell BVRI filters. The 0.5 m (f/6.5) Schmidt-Cassegrain telescope equipped with an Apogee CCD and L,R,G, and B filters and also the 2.4 m (f/10) Ritchey-Chretien telescope equipped with ULTRASPEC CCD and ugriz filters in Thailand. In Chile, we use the 0.6 m Panchromatic Robotic Optical Monitoring and Polarimetry Telescopes (PROMPT).


The General Catalogue of Variable Stars (GCVS) (Kukarkin et al., 1969) and the All-Sky Automated Survey (ASAS) database have largely been used to compile the target list. We only observe the eclipsing binaries that has an orbital period less than two and a half days. This criteria has been applied to all observing sites. More than 1000 eclipsing binaries have been selected. The prediction of ToM has an important role in order to facilitate efficient observation. Using the ephemerides given in Kreiner (2004) for all the eclipsing binaries, the observer can calculate predicted ToM. The ephemerides are provided at http://www.as.up.krakow.pl. Differential photometry method has been applied throughout the observations. A standard reduction of CCD images (bias and dark subtraction, flat-fielding) has been performed using the Image Reduction and Analysis Facility (IRAF). The instrumental magnitudes from each observation are obtained by applying aperture photometry. A computer program has been developed to generate the light curves. The observed ToM are computed using customized Python pipeline. From the observed ToM, we can build an O-C diagram, give the analysis for each eclipsing binaries, and identify the period change, if any. OC diagram is one of tools in close binary evolutionary study. The diagram built from observed of a reference phase substracted by predicted (or calculated) of same reference phase. From the OC diagram we can analyze the physical mechanisms that occur in eclipsing binaries.


Up to now, we have observed 148 eclipsing binaries systems and secured 90 minima (72 primary minima and 18 secondary minima) of 48 eclipsing binaries. Some of the eclipsing binaries have no significant period change, but some of them have significant period change. It is due to either the cyclical magnetic activity or a light-time effect caused by a gravitationally bound third star or mass transfer from one eclipsing star to the other or an abrupt change due to mass loss in the system or more complicated. Our database will be available and can be accessed on a website. We also explore the utilization of two magnitude systems, i.e. log10 and asinh magnitude system in order to increase the level of adaptivity for various quality of observational data. The utilization asinh magnitude system works well on data that has a low Signal-to-Noise ratio (S/N). But, so far, all the obtained observational data have quite high value of S/N so that the application of asinh magnitude will get the same value with the log10 magnitude.


Figure 1. BIMA Website for Open-Database.

Figure 2. Website interface for discussion forum.




1. Khairunnisa, S. A., et al., 2015, The BIMA Project: O-C Diagram Analysis of Four Eclipsing Binary Systems, Seminar Nasional Sains Antariksa, Bandung, Indonesia (awarded as the best poster presentation).
2. Haans, G. K., et al., 2015, The BIMA Project: O-C Diagrams of Eclipsing Binary Systems, Publ. of the Korean Astr. Soc., 30, pp. 205-209.
3. Ramadhan, D. G., et al., 2015, The BIMA project: Two years report and analysis of O-C diagram on V566 Oph, AIP Conf. Proc., 1677, 050012-1-5.


HEAD OF RESEARCH TEAM : Dr. Hakim Luthfi Malasan, M.Sc.

TEAM MEMBERS : Dr. Chatief Kunjaya, Dhimaz G. Ramadhan, Irham T. Andika, Sitti A. Khairunnisa, B.Sc., Gabriela K. Haans, B.Sc, Saeful Akhyar, B.Sc., Janette Suherli, M.Sc., Evaria Puspitaningrum, B.Sc., Dr. Puji Irawati, Dr. Andrea Richichi, Thawicharat Sarotsakulchai and Dr. Boonrucksar Soonthornthum.

OFFICIAL ADDRESS : Astronomy Study Program, Faculty of Mathematics and Natural Sciences, InstitutTeknologi Bandung, Indonesia.
EMAIL : hakim@as.itb.ac.id

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