O-C diagrams

Eclipse timings and O-C diagrams

I have obtained many monitoring observations of eclipsing binary systems and pulsating stars with the aim of determining the precise time of minimum and maximum light, respectively. These timings give the absolutely necessary information for the determination of orbital behavior of the members in a binary system, through the O-C diagrams (Observed time – Calculated time). Specialized observing programs aim to study the O-C diagrams and extract information about the Light-Time effect (LITE), basically due to the presence of a third body orbiting a binary system or a second body orbiting around a single star.

The O-C diagrams for the multiple systems XZ Aql and AT Peg. These diagrams uncovered the existance of an invisible companion, orbiting each system in an eccentric orbit.

The long-term monitoring of the pulsating star V1162 Ori

The international campaign on the pulsating star V1162 Ori was initiated in 1999 by Chris Sterken, and its goal was follow-up observations on this High-amplitude delta Scuti Star (HADS), in order to recover its multiple periodicities. The target appeared to have many pulsation frequencies as expected, as well as a very interesting O-C diagram, which show the presence of an orbiting star around V1162 Ori.

V1162 Ori is a High-amplitude delta Scuti Star (HADS), which was the first target ever observed from the University of Athens Observatory (images after Arentoft et al. 2001). The O-C diagram of the times of maxima revealed the presence of an orbiting star around it.

The binary nature of the pulsating star SZ Lyn

The pulsating star SZ Lyn is a perfect example of a HADS within a binary system. This target was observed for several years (2001-2021) and the O-C diagram has revealed the binary nature of this system (Gazeas et al., 2004, CoAst, Vol. 145, 49 and Gazeas et al., 2004, CoAst, Vol. 144, 26).

The High Amplitude delta Scuti Star SZ Lyn is a member of a binary system. The O-C diagram uncovered an invisible companion, with an orbital period of ∼1180 days.

Collaborators on O-C studies include:

  • Kosmas Gazeas, Panagiotis Niarchos - University of Athens, Greece
  • Alexios Liakos, Nikolaos Nanouris - National Observatory of Athens, Greece
  • Stazsek Zola - Jagiellonian University, Krakow, Poland
  • Marek Wolf, Pavel Mayer, Petr Zasche - Charles University, Prague, Czech Republic
  • Drahomir Chochol - Astronomical Institute, Slovak Academy of Sciences, Slovakia

  • Selected publications on O-C studies and times of minima calculations are:

  • Petropoulou M., Gazeas K., Tzouganatos L., Karampotsiou E., "110 minima timings of eclipsing binaries", 2015, IBVS, 6153, 1

  • Liakos A., Gazeas K., Nanouris N., "105 minima timings of eclipsing binaries", 2014, IBVS, 6095, 1

  • Chochol, D.; Pribulla, T.; Vanko, M.; Mayer, P.; Wolf, M.; Niarchos, P. G.; Gazeas, K. D.; Manimanis, V. N.; Brát, L.; Zejda, M., "Light-Time Effect in the Eclipsing Binaries GO Cyg, GW Cep, AR Aur and V505 Sgr", 2006, Ap&SS, 304, 93

  • Mayer, Pavel; Wolf, Marek; Niarchos, P. G.; Gazeas, K. D.; Manimanis, V. N.; Chochol, Drahomír, "Investigation of Times of Minima of Selected Early-Type Eclipsing Binaries", 2006, Ap&SS, 304, 39

  • Gazeas, K.D., Niarchos, P.G., "The Light-Time Effect in SZ Lyn", 2005, ASPC, 335, 297

  • Gazeas, K.D., Niarchos, P.G., Boutsia, K.A., "SZ Lyn: New pulsational and orbital elements based on old and recent photometric observations", 2004, CoAst, Vol. 145, 49

  • Gazeas, K.D., Niarchos, P.G., Boutsia, K.A., "SZ Lyn: New BVRI CCD observations and improved pulsational and orbital elements", 2004, CoAst, Vol. 144, 26


    Created by K.Gazeas, based on a template from Free CSS Templates