VY Cet: a contact binary in a ternary system
Observed: 26 Dec 2006, 3 Nov 2007, 30 Jan 2009, 31 Oct 2014
|Season||Nb of images|
For the 2006, 2009, 2014 observations, the comparison star is 14CMC 015003.8-193156 (GSC 5857-01140) with the magnitudes B=12.702 V=12.120 Rc=11.790, computed from the CMC14 r' magnitude and the 2MASS magnitudes, owing to the transformations of Bilir et al (2008) and of Smith et al (2002). This a F5-G0 star.
For the 2007 observations, the previous comparison star is not in the field of view. Therefore, another comparison star is used: 14CMC 014852.0-193724 (GSC 5847-02044) with the magnitudes B=11.525 V=10.985 Rc=10.678, computed the same way as with the previous comparison star. This is also a F5-G0 star. However, for the 2007 observations to match the other observations, one needs to correct them by adding to the V magnitudes -0.06 and to the Rc magnitudes -0.02.
An example of light curves:
Blue: magnitudes with the B filter, Green: with the V filter, Red: with the Rc filter. The error bars are the 1-sigma statistical uncertainties (computed as the q-sum of the uncertainties on the variable and of the comparison).
The check star is GSC 5857-01297. The measured magnitudes and the uncertainties
on its measurements are given in the table below. The first ± is
the average of the statistical uncertainties (computed as the q-sum of
the uncertainties on the variable and of the comparison), the second one
is the standard deviation:
In 2006, a time of maximum (not minimum) is observed at 96.283 THJD.
This gives a time of minimum by subtracting P/4. One has then the following
times of minimum (the cycle numbers are computed from the L&N ephemeris):
|2006||96.198 ± 0.005||40,533|
|2007||408.388 ± 0.0015||41,449|
|2014||2962.423 ± 0.0015||48,943|
According to the ephemeris, these are all primary eclipses.
The corresponding O-C diagram from ephemeris of L&P:
With corrections to take into account the period variations, the phase
plot of all the data is:
Blue: with the B filter, Green: with the V filter, Red: with the Rc filter.
After interpolations (because the magnitudes with different filters are
measured alternatively, not simultaneously), the B-V and the V-Rc
phase plots are:
As usual with contact binaries, the color does not vary with the phase, i.e. the two stars are at the same temperature.
Bilir S., Ak S., Karaali S., Cabrera-Lavers A., Chonis T.S., Gaskell C.M. (2008) MNRAS 384 1178.
Kozlowski S.K., Konacki M., Sybilski P. (2011) MNRAS 416 2020.
Liakos A., Niarkos P. (2008) IAU Symposium, arXiv:1404.3124v1 [astro-ph.SR].
Smith J.A., Tucker D.L., Kent S. et al (2002) AJ 123 2121.
MBCAA Observatory. Copyright 2004-2015