RX Cassiopeiae / RX Cas
Light curves and phase diagrams of the DPV:/EB/GS type eclipsing binary RX Cassiopeiae / RX Cas. For an explanation of this type see here.
The following light curve and phase diagram were constructed from photometry of 65 images taken with the Bradford Robotic Telescope Cluster Camera (BRT) between 2012 September 23 and 2016 October 1, and 284 images taken with the Open University COAST telescope between 2017 July 10 and 2023 April 14. The BRT data is in blue, while the COAST data is in black (previous observations) and red (latest additions, 2022 June 7 to 2023 April 14). The COAST observations were made with a Johnson V filter, but the BRT observations were made variously with no filter (CV) and a tri-colour green filter.
The period used for the phase diagram is the 'best fit' period suggested by Peranso. This differs from the catalogued periods, 32.32789d (GCVS) and 32.3257d (AAVSO VSX) [Accessed 2023 May 9].
Monochrome versions of the light curve and phase diagram are given below.
This is a complex system, its variabilty type is given as DPV:/EB/GS by the AAVSO VSX. Not only is there a 'primary' period of approximately 32.3 days, there is also a variation in the values of the maximum magnitudes over periods of approximately 500 days, among other periods. Using Peranso, and removing the 32 day period from the period search ('prewhitening'), a period of 535 days was evident in the above light curve. This period is hinted at in the light curve from my observations as a variation in the maximum magnitudes.
These irregular variations, and the asymmetric phase diagram, might be due to the presence of an accretion disc and mass transfer between the components, as in W Ser type eclipsing binaries, see Anderson et al (1989), Pustylnic et al (2007) and Mennickent et al (2022). This phenomenon has been discussed by D Loughney (2015) where a period of 517 days is suggested from the literature. Also, see AAVSO VSX page for this star for more information.
A 'cartoon' of what this system might be like, generated in PowerPoint(!) appears below, showing an accretion disc around the smaller, hotter star.
A 'cartoon' of what this system might be like, generated in PowerPoint(!) appears below, showing an accretion disc around the smaller, hotter star.
There is ongoing research into this system, and it remains in my current observing program.
[This page updated 2023 May 9]