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Interesting light curve of RZ Cep, with double peak at maximum. Top graph is raw data, bottom a running average of observations to smooth out the noise. Two double peaks seen in raw observations, seen even more clearly in smoothed graph.


ED70, ASI1600MM-C & photometric V filter. 10 sec exposures with a gain of 0.



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1 hour ago, Dave Smith said:

That is an interesting curve. Any idea why two peaks?


I've do idea, but as it happens on two consecutive maximums I don't think its an artifact due to cloud or something.


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James, I may be endeavouring to teach my grandmother to suck eggs:

However the curve is very reminiscent of a "2nd order damping ratio". The curve as observed is also confirmed in a previous paper (attached). One can only assume, correctly or otherwise it is an artefact of the internal workings of the star in question; inasmuch that once the star erupts a harmonic is generated demonstrable by the light curve during which the system is endeavouring to return to equilibrium.  



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Interesting star! I am not an expert either, but VSX lists RZ Cep as RRC/BL, that is overtone pulsator with Blazhko effect. The "double" maximum, or "pre-maximum hump" seems to be a consequence from the particular pulsating frequencies of this star.

See for example:

Cester, B., and I. Todoran. "The variability of RZ Cephei." Memorie della Societa Astronomica Italiana 47 (1976): 217-228. (Link to harvard database)

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