Saturday, November 28, 2020

PMAK V27 Revisited

More than a year ago I registered PMAK V27 (, a variable that I found in my DSLR frames of the T UMi field.

At that time it was classified as NL: (Nova-like, uncertain) based on that it showed long-scale variability and a 'noise' pattern [ASAS-SN data].

Now, as far as new data become available (more ASAS-SN observations, ZTF points, and even a handful of observations posted to the AAVSO database by SFRA observer), and (that is even more important) I gained experience, I decided to work with it some more.

Here is the combined light curve:

DC DFT analysis (VStar) showed a clearly-visible peak corresponding to a period near 2.4 days. After removing the slow trend the peak became even more prominent.

Then I built a phase plot:

Now it looks like a phase plot of a rotating star with spots!

So, the star was reclassified as BY (thanks to Sebastian Otero for the final decision).

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