Affiliation
American Association of Variable Star Observers (AAVSO)
Sun, 01/27/2019 - 05:34
I am attempting to learn light curve analysis as applied to SR variables with more than one period. Method is to pick SRs for which periods have been published in the peer-reviewed literature. Kiss et al (2000) found V CVn to have two periods, 194d and 186d. Using Peranso's CLEANest algorithms I found:
186.5 (theta 3801.6, freq. 0.00536)
195.55 (theta 523.26, freq. 0.00511)
97.7326 (theta 448.97, freq. 0.01023)
It seems to me that the 97.7326 is a harmonic of 195.55 (195.55/2 = 97.775) and thus not a period. I would love some feedback from anyone familiar with light curve analysis on this conclusion. Also, should I expect harmonics to have approximately the same theta-value as the fundamental?
Thanks, Ed
Hi Ed,
There are several references concerning the phases of combination and harmonics that I've seen. Foster's book " Light Curve Analysis" (a great reference if you don't already have it) has some. M. Breger also has some articles that discuss this as well as Dominic Bowman and L.A. Bolona. Most of Breger's and Bowman's stuff is dealing with Delta Scuti or G Dor stars but is relevant to any. Here is a link to one of Bolona's articles: https://watermark.silverchair.com/mnras0422-1092.pdf?token=AQECAHi208BE49Ooan9kkhW_Ercy7Dm3ZL_9Cf3qfKAc485ysgAAAlgwggJUBgkqhkiG9w0BBwagggJFMIICQQIBADCCAjoGCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQMvOjXl-POu7c-UbVtAgEQgIICC-c7C64mALnTLvonu2ZKKtbuE0G24mbzhJ30yN1EjM7RshGJG8ma3AuF7EIoaAJddcwdBaQ80I8-5_25FCD8JswO691mgPf9_sGcMAvYIIY0SJe6KsFviE0AsWDJLQGAaLWD5HfGHWqjo4etaPHq0eS9PwQjPI_axrkaBnrKyyFQMcmOX3_hQHJ3HaD1q6KwQRtA4hK6I4HN4EeMdDM7z_i3IMvQb-gxWj6ACC17SGUBtrOunvJYn_96AkmaG1lHIxlEF5GsO2lsY2cj0vaoOlqHIec4cBjgLEnxGHCcURs-8V-xsSzM_-YnIxjI14uTjLrDcLe3q4U2VCgY7JD_JJ_Vr84lufg32KV6DMsGZ-PfVTj3kNGqEoPpIqbeIZG5CMZNDGhA5kqkHpkWrg0cRbXtRc1wr01MS5il38n8EkbrTLpM2p6nTduwxg5r8yJrkfFPfyPCz9Bngtdn31GPahZ7K1cUxPaeWV8NFed-XFu6ReIuN2aFGqCeCZWGO01FcBH1QRygn1z45XjhZVvUd2ISX-UVFQFfp223DXDSiNoNPVToIBYbQXs7DC5iTYqLfwY5MDzYd1bVhffstVLwglYhzrVwuh5slOfSCsGsU-cFHOunsmcZNcR8FOcqR3-tfTgE2D4sxY97psc__Em6WWgFAwNdLZrQvj9tEgPjkhu3NI6i7dSfK6i9NaU
I hope this helps.
Duane
Thanks, Duane:
The link does not work but simply searching for mnras0422-1092 does. Yes, I have and have read the Foster book and have reviewed many SR variable papers that address multiple period analysis.Thanks for the Balona paper and I think I can get to the others via the lit cit.
One of the problems for one learning a new skill is not so much the theory of something like harmonic signal but finding practical examples where particualr results are rejected and why. Did Kiss et al. (2000) find the 97.7326 (theta 448.97, freq. 0.01023) period signal? Did they reject it as a period because it was a harmonic of 195.55 (195.55/2 = 97.775)? This is the sort of stuff that newbies like me need to learn.
Ed
Hi Ed,
Yes, the ~98d period is the first harmonic of the 196d period. It means that the 196d period does not follow a perfect sinusoidal curve, e.g. the rise may be a bit faster than the fade. There is no reason for the harmonics to have the same power as the main frequency, their power will normally be a lot less as the light curve in many cases only deviates slightly from a sinusoid.
Patrick