Hello everybody,
I am sure my question will be frankly outdated, because I am asking this after a long time of being a member of this association. But, how do we know what we know about light curves? Is there a book that explains why the shape of a given light curve is, lets say, produced by an eclipsing binary? How did we find out that the fin-shark shaped curves are of pulsating variables?
Hope this doesn’t dissapoint (annoy?) anyone.
Cheers,
Enrique Boeneker (BETB)
We all stand on the shoulders of giants who came before… A paraphrase of the original attributed to Sir Isaac Newton.
The accumulation of knowledge.
I suppose, Percy J.R. Understanding variable stars will be enough for the beginning.
In the case of detached eclipsing binary systems (e.g., Algol, beta Per), the light curve can be deduced from careful analysis of the orbital motions of the system. The start and end of each eclipse can be seen clearly, and measurements can provide relative data (ratios) of certain parameters, such as the brightness of the two components of the system and the ratios of the dimensions of the two stars. For close binaries, analysis of the light curves is more complex, where the curves are smooth, and the start and end of each eclipse cannot be seen from the curves.
High resolution spectroscopy of EBs allows radial velocities to be determined throughout the orbital period, and thus provides direct evidence of orbital motions.
In the case of pulsating variable stars, again radial velocity measurements reveal the alternating motion of the surface of the star toward and away from Earth, thus providing direct evidence for pulsations.
Roy
As books go perhaps “Light curves of variable stars: A pictorial atlas” byt C. Sterken and C. Jascheck (1996) Cambridge Univ. Press is one I have.
The AAVSO has a broad general write up here… Types of Variable Stars: A Guide for Beginners | aavso
Enrique:
I also highly recommend Percy’s book to learn about the variable star types!
Ken
Note that Algol is a semidetached binary, not detached. This is a common misunderstanding based on an unfortunate historical use of the term “Algol-type light curves” for the light curves of detached binaries. Detached, semidetached, overcontact and double contact binaries are names based on the physical morphology of the binaries. Algol-type, Beta Lyrae type and W UMa type names come from light curve morphology (shape) and are much less instructive about the physical characteristics of the binary.
On the topic of the original question, you might find this paper by Bob WIlson instructive:
https://binaries.boulder.swri.edu/papers/rew_iappp_94/
There is Percy’s 2007 book of course, as others have recommended. I’d like to also mention “Variable Stars” by Hoffmeister, Richter, and Wenzel. Originally published in German, published in a fine English translation in 1984, by Springer. Extensive information about all types of variable stars, with many many professionally prepared figures. I see it available on Amazon in softcover. I am very glad to have a copy of this book.
Gary Billings
Wow! An expensive book indeed (all of them are expensive, I see). Thanks for the tip!
Yah, none of them are exactly in the “mass market paperback” category.
Enrique,
I would highly recommend the the Classification and Light Curves CHOICE course. In 2025 it will be offered in April. It is well worth the time and effort. If you’re an AAVSO member it might even be less expensive then some of the books. The course descriptions is below.
Usually, the course enrollment opens about two weeks before the class starts. Sign up early!
Phil
Variable Star Classification and Light Curves
This course is an overview of the types of variable stars most often observed by AAVSO observers. We explain the construction of light curves and phase diagrams. We discuss the physical processes behind what makes each type of variable and how this is demonstrated in their light curves. We link these salient features of the light curve to common observing practices for each type. Variable star names and nomenclature are placed in a historical context to aid in understanding today’s classification scheme.
Phil, thank you!
I took the course this year. It was indeed very useful. But I want to get deeper… Thanks for your offer, I indeed recommend this CHOICE course a lot.
Cheers,
Enrique (BETB)