Thu, 12/08/2016 - 14:37
To All
I have been doing EB observations now for about two years. I have been looking for a more detailed discussion of how to interpret the different light curve shapes and what may contribute to their shapes via the stars interaction. I thought that AAVSO might have some info on the website but I have not found anything to this more advanced level.
So far I have not found very much about this topic via web searches; it may be more of a college text book subject.
I am a mechanical egineer by trade and have no formal astrophysics training but I would be interested if anyone in this forum may offer suguestions regarding books etc on this subject.
John R
Hello John,
maybe that book from Hilditch helps you out. It starts with basics and overviews but in many places goes into details as well. I really dare to suggest that book.
https://www.amazon.com/Introduction-Close-Binary-Cambridge-Astrophysics…
Tonisee
Thanks for the link; i will look into it.
Sounds like this is a topic that many have been looking for tooo so I do not feel so bad with the request.
John R
Hi John, you ask a good question. I still haven't found a source that I am totally satisfied with, but here are some comments:
1) did you get to the "Bibliography" page of the EB Section pages? At https://www.aavso.org/content/bibliography The first 4 references are pretty good, but probably won't completely meet what I think you want. I'm thinking you want a treatment in more depth than Percy or Hofstadster, but more easily assimiliated than Hilditch.
2) Kallrath & Milones book (now in 2nd edition) "Eclipsing Binary Stars: Modeling and Analysis", while sounding promising, probably won't serve you either. It plunges in to detail about the Wilson-Devinney code, without doing a lot of development of "intuition" about the parameters.
3) ultimately, the way to understand what a EB lightcurve tells you about the geometry of the system, comes from modelling the lightcurve. I.e. generating a synthetic lightcurve given assumed or trial values of parameters that describe the system. One simple, and free, tool, is at:
http://astro.unl.edu/naap/ebs/animations/ebs.html
It lets you adjust paramaters and see the resulting light curve in real time.
4) the tool I like best is Bradstreet's BinaryMaker3 at binarymaker.com It costs $100. It is pretty full-featured (e.g. handles eccentric systems, with spots, can model different spectral bands incorporating the temperatures of the two stars etc etc). It also comes with a fair bit of tutorial material, as it is meant for a teaching environment. I think it does most of what the canonical Wilson-Devinney codes does, but in an easy-to-use package. (Doesn't do "Differential Corrections" though, i.e. numerically fine-tuning of the system parmeters)
5) PHOEBE (google it) is free, probably the most full-featured tool around, and I understand it has a GUI, but I haven't used it. You may have to compile it yourself... I believe it is the state-of-the-art code
6) for any of these, you are still stuck with figuring out enough of the system to be able to start modeling it yourself. The paper I like the best is Wilson's "Understanding binary stars via light curves", published by IAPPP 1994. At ADS: 1994IAPPP..55....1W
The key how-to bits start at page 9 "How to carry out a solution", and especially the "rules" on page 16. I recommend you do "proofs" or "derivations" of these rules yourself -- you'll learn a lot. Most are easy. Just the past few days I've been researching how to estimate eccentricity and longtitude of periastron "by inspection" of the light curve, i.e. as starting values for modelling and iterating. I have found something, but need to try it first to see how well the forumulae work...
7) model parameters are degenerate, i.e. not independent (someone will doubtless correct me about the niceties of my words here...). Changing one parameter doesn't change just one aspect of a light curve, it affects several, and vice-versa. Getting to a good model is a bit of an art.
8) I last used BinaryMaker to model a system about a year ago. I started with Wilson's "Rules", and tested the effects of varying each individual paramater... After "playing" with parameters for a while, and taking notes about what happened with I changed the parameters, I ended up with a plausible model. I estimate I spent several full days on it.
Obviously much more could be written about this... but hopefully this is a good start for you,
Gary Billings
Hi Gary
Thanks, I have been to the EB section a number of times but that page never "jumped" out as having to do with resource literature. Thanks for the references, I will check out some of these.
The simulator looks interesting, however as you mentioned it would be nice to have a little idea ahead of time as to what causes what shapes. Maybe it is not that predictable, I was hoping to gain some insight before digging that deep.
I have the book "Observing Variable Stars" by Gerry A. Good which details the different classes of variable stars the showns a typical light curve for most of them with little discussion. I was looking for something that might go into more detail obut the interactions etc.
Thanks ALL for your input I will explore these choices.
John R
GM Gary
Thanks for the link to the University of Nebraska-Lincoln simulator. It was very interesting to work the controls to change the parameters and see how it affected the LC. I understand that this simulator does not change the host of variables that BinaryMaker3 must have but it still gave a nice visual.
I ordered a couple of the books from the EB page last night and will read them when they arrive.
Thanks again for your and others suggestions. I think something that addresses this level of addition reference material would be interesting to see as a short CHOICE video like Arne did in the CCD class video on reference material with a little more discussion about the topic.
Wishing ALL a Merry Christmas & Happy New Year
John R
I pretty much echo Gary B.'s comments on BM3. Its pretty easy to use. I like it.
Gary W
Hi John (et al):
At the 2011 Symposium of the Society for Astronomical Sciencs (SAS), Dr. Dirk Terrell gave us a 3-hour workshop on EB lightcurves and modelling. It included a good "intuitive" explanation of how the light curve shape relates to the stars and their orbits.
I can provide a copy to you - contact me at oca_bob@yahoo.com
Bob Buchheim