Welcome to the Eclipsing Binary forum

American Association of Variable Star Observers (AAVSO)
Tue, 06/17/2014 - 16:18

Welcome to the Eclipsing Binary (EB) Forum.  We have set this up to complement the new EB Section web pages.

EBs are interesting to observe!  There are many phenomena we can measure: the light variations due to eclipses, changes to the interval between eclipses, variations in the depth of eclipse, changing intervals between the primary and secondary eclipses, and intrinsic variability of one or both stars.  The time spans range from one night, to years, but all are readily detectable.

AAVSO set up the "Eclipsing Binary Committee" in 1965 -- we expect and hope that observations will continue far in to the future!  Please use this forum to contact other EB observers, and to discuss observations of eclipsing binary stars.

Gerry Samolyk, and Gary Billings

American Association of Variable Star Observers (AAVSO)
Advice for working EB's

Is there a set of guidelines for observing EB's? I've been staring at LPV's for years; looking to try something faster!

- What is an appropriate cadence for observations? Maybe as a function of expected period.

- Do you want just V obs? Is BVI useful?

- Should the data be transformed?

- What is the best source for observation planning? I'm looking at RHO's tool: http://www.rollinghillsobs.org/perl/calcEBephem.pl   Shawn confesses that the EB data is a bit old but has vowed to update it before the new year.

- Is the goal to get a timeseries that spans the whole cycle? Or is just catching the minima/maxima the goal?


American Association of Variable Star Observers (AAVSO)
Working EBs

Hi George...

Have you taken a look at the EB Section web pages?  


There is quite a lot of material there.

Most EB observing is for times of minima (ToMs), usually shot with a single filter, and hence untransformed.  Usually the time series just "covers" an eclipse.  I see that some people "cycle through their filters" as they take a times series.  "Someone" should make a study of this some time, because I worry that these 4 series yield 4 ToMs that are less accurate that one single filter series would produce.

So, what I do, is time series in V only.  I am trying to get to my huge backlog of data:  my intent is to publish the ToMs, and put the differential photometry in the AID.  Three are also a few stars I am observing quite intensively, e.g. V571 Lyr that I discussed at the Spring Meeting.

That said, if you are interested in a particular star, it can be fruitful to build up a full cycle light curve of "proper photometry" (multi-colour transformed), and if you are so inclined, "model" the system.  Note that eclipse depths can change, the individual stars can be intrinsically variable, etc.  More commonly, the system might be eccentric, and there could be apsidal rotation causing the phase of the eclipses to vary.  My point is that there be value in observing more than just the time of primary eclipse, but most observers concentrate on observing ToMs and publishing them, doing continuous time series on one star per night.

So, what do I do personally?  I like to observe the ToMs of EBs with periods greater than 2.5 days (they are less commonly observed), and especially the "Otero+" stars (described on the EB Section web pages), because many of them have not had an eclipse timed since the original publication, many of which were based on observations from 1999-2000.  Many have not been observed enough to tell if the eclipses are total are not, and the predicted eclipse times can be off by many hours.  I have a script that goes through the list of Otero+ stars in a given constellation, determines what might be eclipsing tonight.  Then I check the BRNO site to see if has been observed at all, and perhaps "suss out" if it is an interesting star.  I also search the IBVS for publications of recent ToMs that might not have made it to the BRNO site.  I live at 51 N, and my mount lets me observe below the pole, so I work on stars in the high dec constellations like Cam, Cep, Dra.

Another, more mainstream activity, is to observe the stars in the "Legacy List", for which you can find predicted ToMs for the current year in a document at the EB Section website.  These stars have a long observational history and many show interesting O-C behaviour (see the BRNO site), so it would be fruitful to continue that.  The challenge is that many of these are probably over-observed (there are a lot of EB observers, especially in Europe).  I assess that using the BRNO site.  For most of them a couple of ToMs per year is probably sufficient.

As you probably know, JAAVSO publishes ToMs, but AAVSO does not maintain a current database of ToMs.    I recommend the BRNO website and the LkDB as the most uptodate available.

I hope this helps,

Gary Billings

Royal Astronomical Society of New Zealand, Variable Star Section (RASNZ-VSS)
Multi filter and ToM


One method to do multi colour photometry while finding ToM is to use a sequence like VVVVVBVVVVVBV...  this way you get plenty of saturation in the one colour for finding an accurate ToM plus enough of another colour to transform your data.


Astronomical Society of South Australia (ASSAU)
EBs in South Australia

Hi All

I am glad to see this EB forum up and running.  I have been working on EBs with Variable Stars South and submitting data to AAVSO on a range of far southern EBs; e.g. in Musca.  There is a small interest group in South Australia (members of the Astronomical Society of South Australia) working on EBs including the indomitable creator of VStar, David Benn.


Astronomical Society of South Australia (ASSAU)

In South Australia's case the emphasis is on quality over quantity, eh Robert? laugh

Robert's been doing great work on various eclipsing binaries.

I currently mostly observe pulsating stars (LPVs, Cepheids; visual and DSLR photometry), novae, and sundry others (e.g. eta Car) but I'm certainly interested in making more EB observations. My last was BL Tel (visual and DSLR).

Indeed, I'm especially interested in EBs suitable for wide field DSLR photometry because this suits my equipment and low budget; I have teenagers after all.


A Riddle/Poem for my senior AAVSO members!

Hello fellow Aavso members:

I am new to Aavso and wanted to share a little riddle/poem I wrote this morning that I am sharing with you all.  Oberving Sirius image on Slooh Telescope insired me:

"The hunter follows the bull,

The great dog follows the hunter,

The pup follows the great dog and

I feel like following the pup!"

This is an easy riddle for my senior Aavso binary star members.


But now I need some help:

How could I locate the light curve for Sirius-Alpha Canis Major?

I tried in Light Curve Generator but could not locate it!

Thanks in advance for your help.

American Association of Variable Star Observers (AAVSO)
not eclipsing, not variable

Sirius is a famous binary -- but not an eclpsing binary.   Thus you won't find a light curve showing eclipses.

Finding Sirus in VSX is a little bit tricky.  I searched on the name Sirius, which offered the synonym NSV 17173, which has other synonyms including "alf CMa A" ...   and it is listed as "CST:" .   The CST means it is constant, i.e. not a variable star, the colon means there is some uncertainty.  VSX also says there is only one observation in the AAVSO database.  So that doesn't make for much of a lightcurve.

Photometry of very bright stars, by any means, is challenging...

I hope this helps,

Gary Billings

not eclipsing, not variable

Thank you so much Gary.

This is my learning curve.

However, I am definately interested in Eclipsing binaries for will be looking for more appropriate targets.

Any suggestion for a new beginner like me?

Initially I will be a Visual Observer.  Later I hope to use my 6" Telescope and DSLR with some guidance from my mentor.  I came from the background of Astrophotography and now want to advance my skills to Photometry of Variable Stars!  

Very fascinating field!!

Thanks again for your valuable time!  Sabastian is helping me find a suitable mentor so I can begin my Journey with Aavso.

American Association of Variable Star Observers (AAVSO)
"Legacy" stars

I suggest starting out observing some of the Legacy stars (that were discussed on the webinar, and some info is available via the EB Section web pages).  They are interesting, but the predictions of eclipse times aren't too bad.  

I hope you can connect with a visual observing mentor, who can guide you re what is is suitable for your equipment etc.

Gary Billings