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TU Muscae - O type EB

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Robert Jenkins
Robert Jenkins's picture
TU Muscae - O type EB


To get going with EBs I chose TU Mus - a shortish period EB (1.38d) that is reasonably visible from where I live in Adelaide Australia.  So far I have worked in V band but plan to add B Band and I Band.  TU Mus had some work in 1975 and a suggestion for more work was included in the paper by Anderson and Gronbech.  From the postings in the AAVSO database it appears I am the only one working on it presently.  Does anyone know if anyone else is working on TU Mus? 

Note I am also working on BB Cru, WY Cru, XX Cru, CP Cru, BV Cen, EK Tuc, TT Cet and ZZ Car.  Well working on these is a bit of a mute point at present as Adelaide has been clouded out for the last 3 weeks. 

Robert Jenkins

BGW's picture
Southern EBs

Hi Robert,

I don't know of anyone observing TU Mus, but I'm not well-connected with southern obervers.   Being a relatively rare spectral type, I think it is a worthwhile star to follow.

Not to take you away from the stars that you have selected, but just to advertise:  the Otero+ stars discussed on the EB Section webpages include many many southern stars, as it was based on datamining the ASAS survey (as well as NSVS).  Most of these have few observations other than the discovery data, so predictions of the eclipse times can be off by several hours. A good challenge!

Re multi-colour observations:  are you planning to do fully transformed photometry?  That is great!  "We" should be doing photometry on EBs, over the long term, not just ToMs.  For the purpose of ToMs, I have mixed feelings about multi-colour observations.  I have seen observers publishing 4 ToMs for one night, based on their B,V,R,I data, all taken with one telescope.  What disturbs me is that I have seen the ToMs disagreeing from each other by more than their stated uncertainty.  Either something astrophysically interesting is going on, or all the ToMs are poor because each one is based on a sparse light curve (due to the camera cycling between all the filters).  I suspect the latter, rather than the former.  For purely the purpose of a ToM, it seems to me that it would be better to do just one filter?  Or perhaps two (just enough to transform?).  I am interested in other people's comments on this.

Kind regards,    Gary Billings

PCH's picture
Multi Color Observations EBs

If this is obvious to you Robert, my appogies.  I've been out of touch for a while.

With ToMs, the more observations in the light curve, the better in terms of satistics and curve fitting for ToM determination.  The time between observations as one cycles though the filter wheel would seem to detract from the goal of getting as many observations as possible, as Gary suggests.  The shorter the period of the EB, the more of a negative effect this would have on your period solution.  Yet, color changes of the system during eclipse would add useful astrophysical information.

I'm sure there is a way to quantify the trade off in the number of samples as a function of period, but I don't know it at this point. 

Your work arounds might include doing your multi colored observations from eclipse to eclipse.  One eclipse in B, one in V, etc.  This depends on the observing period of the star.  Another is to cut down your color options to something like B-V or V-I. 

Chuck (PCH)

(Making an appearence after a long absence)

Robert Jenkins
Robert Jenkins's picture
TU Mus

The 1975 research suggests Tu Mus is a semi detached system - not common with O class EB stars.  I intend to do as much work as I can and plan to do fully transformed soon.  The other EBs were chosen as they have reasonable magnitutide for my setup and are in a easily accessible part of the sky from my observatory.  I have been in contact with Tom Richards from Variable Stars South and let him know what stars I am working on.  These 1 to 4 day periods for the stars I have chosen should minimise filter cycling times that you can get with very short period variables where I would only use one filter.


RIX's picture
Southern EBs

Hi Robert

I'd recommend against using transformed data for minima timing. To transform you have to take two data points in different colours made (necessarily) at different times, and that smears the precision of any timing calculation. I use un-transformed data to get minima, then transfornm to get light curves.

Cheers, Tom Richards

Robert Jenkins
Robert Jenkins's picture
Minima and transformed data

Thanks Tom

It has been a long time since I posted this thread so thanks for looking at it..

Luckily I keep my raw images and calibrated images so I wil be able to go back and get the untransformed data.


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