I have just recieved my SRP( Student research project(Experiment)) for science and am wanting to observe this variable star to confirm its variability.
Though I can't find any comparison charts anywhere on the net.I have a 12'' dob with 50mm finderscope.
I was thinking either to use the dob or the finderscope.The variable star is in the 6-7 magnitude range and can be easily seen through the finder.
Do any of you guys know were I can find some comparison charts?
Yep, type in R ARA. To get some mags with VSP, change the FIELD OF VIEW box to 420 (7-deg). Also, change MAGNITUDE LIMIT to 10 so you don't get too many stars showing, and select the YES option for lines to magnitude labels. This will bring up some comp stars - not great for R Ara for visual observing (OK for photometry) - R Ara varies from mag 6.17 to 7.12 - but it looks like all you've got from AAVSO. I did run it out to 15-deg for no benefit. Older RASNZ charts may have a much better range of comp stars but I'm not sure how you get them. I'll look into it.
Joining AAVSO costs money, but you can register as an AAVSO observer for free, and get most of the benefits. You get a 3-digit observer code. Mine is KBJ.
Good luck Orestis! Keep us informed of your progress.
R Arae itself is an algol-type eclipsing binary (mag 6.17 to 7.32).
It is also a component of the close visual binary star (HJ 4866AB), its companion being mag 7.8 about 3.3 arcseconds away.
See here ... http://adsabs.harvard.edu/full/1991Ap%26SS.180..233N
I'm guessing that observations of light variability will be complicated by the close visual star i.e. a composite of both stars.
R Arae itself is an algol-type eclipsing binary (mag 6.17 to 7.32).
It is also a component of the close visual binary star (HJ 4866AB), its companion being mag 7.8 about 3.3 arcseconds away.
See here ... http://adsabs.harvard.edu/full/1991Ap%26SS.180..233N
I'm guessing that observations of light variability will be complicated by the close visual star i.e. a composite of both stars.
Regards, Rob
Hi Rob,
I posted a while back asking if i could do an experiment like this and you gave me very helpfull advice ,you said to confirm historic evidence of a star being variable,so that is what i am going to try to do.
I though that the companian mighty be a problem but then thought that if the companian is of fixed brightness it wouldn't hinder the results.
Right or wrong?
I haven't found any observations of this star by amatuers,and don't know how hard it will be,though i confirmed yesterday through a gap in the clouds that i can see it through my 50mm finderscope.I don't have any good binoculars.
Having the visual companion so close might make it a little difficult to distinguish the variability visually, but it's a pity you don't have a CCD and some UBVRI filters for it. It would be so simple to generate some light curves for the star and having the close companion (so long as it wasn't variable itself) would be a bonus as you would have a good reference star close by with which to compare to any changes in brightness of the variable. It's always good to have at least 2 comparison stars and the more you can have the better your results will turn out. 4 to 6 is usually the optimum number of comparison stars.
Having the visual companion so close might make it a little difficult to distinguish the variability visually, but it's a pity you don't have a CCD and some UBVRI filters for it. It would be so simple to generate some light curves for the star and having the close companion (so long as it wasn't variable itself) would be a bonus as you would have a good reference star close by with which to compare to any changes in brightness of the variable. It's always good to have at least 2 comparison stars and the more you can have the better your results will turn out. 4 to 6 is usually the optimum number of comparison stars.
Thanks,
If this doens't work out does anyone have any other eclipsing binary star suggestions for evening observations.
Cheers Orestis
Last edited by orestis; 04-06-2011 at 03:18 PM.
Reason: spelling
It's not crucial that the experiment "works" exactly to expectation. That's science! You construct your aim, experimental method and gather results. Then analyse and draw your conclusions. If everything does not go to plan e.g. as compared to historical values , you put forward possible reasons for deviation or the inability to reproduce results e.g. equipment used, not enough variation in magnitude or the closeness of the companion to R.
I calculate that visual observations of the composite star (R & companion mag 7.8) should vary from about mag 6 to 6.8 based on the 6.2 to 7.3 for R Arae itself. In comparing historical values you should factor this in.
Here is a table to help you with the composite magnitudes ...
R + companion at 3.3" ---> composite magnitude of the two
6.2, 7.8, 6
6.5, 7.8, 6.2
6.7, 7.8, 6.4
6.9, 7.8, 6.5
7.1, 7.8, 6.6
7.3, 7.8, 6.8
And as Rob said, don't worry if your research doesn't turn out how you expect it...most of the time it never does. There'll always be little (or big) things crop up which throw a curve ball in your results.
I'm a bit lost here about worrying about the influence of the companion. Isn't the objective of observing an eclipsing binary the eclipse itself? If Orestis just wanted a variable star, he could pick any number that aren't binaries.
Outside eclipse, the observed magnitude is the net contribution of both stars, while the deep eclipse is when the dim companion eclipses the brighter companion, and there can be a secondary shallower eclipse where the brighter eclipses the dimmer.
WX Sgr is a nice example in our mid evening skies at the moment, and shows both. Mightn't be ideal for your purposes Orestis, with a period of 51.1 hours and an eclipse lasting 7.3 hours from start to finish. It's not like you'd see it all in one night. Bit dimmer than R Arae too, and similar problem with comp stars. Better magnitude range in AAVSO's VSP if you chart wide, but again you have to go outside the telescopic FOV, very difficult for visual estimates.
Anyway Orestis, you might be able to find a better one than WX Sgr. The eclipses can be quite stunning - here's an animation I did a year ago of WX Sgr 'normally', in eclipse, and back to 'normal'. Look for a star left of centre.
The companion to R is very close and trying to do a visual estimation of the variability will be a lot harder. In the system there's the EA binary, R Ara, and then a close by visual companion (3.3") only a shade dimmer than R itself. It's that close by companion which throws in the extra spanner, for visual observations.
Eclipses in binary systems only occur if the orbital inclination is favourable from our perspective. In EA systems, most only show partial secondaries at best and to detect some of them you need fairly sensitive instruments.
Thanks guys for all you helpfull advice,I was only thinking of doing an Eclipsing binary because i'm absolutely fascinated by them.I could just do a Cepheid instead if i can't find a EB.
I'll get a good one and let you guys know how i go.
If you are keen on an eclipsing binary, easier to observe than R Arae is the beta Lyrae eclipsing binary V1010 Ophiuchi, magnitude 6.1 to 7.0, period 0.6614 days (SIMBAD). It conveniently lies about midway between a magnitude 6.0 star (48 arcminutes away) and 7.1 star (57 arcminutes away), which is close to the range of variability of V1010. There is also a magnitude 6.4 and 6.6 star not too far away. Also, Ophiuchus will be in the evening sky for many months now.
See chart ... http://www.aavso.org/tmp3/d23346.png
If you are keen on an eclipsing binary, easier to observe than R Arae is the beta Lyrae eclipsing binary V1010 Ophiuchi, magnitude 6.1 to 7.0, period 0.6614 days (SIMBAD). It conveniently lies about midway between a magnitude 6.0 star (48 arcminutes away) and 7.1 star (57 arcminutes away), which is close to the range of variability of V1010. There is also a magnitude 6.4 and 6.6 star not too far away. Also, Ophiuchus will be in the evening sky for many months now.
See chart ... http://www.aavso.org/tmp3/d23346.png
It looks like a great star to do with the comparison stars being close.
Though the period is half a day and I don't know if this will be a problem,how many observations should i make in a night.I have printed off charts for it.
I tried last night,I found R arae but the comparison stars were in a very diffcult postion to compare it to the other comparison stars.
I was going to try for V1010 Oph but it clouded up before it rose enough.
,
.I have a 12'' dob with 50mm finderscope.
