Thu, 02/28/2013 - 16:03
hello,
we are student from belgium and on our school we are doing a project on cataclysmic variables.
with our group we are going to use a telescope and at the end use the information to make a lightcurve of a cataclysmic variable.
our question is: wich are the best known cataclysmic variables and are active and visible these days.
thanks already for your help
vlaanderen
PM send from WVS VVS (Belgium)
Several good ones coming up...
Z Cam is now high in the sky. It's currently (as far as I know) going through a standstill.
YZ Cancri is an easily-found, very active Cataclysmic.
SY Cancri is another one.
SS Aurigae
X Leonis
All these have outbursts that are easily seen in small telescopes.
I would recommend HL Canis Major. It has a short period with nice regular variations between 10 or 12th magnitude maximum and 14th magnitude minimum. The only difficulty is its just 9 arc minutes South of the brightest star in the sky - Sirius!
You didn't say whether your observations are to be visual or CCD, or the aperture of the telescope you plan to use (or the quality of sky you have). If you supply this information, it's easier to recommend targets.
But...assuming you mean visual and use a 20cm telescope, then I would recommend AB Dra. It's circumpolar (I think from Belgium) and doesn't suffer from Moon intrusion as would a CV on the ecliptic. This would mean that your light curve would develop quicker. It's fairly bright during outburst (12th magnitude) and around mag. 15 at minimum. It can also have three (occasionally four) outbursts a month. X leo is another good target, but you will struggle to get this at minimum unless you use a large telescope. SY Cnc is good because it's bright in outburst, and at 13.5ish at minimum you will see it in small scopes. Both of these objects will at some time during the month become unobservable due to the Moon. During the morning hours AH Her is a nice star to monitor as it's bright in outburst and doesn't go too faint at minimum. It can (and often does) have standstills though.
Let us know how you plan to monitor these CV's.
Gary [PYG]
IIf you haven't done CVs before I would suggest a couple of reasonably bright old favs- Z Cam or SS Cyg
Z Cam is at high decl . Range is approx 11 during outburst to 14 at min. Interval between outbursts is roughly a month. Its claim to fame is that it has "standstills" -i.e, it gets stuck in between minimum and maximum. In fact it is currently in the standstill state. If your studies show it doesn't change then you have verified it is still in a standstill and if it goes into an outburst you have dcumented the end of the standstill. No way to predict when the standstill will end either.
SS Cyg is probably the best documented CV so it will be an easy task to check your work against others. Currently in the morning sky, it averages a bit under 2 months between outbursts and is currently at minimum. Magnitude range is roughly mag 8 to 12. Given its behavior it should go into outburst fairly early in April.
Both Z Cam & SS Cyg are good targets - but if you want a light curve to analyse, then maybe Z Cam isn't the star for you right now. This current standstill might end tonight, or indeed continue for months. You need to see some variation so that you have something to work with at the end of your project.
It's easy to assume that SS Cyg is an easy target in the morning sky right now, and to seasoned amateurs it is. But if your not used to getting up at 2am to observe in the cold morning sky, then it can be a challenge. If your project runs into the late Spring, then why not add SS Cyg to your list, but you won't get frequent outbursts as you will with other targets. It all depends on how long your project lasts.
Belgium has a very good Variable Star observing group, with a number of very experienced amateurs. Have you asked them for advice? It might be easier to do so in your own language (not that your English is bad, it isn't). You may even get a visit from one of them to give your group a talk on CV's! The web site is...
http://www.vvs.be/werkgroepen/werkgroep-veranderlijke-sterren
Good luck!
Gary [PYG]