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V480 Tau - normal fluctuation or outburst ?

Erwin Schwab's picture
Erwin Schwab
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Joined: 2012-09-09

Hello Experts

I am not an expert in variable Stars and also not in photometry.
I normaly make astrometry of minor planets.

On a series of 18 old frames (October 2011) taken in a total
duration of about 1 hour at Taunus Observatory (60cm Cassegrain+SBIG 11000)
I have seen a variable Star changing brightness. I found out
it is V480 Tau. V480 Tau should have an amplitude of 0,04mag and has a brightness of 5mag.
see:
http://www.sai.msu.su/gcvs/cgi-bin/search.cgi?search=V480+Tau

But for my eyes the amplitude seems to be higher.
Please have a look at my animation here:
http://erwinschwab.de/images/Animation-V480Tauri-ausschnitt.gif

I did not analyse the frames, because Iam not an expert of photometry
and for the astrometry software, which I use, such a wide apertur was not possible.

My question now is: Is that what you can see in the animation the normal fluctuation of 0,04mag?
Does anybody want to have the 18 frames for analyse or is it not so important?

Gruss Erwin
 

V480 Tau
SXN's picture
SXN
Online
Joined: 2010-03-12

Hi Erwin,

V480 Tau is a delta Scuti variable with a known amplitude and period. Range=  5.09 - 5.13 V and the period is 0.042 days. So you are right, the amplitude is much larger than reported in the GCVS.

For future reference, if you had checked VSX instead of the GCVS you would have obtained more accurate data on the star.

http://www.aavso.org/vsx/index.php?view=detail.top&oid=35497

I don't know if anyone is studying this star or needs the data. If you took the time to reduce your data and submitted it to the AAVSO database it would be there for anyone to use if they wished. Alas, we can lead you to water, but we cannot make you drink.

Mike Simonsen
AAVSO

sorry- misread your amplitude
SXN's picture
SXN
Online
Joined: 2010-03-12

My mistake. I read your amplitude as 0.004 not 0.04. It appears GCVS and VSX are in agreement after all.

V480 Tau
HQA's picture
HQA
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Joined: 2010-05-10

Hi Erwin,

Your animation is nice!  However, you are dealing with a 5th magnitude star that is over-exposed on your images.  The known variation of 0.04mag would normally be very difficult to discern on a set of images, so my guess is that the change in brightness during your animation is not real.  Either your software is automatically setting the grey scale differently on each image, and changing the apparent brightness of V480 Tau, or small seeing changes are causing the large variation.


You cannot tell anything about a star's variability unless you properly observe that star.  This means not saturating the star and making sure that you do proper dark subtraction and flatfielding.  You have a good telescope system that is capable of doing lots of good photometry of both asteroids and variable stars.  If you get interested in photometry rather than just measuring positions, let us know and we will give you some guidance and assign you to a mentor if you are a member.

Good luck and clear skies!

Arne

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484