American Association of Variable Star Observers (AAVSO)
Mon, 10/24/2022 - 03:24

According to VSX, LT Dra belongs to false variables CST, but GCVS shows rare type RCB.

Where is right info? Help please to understand :)

American Association of Variable Star Observers (AAVSO)
LT Dra information


In general I would trust VSX because it is updated daily, unlike the GCVS catalog which appears to be largely static.  However, regardless of your initial suspicions, you should then confirm your choice. If you look on GCVS there is a linked paper given which references where the variability classification comes from. The same linked paper is visible in the VSX page under Remarks, however, there is also a second note:

"follow up studies and visual inspection of Messina's light curve show that variability is spurious."

This means that upon further review of the data, the conclusions mentioned in that paper appear to be incorrect and so this star is listed as a false variable. Further proof is given in the references section which shows the follow up studies on this object. This is the best way to test contradicting information, by looking at the remarks/references section. Hope this helps.


Bert Pablo
Staff Astronomer, AAVSO

American Association of Variable Star Observers (AAVSO)
A lot of thanks for your…

A lot of thanks for your kind explanations! Indeed, I have to read remarks.

But, truly speaking, I would prefer to think about huge cloud of carbon black, but not about instrumental effect :) Betelguese gave good example of "serendipity".

American Association of Variable Star Observers (AAVSO)
Revision history

Hi Mikhail,

as Bert explained, VSX is usually more up to date than the GCVS since we constantly revise the information shown. The revision history at the bottom will show you all the changes that were made. That way you will see that the VSX revision came after the GCVS import.
Furthermore, you can click on the revision history number and see how the star record was at a given time.
E.g. Revision #1 says it is an RCB, so the current information is a correction of such original information.

About your theory of a carbon cloud, the light curve would be pretty different. And the star is a K5 giant, there is no reason for it to show such kind of behaviour, you can't compare it with Betelgeuse.
There is no doubt that this star's original variability report was spurious.