Discrepant classification

American Association of Variable Star Observers (AAVSO)
Fri, 10/21/2022 - 16:39

Hi All. I met the subject ASASSN-V J060941.06-090201.8, classified as ROT, but in ASAS-SN website it is classified WVir pulsator. 

How can this discrepancy exist?

Franco Travaglino

American Association of Variable Star Observers (AAVSO)

Hello Franco,

These types of discrepancies are pretty common. There are a couple of reasons why. One is reason, specific to this particular star, is that ASAS-SN classifications are typically done through automatic pipelines and as such sometimes they are incorrect. It is also possible that the classification has changed and VSX is simply out of date. While we try to be as comprehensive as possible, with over 2 million variables there will inevitably be some that are mis-identified. This is one reason why we have the VSX submission process allowing users to research these discrepancies and if they find that VSX is out of date, then submit the proper correction with proof. More on this process can be found here:



Please let us know if you have any more questions.


Bert Pablo
Staff Astronomer, AAVSO

American Association of Variable Star Observers (AAVSO)
Catalogues, inconsistencies, etc.

Hi Franco,

the explanation in this case was more complicated and requires an important revision.
Consistency between catalogues is always work in progress, and as Bert said, revisions are being made constantly.

This star was added to VSX from the ASAS-SN recent list of g-band variables.
But that list is not online. What you find in the ASAS-SN online database is the (older) list of ASAS-SN V-band variables. The identifier is also slightly different, even when the star is the same one.
And the information in the ASAS-SN V-band database is telling you that the object is actually an ATLAS variable and not an ASAS-SN discovery.
Since the ATLAS catalogue hasn't yet been imported to VSX (format, classifications and the way they determine periods is more complex and thus that list has been given a lower priority), the star didn't make it to VSX.

About the CWB clasification in the ASAS-SN database, see that they classify it as such in the V-band catalogue and they published it themselves as ROT in the more recent g-band catalogue. You will find things like this all the time.
My recommendation is sticking to VSX, and submitting a revision, but only if you are sure that the new type you give is the correct one. Here "CWB" is older than "ROT", and there is no relation between the two classifications, they simply don't do a deep analysis.
I have just revised this record, primary name, discoverer and type had to be changed.
We can look for spectral types and Gaia DR3 information to know more about the star's luminosity in order to clasify it properly.
And it turned out it is a dwarf, some 8 magnitudes fainter than a cepheid. And colder. So the proper classification was BY.