the variability of sunlike stars

[notFritzArgelander]

https://phys.org/news/2020-09-starspots ... stars.html

[ThinkerX]

Brings back memories of sifting through the ASCC (All Sky Compiled Catalog). That boasted a column for variable stars, and there were a lot of 'suspected variable' and 'variable or double' entries...but no other info at all that I could find, anywhere.

[notFritzArgelander]

Brings back memories of sifting through the ASCC (All Sky Compiled Catalog). That boasted a column for variable stars, and there were a lot of 'suspected variable' and 'variable or double' entries...but no other info at all that I could find, anywhere.

When I was in school the details about variable stars were maintained from 1948 on https://en.wikipedia.org/wiki/General_C ... able_Stars

Up to date info is at http://cdsarc.u-strasbg.fr/viz-bin/cat/B/gcvs

http://www.sai.msu.ru/gcvs/gcvs/

[ThinkerX]

Fritz, Vizier has an abundance of variable star catalogs - some with tens of thousands of entries. The ASCC actually incorporated a couple of them in a separate column. The ones I was referring to were (probably) in the mid six digit range (I was concerned with only a small slice of the whole.) For those, there was no other information - it looked like decisions made by the Tycho team. (Tycho being one of the base catalogs for the ASCC).

[notFritzArgelander]

Then I don't understand the problem. :Think:

[ThinkerX]

Then I don't understand the problem. :Think:

Went back t the ASCC - notes for the relevant columns:

First note, for stars in the standard catalogs:

Note on v1 : Byte 292 from Tycho-1 file tyc_main.dat This flag is set when the variability is known:
G = variable known in General Catalog of Variable Stars
N = variable known in New Suspected Variables catalog Substituted with blank if no data

Second note, for the Tycho data:

Note on v2 : Byte 294 from Tycho-1 file tyc_main.dat This flag has the following meaning:
U = apparent variability in the Tycho data; may be due to duplicity
V = strong evidence of intrinsic variability
W = suspected intrinsic variability Substituted with blank if no data

Now...one would expect there to be substantial overlap between the two columns: that is a star listed in the 'General Catalog of Variable Stars' would have some sort of flag in the Tycho column. And much of the time, there was. But there were also no small number of cases where that was not the case: the Tycho column missed stars flagged in the 'known variables' column and probably 70%+ of the stars flagged as variable in the Tycho column were not listed in the column for the standard catalogs.

I tried spot checking many (hundreds? not sure) of the 'Tycho only' entries - used a feature of Vizier that searches *all* of the catalogs for info on specific stars. Usually, that flopped big time - the only catalogs indicating variability or duplicity were those based on Tycho. Combined with other issues...well...that was when the 'too many unknowns' mantra began.

(this is probably where Fritz petitions to have me banned from mucking about with gigantic astronomical databases)

[notFritzArgelander]

Yes. The catalogs have problems.