[vsnet-chat 4704] Re: re SARVs - AU Ari

["Sebastian Otero" <varsao@sinectis.com.ar>]

> actually I should have said SARVs may now possibly be known as AU ARI
stars
> [hey you Harry stars perchance ;) ]
>
> Type star of the new Namelist 76 introduced SRS variability type, this
star
> is catalogued as having a magnitude range of 8.45 to 8.69 in the Hipparcos
> Photometric Magnitude system, with no period quoted.

Hi, John, Stan and all:

No period quoted... is it okay for an SR (whatever subclass it is)??
Anyway there is another thing: short amplitude is not the same as short
period.
I'm observing two interesting stars:
NSV 20018 is a K4II-III star that varies with a mean 0.15 mag. amplitude but
this is slightly variable. Maximum range is 6.8 - 7.13 in agreement qith the
available PEP(V) photometry. I have found that the period is between 27 and
30 days so it is a bona-fide SRS star (however it is not a red giant... so I
don't know if it exactly meets the requirements...). Given its amplitude is
also a SARV.
But NSV 6021 also shows small amplitude variations. This is a M2Iab red
supergiant . But it seems to be varying with a period longer than 100 days.
Also a 0.2 mag. amplitude but with mean magnitude changing over time. Range:
6.5 - 7.0.
GCVS classifies it as SRC again with NO period. Well, OK it is only a NSV
star. But it is not a suspected but a confirmed variable. So it deserves to
be in the GCVS but it doesn't STILL deserve an SR classification until we
are sure about the period.
NSV 6021 can be considered as a SARV but it is not an SRS because of its
period. Lots of stars may be in this situation, so
in spite of the new SRS type, I think SARVs may be worth of their own place
in the catalogue.


> Possibly SARVs have finally come home to roust with this definition, but
> interestingly a newly named variable as identified via Hipparcos data has
> been chosen rather than already known variables that have either been
> studied as SARVs by the Mount Johns group[s] or say Percy and the AAVSO
PEP
> groups with their SARV projects over the years.
>
> Especially as Hipparcos epoch photometry isn't ideal for periodicity work,
> and indeed is documented by the Hipparcos people themselves as being
> intrinsically unable to be solved for periods twixt 20 and 100 days, which
> is still within the SRS "window", whilst the above mentioned groups have
> generated fairly long photometry baselines for their project stars.

I'll be sending an interesting story of a very bright misclassified variable
star as soon as I have time.
There are lots of works and succesful projects that didn't make their way to
the catalogues, I don't know why.
As I told John, it looks like it is easier to get a new variable into the
GCVS than to improve or correct data on "old" variables when it becomes
available...

Cheers,
Sebastian.



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