[vsnet-chat 4437] Re: re R Hya

["Stan Walker" <astroman@voyager.co.nz>]

Hallo John,

I presume that I have the same VSOLJ dataset from VSNet that you used.
There's quite a striking change in the shape of the light curve of R Hya
between JD 2425000 and JD 2450000. The early measures show the sharply
peaked light curve typical of many Miras. But the later ones, circa 1990,
have a lower amplitude flat-topped curve. I wondered whather the sequence
had changed in the interval - perhaps the VSOLJ people could comment on this
one. Incidentally, in the interval 27500-30000 the light curve shows a
distinct secondary peak on the rise. From looking at all the data this seems
to be a feature which comes and goes. The early part of the dataset seems to
be a well observed trace from a few good observers - the latter part is more
densely observed but the scatter seems about four times as large. Some of
the RASNZ VSS and AAVSO data on other stars shows the same trends. Quality v
quantity?

This reflects on your other comment - that the period has stopped
decreasing. I've searched the data for periods but the results are
equivocal. There is a spread of periods from 410 to 384 days which could
support both cases. At present I'm trying to get hold of a dataset from one
of our people who has looked at R Hydrae for a long time and whose data is
usually top class. You get better results from using a single prolific
observer's measures. Maybe Sebastian could get hold of something like this
in South America?

Regards,
Stan


----- Original Message -----
From: <crawl@zoom.co.uk>
To: <vsnet-chat@kusastro.kyoto-u.ac.jp>
Sent: Friday, May 11, 2001 10:59 AM
Subject: [vsnet-chat 4434] re R Hya


>
> Hiya Sebastian
>
> If you look at the vsnet image archive you'll find a plot of the long term
> phase and amplitude behaviour for R Hya going back about 90 years which
> vaguely suggests some quasiperiodic long term variation in amplitude, but
I
> wouldn't swear to it.

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