[vsnet-chat 4447] Re: re R Hya

["John Isles" <jisles@voyager.net>]

Stan and John,

For what it's worth, I wrote a piece about R Hya in Sky & Telescope, May
1996, pp. 68-70.  Using AAVSO dates of maxima in conjunction with earlier
elements as reported in the GCVS, I concluded that to a first approximation
the period was decreasing steadily until about 1910.  Since 1937 the period
was contant at 389 days.

Best wishes -- John Isles.

----- Original Message -----
From: "Stan Walker" <astroman@voyager.co.nz>
To: <crawl@zoom.co.uk>; <vsnet-chat@kusastro.kyoto-u.ac.jp>
Sent: Friday, May 11, 2001 5:21 PM
Subject: [vsnet-chat 4437] Re: re R Hya


> 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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