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[vsnet-lpv 67] (fwd) R Hya stanstill (discussion from vsnet-chat)
- Date: Sat, 12 May 2001 16:13:11 +0900 (JST)
- To: vsnet-lpv
- From: Taichi Kato <tkato>
- Subject: [vsnet-lpv 67] (fwd) R Hya stanstill (discussion from vsnet-chat)
- Sender: owner-vsnet-lpv@kusastro.kyoto-u.ac.jp
(fwd) R Hya stanstill (discussion from vsnet-chat)
The discussion is from vsnet-chat:
From: "Sebastian Otero" <varsao@fullzero.com.ar>
Subject: [vsnet-chat 4431] R Hya's standstill
Hi,all:
I'd like to hear some comments on the current standstill of R Hya.
Specially concerning the past behaviour of the star.
Has the lightcurve been showing this feature in the past?
My recent observations indicate that R Hya was in the rising branch at the
end of March and since then has stayed at the same brightness. And it's been
more than a month now...
Observations (already reported to vsnet-obs):
20010218.2 7.9
20010328.1 6.8:
20010407.1 6.7
20010410.1 6.7:
20010415.1 6.7
20010421.0 6.7
20010425.1 6.7
20010426.0 6.7:
20010504.0 6.7
20010510.1 6.7
Best regards,
Sebastian.
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From: Lew Cook <lcoo@yahoo.com>
Subject: [vsnet-chat 4432] Re: R Hya's standstill
Hi Sebastian-
The AAVSO Light Curve generator
http://vsnet.aavso.org/adata/curvegenerator.shtml
for R Hya over the last few cycles shows a short pause on the rising
branch of the light curve. It has occurred in the last 3 cycles (not
counting this one) at magnitudes 6, 6.8 and 5.9.
Regards, Lew
--- Sebastian Otero <varsao@fullzero.com.ar> wrote:
> Hi,all:
> I'd like to hear some comments on the current standstill
> of R Hya.
> Specially concerning the past behaviour of the star.
> Has the lightcurve been showing this feature in the past?
>
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From: "Stan Walker" <astroman@voyager.co.nz>
Subject: [vsnet-chat 4433] Re: R Hya's standstill
Hi Sebastian,
I'm intrigued by your observations. This stillstand has been observed in the
past - it shows in some of Albert Jones' measures about 1960 and also in
photoelectric measures made at Auckland Observatory around 1980. The latter
are interesting as the B-V and U-B colours were rather unusual as the cycle
developed. Unfortunately the project was not continued with. The pe measures
showed a slight decline before the final rise to maximum in the only cycle
we observed even slightly well.
As I mentioned earlier I'm interested in double peaked Miras. One of these
is BH Crucis which is now increasing dramatically in period - about 100 days
in 25 years. R Hydrae, of course, is famous for a period change of the
opposite nature. Since all of the double peaked Miras have periods in the
400-500 day range I have often wondered whether R Hydrae is approaching this
stage. The double peaked nature of BH Crucis is much less pronounced with
the longer period - sometimes the first peak is merely a bump on the light
curve.
It would be useful doing a full analysis of this star. R Centauri is another
of the 500plus day group with a quickly changing period. My feeling is that
the 400+ day Miras (and R Hydrae is still close to this period - it may
bounce back or prove the lower bioundary is ~350 days) are evolving in a
manner much different and faster than the rest of the group.
Keep observing.
Regards,
Stan
----- Original Message -----
From: Sebastian Otero <varsao@fullzero.com.ar>
To: vsnet-chat <vsnet-chat@kusastro.kyoto-u.ac.jp>
Sent: Friday, May 11, 2001 10:40 AM
Subject: [vsnet-chat 4431] R Hya's standstill
> Hi,all:
> I'd like to hear some comments on the current standstill of R
Hya.
> Specially concerning the past behaviour of the star.
> Has the lightcurve been showing this feature in the past?
>
> My recent observations indicate that R Hya was in the rising branch at the
> end of March and since then has stayed at the same brightness. And it's
been
> more than a month now...
>
> Observations (already reported to vsnet-obs):
>
> 20010218.2 7.9
> 20010328.1 6.8:
> 20010407.1 6.7
> 20010410.1 6.7:
> 20010415.1 6.7
> 20010421.0 6.7
> 20010425.1 6.7
> 20010426.0 6.7:
> 20010504.0 6.7
> 20010510.1 6.7
>
>
> Best regards,
> Sebastian.
>
>
> ---
> Outgoing mail is certified Virus Free.
> Checked by AVG anti-virus system (http://vsnet.grisoft.com).
> Version: 6.0.249 / Virus Database: 122 - Release Date: 13/04/01
>
>
From: crawl@zoom.co.uk
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.
[http://vsnet.kusastro.kyoto-u.ac.jp/vsnet/Mail/vsnet-image/msg00038.html]
The x axis is JD -2400000, the left hand y axis is phase in degrees and the
right hand y axis is semi-amplitude in magnitudes.
The red symbols are semiamplitude over time keyed to the right y axis based
on John Howarth's ampscan procedure, whilst the blue symbols are the same
but generated by Grant Foster's inculcation of wavelet analysis. Although
the latter looks "neater", this is primarily because the wavelet analysis
technique is of a far higher computational load than the ampscan technique,
and therefore the data was sampled at a far lower resolution. The ampscan
data is probably more detailed.
The black crosses, by the way, are phase over time.
As you can see, the monotonic period decrease of R Hya ceased around 1940,
with period variation within this star being more or less stochastic about
a mean since then. Of large import is that mean semiamplitude also dropped
markedly about this time.
Some detailed discussion on the behaviour of R Hya periodicity and light
curve can be found in part of the following article [despite the article
being primarily about W Dra], although not much on the amplitude really
http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=2000JAVSO..28..
.18G&db_key=AST&page_ind=4&plate_select=NO&data_type=GIF&type=SCREEN_GIF
(this url will have been word wrapped on transmittal, unwrap it afore usage)
I never did publish the analysis on this star, but it is interesting to
note that professional papers will still seriously quote it as being
decreasing in period, and a prime example of such behaviour, even though it
ain't true and hasn't been for sixty years.
This star has displayed some interesting behaviour over time, and if the
inherent morphology of the lightcurve has undergone a fundamental change,
as suggested by your post, something interesting is occuring.
A good one for visual observers to keep following, extending the already
extant long baseline visual database into the depths of the current century.
[Data used in the analysis is from BAAVSS, AFOEV, VSOLJ and AAVSO, both
independently assessed and as merged etc, &c. BAAVSS data includes
RASNZVSS data due to a reciprocation agreement on certain common near
equatorial stars. No doubt AAVSO data also contains RASNZVSS data as a
subset due to a similar agreement. Everybody are the respective owners of
what belongs to them.]
Cheers
John
[PS Anybody got that data request engine at the aavso website to
work!?!?!?!? I haven't got the damn thing to cough up any data in well
over a year of trying, despite several requests, and unanswered querying
emails re non-receipt! Maybe they don't love me no more!?].
From: Afoevb@aol.com
Subject: [vsnet-chat 4435] R Hya's standstill (vsnet-chat 4431)
In the AFOEV database I found following standstill's
from JD to JD mv
27489 27547 7.3/7.5 58d
27888 27960 8.0->7.5 72d
28268 28296 7.6 28d
44675 44748 6.0 73d
46590 46652 6.7-->6.2 62d
50468 50518 6.0 50d
50840 50895 6.0 55d
51606 51665 5.9 59d
E. Schweitzer - AFOEV
From: Roger Pickard <rdp@star.ukc.ac.uk>
Subject: [vsnet-chat 4436] R Hya's standstill
Dear Sebastian,
You may also care to look at the BAA VSS Web Page:
www.telf-ast.demon.co.uk/
and follow the link to lightcurves and look for R Hya where you will find
a light curve going back (a little scratchily) to 1903. The first time
the ascending branch was covered there was a standstill and that was in 1908.
Regards,
-----
Roger Pickard,
Director, BAA Variable Star Section,
28 Appletons,
Hadlow,
Kent TN11 0DT.
England.
Tel: 01732 850663 (Int: +441732850663)
E-mail: rdp@star.ukc.ac.uk
BAA VSS Web Page: www.telf-ast.demon.co.uk/
From: "Stan Walker" <astroman@voyager.co.nz>
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.
From: crawl@zoom.co.uk
Subject: [vsnet-chat 4438] Re: re R Hya
At 09:21 12/05/01 +1200, Stan Walker wrote:
>Hallo John,
>
>I presume that I have the same VSOLJ dataset from VSNet that you used.
Hi Stan
The VSOLJ data I've got for this star is by far the lesser amount. I've
mostly got BAAVSS and AAVSO data for this star, acquired ages back [on a
floppy via airmail for aavso if I remember rightly!]. It'd be a good
assumption that both of these datasets have a lot of RASNZVSS stuff in
them, probably the same stuff! I did the exercise independently on BAAVSS
data to start, then independently on AAVSO data when it turned up, as a check.
>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?
Split your datasets into two bunches either side of 1940 and DFT them
separately.
The profiles and widths of the main peaks will show you which periodicities
at which epochs are "tighter", although unfortunately there isn't too much
data pre-1940 in the electronic archives [goes back to 1920ish I think],
and this in itself can cause broadening of peaks. Works best if you have
the times of maxima going back for quite some time, then you do an O-C pre
1940 and a separate one post-1940... ...the 1st will give you a goodish
parabola of largish residual range, the 2nd won't.
General question... ...what is the difference between "Helium shell flash"
as hypothesized for period changing Miras a la the original Wood and Zarro
model, and "Helium shell flash" for objects like FG Sge or Sakura's
Object!?!?!?! This has always confused me, as the two types of star are
quite different and the two types of displayed phenomena are quite
different too, yet they are accused of undergoing the same sort of event.
Or is it that FG Sge is commencing Helium _core_ burning????
Cheers
John
From: "Sebastian Otero" <varsao@fullzero.com.ar>
Subject: [vsnet-chat 4440] Re: R Hya's standstill (vsnet-chat 4431)
> from JD to JD mv
> 27489 27547 7.3/7.5 58d
> 27888 27960 8.0->7.5 72d
> 28268 28296 7.6 28d
> 44675 44748 6.0 73d
> 46590 46652 6.7-->6.2 62d
> 50468 50518 6.0 50d
> 50840 50895 6.0 55d
> 51606 51665 5.9 59d
> E. Schweitzer - AFOEV
Dear Emile:
It's true, my own observations show the same standstill
between 5.8 and 5.9 and betweeen JD 2451600 and 2451660. I didn't take car
of my own data!!!
The early light curves of the BAA-VSS (thanks, Roger)
clearly show that the hunp is already present at the beginning of the last
century.
I completely agree with Stan regarding the importance of
individual sets of data for this one. I'll see if someone here have
something. I only have three cycles myself. And in the last two the hunp is
apparent.
If I don't round off magnitudes, I even notice a slight dimming after JD
24512020 (from 6.65 since JD 2452009 to 6.74 in JD 2452026)
It's been 35 days in satndstill. According to Emile's table
maybe there is more or less 20 days left for the hump to keep hanging on.
Let's see.
Regards,
Sebastian.
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