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[vsnet-gcvs 204] Re: [vsnet-chat 5267] Re: theta Apodis
Hi Sebastian, Stan and All,
As Stan noted, multiple cycles is probably closer to reality than a single
mean period.
The observations used in the VSS RASNZ paper are more continuous from about
1993 through 1999. During this interval, the binned periods mostly ranged
from 90-99 days upto 130-139 days, peaking in the 110-119 day range. The
O-C diagram shown for the mean period 115.93 days period suggests a second
much longer cycle of period near 1855 days (about 5 years or 16 cycles) may
also be present but a much more extensive series of observations would be
needed to confirm if this is correct.
This also suggests the period length may currently be decreasing (as seen
by Sebastian) towards a minimum period in the 90-99 day range (as reported
by Stan) during the next year or two, before again increasing. We will
have to watch on Theta Aps over the next few years to confirm this.
The O-C daigram also plots values for an alternative 118.85 day period
which is close to the current GCVS period. This period produces a
continual slope towards lower right which suggest this as a mean period is
a little too long.
Sebastian also mentions L2 Pup, a star currently going through interesting
faint stage. Check out the long term data on this star at the AAVSO light
curve generator. There are still some interesting stars for the binocular
observer.
Regards
Peter Williams
Heathcote NSW
----------
From: Sebastian Otero <varsao@fullzero.com.ar>
To: vsnet-chat <vsnet-chat@kusastro.kyoto-u.ac.jp>;
vsnet-gcvs@kusastro.kyoto-u.ac.jp
Subject: [vsnet-chat 5267] Re: [vsnet-gcvs 201] Re: theta Apodis
Date: Wednesday, 27 March 2002 4:53
Dear all:
Stan wrote:
> 14 UBV measures tend to
> suggest that the variation is from 5.0 to 5.8 at least. I did a
periodogram
> of this and found a main period of 98.8 days although the data didn't fit
> this all too well. I see the GCVS gave 119 days and a range of 6.4-8.6p.
>We concluded that it probably had
> two periods which beat together.
And Peter wrote:
> Theta Aps, appearing in Publications No24 of the VSS RASNZ (April 2000)
> is a paper I prepared based on 553 visual observations between 1959 and
> 1999 from the VSS data base. These indicated a mean visual range of 5.6
to
> 6.4 and extremes of 5.2 to 6.8. An average period of 115.93 days was
> found. Derived elements for maximum are JD 2449558 +/- 115.93 days.
It sounds interesting that my current deduced period (from visual
inspection
fo the lightcurve only) is exactly at the middle of both periods Peter and
Stan quoted:
Peter: 115.9 days
Stan: 98.8 days
Mine: 107 days
From the recent lightcurve is obvious that the ephemeris provided by Peter
don't fit with the observed.
Maybe the period has been shortening (119 - 116 - 107...)
I'll download Hipparcos data and read the papers mentioned by Brian that
must be very interesting.
> I'd imagine that Sebastian has measures during an interval when the beat
> period is low, or has reinforced one or two bright maxima. I didn't see
him
> quote a period and haven't had time to get onto the website.
However I don't find any irregularity or traces of beating between two
periods in the shape of the lightcurve. The beating effect is tremendously
evident in the L2 Puppis case mentiones by Stan.
(See http://ar.geocities.com/varsao/Curva_L2_Pup.htm ) and in other cases
like R Doradus (http://ar.geocities.com/varsao/Curva_R_Dor.htm ) and S
Leporis
(http://ar.geocities.com/varsao/Curva_S_Lep.htm ).
As mentioned in the past these red variables are very interesting and make
up a somewhat overlooked discussion topic.
I can't keep my eyes off of the changong period miras like BH Cru and R Cen
for example !!!
Regards,
Sebastian.
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