[vsnet-chat 3520] R Cen...

[no name <crawl@zoom.co.uk>]

Dear southern hemisphere folk

I have a bit of difficulty keeping up with literature on Southern
variables, especially papers by amateur organisations.

Basically, the [in]famous doubly periodic Mira star R Cen:

has anybody noticed that _both_ its periods are steadily declining, as
indeed are both its amplitudes, in a fairly systematic way?

Indeed, given a few more years of amplitude reduction, instead of
looking like an exotic double peaked Mira, it'll look like quite a few
other doubly periodic SRb stars [though the period ratio is still a
pretty solid 1.99, and ampl. about 3 mag].  Granted, that'll primarily
be based on the arbitrary delimiter of 2.5 mag amplitude twixt Miras and
SRs.

Haven't seen a behaviour like it, except possibly when W Tau stopped
behaving like a very regular single period SRa star in the early 30s and
became a double periodic SRb star at that time, afore descending into
the current near chaos of periodiocities. [Again, W Tau looked SRa, but
would have been called a Mira if it hadn't been of only about 2 mag
amplitude, which begs the question as to what the amplitude may have
been of this object in the past.  There was a steady amplitude decrease
up to the 30s "event", but there's only data back to just about the
20s].

Finally, there's a handful of these "double peak" Miras visible from
Southern climes.  Its a bugger getting hold of data for Southern
hemisphere variables, but the few light curves I've managed to see show
temporary double peaking, and stuff not that dissimilar to what T Cas
and chi Cyg can get up to from time to time.

R Cen is pretty unique though.  Another classed with it is R Normae. 
How similar is "our Normy" R Cen is lightcurve characteristics?

Ta

John

VSNET Home Page

Return to Daisaku Nogami

---

vsnet-adm@kusastro.kyoto-u.ac.jp