[vsnet-chat 114] Re: supercycle of WX Hyi?

[Fraser Farrell <fraserf@dove.net.au>]

G'day all,

On 1997-02-18 tkato@kusastro.kyoto-u.ac.jp said:
   >Fraser Farrell wrote:
   >> noticeably quicker than 14 days.  In fact WX Hyi is now going off
   >>so  frequently that my local observers no longer consider
   >>outbursts to be  worth telephoning me about!

   >It's interesting to hear this particular star actually changes
   >normal cycle length (or outburst frequency) without affecting the
   >supercycle length, since theory predicts there should be a tight
   >relation between the normal cycle length (Tn) and supercycle (Ts)
   >with reasonable assumptions. (cf. Warner B. 1995, ApSS, 226, 187)

I read that somewhere as well.  But theory is derived from observation,
so here's a summary of WX Hyi outbursts since 1995 October 9 (JD
2450000) from the VSS RASNZ Circulars:

JD 2450000+     max mag     rise-max-fall (days)
-----------     -------     --------------------
   004            12.0        0.8-1.4-0.6
   015            12.5        1.2-2.1-1.8
   024            11.9        1.0-0.0-3.3
   033            12.1        0.6-1.2-1.2
   045            11.7        0.8-1.0-2.0
   055            11.8        2.7-6.3-4.0 supermaximum
   070            12.4        1.0-0.2-1.0
   081            12.4        0.6-1.3-0.6
   087            12.8        1.0-0.6-0.4
   093            12.9        1.0-1.0-1.0
   100            12.8        0.3-0.0-0.4
   107            12.5        1.0-0.9-2.0
   114            12.6        1.0-
   123            12.8        0.9-1.0-1.0
   133            12.5        1.8-0.2-3.0
   142            12.4        1.0-
   155            12.4        1.0-1.0-1.0
   168            11.4        0.4-0.5-2.0
   181            11.5        1.0-0.0-1.0
   191            12.6        1.0-1.7-1.3
   206            11.2        3.0-5.6-3.0 supermaximum
   221            12.4        0.4-0.0-0.1
   226            12.5        1.0-1.0-1.0
     236-265 missing Circular (!)
   276            12.0        2.0-0.0-1.6
   292            12.2        0.8-1.0-1.0
   302            12.2        0.6-1.5-0.8
   314            12.2        0.8-0.0-1.2
   326            12.3        1.2-
   339            12.2        1.5-1.3-1.2
   350            12.7        1.0-0.8-0.5
   363            12.0        2.9-5.0-5.7 supermaximum (the odd one)
   380            12.5        1.1-0.0-0.9
   386            12.5        1.4-0.7-1.0
   394            12.4        1.2-0.2-2.3
   406            12.8        2.0-0.0-1.0
   416            12.0        1.8-1.0-1.1

The supermax intervals were 151 and 157 days.  Detecting changes in the
supercycle will take a few more years(!); but, assuming that all other
outbursts are normal (not post-supermax hiccups) the mean cycle for this
listing is  9.9 +/- 2.7 days (1 sigma).  The mean normal outburst
duration is 1.0-0.7-1.2 days, +/- 0.4-0.6-0.7 days.

WX Hyi is circumpolar for most VSS RASNZ observers, and under regular
scrutiny from at least 8 experienced observers every month.  I think
every outburst in this time interval has been seen; and the cycle has
definitely shortened from Ritter's result.

Are we looking at the prototype of the "WX Hyi variables" ??


cheers,

Fraser Farrell
Variable Stars Group
Astronomical Society of South Australia

WWW: http://vsnet.gist.net.au/assa/   email: fraserf@dove.net.au
traditional:  GPO Box 199, Adelaide, SA 5001, Australia

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