[vsnet-chat 97] Re: supercycle of WX Hyi?

[Taichi Kato <tkato>]

Fraser Farrell wrote:

> Ritter's supercycle looks about right, but the normal cycle is now
> 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 think there may be a continuum of possible CV systems, ranging from
> the ER UMa's (or even X-ray bursters?) through the "normal" UG's to the
> NR's and right out to the "hibernating" novae.  However, our recognition
> of the rapid systems has been rather belated ( _V1159_ Ori??) and I'm
> sure there are more of them; misclassified in the GCVS.

    It is now widely believed ER UMa stars essentially obey the same outburst
physics as usual SU UMa stars, but it is not known whether there is a
continuous spectrum covering both ER UMa stars and usual SU UMa stars.
Observationally there seems to be a gap in supercycle lengths between 45
days and 90 days.  I hope Nogami-san especially working on this topic
may have some comments (^_^).

> Maybe if any of these systems was observed for several hundred/thousand
> outburst cycles; it might be discovered that all of them go through a
> very long period cycle of few/no outbursts and "frequent" outbursts??

    As Nogami-san pointed out in PASJ 47, 897 and in Keele CV Conference
(and others?), it would be unlikely the present high activity of ER UMa
stars should represent their secular average -- otherwise it would be
difficult to explain the existence of extremely short Porb systems like
DI UMa or RZ LMi within the widely accepted framework of CV evolution.

    Even if secular interchanges between ER UMa stars and usual SU UMa
stars (or even WZ Sge stars) may exist, it is not yet known whether the
time of ER UMa stars' turning-off is earlier than the SN Betelgeuse or
SN Eta Car ...

Regards,
Taichi Kato

VSNET Home Page

Return to Daisaku Nogami

---

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