[vsnet-alert 25493] Re: SS Cyg: standstill

[Siegfried Vanaverbeke siegfriedvanaverbeke@gmail.com via vsnet-alert]

Are any of these hypotheses about the standstills actually corroborated by
numerical models of the process ?

Siegfried

Op wo 3 mrt. 2021 om 01:42 schreef Taichi Kato <tkato at kusastro.kyoto-u.ac.jp
>:

> Re: SS Cyg: standstill
>
> > Akazawa-san and Kasai-san reported their latest observations.
> > The standstill in SS Cyg seems to be accompanied by oscillatory
> > variations even at this moment.  Their timescale is around a week.
> > It would be important to see if SS Cyg enters Z Cam-type standstill
> > with constant luminosity or repeats oscillations.
>
>    It has been documented that some standstills are
> associated with a hint of mini-outbursts occurring
> within the standstill at the normal interval
> frequency (Szkody and Mattei 1984, PASP 96, 988).
> So, the presence of low-amplitude oscillations
> may not be a surprise.
>
>    It would be noteworthy that the outburst preceding
> this standstill had a "shoulder" in the light curve
> at the end of 2020 Dec., particularly evident in
> Akawaza-san's light curve.  This phenomenon indicates
> that the disk radius reached the tidal truncation
> radius during this outburst.  The angular momentum
> of the disk was maximal during this outburst.
> The present standstill appears (to me) to be a result
> of the insufficient removal of the disk mass and angular
> momentum during this outburst (SS Cyg-type -- currently
> an ironical term -- outbursts reaching the tidal truncation
> radius are usually long ones, but this one lacked
> the flat-topped portion).
>
>    The presence of oscillations during the standstill
> somewhat reminds me of IW And stars.  The present
> phenomenon might provide a clue in understanding
> the IW And-type phenomenon and SS Cyg-type phenomenon
> as a whole.
>
>