[vsnet-alert 25504] Re: SS Cyg: standstill

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

Thanks for the abstract.  These are still effective 1d models ?  A full 3d
treatment has probably not yet been done.

Siegfried

Op do 4 mrt. 2021 om 02:36 schreef Mariko Kimura <
mkimura at kusastro.kyoto-u.ac.jp>:

> I think Fig.10 in our paper is helpful to see the difference between
> the small and long outbursts in SS Cyg-type stars.
> The time evolution of the disk mass and the angular momentum is
> displayed.
> https://ui.adsabs.harvard.edu/abs/2020PASJ...72...22K/abstract
>
> In the long outburst, the disk radius reaches the tidal truncation
> radius and a lot of mass and angular momentum should be
> removed from the disk.
> However, the correct treatment of heating by the tidal torque
> at the disk outer edge is our future work (Actually I have
> investigated a little).
> Our paper also proposed a possible model for IW And-type
> phenomenon on the basis of the suggestion by Kato (2019).
> https://ui.adsabs.harvard.edu/abs/2019PASJ...71...20K/abstract
>
> - Mariko
>
>
> On 2021/03/03 18:29, Siegfried Vanaverbeke
> siegfriedvanaverbeke at gmail.com via vsnet-alert wrote:
> > 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.
> >>
> >>
>
>