[vsnet-alert 25507] Re: [vsnet-outburst 26770] Re: SS Cyg: standstill

[Brian Skiff]

For some historical background see:

https://www.aavso.org/aavso-alert-notice-730

\Brian

On Thu, Mar 4, 2021 at 10:55 PM <kunjaya at as.itb.ac.id> wrote:
>
> Dear Friends,
> Is this the first observed standstill in SS Cygni?
> Is there any long term change of orbital  period?
>
> Thank you,
>
> Best Regards,
> Kunjaya
>
> ----- Original Message -----
> From: Taichi Kato <tkato at kusastro.kyoto-u.ac.jp>
> To: vsnet-alert at ooruri.kusastro.kyoto-u.ac.jp, vsnet-campaign-dn at ooruri.kusastro.kyoto-u.ac.jp, vsnet-outburst at ooruri.kusastro.kyoto-u.ac.jp
> Sent: Wed, 03 Mar 2021 07:42:35 +0700 (WIB)
> Subject: [vsnet-outburst 26770] Re: SS Cyg: standstill
>
> 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.
>
>