[vsnet-alert 25509] Re: SS Cyg: standstill

[Mariko Kimura]

Sorry.  It's me again.
Filtered observations are still encouraged and time-resolved
photometry (even by clear filter) will be helpful for period search.

- Mariko

On 2021/03/03 17:22, Mariko Kimura wrote:
> Let me add more information.
> I'd like to extract orbital light curve at this standstill state of SS 
> Cyg if possible.  I'm using Rc-band data to do this.
> Also, B-V color is helpful to investigate what region is bright in the 
> disk.
> Rc-band time-resolved photometry and B and V-band monitoring are 
> helpful at least for my study.
>
> - Mariko
>
> On 2021/03/03 16:15, Mariko Kimura wrote:
>> Thank you for your suggestions.
>> At least for me, filtered photometry (U, B, V, R, I) is helpful.
>>
>> - Mariko
>>
>> On 2021/03/03 12:23, Brian Skiff wrote:
>>>       Since this event is on-going and occurring on a genuinely 
>>> bright target, would Kato-san or others suggest the most useful 
>>> observations to be made?  I think it would be useful to be a little 
>>> prescriptive about what is to be done with these very many cv 
>>> outbursts.  It seems that the opportunity exists in this case to do 
>>> something more use diagnostic than simple unfiltered photometry 
>>> (i.e. the usual thing).  Would having, say, U, V, I, or Sloan z (= 
>>> Paschen decrement) time-series photometry be helpful? Time-resolved 
>>> H-alpha spectroscopy?  Helium lines? Polarization?  Spectra in the 
>>> near-IR?
>>>
>>>
>>> \Brian
>>>
>>>
>>>
>>> On Mar 2, 2021, at 5:42 PM, Taichi Kato 
>>> <tkato at kusastro.kyoto-u.ac.jp> wrote:
>>>
>>> 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.
>>
>