[vsnet-alert 25438] Re: ZTF20acyxwzf = ASASSN-21au: rapid fading with superhump-like variations

[Kojiguchi Naoto]

     Itoh-san, Tonny Vanmunster, Kubotera-san, Graeme Coates, Kyoto U. team and Maehara-san have reported further observations.
According to their observations, the fading rate of 1.7 mag/d has been constant since last night.
We obtained the superhump-like variations period of 0.0401(1)d during the rapid fading, which is shorter than that of 0.0405d during the plateau.

To judge the stage of the superhump-like variations, time-resolved photometry is encouraged, but this object is at 16 mag.
If possible, time-series observation is encouraged even if this object is faint.

   YYYYMMDD(UT)   mag  code
   20210222.080 15.143CV Van
   20210222.426 15.565C Ioh
   20210222.600 15.958C Kub
   20210222.856 154: Mhh
   20210222.858 15.880CV CGR

On 2021/02/23 9:47, Graeme Coates wrote:
>   ASASSN-21au: Feb 22.857 - 22.967
>
> ( 350mm reflector + ST2000XM, Standlake, UK. )
> Showed variation between ~15.9CV and 16.2CV, with humps supporting the
> period of ~0.04d as per previous message by Kojiguchi-san. (Plot:
> https://britastro.org/observations/observation.php?id=20210223_003812_658d84a1778cfe92).
> Conditions deteriorated and prevented capture of further periods.
>
> Data is uploaded to the BAAVSS and AAVSO databases for further analysis.
>
> GC
>
>
>
> On Mon, 22 Feb 2021 at 02:56, Kojiguchi Naoto <
> kojiguchi at kusastro.kyoto-u.ac.jp> wrote:
>
>> ZTF20acyxwzf = ASASSN-21au: rapid fading with superhump-like variations
>>
>>       Itoh-san, Kubotera-san, Tonny Vanmunster, Kyoto U. team,
>> Tamas Tordai, Moriyama-san and Maehara-san have reported further
>> observations.
>> According to observations by Itoh-san, Kubotera-san and Kyoto U. team,
>> this object shows rapid fading with superhump-like variations on Feb. 21.
>> The superhump-like variations period is 0.0405 d. According to my O-C
>> analysis, the superhump-like variations period seems almost constant, but
>> the phase average profile seems to be changing.
>>
>> This object is showing very interesting behavior.
>>
>> Time-resolved photometry is encouraged.
>> Even if this object is faint, nightly snapshots are important. Because
>> this object is likely to cause rebrightenings.
>>
>>     20210218.058 13.710CV Van
>>     20210218.475 13.575C Kub
>>     20210218.477 13.646C Ioh
>>     20210218.812 13.594CV Trt
>>     20210219.071 13.788CV Van
>>     20210219.422 13.755C Ioh
>>     20210219.430 13.596C Kub
>>     20210219.758 138C Myy
>>     20210219.861 132 Mhh
>>     20210220.424 13.712C Ioh
>>     20210220.503 13.789C Kub
>>     20210220.804 132 Mhh
>>     20210221.417 14.001C Ioh
>>     20210221.586 14.316C Kub
>>
>>