[vsnet-alert 24653] Re: ZTF J235136.47+611250.2 = Gaia20eck fading

[Denis Denisenko d.v.denisenko@gmail.com via vsnet-alert]

There was a similar fading episode in ZTF data on MJD=58696.4 (2019 Aug.
01.4 UT). The star has faded from the average level by 1.0m in r filter and
by 1.3m in g.

Complete ZTF DR3 light curve:
http://scan.sai.msu.ru/~denis/J2351+6112-ZTF-DR3-LC.gif

2019 light curve: http://scan.sai.msu.ru/~denis/J2351+6112-ZTF-LC-2019.gif

Until 2019 June 20th the star was in a stable state showing variations with
P=0.6198(5) d (one maximum per period) or P=1.2396 (if this is an eclipsing
binary with two minima and two maxima). After then, the fadings of various
depth have started.

Galactic extinction E(g-r)=1.3 according to Schlafly and Finkbeiner, 2011.
There is no H_aplha emission in IPHAS. RS CVn classification from ZTF (not
yet added to Vizier) appears to be reasonable. Observations are needed to
see if the dimmings are periodic or quasiperiodic. One can suspect the
beating of two periods (rotation of dark spot on one component and the
orbital motion).

Denis Denisenko

On Sat, Sep 5, 2020 at 10:36 AM Taichi Kato <tkato at kusastro.kyoto-u.ac.jp>
wrote:

> ZTF J235136.47+611250.2 = Gaia20eck fading
>
> http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia20eck/
> Gaia20eck       AT2020slq       2020-09-01 16:57:35     357.90196
>  61.21392        18.56   17.41   0.12    unknown 2020-09-04 11:01:39
>  slow, followed by sharp decline in Gaia source
>
> 235136.4 +611250 (2000.0) ZTFJ235136.47+611250.2 RSCVN g=18.859 r=17.319
> amp=0.187 P=0.6199500
> 235136.4 +611250 (2000.0) ZTFJ235136.47+611250.3 r=17.320 (17.203-17.489)
> P=0.6199
> 235136.474 +611250.16 (2000.0) Gaia_DR2_2011936442952115840
> plx=0.346(0.105) dismod=12.3 pmra=-3.201(0.161) pmdec=-1.604(0.139)
> G=17.332 BP=18.401 RP=16.291
>