[vsnet-alert 26057] ZTF21abilubd: a large-amplitude (~ 7.3 mag) CV candidate with known Gaia parallax

[Kenta TAGUCHI]

Dear friends,

Using my private system scraping MARS ( https://mars.lco.global/ ),
I've just found ZTF21ablazyz out as a large-amplitude (~ 7.3 mag) CV 
candidate from the public ZTF data.
(I'm sorry if someone has already reported it.)

Lasair: https://lasair.roe.ac.uk/object/ZTF21ablazyz/
ALeRCE: https://alerce.online/object/ZTF21ablazyz/
MARS: https://mars.lco.global/?objectId=ZTF21ablazyz

According to ALeRCE, the position is (RA, Dec) = (19:32:25.080, -9:19:33.23)

Last non-detections by ZTF:
g > 20.266 on 2021-07-10.32 (ZTF, 'difference mag' via ALeRCE)

First detections by ZTF:
g = 14.539 +/- 0.030 on 2021-07-12.28 (ZTF, 'difference mag' via ALeRCE)
g = 13.198 +/- 0.029 on 2021-07-15.34 (ZTF, 'difference mag' via ALeRCE)

The result of ASAS-SN Sky Patrol: 
https://asas-sn.osu.edu/sky-patrol/coordinate/e65084ea-340f-4913-b668-f01880ac9016
It looks that a nearby star is contaminated to the quiescent magnitude, 
however, it also confirms the proceeding outburst.
No such large past outbursts seem to be recorded.
g = 16.523 on 2021-07-09.8528981 (the last data before the outburst, may 
be contaminated)
g = 14.365 on 2021-07-12.2723774 (the first data after outburst started)
g = 13.232 on 2021-07-15.3720369 (the most recent data)

There is a possible counterpart in PS1 data: r = 20.42, i = 20.48, y = 
19.53, z = 19.75
g magnitude is not recorded in PS1 mean object catalog.

However, g = 20.49 is recorded in the Gaia catalog (so, the amplitude of 
the outburst is ~ 7.3 mag)
Its parallax is 2.6904043184599056 +/- 1.3597997 mas.
So, the distance modulus is ~7.85 (errors: +1.53 mag, -0.88 mag).

No known minor planets are found by the Minor Planet Checker
(https://www.minorplanetcenter.net/cgi-bin/checkmp.cgi).

Best Regards and Clear Skies,
Kenta
-- 
________________________________________________________________
  田口 健太　(TAGUCHI, Kenta)
  京都大学大学院理学研究科宇宙物理学教室
  (Department of Astronomy, Graduate School of Science, Kyoto University)
kentagch at kusastro.kyoto-u.ac.jp <mailto:kentagch at kusastro.kyoto-u.ac.jp>
  09090536980