[vsnet-alert 25978] ZTF21abgmexs = ATLAS21wuw: large-amplitude 15m object in Hercules

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

ATLAS team reported the new 15m transient AT 2021qea = ATLAS21wuw on 2021
June 16th. It was caught on the rise by ZTF a night before.

ZTF position: 17 49 35.14 +17 13 01.1
TNS position: 17 49 35.14 +17 13 01.0 (Tonry et al., ATLAS)

ZTF Lasair data: https://lasair.roe.ac.uk/object/ZTF21abgmexs/
Transient Name Server page: https://www.wis-tns.org/object/2021qea
ASAS-SN light curve for last 20 days:
https://asas-sn.osu.edu/sky-patrol/coordinate/5aca714f-9855-4c1a-848f-decf62b3f098

ATLAS21wuw = ZTF21abgmexs
  20210614.3605  >174g   ASAS-SN  Last non-detection
  20210615.3096  15.79g  ZTF (Masci et al., 2019)
  20210615.3572  15.98r  ZTF
  20210616.3369  14.91g  ASAS-SN (Shappee et al., 2014; Kochanek et al.,
2017)
  20210616.3394  14.84g  ASAS-SN
  20210616.3509  14.94g  ASAS-SN
  20210616.4049  15.01c  ATLAS (Tonry et al., 2018)
  20210616.4181  15.02c  ATLAS

1992 outburst on DSS plates (as GSC2.2 N10010229177):

ATLAS21wuw = ZTF21abgmexs
  19920604.38  <19.5I  Non-detection
  19920626.31  15.19R  USNO-B1.0  Outburst!
  19920628.29  14.74B  USNO-B1.0  Outburst continues
  19920725.22  <20.8R  Outburst is over

Color-combined DSS plate (10'x10' FOV):
http://scan.sai.msu.ru/~denis/AT2021qea-BRIR.jpg

GSC position: 17 49 35.13 +17 13 01.0
Note that GSC 2.2 gives Rmag=13.93 instead of R2=15.19 in USNO-B1.0
measured from the same POSS-II Red plate. USNO-B value is more realistic.

Extremely faint object (~23m) is visible on the combined PanSTARRS-1 images
in g, r and i filters. Outburst amplitude is about 8 magnitudes. No
outbursts were detected by Catalina Sky Survey. Excellent candidate for WZ
Sge-type dwarf nova.

Denis Denisenko