ZTF20acmlrfz, an unusual dwarf nova in Cassiopeia

Affiliation
American Association of Variable Star Observers (AAVSO)
Thu, 06/10/2021 - 18:21

This object, classified as dwarf nova by the ALeRCE ZTF Explorer, seems to be rather unusual.

https://alerce.online/object/ZTF20acmlrfz

(I prefer Lasair for visualization)

https://lasair.roe.ac.uk/object/ZTF20acmlrfz/

https://www.aavso.org/vsx/index.php?view=detail.top&oid=2222768

The object is in Cassiopeia at 00 47 33.77 +52 17 36.9 (J2000.0).

It is not present in any astrometric catalogue. It doesn't show up on Pan-STARRS1 images down to mag. 23.
However, it appears to be a blue dwarf nova ranging from g= 16.8 to 20.0 since at least November 11, 2020.

Previously, an outburst to mag. 17.1 was detected on October 22, 2020.

It looks like this object had an amplitude >6 magnitudes and has then suddenly brightened its quiescence level while reducing its amplitude to 3 mag.
It doesn't look like a UGZ/IW in a very long standstill...

An object worth following.

Cheers,
Sebastian

Affiliation
American Association of Variable Star Observers (AAVSO)
ZTF20acmlrfz Sequence

ZTF20acmlrfz Now has a sequence ~ 150-193V

Good Observing & Ad Astra,

Tim Crawford, Sequence Team