[vsnet-alert 23621] CP Lac (Nova Lac 1936) deep fading episode

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

Gaia Alerts team (Hodgkin et al.) has reported an "anti-transient"
coincident with the known variable CP Lac (Nova Lacertae 1936):

http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19elx/ and
https://wis-tns.weizmann.ac.il/object/2019sbz

Comments from Gaia team: blue star fades by 3.5 mags

Gaia19elx = AT 2019sbz = CP Lac
  20190425.8928  16.53G  Gaia
  20190605.0540  17.11G  Gaia
  20191005.4890  19.52G  Gaia
  20191005.5630  19.51G  Gaia

Previous similar fading has occured in July-December 2010, according
to AAVSO data. Minimum magnitude was about 20.0 CV with one point as
low as 20.4 CV. During 2014-2018 the star was varying from 15.5 to
16.0 G in Gaia and from 15.5 to 16.5 CV in AAVSO database. Pan-STARRS
DR1 is giving g=19.54 r=19.32 i=17.14 z=16.75. With Gaia DR2 parallax
0.86+/-0.04 mas, distance modulus (m-M) is 10.3.

AAVSO VSX entry for CP Lac (type NA, range 2.0-17.7 V):
https://www.aavso.org/vsx/index.php?view=detail.top&oid=16705

Also notable on the images at
http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia19elx/ (both DSS colored
and especially PanSTARRS DR1 color) are concentric shells around the
variable.

Denis Denisenko