[vsnet-alert 24199] CSS J181252.2+330406 in outburst now

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

This unusual CV in Hercules is now definitely brighter than its 17.7 Gmag
western neighbor, while it was only marginally detectable on Apr. 03 image
with the same T11 instrument in Mayhill, NM (3x60-sec unfiltered exposures
with 0.50-m reflector + CCD).

CSS J181252.2+330406
  20200403.474  <188CV  T11
  20200418.441  16.26CV T11  Outburst!

Visual inspection of ZTF image from Apr. 17 confirms the outburst has not
yet started 24 hours ago. Real-time ZTF Lasair data with the crops of
recent images: https://lasair.roe.ac.uk/object/ZTF18aajsdfc/

ZTF18aajsdfc
  20200331.489  17.61r
  20200404.433  17.45g
  20200404.487  17.20r
  20200414.454  17.18r
  20200417.465  17.46g  ZTF Lasair (last image in the faint state)

In [vsnet-alert 24132] Taichi Kato wrote:

>   According to ZTF and Gaia data, this object
> (=CSS160406:181252+330407) is essentially a CV in low state.
> Deep fading in 2018 June-Aug.
> The Mv at maximum is too faint for a dwarf nova.

Gaia DR2 has BP-RP=0.0193 and Mabs=9.1 (Gmag=18.12, distance modulus
m-M=9.04). Magnitude at outburst corresponds to M=+7.2.

Here is the light curve from ZTF DR2 (Masci et al., 2019PASP..131a8003M):
http://scan.sai.msu.ru/~denis/J1812+3304-ZTF-LC.gif

And the zoomed view in April-June 2018:
http://scan.sai.msu.ru/~denis/J1812+3304-ZTF-Apr-Jun-2018.gif

Pretty exotic! Perhaps VSX range should be revised to reflect the minimum
magnitude from ZTF (19.6g). CRTS data were likely contaminated by the
neighbor.

Denis Denisenko