[vsnet-alert 22993] DDE 158 = GALEX J140934.6-384610 outburst

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

The peculiar variable in Centaurus DDE 158 (GALEX J140934.6-384610) is
in outburst on the recent iTelescope.Net T31 images having brightened
by 0.4m in the last 24 hours (from Feb. 09.765 to 10.727 UT). The star
is currently 0.8 mag above the quiescent level, and the range of
variability in Siding Spring Survey data is 0.8m (from 16.2 to 15.4
unfiltered with V zero point).

The light curve of this star does not fit the patterns of any types of
cataclysmic variables. Based on its absolute magnitude from Gaia DR2
distance (103+/-1 parsec) it was called a micronova (M=11.1 at
minimum, M=10.3 in outburst). We are likely dealing with a new subtype
of variable stars here, or maybe even with the new type or class of
variability! See https://arxiv.org/abs/1807.04574 for more details.

Little is known about this star so far, except for the range of
variability. I am issuing a call to CCD observers in South Africa,
Chile and Australia to run the time series of DDE 158 in an attempt to
determine its orbital period. Of course, the spectrum would be much
desired as well, or at least the multicolor photometry in R, I and
Halpha filters.

The star is very red, so the magnitude in Clear filter will be about
1.5m brighter than in Luminance. NUV-W1 color index is 8.9, although
the star is blue in ultraviolet (GALEX FUV-NUV=0.28). See
http://scan.sai.msu.ru/~denis/DDE158-CVs-NUV-W1-W2.gif for the UV vs
IR colors of DDE 158 among all cataclysmic variables detected by both
WISE and GALEX.

Denis Denisenko (DDE)
http://scan.sai.msu.ru/~denis/VarDDE.html