[vsnet-alert 19394] 1RXS J015017.0+375614 recent activity

[Denis Denisenko]

Eddy Muyllaert has reported an outburst of this unusual variable in
Andromeda on the first day of 2016 in [cvnet-outburst 6828]. I have
caught this star on the rise on Dec. 30 also with Bradford Robotic
Telescope. Here is the summary of the recent observations. The star
was still bright two hours ago on the iTelescope.Net image taken
remotely from Mayhill, NM.

1RXS J015017.0+375614 = MASTER OT J015016.17+375620.5
  20150914.154  18.24CV  BRT
  20150929.191  17.67CV  BRT
  20151012.132  17.91CV  BRT
  20151030.083  17.52CV  BRT
  20151119.989  17.37CV  BRT
  20151204.035  17.65CV  BRT
  20151218.972  17.98CV  BRT
  20151230.965  16.95CV  BRT
  20160101.971  14.78C   BRT (Eddy Muyllaert) OUTBURST
  20160104.208  15.18CV  T21

I have used nearby reference star labeled 145 (V=14.52) in AAVSO sequence.

Light curve from Catalina Sky Survey shows another short outburst two
months ago:
http://nesssi.cacr.caltech.edu/catalina/20131023/1310231380084126804p.html

  20151011.480  17.55CV  CSS
  20151023.440  17.61CV  CSS
  20151106.560  14.54CV  CSS  OUTBURST
  20151112.520  17.33CV  CSS
  20151130.560  17.21CV  CSS
  20151208.560  17.53CV  CSS
  20151218.560  17.53CV  CSS

Overall range is 14.2-19.1. This variable was doing weird stuff in
September-October 2013. See more details in [vsnet-alert 16552]. The
outburst pattern is atypical for both UGZ and UGSU variables. My
hypothesis suggests that 1RXS J015017.0+375614 is some transition
object with the combination of orbital radius and accretion rate
exactly at the border between UGZ and UGSU dwarf novae. When accretion
rate fluctuates above this boundary value, this 'chameleon' star
behaves like an UGZ. Otherwise it looks more like a dwarf nova with
plain minima between outbursts. This may be a short evolutionary stage
when the star cannot decide where it belongs to. Orbital period is yet
to be determined.

Denis Denisenko
Sternberg Astronomical Institute of Moscow State University