[vsnet-alert 21813] ASASSN-18bf: new SU UMa type dwarf nova in Lynx

[Denis Denisenko]

ASASSN-18bf was detected as a transient on January 20th, see
http://www.astronomy.ohio-state.edu/~assassin/transients.html

ASASSN-18bf
  20180115.29  <19.1g  ASAS-SN (Shappee et al., 2014)
  20180120.31   16.4g  ASAS-SN
  20180121.32   16.0g  ASAS-SN
  20180123.28   16.1g  ASAS-SN

The object at quiescence is identical to SDSS J091256.64+424313.6
(u=21.79 g=21.79 r=21.67 i=21.90 z=21.21). Outburst amplitude is
almost 6 magnitudes.

Observations with iTelescope T05 (0.25-m reflector in Mayhill) on Jan.
25.36-25.43 UT have shown a superhump with a total amplitude of 0.2m
and a period about 1.5 hours. The object magnitude was varying between
16.4 and 16.6 (unfiltered with V zero point).

Longer run on Jan. 25.81-26.00 UT by Sergey Nazarov in Crimean
Astrophysical Observatory with 0.20-m reflector has shown 3 superhump
maxima. Range was 16.5-16.7m. Combined dataset is giving the best
superhump period of 0.0604 d. The data will be sent to VSNet.

Finder chart with two comparison stars labeled:
http://scan.sai.msu.ru/~denis/ASASSN-18bf-BRIR.jpg (10'x10' FOV).
APASS magnitudes for the reference stars:
152 V=15.211+/-0.087 B=15.579+/-0.067
156 V=15.618+/-0.114 B=16.464+/-0.043

Further observations are encouraged to improve the period measurement.

Denis Denisenko