MASTER: 4 optical transients

ATel #8020; O. Gress, P. Balanutsa, V. Lipunov, E. Gorbovskoy (Lomonosov MSU), D. Buckley (SAAO), R. Rebolo, M. Serra-Ricart, N. Lodieu, G. Israelian (The Instituto de Astrofisica de Canarias), N. Samus(INASAN, SAI MSU), V. Kornilov, N. Tiurina, A. Kuznetsov, I. Gorbunov, V. Chazov, D. Vlasenko (Lomonosov Moscow State University, Sternberg Astronomical Institute), S. Potter, M. Kotze (South African Astronomical Observatory), N. M. Budnev, K. Ivanov (Applied Physics Institute, Irkutsk State University), A. Tlatov, D. Dormidontov, V. Senik (Kislovodsk Solar Station of the Pulkovo Observatory), V. Krushinski, I. Zalozhnykh (Ural Federal University), Yu. Sergienko, A. Gabovich, V. Yurkov (Blagoveschensk Educational State University)
on 8 Sep 2015; 22:30 UT
Credential Certification: Nataly Tyurina (tiurina@sai.msu.ru)

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MASTER OT J090639.19-275335.5 detection - dwarf nova outburst, Ampl>5m

MASTER-SAAO auto-detection system ( Lipunov et al., Advances in Astronomy, MASTER Global Robotic Net, 2010 ) discovered OT source at (RA, Dec) = 09h 06m 39.19s -27d 53m 35.5s on 2015-09-08.15233 UT.
The OT unfiltered magnitude is 16.7m (the limit is 18.5m).
There are 6 images with OT. There is no minor planet at this place. We have reference images without OT on 2015-01-17.85620 UT with 20.3 unfiltered magnitude limit, on 2015-03-30.914 with m_lim=19.3. There is GSC2.3 star with only blue j=21.68 (1978y).So we can suggest the dwarf nova outburst with amplitude more then 5m.
Spectral observations are required.
The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/090639.19-275335.5.png

MASTER OT J091631.68-330230.1 detection - possible dwarf outburst, Ampl>4m

MASTER-SAAO auto-detection system discovered OT source at (RA, Dec) = 09h 16m 31.68s -33d 02m 30.1s on 2015-09-08.15676 UT. The OT unfiltered magnitude is 16.4m (limit 17.7m).
There are 2 images with OT(confirmation is on 2015-09-08.16119UT). There is no minor planet at this place. We have reference image without OT on 2014-12-24.01812 UT with unfiltered magnitude limit 20.0m.
There is GSC2.3 star with only blue j=21.27 (USNOB1=19.87-20.88), so we can suggest the dwarf nova outburst with amplitude more then 4m.
Spectral observations are required.
The discovery and reference images are available at http://master.sai.msu.ru/static/OT/MASTEROTJ091631.68-330230.1.png

MASTER OT J231846.26+044416.1 detection - optical transient, Ampl>3m

MASTER-IAC auto-detection system discovered OT source at (RA, Dec) = 23h 18m 46.26s +04d 44m 16.1s on 2015-09-07.01255 UT.
The OT unfiltered magnitude is 18.1m (the limit is 20.5m).
There are 3 images with OT on 2015-09-06.9968(m_OT=19.9),07.01255(m_OT=18.1), 07.020UT(m_OT=19.4) and 2 images on 2015-09-(07.975-07.979) with m_OT~20.8m. There is no minor planet at this place. We have reference image without OT on 2015-07-28.14510 UT with unfiltered magnitude limit 19.8m. There is a red star with r=20.99, g=22.4, so we can suggest an UVCet-type flare.
Spectral observations are required.
The discovery and reference images are http://observ.pereplet.ru/images/MASTEROTJ231846.26+044416.1.jpg

MASTER OT J190155.95-760928.3 discovery - new dwarf nova outburst, no VIZIER source, Ampl>3.3m

MASTER-SAAO auto-detection system discovered OT source at (RA, Dec) = 19h 01m 55.95s -76d 09m 28.3s on 2015-09-08.80975 UT.
The OT unfiltered magnitude is 18.7m (limit 19.5m).
The OT is seen in 3 images. There is no minor planet at this place. We have reference image without OT on 2015-01-24.06793 UT with unfiltered magnitude limit 20.0m. There is no any source inside 5" in VIZIER database. So we can suggest the dwarf nova outburst with amplitude more then 3.3m.
Spectral observations are required.
The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/190155.95-760928.3_1.png

MASTER Global Robotic Net