High amplitude dwarf nova outburst, detected by MASTER

ATel #8978; V. Shumkov, O. Gress, N. Tiurina, T. Pogrosheva, V. Lipunov (Lomonosov MSU), D. Buckley (SAAO), R. Rebolo Lopez(IAC), E. Gorbovskoy, P. Balanutsa, A. Kuznetsov, V. Kornilov, I. Gorbunov, V. Vladimirov, E. Popova(Lomonosov Moscow State University, SAI), S. Potter A. Kniazev (SAAO), M. Serra Ricart, G. Israelian (IAC), N. Budnev, K. Ivanov (API, Irkutsk State University)
on 22 Apr 2016; 16:35 UT
Credential Certification: Nataly Tyurina (tiurina@sai.msu.ru)

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MASTER OT J063429.91-300200.2 discovery - bright high amplitude (>6.4m) dwarf nova outburst

MASTER-SAAO auto-detection system ( Lipunov et al., "MASTER Global Robotic Net", Advances in Astronomy, 2010, 349171 ) discovered OT source at (RA, Dec) = 06h 34m 29.91s -30d 02m 00.2s on 2016-04-21.79961 UT.
The OT unfiltered magnitude is 14.9m (limit 18.0m).
The OT is seen in 2 images. There is no minor planet at this place.
We have reference image without OT on 2015-02-19.95449 UT with unfiltered magnitude limit 19.7m.
There is GSC 2.3.2 star with only blue 21.29mag, so we suggest the amplitude of outburst more then 6.4m
. There is GALEX source in 2.8".
Spectral observations are required.
The discovery and reference images are available at http://master.sai.msu.ru/static/OT/063429.91-300200.2.png

MASTER OT J154801.52-292515.0 discovery - bright dwarf nova outburst with ampl>4.6

MASTER-IAC auto-detection system discovered OT source at (RA, Dec) = 15h 48m 01.52s -29d 25m 15.0s on 2016-04-19.13267 UT.
The OT unfiltered magnitude is 15.4m (limit 17.6m).
The OT is seen in 6 images. We have reference image without OT on 2016-03-18 01:58:39UT with m_lim=20.1 in MASTER-SAAO database and on 2015-07-06.93472 UT with unfiltered m_lim=18.8m in MASTER-IAC database.
There is previous outburst on 2015-01-21 01:15:56.294 with m_OT=16.6 in MASTER-SAAO database, and reference image without OT on 2015-06-19 21:06:18 with m_lim=20.1.
Spectral observations are required.
The discovery and reference images are available at http://master.sai.msu.ru/static/OT/154801.52-292515.0.png

MASTER OT J202523.12-532407.9 discovery - bright dwarf nova outburst, Ampl>4.3m

MASTER-SAAO auto-detection system discovered OT source at (RA, Dec) = 20h 25m 23.12s -53d 24m 07.9s on 2016-04-19.98108 UT.
The OT unfiltered magnitude is 16.3m (limit 18.8m).
The OT is seen in 5 images. There is no minor planet at this place.
We have reference unfiltered images without OT on
2015-10-11.78266UT m_lim=20.9m
2015-11-30 19:51:59UT m_lim=19.2
2015-11-23 20:11:49UT m_lim=18.7
2015-10-11 18:47:02UT m_lim=20.9
There is USNO-B1 star with R1=17.58m, B2=21.41. There is GALEX source, so there is accretion to the white dwarf.

We checked colleagues' lists and found, that ASAS detected this source as PSN on 2015-10-24.06 with possibility to be CV in ATEL #8214.

MASTER discovery and reference images are available at http://master.sai.msu.ru/static/OT/202523.12-532407.9.png

MASTER OT J133352.93-375140.8 discovery - optical transient, outburst's ampl>2.4m, possibly dwarf nova

MASTER-SAAO auto-detection system discovered OT source at (RA, Dec) = 13h 33m 52.93s -37d 51m 40.8s on 2016-04-14.91277 UT.
The OT unfiltered magnitude is 18.7m (limit 19.6m).
The OT is seen in 5 images.We have reference image without OT on 2015-02-23.02387 UT with unfiltered magnitude limit 21.1m.
Spectral observations are required.
The discovery and reference images are available at http://master.sai.msu.ru/static/OT/133352.93-375140.8.png

MASTER Global Robotic Net