MASTER: 3 dwarf nova outbursts

ATel #7689; O. Gress (ISU), V. Lipunov (Lomonosov MSU), D. Buckley (SAAO), E. Gorbovsokoy, N. Tiurina, S. Antipin, V. Kornilov, P. Balanutsa, A. Kuznetsov, V. Chazov, E. Popova, V. Vladimirov (Lomonosov Moscow State University, Sternberg Astronomical Institute), S. Potter, A. Kniazev, M. Kotze (The South African Astronomical Observatory), N. Budnev, K. Ivanov (Applied Physics Institute, Irkutsk State University), V. Krushinsky (Ural Federal University), A. Tlatov, D. Dormidontov, V. Senik (Kislovodsk solar station of the Pulkovo observatory RAS), Yu. Sergienko, V. Yurkov, A. Gabovich (Blagoveschensk State Educational University), V. Shumkov (MASTER-team)
on 22 Jun 2015; 16:49 UT
Credential Certification: Nataly Tyurina (tiurina@sai.msu.ru)

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MASTER OT J150034.62-395849.0 - Dwarf Nova outburst with Ampl>4.3
MASTER-SAAO auto-detection system ( Lipunov et al., Advances in Astronomy, MASTER Global Robotic Net, 2010 ) discovered OT source at (RA, Dec) = 15h 00m 34.62s -39d 58m 49.0s on 2015-06-21.78946 UT.
The OT unfiltered magnitude is 17.7m (limit 19.4m).
There are 3 images with this OT. There is no minor planet at this place.
We have reference images without OT on 2015-04-26.05741 UT with 19.6 unfiltered magnitude limit, on 2015-01.01.090UT with m_lim=19.0.
There is no any source in VIZIER database, CRTS covered this area, but no objects were found. So we can suggest the Dwarf Nova outburst with Ampl>4.3 (taking into account the limit of the deepest surveys, that are used in VIZIER).

Spectral observations are required.
The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/150034.62-395849.0.png

MASTER OT J174920.10-652248.7 discovery - possible dwarf nova outburst, Ampl>5m

MASTER-SAAO auto-detection system discovered OT source at (RA, Dec) = 17h 49m 20.10s -65d 22m 48.7s on 2015-06-20.77095 UT.
The OT unfiltered magnitude is 16.8m (the limit is 19.5m).
There are 3 images with OT. There is no minor planet at this place.
We have reference image without OT on 2015-01-21.07736 UT with 19.4 unfiltered magnitude limit. There is only GALEX source with FUV=19.904 in VIZIER database. CRTS observed this area, but have never seen any source. So we can suggest the dwarf nova outburst with Ampl>5m .
Spectral observations are required.
The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/174920.10-652248.7.png

MASTER OT J203309.21+255107.7 discovery - dwarf nova outburst with previous outbursts in 2010 and in 2012

MASTER-Tunka auto-detection system discovered OT source at (RA, Dec) = 20h 33m 09.21s +25d 51m 07.7s on 2015-06-20.65939 UT.
The OT unfiltered magnitude is
16.9m (the limit is 18.2m). This OT is seen in 3 images. There is no minor planet at this place.
We have more then 200 reference images without OT in MASTER-Net, for ex., on 2012-08-20.62377 UT with 18.8 unfiltered magnitude limit.
We have 2 previous outbursts:
on 2010-09-17.741 and on 2010-09-17.776 with unfiltered m_OT=16.8 (MASTER-Kislovodsk database),
and on 2012-10-06.554 and on 2012-10-06.586 with unfiltered m_OT=16.8 (MASTER-Amur database).
There is USNO-B1 star with B2=20.49. So we can suggest the dwarf nova outburst.
Spectral observations are required.
The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/MASTEROTJ203309.21+255107.jpg

MASTER Global Robotic Net