MASTER: high amplitude OT outbursts

ATel #12750; T. Pogrosheva, V. Lipunov (Lomonosov MSU), R. Podesta, F. Podesta, C. Francile (OAFA SJNU), H. Levato (ICATE SJNU), D. Buckley (SAAO), E. Gorbovskoy, N. Tiurina, P. Balanutsa, V. Kornilov, D. Zimnukhov, A. Kuznetsov, D. Vlasenko, V. Vladimirov, A. Chasovnikov, F. Balakin, V. Topolev, A. Pozdnyakov, K. Zhirkov, V. Grinshpun (Lomonosov MSU), R. Rebolo, M. Serra (IAC), O. Gress, N. Budnev, O. Ershova (ISU), V. Yurkov, Y. Sergienko, A. Gabovich (BSPU), V. Senik, A. Tlatov, D. Dormidontov (Kislovodsk solar station of the Pulkovo observatory RAS)
on 13 May 2019; 10:55 UT
Credential Certification: Nataly Tyurina (tiurina@sai.msu.ru)

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MASTER OT J123011.71-425258.9 detection - prelim. dwarf nova outburst, ampl>6m

MASTER-OAFA auto-detection system ( Lipunov et al., "MASTER Global Robotic Net", Advances in Astronomy, 2010, 30L )
discovered OT source at (RA, Dec) = 12h 30m 11.71s -42d 52m 58.9s on 2019-05-09.07435 UT.
The OT unfiltered magnitude is 15.8m (mlim=18.9m).
The OT is seen in 4 images (2019-05-10 02:00:39,02:11:39; 2019-05-09 01:47:04,01:38:01UT). There is no minor planet at this place.
We have reference images without OT on
2019-04-30 01:32:50 with unfiltered mlim=19.1 (MASTER-OAFA),
2019-04-24 23:11:15 with unfiltered mlim=20.0 (MASTER-SAAO),
2018-06-14.98395 UT with mlim=20.1m.
There is GALEX source (=> accretion process), USNO-B1 source with known blue B2=20.45, and without R2,B1,R1, that means 22m limit and more then 6mag of current outburst amplitude
Spectral observations are required.
The discovery and reference images are available at:
http://master.sai.msu.ru/static/OT/123011.71-425258.9.png

MASTER183008.37-372142.1 detection - amplitude >5.9m

MASTER-IAC auto-detection system discovered OT source at (RA, Dec) = 18h 30m 08.37s -37d 21m 42.1s on 2019-05-13.05601 UT.
The OT unfiltered magnitude is 16.1m (limit 17.8m).
The OT is seen in 2 images (MASTER-IAC) and in 2 images on 2019-05-13 07:06:16UT (MASTER-OAFA) with m_OT=16.0.
We have reference images without OT on 2019-04-13 04:39:23UT with unfilt.mlim=18.0, 2015-02-23.11400 UT with unfiltered magnitude limit 19.4m.
There is USNO-B1 star in 4.8", but if you see the DSS images and position from VIZIER, all source positions are not in the center of DSS blue object (R2,B2 DSS 22mag limit). So the amplitude is more then about 5.9m
Spectral observations are required.
The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/183008.37-372142.1.png

MASTER Global Robotic Net