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MASTER: bright outbursts with 7.5m and 5.3m amplitude

ATel #8472; V. Lipunov, E. Popova, E. Gorbovskoy (Lomonosov MSU), D. Buckley (SAAO), N. Tiurina, A. Kuznetsov, V. Vladimirov, V. Kornilov, D. Vlasenko, V. Shumkov, I. Gorbunov (M. V.Lomonosov Moscow State University, SAI), S. Potter, M. Kotze (The South African Astronomical Observatory) ,O. Gress, N. Budnev, K. Ivanov (Applied physics institute, ISU)
on 29 Dec 2015; 23:13 UT
Credential Certification: Nataly Tyurina (tiurina@sai.msu.ru)

Subjects: Optical, Request for Observations, Cataclysmic Variable, Transient, Variables

MASTER OT J150113.71-734333.8 discovery - bright (14.5) high amplitude (>7.5mag) outburst. Dwarf Nova?

MASTER-SAAO auto-detection system ( Lipunov et al., "MASTER Global Robotic Net", Advances in Astronomy, 2010, 349171 ) discovered OT source at (RA, Dec) = 15h 01m 13.71s -73d 43m 33.8s on 2015-12-25.016 UT.
The OT unfiltered magnitude is 14.5m (the limit was 18.0m). MASTER reobserved it on the 29th of Dec. Preliminary photometry of this OT is the following
Date,UT m_OT
2015-12-25 00:23:18.41 14.5
2015-12-25 00:28:38.099 14.5
2015-12-25 00:33:55.848 14.5
2015-12-29 00:21:10.577 15.3
2015-12-29 00:22:43.475 15.3
2015-12-29 00:43:39.745 15.3

We have reference images without OT on 2015-03-02.94361 UT with unfiltered magnitude limit 19.7m. There is no any source in VIZIER database, it means the 22m max POSS limit and more then 7.5mag amplitude of the current outburst (dwarf nova?)
Spectral observations are required.
The discovery and reference images are available at http://master.sai.msu.ru/static/OT/150113.71-734333.8.png

MASTER OT J144248.29+673944.7 discovery - bright (14.6) dwarf nova outburst with ampl>5.3m
MASTER-Amur auto-detection system discovered OT source at (RA, Dec) = 14h 42m 48.29s +67d 39m 44.7s on 2015-12-15.793 UT.
The OT unfiltered magnitude is 14.6m (the limit was 17.9m).
The OT photometry is the following 2015-12-15 19:02:04.248 14.6 2015-12-15 19:25:07.47 14.6 2015-12-24 17:15:58.285 15.7 2015-12-25 17:58:46.23 15.7
We have reference image without OT on 2013-02-14.81557 UT with unfiltered magnitude limit 18.7m.
There is USNO-B1 star with B2=19.86,R2=19.92,I=19.55, also known as UV source(GALEX), so we suggest the dwarf nova outburst with Ampl>5.3.
Spectral observations are required.
The discovery and reference images are available at http://observ.pereplet.ru/images/MASTEROTJ144248.29+673944.7.jpg

List of Optical Transients discovered by MASTER

MASTER Global Robotic Net