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MASTER dwarf nova outbursts

ATel #8459; P. Balanutsa, V. Shumkov, V. Lipunov, E. Gorbovskoy (Lomonosov MSU), D. Buckley (SAAO), N. Tiurina, V. Kornilov, A. Kuznetsov, O. Gress, D. Vlasenko, I. Gorbunov, V. Vladimirov, E. Popova, S. Shurpakov (M. V.Lomonosov Moscow State Univerity, SAI), A. Tlatov, V. Senik, D. Dormidontov, A. Parkhomenko (Kislovodsk Solar Station of the Pulkovo Observatory, RAS), S. Potter, M. Kotze, A. Kniazev (The South African Astronomical Observatory)
on 23 Dec 2015; 22:25 UT
Credential Certification: Nataly Tyurina (tiurina@sai.msu.ru)

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

Referred to by ATel #: 8512, 8520

MASTER OT J072021.94-044509.3 discovery - possible dwarf nova outburst with ampl>4m

MASTER-Kislovodsk auto-detection system ( Lipunov et al., "MASTER Global Robotic Net", Advances in Astronomy, 2010, 349171 ) discovered OT source at (RA, Dec) = 07h 20m 21.94s -04d 45m 09.3s on 2015-12-19.86249 UT.
The OT unfiltered magnitude is 16.5m (limit 18.5m).
The OT is seen in 2 images. There is no minor planet at this place.
We have reference image without OT on 2015-12-04.98920 UT with unfiltered magnitude limit 17.3m. on 2015-01-19 20:42:10 m_lim=18.8, 2010-10-07 01:44:10 with m_lim=18.7. There is a GSC2.3.2 star with blue_mag=20.09, red_mag=20.66 in 0.4arcsec, so we 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/MASTEROTJ072021.94-044509.3.png

MASTER OT J072503.19-575015.1 discovery - possibly dwarf nova outburst, Ampl>2.8m (no VIZIER)

MASTER-SAAO auto-detection system discovered OT source at (RA, Dec) = 07h 25m 03.19s -57d 50m 15.1s on 2015-12-17.94416 UT.
The OT unfiltered magnitude is 19.2m (the limit is 20.2m).
The OT is seen in 5 images (2015-12-17 23:28:43.585-22:35:54.825). We reobserved it on 2015-12-21 22:23:22 with m_lim=20.2, and m_OT~20.3(marginally seen). We have reference image without OT on 2014-12-25.00451 UT with unfiltered magnitude limit 20.0m. There is no any source in VIZIER database( it means the POSS 22m limit), so we suggest the dwarf nova outburst with amplitude more then 2.8m
Spectral observations are required.
The discovery and reference images are available at http://master.sai.msu.ru/static/OT/072503.19-575015.1.png

The list of Optical Transients discovered by MASTER

MASTER Global Robotic Net