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MASTER-SAAO Discovery of two Dwarf Novae

ATel #7501; D. Denisenko, V. Lipunov, E. Gorbovskoy (Lomonosov MSU), D. Buckley (SAAO), S. Antipin, N. Tiurina, P. Balanutsa, V. Kornilov, A. Kuznetsov, V. Chazov, E. Popova, V. Vladimirov (Lomonosov Moscow State University, SAI), S. Potter, A. Kniazev, M. Kotze (The South African Astronomical Observatory), N. Budnev, K. Ivanov, O. Gress, S. Yazev, V. Poleshchuk (Irkutsk State University), A. Tlatov, D. Dormidontov, V. Senik, A. Parkhomenko (Kislovodsk solar station of the Pulkovo observatory RAS), V. Krushinsky, I. Zalozhnih, A. Popov, A. Bourdanov (Ural Federal University), Yu. Sergienko, V. Yurkov, A. Gabovich (Blagoveschensk State Educational University), V. Shumkov, S. Shurpakov (MASTER-Team)
on 13 May 2015; 08:19 UT
Credential Certification: Nataly Tyurina (tiurina@sai.msu.ru)

Subjects: Optical, Cataclysmic Variable, Transient

MASTER OT J130005.14-411548.9 - new cataclysmic variable

MASTER-SAAO auto-detection system ( Lipunov et al., Advances in Astronomy, MASTER Global Robotic Net, 2010 ) discovered OT source at (RA, Dec) = 13h 00m 05.14s -41d 15m 48.9s on 2015-05-10.84706 UT. The OT unfiltered magnitude is 18.3m (limit 20.1m). The OT is seen in 6 images. We have reference image without OT on 2015-03-28.87264 UT with unfiltered magnitude limit 19.4m.

There is a faint star within 1" of the OT (13 00 05.09 -41 15 49.5) with jmag=21.97 in GSC 2.3.2. Color-combined DSS finder chart is uploaded to http://master.sai.msu.ru/static/OT/J130005-411549-JRIR5x5.jpg (2x zoom).

Based on the outburst amplitude, MASTER OT J130005.14-411548.9 is likely a dwarf nova in outburst. Spectral confirmation is required. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/130005.14-411548.9.png

MASTER OT J143615.49-360416.9 - new cataclysmic variable

MASTER-SAAO auto-detection system discovered OT source at (RA, Dec) = 14h 36m 15.49s -36d 04m 16.9s on 2015-05-10.89203 UT. The OT unfiltered magnitude is 16.1m (limit 19.4m). The OT is seen in 4 images. We have reference image without OT on 2015-03-30.95931 UT with unfiltered magnitude limit 19.3m.

The OT is identical to ASASSN-15iv discovered independently by ASAS-SN about 7 hours later (V=15.8 on 2015-05-11.20 UT). There is a faint star USNO-B1.0 0539-0321410 at this position (14 36 15.53 -36 04 16.7 B2=21.98 R2=18.90) with Fmag=20.44 and jmag=22.19 in GSC 2.3.2. Color-combined DSS finder chart is uploaded to http://master.sai.msu.ru/static/OT/J143615-360417-JRIR5x5.jpg (2x zoom). The object has an UV counterpart GALEX J143615.5-360415 (FUV=21.79+/-0.36 NUV=20.97+/-0.23).

There are previous detections in Siding Spring Survey Orphancat: to 16.9m on MJD=53817 and 17.1-17.4m on MJD 54910-54923. The star is listed in CMC15 with r'mag=16.39 (also in outburst). MASTER OT J143615.49-360416.9 is a dwarf nova. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/143615.49-360416.9.png

List of Optical Transients discovered by MASTER

Global MASTER Robotic Net