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Peculiar variable object in Ophiuchus discovered by MASTER

ATel #6333; D. Denisenko, V. Lipunov, E. Gorbovskoy, N. Tiurina, P. Balanutsa, V. Kornilov, N. Shatskiy, V. Chazov, A. Kuznetsov, V. Vladimirov, V. Yecheistov (Moscow State University, SAI), A. Parkhomenko, A. Tlatov, D. Dormidontov, V. Senik (Kislovodsk Solar Station of Pulkovo Observatory), K. Ivanov, S. Yazev, N. Budnev, E. Konstantinov, O. Chuvalaev, V. Poleshchuk, O. Gress (Irkutsk State University), V. Yurkov, Y. Sergienko, D. Varda, E. Sinyakov, A. Gabovich (Blagoveshchensk Educational University), V. Krushinsky, I. Zalozhnih, A. Popov, A. Bourdanov (Ural Federal University), P. Podvorotny, V. Shumkov, S. Shurpakov (MASTER team members), H. Levato, C. Saffe (ICATE), C. Mallamaci, C. Lopez, F. Podest (OAFA)
on 21 Jul 2014; 20:55 UT
Credential Certification: Nataly Tyurina (tiurina@sai.msu.ru)

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

MASTER OT J163838.07-054846.0 - outburst of SDSS J163837.89-054847.5 = WISE J163837.92-054847.5

MASTER-Kislovodsk auto-detection system discovered OT source at (RA, Dec) = 16h 38m 38.07s -05d 48m 46.0s on 2014-07-21.77098 UT. The OT unfiltered magnitude is 17.0m (limit 18.8m). The OT is seen in 3 images. There is no minor planet at this place. We have reference image without OT on 2012-06-12.91684 UT with unfiltered magnitude limit 19.5m.

The object at quiescence is identical to SDSS J163837.89-054847.5 (u=19.87 g=19.32 r=18.83 i=18.48 z=18.14). Despite quite a white color in optical band, there is unusually large infrared excess: WISE J163837.92-054847.5 (W1=15.37 W2=15.01 W3=10.96 W4=7.69). Object is also present in USNO catalog as USNO-B1.0 0841-0297337 (16 38 37.886 -05 48 47.68 B2=20.39 R2=19.40). Color-combined DSS finder chart is uploaded to http://master.sai.msu.ru/static/OT/J163838-054846-JRIR5x5.jpg (2x zoom). Carlsberg Meridian Catalog has CMC15 163837.8-054847 at r'mag=17.425. There is nothing at this position in NED, Simbad and AAVSO VSX.

The object was observed by Palomar/NEAT with good quality images obtained on 24 nights from June 1997 to Aug. 2005. Three similar outbursts were detected on 2001-06-19, 2002-06-01 and 2005-08-28. Photometrically, the object appears to be a dwarf nova. However, the large IR excess in WISE data is rather characteristic of the extragalactic origin. Taking into account this peculiarity, spectral identification is required. The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/163838.07-054846.0.jpg

List of Optical Transients discovered by MASTER

Global MASTER Robotic Net