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Two bright OTs discovery by MASTER

ATel #4428; N. Tiurina, D. Denisenko, P. Balanutsa, P. Podvorotny, S. Shurpakov, E. Gorbovskoy, V. Lipunov, V. Kornilov, A. Belinski, N. Shatskiy, V. Chazov, A. Kuznetsov, D. Zimnukhov (Moscow State University, SAI), V. Krushinsky, I. Zalozhnih, A. Popov, A. Bourdanov, A. Punanova (Ural Federal University), K. Ivanov, S. Yazev, N. Budnev, E. Konstantinov, O. Chuvalaev, V. Poleshchuk, O. Gress (Irkutsk State University), A. Parkhomenko, A. Tlatov, D. Dormidontov, V. Senik (Kislovodsk solar station of the Pulkovo observatory RAS), V. Yurkov, Y. Sergienko, D. Varda, E. Sinyakov (Blagoveshchensk Educational University), V. Shumkov, (MASTER team members), H. Levato, C. Saffe (ICATE), C. Mallamaci, C. Lopez and F. Podest (Observatorio Astronomico Felix Aguilar; OAFA)
on 27 Sep 2012; 13:13 UT
Credential Certification: Vladimir Lipunov (lipunov2007@gmail.com)

Subjects: Optical, Cataclysmic Variable, Supernovae, Transient

Referred to by ATel #: 4429

MASTER OT J045804.40+212306.8 - New bright CV or PSN

MASTER-Amur auto-detection system discovered OT source at (RA, Dec) = 04h 58m 04.40s +21d 23m 06.8s on 2012-09-26.76811 UT. The OT unfiltered magnitude is 14.9m (limit 18.9m). The OT is seen in 2 images. We have reference image without OT on 2011-11-29.76346 UT with magnitude limit in 'R' filter 18.6m.

Nothing is visible at this position on 6 Palomar plates and on their combination down to limiting magnitude 21.5. This area was observed by Palomar/NEAT project on 6 nights from 1997 Jan. 14 to 2003 Apr. 14. No previous outbursts were detected. There is a faint star (magnitude 20.5) visible at the position of the OT on the combination of 6 NEAT images obtained in December of 2001. There is nothing at this position in USNO-B1.0, 2MASS, GALEX, 1RXS and GCVS catalogs, as well as in AAVSO VSX and CRTS database. This area is not covered by SDSS.

Based on the amplitude of variability (more than 6m) we suggest that MASTER OT J045804.40+212306.8 is most likely a new cataclysmic variable (dwarf nova) in outburst. Follow up observations are required.

The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/045804.40212306.8.png

MASTER OT J063748.27+442910.9 - outburst of BY Aur (dwarf nova, not a Mira!)

MASTER-Kislovodsk auto-detection system discovered OT source at (RA, Dec) = 06h 37m 48.27s +44d 29m 10.9s on 2012-09-27.05770 UT. The OT unfiltered magnitude is 14.4m (limit 19.9m). The OT is seen in 11 images. We have reference image without OT on 2011-11-04.97069 UT with unfiltered magnitude limit 20.4m.

This object is identical to the 17-18th mag. star USNO-B1.0 1344-0174217 (R.A.=06 37 48.330 Dec.=+44 29 11.10 B1=18.56 R1=17.24 B2=17.94 R2=17.07 I=16.47) and to the infrared object 2MASS 06374833+4429107 (J=15.95+/-0.08 H=15.29+/-0.09 K=14.95+/-0.11). There is also an ultraviolet object at the same position GALEX J063748.3+442911 (FUV=21.76+/-0.33 NUV=21.63+/-0.28).

We note that there is a variable star BY Aur (formerly Harvard Variable 7656) with GCVS position 21" away from MASTER OT J063748.27+442910.9. It is listed in catalogues of variable stars as Mira-type variable. Its 1900.0 coordinates from the original paper (H. Shapley and C. Boyd, 1937) were given with the precision of 1s in R.A. and 0.1' in Dec.: 6h30m32s, +44o34.0'. Precessed to J2000.0 epoch this gives 6h37m49s, +44o29.0' (keeping the original precision). This is 13" (0.2') from USNO-B1.0 1344-0174217. The next star (USNO-B1.0 1344-0174211) is 19" (0.3') away and is not variable.

This area was observed by Palomar/NEAT project with 30 images obtained in 10 different nights from 1997 Oct. 29 to 2003 Feb. 10. OT J063748.27+442910.9 was found in outburst to 16.2m on three images taken on 2003 Feb. 10 and at quiescent level (17.3-17.5m) on all other images.

There was also an outburst to 15.1m on JD=2455294 in CRTS data and possible another one to 16.2m on JD=2455679.

Based on the shape of the archival light curve and detection of previous outbursts we conclude that MASTER OT J063748.27+442910.9 is a dwarf nova identical to the variable BY Aur whose previous identification was incorrect. Follow up observations are required.

The discovery and reference images are available at: http://master.sai.msu.ru/static/OT/063748.27442910.9.png

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