Possible Gravitational Lensing Event detected by MASTER

ATel #5391; D. Denisenko, V. Yecheistov, V. Lipunov, E. Gorbovskoy, N. Tiurina, P. Balanutsa, V. Kornilov, N. Shatskiy, V. Chazov, A. Kuznetsov, V. Vladimirov (Moscow State University, SAI), K. Ivanov, S. Yazev, N. Budnev, E. Konstantinov, O. Chuvalaev, V. Poleshchuk, O. Gress, A. Frolova (Irkutsk State University), A. Parkhomenko, A. Tlatov, D. Dormidontov, V. Senik (Kislovodsk Solar Station of Pulkovo Observatory), 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 and F. Podest (OAFA)
on 13 Sep 2013; 15:12 UT
Credential Certification: Vladimir Lipunov (lipunov2007@gmail.com)

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MASTER OT J000521.07+264915.3 - possible gravitational lensing event

MASTER-Tunka auto-detection system discovered OT source at (RA, Dec) = 00h 05m 21.07s +26d 49m 15.3s on 2013-09-09.867 UT. The OT unfiltered magnitude is 16.9m (limit 18.6m). The OT is seen in 18 images from Aug. 2010 to Sep. 2013. We have unfiltered reference image with OT at 17.6m on 2010-08-19.731 UT (limit 19.6m).

The OT is identical to the stellar object USNO-B1.0 1168-0001488 (00 05 20.958 +26 49 15.71 pmRA=0 pmDE=0 B1=20.94 R1=19.94 B2=20.03 R2=19.37 I=19.08) which shows variability between the 1st and 2nd epoch Palomar plates, brightening by 0.6-0.9m in 40 years from 1950-1953 (POSS-I) to 1990-1993 (POSS-II). It is also present in SDSS catalogue as SDSS J000520.95+264915.6 with Type=STAR and following magnitudes: u=20.93 g=19.67 r=19.33 i=19.28 z=19.17. There is nothing at this position in 1RXS, GALEX and 2MASS catalogs, as well as in NASA Extragalactic Database (NED). However, there is an infrared object WISE J000520.98+264916.4 (W1=16.48+/-0.08 W2=16.03+/-0.21 W3=11.40+/-0.20) positionally consistent with USNO-B and SDSS coordinates.

Light curve from Catalina Real-time Transient Survey (Drake et al., 2009, ApJ Vol. 696, p. 870) downloaded from CRTS DR2 website is posted here. It shows gradual brightening at the rate of 0.15m per year, several times faster than in the interval from 1950 to 1990. Such long-term behavior is absolutely non-typical for variable stars, being more similar to the extragalactic objects (quasars). Also, SDSS (u-g) color index is too large for cataclysmic variables, and single white dwarfs do not brighten by ~3m. On the other hand, the lack of gamma, X-ray and radio detection is unusual for active quasars as bright as ~17m.

Taking into account the increasing rate of brightening over the last five decades, we suggest that MASTER OT J000521.07+264915.3 can be a gravitational lensing of the distant quasar by another object at the line of sight. If this hypothesis is correct, the object should reach the maximum light within a few weeks, after which its light curve will show the symmetrical fading. Follow up multi-wavelength monitoring and spectral observations are required. MASTER-Tunka discovery and reference images are available at: http://master.sai.msu.ru/static/OT/000521.07264915.3.jpg

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