Optical classification of GAIA18aak/AT2018C as SU UMa type dwarf nova

ATel #11155; A. Simon (National Taras Shevchenko University of Kyiv, Ukraine), E. Pavlenko (Crimean astrophysical observatory, Republic of Crimea), V. Vasylenko (National Taras Shevchenko University of Kyiv, Ukraine)
on 11 Jan 2018; 00:29 UT
Credential Certification: Andrew Simon (skazhenijandrew@gmail.com)

Subjects: Optical, Cataclysmic Variable, Transient

We report the results of VRI photometrical observations of the GAIA18aak/AT2018C performed with the AZT-8 0.7-m f/4 reflector at the Lisnyky Observatory.

The blue hostless transient GAIA18aak/AT2018C was discovered on 2018-01-01 and reported on 2018-01-03 by A. Delgado, D. Harrison, S. Hodgkin, M. van Leeuwen, G. Rixon, A. Yoldas (University of Cambridge), on behalf of Gaia Alerts team at magnitude G = 16.48. On GAIA images from 2017-12-20 the object was fainter than limiting magnitude G = 21.5. So the object became brighter on more than 5 magnitudes. We detected Gaia18aak (Fig.1) on the images taken on 2018-01-09 (MJD 58127.85). Using the AAVSO catalogue for photometric calibration we obtained the following magnitudes of the source (not corrected for the Galactic foreground extinction): V = 17.10 ± 0.07, R = 17.23 ± 0.09, I = 17.47 ± 0.26. On light curve obtained over 3 hours in R-band we detected variations with the period of about 0.068d and amplitude 0.15m (Fig.2). Taking into account all these data we can suggest that this object may be a cataclysmic variable - SU UMa type dwarf nova during superoutburst. Further observations are encouraged to confirm the object classification and update the period.

We acknowledge ESA Gaia, DPAC and the Photometric Science Alerts Team (http://gsaweb.ast.cam.ac.uk/alerts).