Superhumps in the lightcurve of the SU UMa type dwarf nova candidate ZTF19aaumtxz/Gaia19btn are detected
A. Simon (National Taras Shevchenko University of Kyiv, Ukraine), E. Pavlenko (Crimean Astrophysical Observatory, Republic of Crimea), O. Antonyuk (Crimean Astrophysical Observatory, Republic of Crimea), N. Pit (Crimean Astrophysical Observatory, Republic of Crimea), V. Godunova (ICAMER Observatory, Ukraine), V. Vasylenko (National Taras Shevchenko University of Kyiv, Ukraine), A. Baransky (National Taras Shevchenko University of Kyiv, Ukraine), O. Ostapenko (National Taras Shevchenko University of Kyiv, Ukraine)
We report the results of recent observations of ZTF19aaumtxz/Gaia19btn performed on 2019 May 15-18 with the AZT-11 1.25-m f/8 reflector at the Crimean Astrophysical Observatory (unfiltered observations) and the AZT-8 0.7-m f/4 reflector at the Lisnyky Observatory near Kyiv (BVRI photometry). The blue hostless transient ZTF19aaumtxz/Gaia19btn/AT2019fda was discovered on 2019-05-09 by J. Nordin, V. Brinnel, M. Giomi, J. van Santen (HU Berlin), A. Gal-Yam, O. Yaron, S. Schulze (Weizmann) on behalf of ZTF team at magnitude r-ZTF = 15.43 and rediscovered on 2019-05-12 by A. Delgado, D. Harrison, S. Hodgkin, M. van Leeuwen, G. Rixon, A. Yoldas (University of Cambridge), on behalf of the Gaia Alerts Team. In the ZTF images from 2019-05-05 the object was fainter than limiting AB magnitude g-ZTF = 20.7654, thus it became brighter by more than 5.5 mags. From unfiltered observations taken on 2019-05-15 (MJD 58618.88), we detected the well-defined superhumps in the Gaia19btn light curve (Fig.1) with a period of 0.0581d and amplitude of 0.15. Using the Gaia Calibration Server for the photometric calibration of datasets from 2019-05-17 (MJD 58620.94), we obtained the following magnitudes of the source (not corrected for the Galactic foreground extinction): B = 16.60 ± 0.04, V = 16.55 ± 0.08, R = 17.03 ± 0.04, I = 16.89 ± 0.06. Taking into account all these data we can suggest that this object appears to be a cataclysmic variable, namely a SU UMa type dwarf nova during a superoutburst. Further observations are encouraged. We acknowledge the ZTF-team, as well as ESA Gaia, DPAC and the Photometric Science Alerts Team (http://gsaweb.ast.cam.ac.uk/alerts).
optical,cataclysmic variable,nova,transient,variables