Activity of (6478) Gault during 2019 January 13-March 28

We present the results of photometric observations of active asteroid (6478) Gault performed at heliocentric distances from 2.46 to 2.30 au and geocentric distances from 1.79 to 1.42 au between 2019 January 15 and March 28. Observations were carried out at the 2.5-m telescope of SAI MSU (Caucasian Mountain Observatory) on 2019 January 15 and at the 1.3 and 0.61-m telescopes (SPb) on 2019 February 6 and March 28, respectively. The direct images of the asteroid were obtained with the broad-band B, V, and R filters. Comet-like structures were detected at all observation dates. Colour maps were built and colour variations along the tail for the observation made on 2019 January 15 were analysed. The Af rho was calculated for the R filter, and the evaluated value varies from 47 to 32 cm for the period from 2019 January to the end of March. The rotational period of the body is estimated from the light curve by different methods and is about 1.79 h. Possible mechanisms of triggering Gault's activity are discussed.