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Multi-color observation of active comets

In general, due to a high temperature and a presence of gas sublimation leading to coma emission, a comet is supposed to be active when it is close to the Sun. We start to investigate photometric information from some special active comets. The data were obtained with the 1-m wide field optical telescope (hereafter NOWT) at Nanshan Observatory in Xinjiang. This project was started in 2017. By multi-color observation and cometary morphological studies, we can estimate the surface brightness profiles, Afρ parameters, mass production rates, the sizes of nuclei radii and coma colors. Meanwhile the physical driving mechanism of activity in comets needs to be discussed. Here we will give a brief description of our photometric observations of comet C/2015 O1 with NOWT. Object C/2015 O1 was discovered on 2015 July 19 by the Pan-STARRS 1 telescope. The followup observations with NOWT were carried out starting 2017 August 31. In total, the number of observations collected of C/2015 O1 for B, V, R bands are 44, 36, and 37, respectively. The standard IRAF packages were used to measure the core magnitude of coma. We also gave a rough estimate of the possible outside structure of C/2015 O1. Finallywe conclude that C/2015 O1 has a lower activity than expected. And a solar radiation pressure model can be used to explain the surface brightness profiles of C/2015 O1.