Photometric Study of Comet C/2014 S2 (PANSTARRS) After the Perihelion

Abstract

We analyzed the BVR photometry of comet C/2014 S2 obtained between March and June 2016, in observatories installed in Europe and the United States. Using the Lomb–Scargle periodogram, we found that the most probable periodicity deduced from the V-band magnitudes is 2.70 days, suggesting that it is the period of rotation of the nucleus of this comet is 2.70 ± 0.07 days or 68 ± 2 h, with a peak-to-peak light curve amplitude of 0.4 ± 0.1 magnitudes. We verify that the absolute magnitude H0 and the activity index n differ from each other when they are calculated from the visual or CCD magnitudes. Considering the absolute magnitude Hv0= 6.0, obtained from visual magnitudes, we estimate that the lower limit of nuclear radius is 1.3 km. Analyzing the variation of magnitude R with the photometric aperture, we suggest that the coma of this object was in steady-state within the time limits of our observational interval. The coma had a mean color index B–V= 0.79 ± 0.22 , which is typical of active comets. Additionally, we have shown that the use of a variable photometric aperture, linked to geocentric distance, is probably unnecessary for the comet PANSTARRS.