Comet C/2011 J2 (LINEAR): Photometry and stellar transit

We present results of two-year photometric monitoring of Comet C/2011 J2 (LINEAR) that spans the time period from February 2013 through December 2014, before and after perihelion passage. The observations were conducted with broadband R filter. Analysis of observations of Comet C/2011 J2 (LINEAR) allows estimating the nucleus radius as function of geometric albedo and phase-darkening coefficient. Furthermore, our observations showed split of the comet. Fragment (B) additional to the primary C/2011 J2 nucleus was unambiguously detected; relative velocity is estimated to be ~0.17 ″/day. We derive the Afρ parameter and estimate the dust production rate in Comet C/2011 J2 (LINEAR) over the entire run of observations. We found a noticeable increase in Afρ parameter between September 18, 2014 and November 5, 2014, epoch when the nucleus presumably got split. On September 28, 2014, we observed a transit of the 16-magnitude star (USNO-A2 1275-18299027) near nucleus of the Comet C/2011 J2 (LINEAR). We retrieve the optical depth of the coma τ=0.034±0.1. The filling factor f that corresponds to such optical depth is in good quantitative agreement with the value that can be derived from the Afρ parameter under reasonable assumption on geometric albedo of cometary dust.