Comet P/2013 R3 (Catalina-Panstarrs)

Apparently independent discoveries of a new comet have been made via the Catalina Sky Survey's 0.68-m Schmidt telescope (with no mention of the appearance of the object; observer R. E. Hill) and by Bryce Bolin, Jan Kleyna, Larry Denneau, and Richard Wainscoat from images obtained with the 1.8-m Pan-STARRS1 telescope on Haleakala (discovery observations tabulated below). Bolin et al. wrote that the discovery images show two distinct nuclear components separated by approximately 3" towards a position angle of 240 degrees, and a diffuse tail that extends for approximately 14" towards p.a. 240 degrees; the leading (northeast) nuclear component appears to be slightly sharper than the trailing (southwest) component. All of the reported astrometry evidently refers to the southwest component. 2013 UT R.A. (2000) Decl. Mag. Observer Sept.15.37916 0 53 26.14 + 6 22 13.3 Hill 15.38549 0 53 25.93 + 6 22 13.9 " 15.39188 0 53 25.69 + 6 22 13.2 18.0 " 15.54368 0 53 20.52 + 6 21 48.1 20.5 Pan-STARRS 15.55740 0 53 20.02 + 6 21 45.7 20.8 " 15.57121 0 53 19.52 + 6 21 43.4 19.9 " 15.58505 0 53 19.01 + 6 21 41.0 20.3 " Marco Micheli reorts that twelve stacked w-filtered follow-up images obtained by James D. Armstrong on Sept. 17.2 UT with the 1.0-m LCOGT telescope (dome B) at Cerro Tololo (and analyzed by Armstrong, Micheli, and Kelcie M. Molina) show a clear tail-like extension about 10" long in p.a. 250 deg with a central coma that is distinctly elongated in p.a. 60 deg. Additional w-band images obtained by Armstrong with the 1.0-m LCOGT telescope at the South African Astronomical Observatory in Sutherland on Sept. 24.1 reveal a clearly diffuse object with a tail approximately 20" long in p.a. about 240 deg; another set of w-band images was obtained around Sept. 24.2 with the 1.0-m LCOGT telescope at Cerro Tololo, showing a tail approximately 60" long in p.a. 245 deg and a small, diffuse coma. The Cerro Tololo images clearly show the existence of an additional co-moving condensation approximately 3" away from the center of the main coma, toward p.a. about 50 deg, with the gap between the main condensation and the secondary one being more evident in some good-seeing frames, while it seems to merge with the main coma when the image quality is poorer. After posting on the Minor Planet Center's NEOCP webpage, H. Sato (Tokyo, Japan) has also reported on the object's cometary appearance from luminance-filtered images obtained on Sept. 16.1 with an iTelescope 0.32-m f/8 astrograph near Nerpio, Spain, and on Sept. 26.5 with an iTelescope 0.51-m f/6.8 astrograph at Siding Spring, the object showing a strongly condensed coma of outer diameter of 12"-15" and 20" on the two nights, respectively; a 15"-long tail in p.a. 245 degrees was seen on the first night, while a 90" tail in p.a. 240 deg was seen on the second night. Sato notes that the magnitude as measured within a circular aperture of radius 8".8 on Sept. 16.1 was 18.7, while with a radius of 10".9 on Sept. 26.5, the magnitude was 17.3, adding that the outer coma is faint. It does appear that the comet has brightened by a magnitude or more in the week and a half since discovery.