Comet P/2019 A4 (Panstarrs)

R. Wainscoat, Y. Ramanjooloo, and R. Weryk, Institute for Astronomy, University of Hawaii, report the discovery of a comet in three 45-s w-band exposures taken with the 1.8-m Ritchey-Chretien Pan-STARRS1 telescope on Jan. 10.4 UT (discovery observations tabulated below, along with pre-discovery Pan-STARRS1 observations from Jan. 3 that were reported later by Weryk), the object then showing a tail about 7" long in p.a. about 275 degrees, with full-width-at-half-maximum of the head/coma being about 3".6 (vs. about 1".6 for nearby stars). The Jan. 3 observations (four 45-s w-band images) also show a tail extending toward the west for about 8", with FWHM about 2".2 in 1".3 seeing. 2019 UT R.A. (2000) Decl. Mag. Jan. 3.54298 7 42 48.97 +17 25 50.6 3.55524 7 42 48.25 +17 25 56.6 20.1 3.56748 7 42 47.55 +17 26 02.7 20.0 10.36534 7 36 21.79 +18 24 35.8 20.6 10.37717 7 36 21.05 +18 24 42.3 20.5 10.38916 7 36 20.34 +18 24 48.6 20.6 Weryk adds that Wainscoat and he obtained three follow-up 60-s gri-band exposures on Jan. 11.37 UT with the 3.6-m Canada-France-Hawaii Telescope at Mauna Kea (queue observer L. Wells; coordinator S. Prunet), which show a tail extending for 10" towards p.a. 280 deg (FWHM = 1".34 in 0".66 seeing). After the comet was posted on the Minor Planet Center's PCCP webpage, other CCD astrometrists also commented on the cometary appearance. R. A. Mastaler notes that images taken on Jan. 12.3 with the Spacewatch 0.9-m f/3 reflector at Kitt Peak in 1".4 seeing show a faint coma of red mag 19.6-19.8 with a tail about 4" to 6" long in p.a. about 280 degrees. H. Sato, Tokyo, Japan, writes that ten stacked 60-s exposures taken on Jan. 12.6 with an iTelescope 0.51-m f/6.8 astrograph at Siding Spring show a strongly condensed coma 8" in diameter with a hint of tail 10" long toward p.a. 280 degrees; the magnitude was 19.3 as measured within a circular aperture of radius 4".9.