Electronic Telegram No. 4318
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


COMET C/2016 R2 (PANSTARRS)
     R. Weryk and R. Wainscoat report the discovery of an apparent comet in
three w-band exposures obtained with the 1.8-m Pan-STARRS1 telescope at
Haleakala on Sept. 7 UT (discovery observations tabulated below, along with
pre-discovery images from Aug. 30); the object is clearly cometary, with its
coma visible out to at least 20" in radius.

     2016 UT             R.A. (2000) Decl.       Mag.
     Aug. 30.62523    3 53 13.31   -37 25 54.7   18.9
          30.63371    3 53 13.37   -37 25 57.7   18.9
     Sept. 7.58803    3 53 22.95   -38 07 09.6   19.1
           7.59769    3 53 22.93   -38 07 13.0   19.0
           7.60737    3 53 22.91   -38 07 15.7   19.1
           7.62251    3 53 22.85   -38 07 20.8   18.8

R. J. Wainscoat and P. Forshay obtained three 60-s gri-filtered follow-up CCD
exposures using 3.6-m the Canada-France-Hawaii Telescope at Mauna Kea on Sept.
8.6 UT, confirming the new object's cometary appearance, as it displays an
obvious large coma, with an extended point-spread function; the core of the
coma has a FWHM of about 1".4, compared to 0".9 for nearby stars.  D. J.
Tholen finds that images taken on Sept. 8.64 by Z. Claytor and Y. Ramanjooloo
with the 2.24-m University of Hawaii reflector in morning nautical twilight
shows the comet to be very diffuse, with the measured width being more than
twice that of nearby stars (which averaged 1".2), and no obvious tail; the
red magnitude was measured to be 18.0-18.1.
     The available astrometry, the following preliminary elliptical orbital
elements by G. V. Williams (from 21 observations spanning Aug. 30-Sept. 8),
and an ephemeris appear on MPEC 2016-R107.

                    Epoch = 2018 May   2.0 TT
     T = 2018 May  16.7568 TT         Peri. =  33.0710
     e = 0.978153                     Node  =  80.7156  2000.0
     q = 2.635985 AU                  Incl. =  58.1612


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2016 CBAT
2016 September 9                 (CBET 4318)              Daniel W. E. Green