Electronic Telegram No. 4220
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)
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Prepared using the Tamkin Foundation Computer Network


COMET C/2015 X5 (PANSTARRS)
     R. Weryk, Institute for Astronomy, University of Hawaii, together with
E. Lilly and R. J. Wainscoat, report the discovery of another comet in four
r-band exposures taken with the 1.8-m Pan-STARRS1 telescope on Haleakala (the
Dec. 6 discovery observations tabulated below), the object described as having
an extended profile (stacked images showing a coma with FWHM approximately
1".5 in 0".9 seeing).  Three 60-s ollow-up exposures obtained by Wainscoat and
L. Wells on Dec. 8.61 UT with the 3.6-m Canada-France-Hawaii Telescope at
Mauna Kea show the object to be clearly cometary, tail a tail about 12" long
in p.a. 175 deg and a coma with FWHM approximately 1".0 in 0".5 seeing (red
magnitude 20.6-20.8), as measured by M. Micheli and Wainscoat.

     2015 UT             R.A. (2000) Decl.       Mag.
     Dec.  6.55364    9 14 35.06   - 5 21 13.9   21.3
           6.56590    9 14 34.83   - 5 21 12.6   21.2
           6.57764    9 14 34.62   - 5 21 11.4   21.4
           6.58941    9 14 34.42   - 5 21 10.5   21.2

After the object was posted on the Minor Planet Center's NEOCP and PCCP
webpages, other CCD astrometrists also noted the object's cometary appearance.
V-band images taken by W. H. Ryan and E. V. Ryan with the Magdalena Ridge
Observatory 2.4-m f/8.9 reflector on Dec. 8.4 UT show a tail in p.a. about
170 deg.  H. Sato, Tokyo, Japan, writes that forty stacked 60-s exposures
taken with a 0.43-m f/6.8 astrograph (+ r-band filter) near Mayhill, NM, USA,
show the coomet to be moderately condensed with a coma 6" in diameter and no
tail detected.
     The available astrometry, the following preliminary parabolic orbital
elements by G. V. Williams, and an ephemeris appear on MPEC 2015-X179.

     T = 2013 Aug. 31.6263 TT         Peri. = 251.5131
                                      Node  = 127.6562  2000.0
     q = 4.000543 AU                  Incl. = 111.5082


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2015 CBAT
2015 December 16                 (CBET 4220)              Daniel W. E. Green