Electronic Telegram No. 3735
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director:  Daniel W. E. Green; 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/2013 W2 (PANSTARRS)
     Bryce Bolin, Richard Wainscoat, Peter Veres, Larry Denneau, and Serge
Chastel report the discovery of a comet with a diffuse, non-stellar appearance
and a faint tail approximately 1".5 long in p.a. approximately 275 degrees on
four 45-s w-band exposures from the Pan-STARRS1 telescope at Haleakala
(discovery observations tabulated below).

     2013 UT             R.A. (2000) Decl.       Mag.
     Nov. 27.36846    5 25 05.03   +17 43 09.4   20.9
          27.38369    5 25 04.61   +17 43 08.7   20.9
          27.39894    5 25 04.19   +17 43 07.9   20.9

Marco Micheli and Richard Wainscoat obtained follow-up images on Nov. 30.4 UT
with the 3.6-m Canada-France-Hawaii Telescope (queue observer Adam Draginda);
six 60-s r-band exposures show a non-stellar point-spread function (PSF; with
FWHM about 1".0 in 0".8 seeing conditions) and possibly a short tail in p.a.
about 270 deg, the object's magnitude given as 20.0-20.2.  After the object
was posted on the Minor Planet Center's PCCP webpage, other CCD astrometrists
have also commented on the object's cometary appearance.  W. H. Ryan
(Magdalena Ridge Observatory, 2.4-m f/8.9 reflector; Nov. 29.3) reports a PSF
about 1.8 times larger than that of nearby field stars with slight evidence
of a tail in p.a. about 270 deg; his R-band exposures yield mag 20.0-20.1 for
the comet.  H. Sato (Tokyo, Japan; remotely with an iTelescope 0.43-m f/6.8
astrograph near Mayhill, NM, U.S.A.; Nov. 29.45) reports a moderately
condensed coma 8" in diameter on twenty stacked 60-s exposures.
     The available astrometry, the following preliminary orbital elements by
G. V. Williams, and an ephemeris appear on MPEC 2013-X26.

     T = 2014 Nov.  4.4451 TT         Peri. = 299.2510
     e = 0.542953                     Node  = 179.9891  2000.0
     q = 4.533495 AU                  Incl. =   4.5090
       a =  9.919099 AU    n = 0.0315497    P =  31.2 years


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2013 CBAT
2013 December 5                  (CBET 3735)              Daniel W. E. Green