Electronic Telegram No. 4119
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/2015 O1 (PANSTARRS)
     E. Lilly and R. J. Wainscoat report the discovery of a comet in four
w-band exposures taken with the 1.8-m Pan-STARRS1 telescope at Haleakala
on July 19.5 UT (discovery observations tabulated below), noting its image to
have a full-width-at-half-maximum of 1".5 (vs. 0".9 for nearby stars), and
adding that there is evidence of a short tail extending for approximately 2".5
towards position angle approximately 100 degrees.

     2015 UT             R.A. (2000) Decl.       Mag.
     July 19.47014   20 37 14.00   -25 09 55.7   19.6
          19.48149   20 37 13.51   -25 09 56.0   19.7
          19.49288   20 37 13.04   -25 09 56.4   19.6
          19.50426   20 37 12.56   -25 09 56.8   19.6

Follow-up observations obtained by Wainscoat, M. Micheli, and D. Woodworth
with the 3.6-m Canada-France-Hawaii Telescope at Mauna Kea on July 20.47
show the object to be clearly cometary with a tail about 4" tail long in
p.a. 100 deg and a clear coma visible with FWHM = 1".1 in 0".7 seeing; the
red magnitude was given as 19.8-19.9.
     After the object was posted on the Minor Planet Center's PCCP webpage,
A. Maury and J.-F. Soulier report that their unfiltered CCD images taken on
July 21.12-21.19 UT with a 0.4-m f/8 Ritchey-Chretien reflector at San Pedro
de Atacama, Chile, show a coma of size 15" x 17" with a likely tail toward
p.a. 120 deg; they measured red mag 18.5-18.8 within an aperture of radius
6".2.
     The available astrometry, the following preliminary parabolic orbital
elements by G. V. Williams, and an ephemeris appear on MPEC 2015-O34.

     T = 2017 Feb.  3.2443 TT         Peri. = 127.3535
                                      Node  = 306.1024  2000.0
     q = 1.044562 AU                  Incl. =  67.6832


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2015 CBAT
2015 July 22                     (CBET 4119)              Daniel W. E. Green