Electronic Telegram No. 4378
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/2017 D5 (PANSTARRS)
     R. J. Wainscoat, M. Micheli and R. Weryk report the discovery of another
comet on trailed images obtained with the 1.8-m Pan-STARRS1 telescope at
Haleakala on Feb. 23 (with pre-discovery images also identified on exposures
taken on Feb. 10); the discovery and pre-discovery observations are tabulated
below.  Based upon suspicious cometary appearance on the discovery images
(which were trailed due to the fast motion of the object), the group obtained
three 90-s w-band exposures using the 3.6-m Canada-France-Hawaii Telescope at
Mauna Kea on Feb. 24 (queue observer C. Wipper) that show a point-like nuclear
condesnsation with a faint, broad, low-surface-brightness tail appears to
extend to the east for approximately 5" in each image.

     2017 UT             R.A. (2000) Decl.       Mag.
     Feb. 10.32475    7 47 14.01   -44 18 57.4
          10.34076    7 47 09.19   -44 18 11.7   21.3
          10.34875    7 47 06.81   -44 17 48.7
          23.23900    6 56 45.20   -32 53 36.0   20.4
          23.25836    6 56 41.71   -32 52 32.3   20.6
          23.26803    6 56 39.98   -32 52 00.2   20.6

Wainscoat and D. Woodworth also obtained twenty four 90-s exposures with the
CFHT on Feb. 27.4 UT through clouds, in which the four clearest exposures
suggest the existence of a very faint tail to the east-northeast.
Wainscoat and L. Wells further obtained three 120-s gri-filtered CFHT
exposures on Mar. 31.3 that confirm a weak but definite cometary activity is
clearly present, in the form of a faint tail extending to the east of the
nuclear condensation (measured by Micheli and Wainscoat).
     After the comet was posted on the Minor Planet Center's PCCP webpage,
other CCD astrometrists also commented on the cometary appearance.  H. Sato,
Tokyo, Japan, writes that twenty 30-s exposures taken with a 0.51-m f/6.8
astrograph at Siding Spring on Feb. 24.6 UT show a 5" coma and no tail,
with the coma's FWHM being 4".5 vs. 3".5 for a nearby star; the w-band
magnitude was 20.6 as measured within a circular aperture of radius 4".9.
T. H. Bressi obtained exposures on Mar. 30.17 with the Spacewatch 1.8-m
f/2.7 reflector (+ broadband Schott OG-515 filter) at Kitt Peak in 2".0
seeing that show the comet to be slightly extended with a soft appearance
in comparison with nearby field stars.
     The available astrometry, the following retrograde elliptical orbital
elements by G. V. Williams (from 71 observations spanning Feb. 10-Mar. 31),
and an ephemeris appear on MPEC 2017-G04.

                    Epoch = 2017 Jan.  7.0 TT
     T = 2017 Jan.  8.8593 TT         Peri. = 287.8187
     e = 0.980847                     Node  =  92.7199  2000.0
     q = 2.167185 AU                  Incl. = 131.0390


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

                         (C) Copyright 2017 CBAT
2017 April 2                     (CBET 4378)              Daniel W. E. Green