[Iaude] CBET 4432: 20170927 : COMET C/2017 S3 (PANSTARRS)

[quai at eps.harvard.edu]

                                                  Electronic Telegram No. 4432
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau at eps.harvard.edu (alternate cbat at iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


COMET C/2017 S3 (PANSTARRS)
     R. J. Wainscoat and R. Weryk, Institute for Astronomy, University of
Hawaii, report the discovery of another apparent comet on four w-band CCD
exposures taken with the 1.8-m Pan-STARRS1 telescope at Haleakala on Sept. 23
UT (discovery astrometry tabulated below, together with earlier Pan-STARRS1
observations found subsequently).  The object was noted to be very faint
with possible asymmetry to the east; a stacked image showed the comet
to have full-width-at-half-maximum of 1".75 in 1".25 seeing.

     2017 UT             R.A. (2000) Decl.       Mag.
     Aug. 17.32045   18 25 34.17   +80 16 42.3   21.8
          17.33433   18 25 31.93   +80 16 36.5   21.8
          17.34824   18 25 29.72   +80 16 30.1   22.1
          17.36213   18 25 27.35   +80 16 23.9   22.2
     Sept. 7.25160   17 51 42.92   +77 02 16.6   21.0
           7.26597   17 51 42.23   +77 02 06.7   21.8
           7.28035   17 51 41.61   +77 01 57.3   21.0
          23.24099   17 48 04.92   +73 58 18.7   21.5
          23.25214   17 48 05.04   +73 58 10.2   21.2
          23.26330   17 48 05.19   +73 58 02.1   21.3
          23.27443   17 48 05.30   +73 57 54.1   21.3

M. Micheli, Wainscoat, and Weryk looked at images obtained on Sept. 24.2 UT
by Wainscoat and D. Woodworth with the 3.6-m Canada-France-Hawaii Telescope
at Mauna Kea; these images show magnitude 20.9-21.3, a coma with FWHM = 1".1
in 0".85 seeing, and a possible short tail toward the east.
     After the object was posted on the Minor Planet Center's PCCP webpage,
H. Sato, Tokyo, Japan, notes that twenty stacked 60-s exposures taken on
Sept. 25.15-25.16 UT with a 0.51-m f/6.8 astrograph near Mayhill, NM, USA,
show the comet to be weakly condensed with a coma 8" in diameter and no tail;
the total w-band magnitude was 20.8 as measured within a circular aperture of
radius 4".9.
     The available astrometry, the following elliptical orbital elements by
G. V. Williams (from 29 observations spanning Aug. 17-Sept. 26; mean residual
0".4), and an ephemeris appear on MPEC 2017-S160.

                    Epoch = 2018 Aug. 30.0 TT
     T = 2018 Aug. 15.8989 TT         Peri. = 255.8998
     e = 1.000077                     Node  = 171.0978  2000.0
     q = 0.208464 AU                  Incl. =  99.0292


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

                         (C) Copyright 2017 CBAT
2017 September 27                (CBET 4432)              Daniel W. E. Green