[Iaude] CBET 4431: 20170922 : COMET C/2017 S2 (PANSTARRS)

[quai at eps.harvard.edu]

                                                  Electronic Telegram No. 4431
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 S2 (PANSTARRS)
     E. Lilly, Institute for Astronomy, University of Hawaii, reports that
she and R. Weryk found an apparent comet on four w-band Pan-STARRS1 images
taken with the 1.8-m Pan-STARRS1 telescope at Haleakala on Sept. 16 UT
(discovery astrometry tabulated below, together with earlier Pan-STARRS1
observations found subsequently), with the object showing evidence for a
faint tail 4" long toward the west but with the head appearing essentially
stellar (same FWHM as that of nearby stars).

     2017 UT             R.A. (2000) Decl.       Mag.
     Aug. 22.53736    1 35 20.63   - 4 00 54.9   21.5
          22.53813    1 35 20.64   - 4 00 55.0   21.9
          22.55134    1 35 20.69   - 4 00 55.2   21.0
          22.56532    1 35 20.75   - 4 00 55.8   21.6
          22.56607    1 35 20.76   - 4 00 55.9   21.1
          22.57932    1 35 20.83   - 4 00 56.1   21.6
          22.58006    1 35 20.82   - 4 00 56.2   21.5
     Sept.16.49961    1 32 39.25   - 4 24 38.7   20.9
          16.55924    1 32 38.12   - 4 24 42.9   20.8
          16.57379    1 32 37.85   - 4 24 44.0   20.9
          16.58835    1 32 37.57   - 4 24 45.1   21.0

M. Micheli and R. J. Wainscoat write that the cometary nature has been
confirmed on three 60-s gri-filtered CCD images taken by Wainscoat and C.
Crowder with the 3.6-m Canada-France-Hawaii Telescope at Mauna Kea on Sept.
17.4 UT, which show a tail about 7" long toward p.a. 250 deg.
     After the object was posted on the Minor Planet Center's PCCP webpage,
H. Sato, Tokyo, Japan, notes that twelve stacked 60-s exposures taken on
Sept. 17.6 UT with a 0.51-m f/6.8 astrograph at Siding Spring Observatory
shows the comet to be strongly condensed with a round coma 8" in diameter
and no tail; the total w-band magnitude was 19.7 as measured within a
circular aperture of radius 4".9.
     The available astrometry, the following elliptical orbital elements by
G. V. Williams (from 27 observations spanning Aug. 22-Sept. 20; mean
residual 0".4), and an ephemeris appear on MPEC 2017-S98.

                    Epoch = 2017 Sept. 4.0 TT
     T = 2017 Aug. 29.1588 TT         Peri. = 305.9284
     e = 0.822010                     Node  =  62.4249  2000.0
     q = 3.610340 AU                  Incl. =  12.6774
       a = 20.283921 AU    n = 0.0107889    P =  91.35 years


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

                         (C) Copyright 2017 CBAT
2017 September 22                (CBET 4431)              Daniel W. E. Green