Electronic Telegram No. 4385
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
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Prepared using the Tamkin Foundation Computer Network


COMET P/2017 G2 (PANSTARRS)
[Editor's note:  this text replaces that on CBET 4384.]
     R. Weryk, Institute for Astronomy, University of Hawaii, writes that
stacked images obtained on Apr. 3.4 UT with the 1.8-m Pan-STARRS1 telescope at
Haleakala show a possible very short tail toward the southwest; the
full-width-at-half-maximum of this object was about 1".3, versus 1".1 for
neighboring stars (discovery observations tabulated below, together with
pre-discovery Pan-STARRS1 images from Mar. 18).

     2017 UT             R.A. (2000) Decl.       Mag.
     Mar. 18.54589   13 09 19.63   +67 53 26.1   20.5
          18.55753   13 09 18.77   +67 53 26.7   20.6
     Apr.  3.41036   12 50 00.31   +67 22 10.5   20.4
           3.42330   12 49 59.33   +67 22 06.3   20.2
           3.43628   12 49 58.33   +67 22 02.3   20.4
           3.44924   12 49 57.30   +67 21 58.2   20.3

R. Wainscoat, M. Micheli, and R. Weryk obtained three 60-s gri-filtered
exposures of this object using the 3.6-m Canada-France-Hawaii Telescope at
Mauna Kea (queue observer D. Woodworth) on Apr. 4.3 UT, which confirm the
cometary nature via a short tail to the southwest.  Wainscoat adds that
three follow-up 60-s w-band exposures with the CFHT on Apr. 20 (queue observer
L. Wells) show a very-low-surface-brightness tail extending towards position
angle approximately 210 degrees for approximately 3", with an extended core
having FHWM = 0".85 (vs. adjacent stars with FWHM 0".65).
     After the object was posted on the Minor Planet Center's PCCP webpage,
H. Sato (Tokyo, Japan) writes that sixteen stacked 60-s exposures taken on
Apr. 16.19 UT with an iTelescope 0.51-m f/6.8 astrograph (+ luminance filter)
near Mayhill, NM, USA, show a strongly condensed coma 8" in diameter with no
tail; the w-band magnitude was 20.3 as measured within a circular aperture
of radius 4".9.
     The available astrometry, the following elliptical orbital elements by
G. V. Williams (from 63 observations spanning Mar. 18-Apr. 19; mean residual
0".4), and an ephemeris appear on MPEC 2017-H41.

                    Epoch = 2017 June 16.0 TT
     T = 2017 June 13.9639 TT         Peri. = 105.9569
     e = 0.650414                     Node  =  79.8169  2000.0
     q = 2.846004 AU                  Incl. =  47.9056
       a =  8.141077 AU    n = 0.0424308    P =  23.23 years


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

                         (C) Copyright 2017 CBAT
2017 April 21                    (CBET 4385)              Daniel W. E. Green