Electronic Telegram No. 4351
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)
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Prepared using the Tamkin Foundation Computer Network


COMET C/2016 VZ_18 (PANSTARRS)
[Editor's note:  the text below replaces that on CBET 4350]
     An apparently asteroidal object found on 2016 Nov. 6 with the 1.8-m
Ritchey-Chretien Pan-STARRS1 telescope at Haleakala (and then given the
minor-planet designation 2016 VZ_18; cf. MPEC 2016-Y02 and MPS 752865;
discovery observations tabulated below) has been found to show cometary
appearance by CCD astrometrists elsewhere.

     2016 UT             R.A. (2000) Decl.       Mag.
     Nov.  6.43579    2 56 05.80   -22 26 25.9   21.8
           6.45797    2 56 03.95   -22 26 34.5   21.8
           6.46909    2 56 03.00   -22 26 39.1   21.5

H. Sato, Tokyo, Japan, writes that thirteen stacked 30-s exposures taken on
2016 Dec. 26.45 UT with an iTelescope 0.51-m f/6.8 astrograph (+ luminance
filter) at Siding Spring show a stellar head with a hint of a tail 10" long
toward p.a. 255 degrees; the w-band magnitude was 20.1 as measured within a
circular aperture of radius 4".9.  Twelve 90-s images obtained by M. Micheli
together with D. Koschny, A. Knoefel, M. Busch, E. Schwab, and D. Abreu on
2017 Jan. 27.9 with the European Space Agency's 1-m Optical Ground Station
telescope at Tenerife, Canary Islands, show clear cometary activity in the
form of a diffuse and broad tail extending about 15" to the west; the
G-band magnitude was measured as 19.5-19.7.
     The available astrometry (including Pan-STARRS1 pre-discovery
observations from 2016 Oct. 8, when the magnitude was given as 22.4-23.1),
the following elliptical orbital elements by Williams (from 86 observations
spanning 2016 Oct. 8-2017 Jan. 27), and an ephemeris appear on MPEC 2017-B83.

                    Epoch = 2017 Feb. 16.0 TT
     T = 2017 Mar.  7.3799 TT         Peri. =  36.3857
     e = 0.995325                     Node  =  98.9551  2000.0
     q = 0.910268 AU                  Incl. =  24.0356


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2017 CBAT
2017 January 29                  (CBET 4351)              Daniel W. E. Green