Electronic Telegram No. 4215
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 P/2015 X3 (PANSTARRS)
     R. J. Wainscoat reports that an object found on four r-band exposures
obtained on Dec. 1.4 UT with the 1.8-m Pan-STARRS1 telescope on Haleakala
shows hints of being extended (discovery observations tabulated below,
together with pre-discovery Pan-STARRS1 observations from November that were
found later), and he obtained three 60-s w-band follow-up observations using
the 3.6-m Canada-France-Hawaii Telescope on Dec. 5.50 with M. Micheli and C.
Wipper that show the object to be distinctly extended (FWHM 1".7 in 0".9
seeing) with a broad, low-surface-brightness tail extending for approximately
3" to the south (with red mag 20.4-20.5 measured).

     2015 UT             R.A. (2000) Decl.       Mag.
     Nov.  6.38775    3 35 39.77   + 0 21 04.1   20.6
           6.39946    3 35 39.16   + 0 21 06.9   20.7
          15.40784    3 28 02.43   + 1 03 45.1   20.4
          15.41997    3 28 01.82   + 1 03 49.3   20.5
          15.43213    3 28 01.17   + 1 03 53.1   20.5
          15.44436    3 28 00.50   + 1 03 57.0   20.5
     Dec.  1.40586    3 15 03.71   + 2 47 07.8   21.1
           1.41720    3 15 03.20   + 2 47 12.7   21.4
           1.42863    3 15 02.67   + 2 47 17.9   21.1
           1.43976    3 15 02.17   + 2 47 23.2   20.8

After the comet was posted on the Minor Planet Center's PCCP webpage, other
CCD astrometrists also noted the object's cometary appearance.  H. Sato,
Tokyo, Japan, writes that twelve stacked 60-s exposures taken with an
iTelescope 0.51-m f/6.8 astrograph (+ luminance filter) near Mayhill, NM,
U.S.A., on Dec. 7.22 UT shows the comet to be strongly condensed with a coma
6" in diameter and no tail; the w-band magnitude was 20.0 as measured within
a circular aperture of radius 4".9.  V-band images taken by W. H. Ryan and
E. V. Ryan with the Magdalena Ridge Observatory 2.4-m f/8.9 reflector on Dec.
8.3 show a coma with a faint, wide tail at p.a. about 170 deg.
     The available astrometry, the following elliptical orbital elements by
G. V. Williams, and an ephemeris appear on MPEC 2015-X104.

                    Epoch = 2015 Aug.  6.0 TT
     T = 2015 Aug.  7.7971 TT         Peri. = 306.8911
     e = 0.438323                     Node  =  77.3265  2000.0
     q = 2.822575 AU                  Incl. =  24.3793
       a =  5.025262 AU    n = 0.0874915    P =  11.3 years


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

                         (C) Copyright 2015 CBAT
2015 December 8                  (CBET 4215)              Daniel W. E. Green