[IAUC] CBET 4212: 20151206 : COMET P/2015 X1 (PANSTARRS)

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                                                  Electronic Telegram No. 4212
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau en eps.harvard.edu (alternate cbat en iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


COMET P/2015 X1 (PANSTARRS)
     Eva Lilly, Robert Weryk, and Richard Wainscoat report the discovery of an
apparent comet on four w-band CCD frames taken on Dec. 1.3 UT with the 1.8-m
Pan-STARRS1 telescope on Haleakala (discovery observations tabulated below),
the object showing evidence of a very faint tail extending towards the north
for approximately 1".5.

     2015 UT             R.A. (2000) Decl.       Mag.
     Dec.  1.29904    1 34 38.92   - 7 32 38.3   20.4
           1.31099    1 34 39.08   - 7 32 35.3   20.4
           1.32296    1 34 39.24   - 7 32 32.3   20.4
           1.33491    1 34 39.41   - 7 32 29.3   20.4

Three 60-s confirming exposures were obtained by M. Micheli and Wainscoat
(queue observer C. Wipper) using the 3.6-m Canada-France-Hawaii Telescope on
Dec. 5.3 UT, which show a diffuse appearance with a faint coma (FWHM about
0".85, compared to 0".7 for nearby stars) and a short tail-like extension
about 3" long to the north is also visible; the red magnitude was measured as
19.9-20.0.  After the comet was posted on the Minor Planet Center's PCCP
webpage, other CCD astrometrists also noted the object's cometary appearance.
V-band images obtained by W. H. Ryan and E. V. Ryan with the Magdalena Ridge
Observatory 2.4-m f/8.9 reflector on Dec. 2.2 show a wide tail spanning p.a.
about 0-45 deg; similar frames taken on Dec. 3.3 and 4.2 show the wide tail
at p.a. about 0 deg and slightly east of 0 deg, respectively.  H. Sato,
Tokyo, Japan, writes that twelve stacked 60-s exposures takenon Dec. 2.22
with an iTelescope 0.51-m f/6.8 astrograph (+ luminance filter) near Mayhill,
NM, USA, show a moderately consensed coma 8" in diameter with no tail, with
w-band magnitude 20.3 as measured within a circular aperture of radius 4".9.
J.-F. Soulier obtained unfiltered images with a 0.30-m f/3.8 Newtonian
reflector at Maisoncelles, France, on Dec. 4.84-4.87 that show a 15" coma and
a 12"-long tail toward p.a. 45 deg, with the red magnitude given as 19.5-19.6.
     The available astrometry (including pre-discovery observations from the
Pan-STARRS1 telescope on Aug. 12.6 UT at mag 21.5-22.0 and Sept. 23.43-23.47
at mag 20.0-20.2, and from the Catalina Sky Survey on Oct. 9.4 at mag
19.6-20.4 and Oct. 15.4 at mag 19.5-19.9), the following elliptical orbital
elements by G. V. Williams, and an ephemeris appear on MPEC 2015-X58.

                    Epoch = 2015 Oct. 25.0 TT
     T = 2015 Oct. 10.6735 TT         Peri. = 219.0286
     e = 0.420412                     Node  = 161.7914  2000.0
     q = 2.103559 AU                  Incl. =  12.1623
       a =  3.629401 AU    n = 0.1425449    P =   6.91 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 6                  (CBET 4212)              Daniel W. E. Green