Electronic Telegram No. 4109
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director:  Daniel W. E. Green; Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


COMET C/2015 GX (PANSTARRS)
     An apparently asteroidal object discovered with the 1.8-m Pan-STARRS1
telescope at Haleakala on Apr. 8.6 UT (discovery observations tabulated
below), and announced with the minor-planet designation 2015 GX on MPS 598613,
has been found to show cometary appearance by CCD astrometrists elsewhere.

     2015 UT             R.A. (2000) Decl.       Mag.
     Apr.  8.58495   18 07 24.39   +40 07 38.4   20.0
           8.59564   18 07 24.73   +40 08 05.1   19.9
           8.60629   18 07 25.04   +40 08 31.8   19.8
           8.61698   18 07 25.37   +40 08 58.3   20.0

R. Haver, Frasso Sabino, Italy, reported that twenty stacked 90-s unfiltered
images taken on May 9.94-9.95 with a 37-cm Cassegrain reflector show a
possible faint coma elongated slightly southward; the comet was very faint
(mag 19.2 with a limiting mag of about 21).  Haver's follow-up images taken
on May 18.0 continued to show a faint cometary appearance, with an apparent
elongation toward the south; he adds that additional images taken on May 25.0
again appear to show a faint coma of diameter about 7", elongated southward,
noting that the coma was now more obvious than previously.  L. Buzzi reports
that thirty stacked 30-s images obtained with a 1.0-m f/8 Ritchey-Chretien
telescope at McDonald Observatory on May 25.4 show a central condensation
surrounded by a coma at least 6" wide, with a hint of a tail suspected toward
the south; thirty stacked 30-s follow-up images on May 27.4 show a compact coma
5" across with a short, faint, fan-shaped tail in p.a. around 190 deg.
H. Sato, Tokyo, Japan, writes that twelve stacked 60-s exposures
taken on May 26.3 with an iTelescope 0.51-m f/6.8 astrograph (+ luminance
filter) near Mayhill, NM, USA, show the object to be strongly condensed with
a coma 10" in diameter and no tail; the w-band magnitude was 19.0 as measured
within a circular aperture of radius 6".5.
     The available astrometry, the following elliptical orbital elements by
G. V. Williams, and an ephemeris appear on MPEC 2015-L07.

                    Epoch = 2015 Sept.15.0 TT
     T = 2015 Aug. 26.6369 TT         Peri. = 108.9414
     e = 0.878083                     Node  = 235.5137  2000.0
     q = 1.971992 AU                  Incl. =  90.2538
       a = 16.174887 AU    n = 0.0151510    P =  65.05 years


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

                         (C) Copyright 2015 CBAT
2015 June 4                      (CBET 4109)              Daniel W. E. Green