Electronic Telegram No. 4096
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 H2 (PANSTARRS)
     R. Weryk and R. Wainscoat, Institute for Astronomy, University of Hawaii,
report the discovery of another apparent comet in four i-band exposures taken
with the 1.8-m Pan-STARRS1 telescope at Haleakala on Apr. 24.4 UT (discovery
observations tabulated below); the object shows a faint tail visible in each
image, extending for approximately 16" towards position angle approximately
330 degrees.

     2015 UT             R.A. (2000) Decl.       Mag.
     Apr. 24.39562   13 39 03.40   -44 06 21.8   19.7
          24.40359   13 39 03.08   -44 06 21.9   19.5
          24.41161   13 39 02.82   -44 06 22.1   19.6
          24.41963   13 39 02.51   -44 06 22.3   19.8

M. Micheli writes that Wainscoat and he obtained three 60-s follow-up
exposures using the 3.6-m Canada-France-Hawaii Telescope on Apr. 27.4 UT
(queue observer L. Wells), which show that the object has a diffuse appearance
(coma diameter about 1".2 in 0".7 seeing) with a broad tail about 7" long
extending to the north (p.a. about 350 deg) of the nuclear condensation; the
red magnitude was 19.3-19.7.  After the object was posted on the Minor Planet
Center's PCCP webpage, other CCD astrometrists also have commented on the
cometary appearance.  Images taken on Apr. 25.3 by A. Maury and J.-F. Soulier
with a 0.4-m f/8 Ritchey-Chretien reflector at San Pedro de Atacama, Chile,
show a coma of size around 11" and no visible tail.  H. Sato, Tokyo, Japan,
notes that twelve stacked 60-s exposures taken with an iTelescope 0.70-m
f/6.6 astrograph (+ luminance filter) at Siding Spring on Apr. 27.6 show the
comet to be strongly condensed with a coma 5" in diameter and w-band
magnitude 18.9 as measured within a circular aperture of radius 2".8; there
was no visible tail.  M. Kusiak, Zywiec, Poland; R. Reszelewski, Swidwin,
Poland; M. Zolnowski, Krakow, Poland; and M. Gedek, Oborniki, Poland, report
that they found pre-discovery images of the comet (estimated magnitude 19.7)
on survey images taken on Apr. 20.1 with the Polonia Observatory 0.25-m
f/3.6 astrograph at San Pedro de Atacama, Chile.

     The available astrometry, the following preliminary parabolic orbital
elements by G. V. Williams, and an ephemeris appear on MPEC 2015-J04.

     T = 2016 Sept. 6.9544 TT         Peri. = 287.5810
                                      Node  = 350.3666  2000.0
     q = 4.972735 AU                  Incl. =  33.5489


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

                         (C) Copyright 2015 CBAT
2015 May 2                       (CBET 4096)              Daniel W. E. Green