Electronic Telegram No. 4108
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 K4 (PANSTARRS)
     E. Lilly, Institute for Astronomy, University of Hawaii, reports the
discovery of another apparent comet in three w-band exposures taken with the
1.8-m Pan-STARRS1 telescope at Haleakala on May 24.5 UT (discovery
observations tabulated below); the object shows a broad tail approximately
5" long towards p.a. approximately 200 degrees in each image.

     2015 UT             R.A. (2000) Decl.       Mag.
     May  24.46862   17 27 39.80   - 6 53 26.0   19.0
          24.48085   17 27 37.86   - 6 52 42.0   19.0
          24.49307   17 27 35.90   - 6 51 58.1   18.5

R. Wainscoat obtained three 60-s r-band exposures of the comet using the 3.6-m
Canada-France-Hawaii Telescope on May 25.57 UT (queue observer L. Wells),
tracked using the predicted motion of the object; the object has a compact
core with a substantial amount of extended emission in the area surrounding
the core, and a clear low-surface-brightness-tail is seen extending for more
than 60" toward p.a. 210 degrees (measurements done with M. Micheli).  After
the object was posted on the Minor Planet Center's NEOCP webpage, L. Buzzi,
Varese, Italy, wrote that stacked exposures taken in good seeing with a
0.60-m f/4.6 reflector on May 24.95-24.97 show a compact coma 15" wide and
a broad, fan-shaped tail at least 60" long in p.a. 210 deg.
     After the comet was posted on the Minor Planet Center's PCCP webpage,
other CCD astrometrists have also noted the object's cometary appearance.
A. Maury and J.-F. Soulier find that images taken on May 25.3 with a 0.4-m
f/8 Ritchey-Chretien reflector at San Pedro de Atacama, Chile, show a 13"
coma and a tail 27" long in p.a. 240 deg; the magnitude was about 18.4 in an
aperture of radius 6".9.  H. Sato, Tokyo, Japan, notes that sixteen stacked
30-s exposures taken with an iTelescope 0.51-m f/6.8 astrograph (+ luminance
filter) near Mayhill, NM, USA, on May 25.44 show a strongly condensed coma of
10" in diameter, with w-band magnitude 17.5 as measured within a circular
aperture of radius 6".5; no tail was seen.  E. Guido, Castellammare di
Stabia, Italy, reports that twenty stacked 30-s unfiltered exposures taken by
N. Howes and himself on May 26.3 with an iTelescope 0.61-m f/6.5 astrograph
near Auberry, CA, USA, show an ill-defined central condensation surrounded by
a diffuse, irregular coma about 6" in diameter; the red magnitude was near 18.

     The available astrometry, the following preliminary parabolic orbital
elements by G. V. Williams, and an ephemeris appear on MPEC 2015-K114.

     T = 2015 May   1.7936 TT         Peri. = 357.5525
                                      Node  = 250.7711  2000.0
     q = 2.007695 AU                  Incl. =  80.2545


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

                         (C) Copyright 2015 CBAT
2015 May 27                      (CBET 4108)              Daniel W. E. Green