Electronic Telegram No. 4065
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 B2 (PANSTARRS)
     R. Wainscoat, R. Weryk, and L. Denneau report the discovery of an
apparent comet in four w-band exposures taken with the 1.8-m Pan-STARRS1
telescope at Haleakala on Jan. 29 UT (discovery observations tabulated below);
the object shows an extended point-spread function, with full-width-at-half-
maximum of 1".5, compared to 1".2 for adjacent stars.  Weryk and Wainscoat
add that three i-band Pan-STARRS1 images from Jan. 31.5 UT show a similar
appearance.

     2015 UT             R.A. (2000) Decl.       Mag.
     Jan. 29.43687    9 50 42.78   -23 38 54.0   19.8
          29.44746    9 50 42.06   -23 38 56.6   19.8
          29.45810    9 50 41.34   -23 38 59.7   19.8
          29.46875    9 50 40.60   -23 39 02.4   19.9

After the object was posted on the Minor Planet Center's PCCP webpage, other
CCD astrometrists have reported cometary appearance for this object.  H. Sato,
Tokyo, Japan, writes that ten stacked 60-s exposures taken with an iTelescope
0.51-m f/6.8 astrograph (+ luminance filter) at Siding Spring on Jan. 30.75
show the comet to be strongly condensed with a round coma 10" in diameter and
w-band magnitude 18.3 as measured within a circular aperture of radius 6".6.
W. H. Ryan (Magdalena Ridge Observatory 2.4-m f/8.9 reflector) notes that
R-band images taken on Feb. 10.4 yield mag 18.8-19.0 with a distinct coma
that is elongated at p.a. around 0 deg.
     The available astrometry (including three Pan-STARRS1 images from Jan.
6 that suggest the comet was then about a magnitude fainter), the following
elliptical orbital elements by G. V. Williams, and an ephemeris appear on
MPEC 2015-C71.

                    Epoch = 2016 May  12.0 TT
     T = 2016 May   6.7401 TT         Peri. = 284.8044
     e = 0.999606                     Node  = 341.8957  2000.0
     q = 3.368342 AU                  Incl. = 105.0789


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2015 CBAT
2015 February 13                 (CBET 4065)              Daniel W. E. Green