Electronic Telegram No. 4277
Central Bureau for Astronomical Telegrams
Mailing address:  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/2016 J2 (DENNEAU)
     Larry Denneau, University of Hawaii, reports the discovery of a highly
diffuse comet with the new ATLAS 0.5-m f/2.0 Schmidt telescope at Haleakala
(cf. CBET 4223) on four "cyan" (g + r bands) CCD exposures taken on May 6
(discovery observations tabulated below); the FWHM of adjacent stars is 6".8,
while this object has FWHM of approximately 7".7.

     2016 UT             R.A. (2000) Decl.       Mag.
     May   6.24167   10 11 17.51   -26 12 41.4   18.1
           6.24796   10 11 17.16   -26 11 55.1   17.8
           6.25667   10 11 16.82   -26 10 50.3   18.1
           6.26791   10 11 16.31   -26 09 28.1   18.1

     Three 60-s follow-up exposures were obtained by M. Micheli, R. Wainscoat,
and L. Wells with the Canada-France-Hawaii Telescope on May 7.3 UT, confirming
that the object is clearly cometary, displaying a diffuse coma and diffuse
elongation at least 15" long toward p.a. of 110 deg.  After the object was
posted on the Minor Planet Center's PCCP webpage, other CCD astrometrists have
commented on the object's cometary appearance.  Stacked images taken by A. C.
Gilmore and P. M. Kilmartin with the Mt. John Observatory 1.0-m f/7.7
reflector on May 6.36 show a condensed head about 5" in diameter with a
diffuse tail 25" long in p.a. 110 degrees.  H. Sato, Tokyo, Japan, notes that
sixteen stacked 15-s exposures taken on May 6.44 with a 0.51-m f/6.8
astrograph (+ luminance filter) at Siding Spring show the comet to be strongly
condensed with a coma 50" in diameter and a fan-like tail 45" long spanning
p.a. 40-110 degrees; the total w-band magnitude was 15.6 as measured within a
circular aperture of radius 26".4.  Twelve stacked 60-s exposures taken by
L. Buzzi, P. Concari, S. Foglia, G. Galli, and M. Tombelli with a 0.15-m f/7
refractor at Siding Spring on May 6.6 reveal a very diffuse round coma 15" in
diameter; their image is posted at http://asteroidi.uai.it/neocp/A100Amf.jpg.
Three stacked 60-s images taken by C. Jacques, E. Pimentel, and J. Barros
with a 0.45-m f/2.9 reflector at the SONEAR Observatory, Oliveira, Brazil,
show a strong central condensation 8" in diameter in a coma that is elongated
21" toward p.a. 133 deg.  V-band images taken by W. H. Ryan and E. V. Ryan
with the Magdalena Ridge Observatory 2.4-m f/8.9 reflector on May 7.1 show
a distinct coma and a tail in p.a. about 110 deg.
     The available astrometry (spanning May 6-8), the following preliminary
parabolic orbital elements by G. V. Williams, and an ephemeris appear on MPEC
2016-J91.

     T = 2016 Apr. 12.2902 TT         Peri. = 318.7613
                                      Node  = 186.2253  2000.0
     q = 1.519970 AU                  Incl. = 130.2597


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

                         (C) Copyright 2016 CBAT
2016 May 9                       (CBET 4277)              Daniel W. E. Green