Electronic Telegram No. 4325
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)
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Prepared using the Tamkin Foundation Computer Network


COMET P/2016 R4 (GIBBS)
     A. R. Gibbs reports his discovery of a comet on CCD images obtained with
the Mount Lemmon 1.5-m reflector on Sept. 10 UT (discovery observations
tabulated below); he noted a "fuzzy" coma of size 12" x 9", elongated in
p.a. 90/270 deg with a tapered tail 12" long in p.a. 260 deg in four co-added
30-s unfiltered exposures in average seeing.  In follow-up similar stacked
follow-up images taken around Sept. 10.42-10.44, a 15"-long tail appears to
start at p.a. 270 degrees before curving toward p.a. 250 deg.

     2016 UT             R.A. (2000) Decl.       Mag.   Observer
     Sept.10.32267    0 01 57.22   - 2 04 09.4   18.9   Gibbs
          10.32649    0 01 57.03   - 2 04 11.2   18.5     "
          10.33031    0 01 57.00   - 2 04 13.2   18.9     "
          10.33413    0 01 56.86   - 2 04 14.7   18.7     "
          10.41949    0 01 54.61   - 2 04 53.9   18.9     "
          10.44199    0 01 54.03   - 2 05 04.1   18.5     "
          10.46392    0 01 53.44   - 2 05 14.0   18.9     "
          10.47098    0 01 53.28   - 2 05 17.2   18.8     "
          10.47572    0 01 53.08   - 2 05 19.7   18.9     "
          10.48371    0 01 52.90   - 2 05 23.5   18.9     "

After the comet was posted on the Minor Planet Center's PCCP webpage, other
CCD astrometrists have commented on the cometary appearance.  H. Sato, Tokyo,
Japan, writes that ten stacked 60-s exposures taken with an iTelescope 0.61-m
f/6.5 astrograph (+ luminance filter) at the Sierra Remote Observatory near
Auberry, CA, USA, on Sept. 12.39 UT show a moderately condensed, elongated
coma of size 5" x 8" with a hint of tail 10" long toward p.a. 270 degrees;
the w-band magnitude was 18.9 as measured within a circular aperture of
radius 5".0.  L. Buzzi, Varese, Italy, notes that stacked images obtained
by M. Lucchetta and himself with a 0.60-m f/4.64 reflector on Sept. 13.0 in
good seeing show a compact coma 8" in size with a faint extension toward the
east; the red magnitude was measured to be 18.8.  J.-F. Soulier, Maisoncelles,
France, measured a 21" coma (with red mag 18.3-18.6) and a possible diffuse
tail longer than 19" in p.a. 250 deg in stacked unfiltered images obtained
on Sept. 23.89-23.97 with a 0.30-m f/3.8 Newtonian reflector.
     The available astrometry [including pre-discovery observations made on
July 18.55-18.59 (magnitude 21.0-21.4) and Aug. 14.6 (magnitude 20.6-20.7)
with the 1.8-m Pan-STARRS1 telescope at Haleakala; on Aug. 28.4 (mag 19.2-19.4)
at Mount Lemmon; and on Sept. 10.3 (mag 18.9-19.2) at Crni Vrh, Slovenia],
along with the following elliptical orbital elements by G. V. Williams and
an ephemeris, appear on MPEC 2016-S94.

                    Epoch = 2016 July 31.0 TT
     T = 2016 July 20.52099 TT        Peri. = 174.06429
     e = 0.4750068                    Node  = 168.34700 2000.0
     q = 2.8005952 AU                 Incl. =  10.86235
       a =  5.3345359 AU   n = 0.07999431   P =  12.32 years


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

                         (C) Copyright 2016 CBAT
2016 September 29                (CBET 4325)              Daniel W. E. Green