[IAUC] IAUC 9234: P/2011 S1; C/2011 S2 [25139-2012/04-R1]

[quai en eps.harvard.edu]

                                                  Circular No. 9234
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
New postal address:  Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
CBATIAU en EPS.HARVARD.EDU           ISSN 0081-0304
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Prepared using the Tamkin Foundation Computer Network


COMET P/2011 S1 (GIBBS)
     As first announced on CBET 2822, A. R. Gibbs reports the
discovery of a comet on CCD images obtained by Gibbs and S. F.
Tornero with the Mt. Lemmon 1.5-m reflector (discovery observations
tabulated below), when four co-added 30-s frames taken in good
seeing showed a stellar nuclear condensation with no coma but a
broad tail 7" long in p.a. 260 deg; four co-added 80-s follow-up
images taken in good seeing by Gibbs on Sept. 19.4 UT show a
compact coma of size 3" x 5", elongated in p.a. 260 deg (with a
very faint "haze" in the same p.a.).  Following posting on the
Minor Planet Center's NEOCP webpage, other CCD astrometrists have
also noticed cometary appearance, as detailed on CBET 2822.

     2011 UT             R.A. (2000) Decl.       Mag.   Observer
     Sept.18.27457   23 26 06.43   - 1 12 22.3   21.2   Gibbs
          18.29549   23 26 05.92   - 1 12 24.3   20.3     "

The initial astrometry appeared on MPEC 2011-S28; revised
elliptical orbital elements by G. V. Williams from MPEC 2011-V31:
epoch 2014 Sept. 20.0 TT, T = 2014 Sept. 5.5808 TT, q = 6.952508 AU,
e = 0.187810, Peri. = 193.3855 deg, Node = 218.7246 deg, i = 2.6890
deg (equinox 2000.0), P = 25.04 years.


COMET C/2011 S2 (KOWALSKI)
     As first announced on CBET 2852, R. A. Kowalski reports the
discovery of a comet on CCD images obtained with the Catalina Sky
Survey's 0.68-m Schmidt reflector (discovery observations tabulated
below), the object having a bright, condensed 15" coma with a broad
tail at least 1' long in p.a. 300 deg.  Follow-up observations by
A. R. Gibbs with the Mt. Lemmon 1.5-m reflector on Oct. 1.51 UT
show a 55" tail in p.a. 300 deg.  After posting on the NEOCP
webpage, numerous other CCD astrometrists commented on the object's
cometary appearance, as detailed on CBET 2852.

     2011 UT             R.A. (2000) Decl.       Mag.   Observer
     Sept.30.48411    9 12 10.05   +20 18 30.3   15.7   Kowalski
          30.49094    9 12 11.83   +20 18 15.9   15.7     "

The initial astrometry appeared on MPEC 2011-S28; revised
elliptical orbital elements by G. V. Williams from MPEC 2011-V31:
epoch 2011 Nov. 15.0 TT, T = 2011 Oct. 26.3511 TT, q = 1.115124 AU,
e = 0.931585, Peri. = 192.1934 deg, Node = 288.0709 deg, i =
17.5729 deg (equinox 2000.0), P = 65.8 years.  Similarity to the
orbital elements of P/2006 T1 (cf. CBET 2852) has been dismissed
via additional astrometry.

                      (C) Copyright 2011 CBAT
2011 November 9                (9234)            Daniel W. E. Green