[IAUC] IAUC 9231: P/2011 R2 [25139-2012/04-R1]

[quai en eps.harvard.edu]

                                                  Circular No. 9231
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 R2 (PANSTARRS)
     As first announced on CBET 2811, L. Denneau and R. Wainscoat,
Institute for Astronomy, University of Hawaii, report the discovery
of a comet on two i-band images taken with the 1.8-m "Pan-STARRS 1"
telescope at Haleakala (discovery observation tabulated below), the
object having a central condensation and being distinctly extended
with an extension to the west that appears to be a faint tail.  R.
Wainscoat and M. Micheli obtained r-band observations with the
Canada-France Hawaii Telescope on Sept. 6 UT that show the object
to be distinctly non-stellar, with a tail in p.a. approximately 257
deg that extends for 15" from the nuclear condensation.  After
posting on the Minor Planet Center's NEOCP webpage, numerous other
CCD astrometrists have noted the object's cometary nature.  Stacked
images taken by R. Holmes (Ashmore, IL, USA, 0.81-m astrograph;
Sept. 6.3) -- and measured by T. Vorobjov, S. Foglia, and L. Buzzi
-- show a round 12" coma and a faint tail about 18" long in p.a.
270 deg.  Stacked images taken remotely by E. Guido, G. Sostero,
and N. Howes (0.25-m reflector at the GRAS Observatory near Mayhill,
NM, U.S.A., Sept. 6.3) show a condensed coma about 8" in diameter,
elongated toward p.a. 250 deg; Howes, Sostero, and Guido also
obtained four 30-s R-band images remotely with the 2.0-m "Faulkes
Telescope South" at Siding Spring on Sept. 6.5, revealing a well-
condensed coma nearly 5" in diameter and a broad tail about 8" long
in p.a. 251 deg.  Stacked images taken remotely by R. Ligustri
(Udine, Italy; 0.50-m reflector at the GRAS Observatory near
Mayhill; Sept. 6.4) show red mag 17.2 and a 25" tail in p.a. 240
deg.  Stacked images obtained by G. Masi, U. Masi, and G. Luccone
(Ceccano, Italy, 0.43-m reflector; Sept. 6.9) show a coma about 15"
in size, slightly elongated in the northeast-southwest direction.
Images taken by P. Birtwhistle (Great Shefford, Berkshire, England,
0.40-m reflector) on Sept. 6.9 show the object to be diffuse, with
a poorly concentrated center 6" in diameter and indications of a
straight tail up to 30" long in p.a. 260 deg; images taken in
better conditions on Sept. 7.04-7.05 show a coma of diameter 10"
and red mag 17.5, only moderately condensed, with a distinct,
narrow, straight tail 33" long in p.a. 255 deg.

     2011 UT             R.A. (2000) Decl.       Mag.
     Sept. 4.50500   23 31 05.15   - 6 30 28.4   18.7

The initial astrometry appears on MPCs 75832-75833.  Preliminary
elliptical orbital elements by G. V. Williams from 59 observations,
Sept. 4-8:  T = 2011 Nov. 23.0502 TT, q = 2.032561 AU, e = 0.410383,
Peri. = 230.8459 deg, Node = 146.8063 deg, i = 4.8932 deg (equinox
2000.0), P = 6.40 years.

                      (C) Copyright 2011 CBAT
2011 September 12              (9231)            Daniel W. E. Green