Electronic Telegram No. 2798
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 213P/VAN NESS
     As first published on MPECs 2011-P25 and 2011-P37, a secondary nuclear
condensation (component B) was found in July and confirmed in early August.
H. Hanayama (Ishigakijima Astronomical Observatory, Mizusawa VLBI Observatory,
National Astronomical Observatory of Japan) reported finding a cometary
condensation of mag 20-21 located 5'.0 in p.a. 238.4 deg from the primary
condensation of comet 213P on Cousins R images taken on July 29.62-29.83 UT
with the IAO 1.05-m reflector, noting a tail of length 1'.0 from component B;
images taken on July 30.75-30.84 showed component B at 5'.1 in p.a. 239.2 deg.
S. Nakano, Sumoto, Japan, measured a separation between component B and the
primary component A of 5'.26 in p.a. 239.6 deg on Aug. 9.701 UT from CCD
images taken by A. Asami and N. Hashimoto with a 1.0-m f/3 reflector at the
Bisei Spaceguard Center.
     N. Howes, H. Blyth, G. Sostero, and E. Guido stacked five 120-s CCD
images taken remotely on Aug. 5.5 UT with the 2.0-m f/10 Ritchey-Chretien
"Faulkes Telescope North" (+ Bessel R filter) at Haleakala under good seeing
conditions, showing component B to be 5'.3 in p.a. 239 from component A.
The secondary showed a tiny coma nearly 5" in diameter with a tail at least
22" long in p.a. 235.  They add that comet 213P showed a dust anti-tail
at least 6' long in p.a. 56 deg.  Additional images taken on Aug. 9.6
with the same instrumentation under good seeing conditions showed that
the central condensation of component B appeared to have dropped by about
half a magnitude and appeared elongated, extending nearly 3" in p.a. 235
deg with a tail nearly 16" long in p.a. 233 deg.
     P. Bacci, L. Tesi, and G. Fagioli write that thirty stacked 60-s
images taken with a 0.60-m f/4 reflector at San Marcello Pistoiese,
Italy, on Aug. 6.0 UT show a coma about 10" in diameter (total red mag
about 19) and a 22" tail in p.a. about 230 deg; their images on Aug. 8.9
show component B to be 5'.15 in p.a. 239 with respect to component A.

     Z. Sekanina, Jet Propulsion Laboratory, writes that an improved solution
for companion B of comet 213P, which includes the differential planetary
perturbations and is based on 72 offsets between 2011 July 12 and Aug. 25,
shows that this fragment separated from the parent comet during the previous
return in 2005.  There is a distinct possibility that the presence of
component B could be detected in images exposed in 2009 and/or in April-June
2011.  Solving for the fragmentation time yields T(sep) = 2005 July 24, with
a formal r.m.s. uncertainty of +/- 40 days.  An assumption that the
fragmentation time coincided with 2005 Sept. 9, a time shortly before the
comet was discovered, leads to a solution with essentially the same r.m.s.
and thus represents a sound choice, supporting a notion based on the author's
unpublished study of the comet's 2005 light curve that the discovery took
place during a multistage outburst that began 7 months after perihelion.  The
differential nongravitational deceleration of the companion relative to the
principal nucleus comes out to be 2.2 +/- 0.1 units of 10**(-5) the sun's
gravitational acceleration, with the separation velocity pointing nearly in
the direction below the orbit plane, being equal to 0.3 +/- 0.1 m/s.  The
ephemeris from the solution with the fragmentation time of 2005 Sept. 9 is
below; the solution with the fragmentation time in July 2005 yields the 2009
separations greater by 2"-3".  The predicted separation distance and position
angle of B relative to A for 0h TT:  2009 Jan. 29, 30", 296 deg; Feb. 18, 31",
297 deg; Mar. 10, 30", 297 deg; Mar. 30, 29", 298 deg; Apr. 19, 27", 299 deg;
2011 Apr. 9, 169", 242.1 deg; Apr. 29, 184" 239.4 deg; May 19, 201", 237.7 deg;
June 8, 222", 237.1 deg; June 28, 250", 237.5 deg; July 18, 284", 238.5 deg;
Aug. 7, 322", 239.6 deg; Aug. 27, 349", 240.1 deg; Sept. 16, 346", 239.8 deg;
Oct. 6, 312", 239.0 deg; Oct. 26, 266", 238.4 deg; Nov. 15, 223", 238.1 deg.

     Visual total-magnitude estimates of component A by J. J. Gonzalez, Leon,
Spain (0.20-m reflector):  June 4.09 UT, 12.2; July 5.07, 12.0; 28.11, 12.0;
Aug. 8.09, 11.8; 26.98, 11.2.


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

                         (C) Copyright 2011 CBAT
2011 August 31                   (CBET 2798)              Daniel W. E. Green