[IAUC] IAUC 9246: C/2011 W3 [25139-2012/04-R1]

[quai en eps.harvard.edu]

                                                  Circular No. 9246
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 C/2011 W3 (LOVEJOY)
     Further to IAUC 9245, preliminary parabolic orbital elements
by G. V. Williams (MPEC 2011-X16) showed the comet to be a Kreutz
sungrazer.  The faintness of the comet (H_8 about 14) in a bright
sky at small solar elongation (< 25 deg during Dec. 7-25) made/make
ground-based astrometric observations in this period difficult.
The following orbital elements by Williams are from 94 observations
spanning Nov. 27-Dec. 10 (mean residual 0".8):

                    Epoch = 2011 Dec. 12.0 TT
     T = 2011 Dec. 16.0121 TT         Peri. =  53.5633
     e = 0.999928                     Node  = 326.4459  2000.0
     q = 0.005554 AU                  Incl. = 134.3817

     K. Battams, Naval Research Laboratory, writes that the comet
appeared in the SOHO/LASCO C3 field-of-view early on Dec. 14, and
the comet brightened, soon saturating the C3 images (peaking at mag
-3 or brighter).  In addition to a very dense, several-degree-long
tail was an obvious, though much fainter, ion tail (which was also
visible throughout the LASCO C2 images).  Images were also obtained
with the coronagraphs on both STEREO satellites.  At perihelion,
the comet was observed in several extreme-ultraviolet wavelengths
of the AIA instrument on NASA's SDO satellite, and via the SWAP
instrument on the ESA's PROBA2 satellite.  The comet could be seen
clearly as an extended, diffuse object with no apparent nuclear
condensation.  The comet was subsequently seen to emerge from the
solar corona and re-emerge back into the LASCO field-of-view.
After re-emergence, the comet was highly condensed but
intrinsically very bright (conservatively mag 1.5 immediately after
reappearing from behind the occulting disk), with minimal
discernable tail.  Meanwhile, the "original tail" was still visible
as an extended diffuse cloud along the pre-perihelion orbital path.
Several hours after perihelion the both the dust and ion tail
reformed, the former not being as long or quite as wide as pre-
perihelion; the brightness also increased again noticeably as the
comet pulled away from the sun in the C3 images.  The inner coma
was visible also in images obtained with the Solar Optical
Telescope onboard the Japanese Hinode spacecraft.
     A. Amorim, Florianopolis, Brazil, reports his visual detection
of the comet on Dec. 17.34 UT with 10x50 binoculars, when the comet
was at altitude 4 deg and the sun was 0.9 deg below the horizon; he
estimates magnitude -2.9 (corrected for atmospheric extinction;
using Mercury for comparison) and coma diameter < 1', with a 0.2-
deg tail visible in p.a. 240 deg.

                      (C) Copyright 2011 CBAT
2011 December 18               (9246)            Daniel W. E. Green