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IAUC 9266: C/2012 S1; V1369 Cen = N Cen 2013

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                                                  Circular No. 9266
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@EPS.HARVARD.EDU           ISSN 0081-0304
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Prepared using the Tamkin Foundation Computer Network


COMET C/2012 S1 (ISON)
     M. R. Combi, University of Michigan; J.-L. Bertaux and E.
Quemerais, Service d'Aeronomie, CNRS, Universite de Versailles
Saint-Quentin-en-Yvelines; J. T. T. Maekinen, Finnish
Meteorological Institute; and S. Ferron, ACRI-ST, Sophia-Antipolis,
France, report that the Solar Wind Anisotropies (SWAN) camera on
the Solar and Heliospheric Observer (SOHO) spacecraft, located at
the earth-sun L_1 Lagrange point, makes daily full-sky images of
hydrogen Lyman-alpha.  SWAN detected comet C/2012 S1 for one month
spanning Oct. 24-Nov. 23 (as the comet moved from r = 1.16 to 0.32
AU and from Delta = 1.42 to 0.84 AU), when the comet moved into the
SWAN solar avoidance area.  An analysis of the images of the
hydrogen Lyman-alpha coma within a circular aperture of radius 8
degrees was used to determine average water-production rates for
each of the usable 22 images.  The activity was generally fairly
steady from Oct. 24.9 through Nov. 6.9, roughly between 2 and 3 x
10**28 molecules/s.  Between Nov. 6.9 and 8.9, the water-production
rate increased by about a factor of two and then decreased somewhat
through Nov. 12.9.  Subsequently, there were several jumps in
production rate, by factors of 2-5 each jump, until Nov. 21.6, when
it reached a value of 2 x 10**30 molecules/s; it then stayed near
that level until the comet was too close to the sun to be observed
by SWAN.  The edge of the hydrogen coma could be seen in the image
of Nov. 24.6 at a similar level to that on Nov. 23.6.  The Dec. 3.7
image, the first post-perihelion image where the comet should be
visible outside the SWAN solar avoidance area, shows no detectable
signal.  The actual computed water-production rates (and
uncertainties in parentheses) are given in units of 10**28
molecules/s:  Oct. 24.9 UT, 1.8 (0.6); Oct. 25.9, 3.2 (0.3); Oct.
28.9, 2.2 (0.4); Oct. 29.9, 1.9 (0.8); Oct. 30.9, 2.5 (0.4); Oct.
31.9, 2.5 (0.6); Nov. 1.9, 2.3 (0.4); Nov. 3.9, 2.6 (0.2); Nov.
5.9, 2.2 (0.4); Nov. 6.9, 2.0 (0.5); Nov. 8.9, 3.8 (0.3); Nov. 9.9,
3.6 (0.3); Nov. 10.9, 3.9 (0.3); Nov. 11.9, 3.1 (0.4); Nov. 12.9,
3.0 (0.3); Nov. 13.9, 6.4 (0.5); Nov. 14.9, 14 (1); Nov. 16.6, 40
(3); Nov. 19.6, 42 (3); Nov. 21.6, 200 (16); Nov. 22.6, 160 (13);
Nov. 23.6, 230 (19).


V1369 CENTAURI = NOVA CENTAURI 2013
     Additional visual magnitude estimates (cf. IAUC 9265), showing
the continued brightening of the nova:  Dec. 5.28 UT, 3.9 (Jose G.
de S. Aguiar, Campinas, Brazil); 5.674, 3.3 (John Seach, Chatsworth
Island, NSW, Australia); 6.50, 4.3 (David Seargent, Cowra, NSW,
Australia); 7.166, 4.0 (R. Salvo, Montevideo, Uruguay).

                      (C) Copyright 2013 CBAT
2013 December 7                (9266)            Daniel W. E. Green

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