Electronic Telegram No. 3711
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 C/2012 S1 (ISON)
 
     C. Opitom, E. Jehin, J. Manfroid, and M. Gillon, Liege University,
report
on the detection of a large outburst of comet C/2012 S1 that started between
Nov. 11.37 and 12.37 UT, in observations made with the robotic TRAPPIST 0.6-m
telescope at the European Southern Observatory at La Silla.  All the gas-
production rates derived from narrow band photometry were multiplied by a
factor af about 1.5 between Nov. 11.37 and 12.37 and then by a factor of
about
8 in the following 24 hours.  The dust production increased at the same rate,
with a factor larger than 10 in the last 48 hours.  The following gas-
production rates were computed at 10000 km from the comet's nucleus using a
Haser Model (V_p = V_d = 1 km/s), and Af(rho) was measured in the blue
continuum at 10000 km:  Nov. 12.37 (r = 0.70 AU, Delta = 0.95 AU), Q(OH) =
8.19 (+/- 2.39) x 10**27 molecules/s, Q(CN) = 5.85 (+/- 0.37) x 10**25
molecules/s, Q(C_2) = 8.35 (+/- 0.26) x 10**25 molecules/s, Af(rho) = 209 +/-
37 cm; Nov. 14.37 (r = 0.64 AU, Delta = 0.92 AU), Q(OH) = 1.01 (+/- 0.28) x
10**29 molecules/s, Q(CN) = 6.75 (+/- 0.43) x 10**26 molecules/s, Q(C_2) =
1.14 (+/- 0.03) x 10**27 molecules/s, Af(rho) = 2400 +/- 296 cm.  Two jets
are now also visible in OH band and in the dust continuum at the same
position as the CN and C_2 jets.  There is no indication yet of disruption,
the inner coma is very sharp (4") and round in the dust continuum windows,
and there is no other special features in the coma.

     Additional selected visual total-magnitude and coma-diameter estimates
(cf. IAUC 9261):  Oct. 31.20 UT, 8.3, 6' (J. J. Gonzalez, Leon, Spain, 10x50
binoculars); Nov. 4.48, 8.3, 5' (Carl Hergenrother, Tucson, Arizona, 10x50
binoculars); 8.17, 8.0, 5' (T. Karhula, Vasteras, Sweden, 10x50 binoculars);
10.18, 8.0, 5' (N. Biver, Pico Veleta, Spain, 7x50 binoculars); 13.20,
7.7, 4'
(B. H. Granslo, Roverkollen, Oslo, Norway, 10x50 binoculars); 13.39, 7.3, 8'
(D. W. E. Green, Nelson Island, MA, 12x50 binoculars); 13.41, 7.4, & 7' (John
Bortle, Stormville, NY, 15x70 binoculars); 14.21, 6.3, 3' (N. Biver, Pico
Veleta, Spain, 7x50 binoculars; mag 6.2 via naked eye); 14.22, 6.1, 3'
(Gonzalez; 0.7-deg tail); 14.30, 6.1, 2' (W. Souza, Sao Paulo, BRazil, 10x50
binoculars); 14.41, 5.4, 5' (Bortle); 14.52, 5.7, 2' (Hergenrother).


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2013 CBAT
2013 November 14                 (CBET 3711)              Daniel W. E. Green