Central Bureau for Astronomical Telegrams
IAUC 9261: C/2012 S1
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Circular No. 9261
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
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network
COMET C/2012 S1 (ISON)
J. V. Keane, K. J. Meech, M. J. Mumma, M. A. DiSanti, L.
Paganini, B. P. Bonev, and G. L. Villanueva report that on Oct. 22
UT, using the NIRSPEC spectrometer at the W. M. Keck Observatory, a
combined team from the University of Hawaii and from the Goddard
Space Flight Center, NASA, has achieved the first direct detection
of H_2O (water) in comet C/2012 S1. Based on four spectral lines,
the preliminary production rate was (1.4 +/- 0.3) x 10**28
molecules/s.
M. J. Mumma, M. A. DiSanti, L. Paganini, G. L. Villanueva, B.
P. Bonev, J. V. Keane, and K. J. Meech report that using the Keck
II telescope (+ NIRSPEC), a combined team from Goddard Space Flight
Center, NASA, and from the University of Hawaii has achieved direct
detections of H_2O (water) emission lines in comet C/2012 S1.
Based on four spectral lines on Oct. 24 UT, the derived production
rate was (1.2 +/- 0.3) x 10**28 molecules/s. Based on six spectral
lines observed on Oct. 25, the preliminary production rate was (1.6
+/- 0.4) x 10**28 molecules/s. The rotational temperature was
consistent with 50 K. Analyses of abundances/upper limits for
trace volatiles (CO, CH_4, CH_3OH, C_2H_6, HCN, etc.) are in
progress.
A. Fitzsimmons and P. Lacerda, Queen's University, Belfast; S.
Lowry, University of Kent; G. Jones and Y. Ramanjooloo, Mullard
Space Science Laboratory, University College, London; and J.
Marchant, Liverpool John Moores University, report on CCD imaging
of the coma of comet C/2012 S1 over heliocentric distances r = 1.57
to 1.09 AU, using the 2.0-m Liverpool Telescope. Af(rho)
measurements with an SDSS i' filter through an aperture of
effective radius 10000 km are as follows: Oct. 5.3 UT, 258 cm;
Oct. 8.3, 248 cm; Oct. 11.2, 237 cm; Oct. 17.2, 205 cm; Oct. 24.2,
196 cm; Oct. 27.3, 188 cm. Correcting for a nominal dust-
scattering phase function, these measurements transform to 373,
373, 370, 345, 355, and 354 cm, respectively. These values imply
a dust-production rate slowly increasing as r**-0.3 over this
period, assuming an outflow velocity proportional to r**-0.5 and
constant dust-particle properties.
Total-magnitude and coma-diameter estimates (visual unless
noted otherwise): Sept. 13.19 UT, 10.8, 2'.5 (J. J. Gonzalez,
Leon, Spain, 20-cm reflector); Oct. 1.15, 11.3, 3'.5 (M. Lehky,
Hradec Kralove, Czech Rep., 42-cm reflector); 3.75, 10.9, 2'.4 (C.
Wyatt, Walcha, NSW, Australia, 25-cm reflector); 9.74, 10.1, 2'.5
(Wyatt); 16.49, 10.1, 3' (C. Hergenrother, Tucson, AZ, U.S.A.,
30x125 binoculars); 20.79, 10.3, -- (K. Kadota, Ageo, Japan,
25-cm reflector + CCD); 23.15, 9.1, 2'.2 (M. L. Paradowski,
Lublin, Poland, 6.8-cm refractor + CCD + V filter); 26.80, 9.7, --
(Kadota).
(C) Copyright 2013 CBAT
2013 October 29 (9261) Daniel W. E. Green
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