Electronic Telegram No. 3622
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


COMETS C/2012 S1 (ISON), C/2012 K1 (PANSTARRS) AND C/2010 S1 (LINEAR)
     B. Yang, University of Hawaii, reports near-infrared (0.8- to 2.5-micron)
spectra of comets C/2012 S1 on May 18 and 24 UT, and C/2012 K1 and C/2010 S1
on July 5, taken with the 3.0-m NASA Infrared Telescope Facility atop Mauna
Kea.  Comet C/2012 S1 appears generally featureless with no diagnostic
absorption features.  Reflectance spectra of C/2012 S1 consistently exhibit a
neutral/flat spectral slope in the near-infrared; the neutral spectrum is
consistent with a coma dominated by particles similar in size to wavelengths
of radiation (i.e., micron-sized grains).  Two broad absorption bands of water
ice were detected centered at 1.5 microns (the depth being 5 percent of the
continuum) and 2.0 microns (10 percent in depth), respectively, in the
reflectance spectra of C/2012 K1 and C/2010 S1; these features suggest the
presence of abundant water-ice grains in the central coma of these two comets.


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2013 CBAT
2013 August 8                    (CBET 3622)              Daniel W. E. Green