Electronic Telegram No. 3429
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/2011 L4 (PANSTARRS)
     M. Drahus, California Institute of Technology; B. Sandor, Space Science
Institute; W. Montgomerie, Joint Astronomy Centre (JAC); I. Coulson, JAC; and
J. Hoge, JAC, report the detection of HCN in comet C/2011 L4 on Mar. 1.963 UT
when at heliocentric distance r = 0.392 AU.  A spectrogram taken at the James
Clerk Maxwell Telescope atop Mauna Kea shows the J = 4-3 line with area about
1.5 K km/s in the main-beam brightness temperature scale.  Assuming an
isotropic production of gas at velocity 1.25 km/s and a Boltzmann distribution
of energy levels at 100 K, the derived HCN production rate is 5 x 10**26
molecules/s.

     Further visual total-magnitude and coma-diameter estimates (cf. CBET
3230):  Jan. 7.31 UT, 8.0, 2' (W. Souza, Sao Paulo, Brazil, 0.1-m refractor);
16.73, 7.9, 2' (M. Mattiazzo, Castlemaine, Victoria, Australia, 25x100
binoculars); 23.81, 7.5, 2'.5 (A. Pearce, Nedlands, W. Australia, 0.10-m
reflector); 31.84, 6.9, 3' (Pearce); Feb. 2.30, 6.4, 5' (Souza, 20x60
binoculars); 5.30, 6.3, 5' (Jose G. de S. Aguiar, Campinas, Brazil, 11x80
binoculars); 12.74, 5.5, -- (David A. J. Seargent, Cowra, NSW, Australia, 6x35
binoculars); 15.73, 5.0, -- (Seargent, naked eye); 17.33, 5.2, 3' (A. Amorim,
Florianopolis, Brazil, 0.07-m refractor; altitude 8 deg); 19.85, 4.2, 2'.5
(Pearce; altitude 4 deg).


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      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2013 CBAT
2013 March 4                     (CBET 3429)              Daniel W. E. Green