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IAUC 4411: 1987A; 1986l; 1986m

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                                                  Circular No. 4411
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM    Telephone 617-495-7244/7440/7444

     M. Hamuy and N. Suntzeff, Cerro Tololo Interamerican Observatory,
report that SN 1987A is beginning to fade less rapidly in all
optical colors.  Nightly UBVRI photometry with the CTIO 0.4-m
reflector during June 22.0-25.0 UT show that the SN was fading 0.030
and 0.027 mag/day in V and I, respectively.  Photometry on June
25.0: V = 4.27, B-V = +1.74, U-B = +2.59, V-R = +0.97, V-I = +0.38.
     Visual magnitude estimates:  June 16.39 UT, 3.3 (G. W. Wolf,
Wellington, N.Z.); 17.46, 3.7 (R. H. McNaught, Siding Spring
Observatory); 18.37, 3.9 (A. C. Beresford, Adelaide, South Australia);
19.59, 3.8 (Beresford); 20.36, 4.1 (Beresford); 20.85, 4.0
(Beresford); 22.35, 4.1 (D. A. J. Seargent, The Entrance, N.S.W.);
24.53, 4.3 (Beresford); 25.33, 4.2 (Beresford).
     Corrigendum.  On IAUC 4410, line 26, for  Seargeant  read

     J. Crovisier, Observatoire de Meudon; D. Despois, Observatoire
de Bordeaux; and D. Bockelee-Morvan and E. Gerard, Observatoire de
Meudon, telex:  "We searched for HCN in comet Wilson 1986l with the
IRAM 30-m telescope on June 16-19.  The (J = 1-0, F = 2-1) line was
observed at the 3-sigma level.  The signal corresponds to a HCN
production rate of 3 x 10E25 sE-1.  When compared with the OH production
rate (around 6 x 10E28 sE-1 in the first half of June from
observations with the Nancay radio telescope), this suggests a smaller
abundance of HCN in comet 1986l than in P/Halley."
     Total visual magnitude estimates (cf. IAUC 4403):  June 3.16
UT, 6.8 (A. Hale, Las Cruces, NM, 0.20-m reflector; moonlight, low
altitude); 6.28, 7.3 (G. W. Wolf, Wellington, N.Z., 7x50 binoculars);
12.45, 7.6 (Wolf); 16.38, 7.7 (Wolf); 18.39, 7.8 (Wolf).

     Total visual magnitude estimates (cf. IAUC 4410):  June 14.19
UT, 11.7 (A. Hale, Las Cruces, NM, 0.41-m reflector); 15.23, 11.5
(C. S. Morris, Lockwood Valley, CA, 0.26-m reflector); 18.22, 12.3
(Morris, Whitaker Peak, CA); 23.20, 11.8 (Morris).

1987 June 25                   (4411)            Daniel W. E. Green

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