Central Bureau for Astronomical Telegrams
IAUC 4254: SATURN VI (TITAN); 4U 1820-30; 1986G
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Circular No. 4254
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
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
SATURN VI (TITAN)
E. Gerard, Observatoire de Meudon, telexes: "G. Paubert,
Institut de Radio Astronomie Millimetrique; and A. Marten, C.
Rosolen, D. Gautier, and R. Courtin, Observatoire de Meudon, report
the detection of the J = 1-0 line at 88.6 GHz of the HCN molecule
in the atmosphere of Titan with the IRAM 30-m radio telescope.
With a total integration time of 320 min on Sept. 7, 8, and 9, the
line appears in emission with an antenna temperature of 36 +/- 4 mK.
The comparison with models of Paubert et al. (1984, Icarus 60, 599)
confirms that HCN must be formed in the upper atmosphere of Titan."
4U 1820-30
E. H. Morgan and R. A. Remillard, Center for Space Research,
Massachusetts Institute of Technology, write: "SAS-3 observations of
the x-ray burster and QPO source 4U 1820-30 in the globular cluster
NGC 6624 have confirmed the EXOSAT period of 685 s reported by
Priedhorsky et al. (IAUC 4247). Pointed observations with the
horizontal tube collimator (1.2-6 keV) were detrended and Fourier
analyzed. The following are observation dates, percent duty cycle,
period in s, and percent modulation: 1976 Jan. 23.8-29.3 UT, 23,
684.86 +/- 0.25, 1.6; Mar. 27.5-Apr. 8.7, 5, 685.01 +/- 0.08, 1.3; Aug.
27.8-28.5, 52, 685.0 +/- 1.9, 1.8; Sept. 28.0-Oct. 1.8, 17, 685.01 +/-
0.22, 1.9; 1977 Feb. 22.0-22.8, 45, 685.0 +/- 2.0, 3.6; Sept. 19.5-
19.7, 58, 683.1 +/- 9.8, 4.0. An upper limit (3 sigma) of P-dot/P <
2.3 x 10**-4 yr**-1 is obtained by comparing our observations with the
reported EXOSAT period (weighted mean 685.17 +/- 1.41, 3 sigma). Our
results strongly support the interpretation by Priedhorsky et al.
that the 11-min period is the orbital period of the binary system."
SUPERNOVA 1986G IN NGC 5128
With reference to the final remark on IAUC 4216, R. O. Evans,
Hazelbrook, N.S.W., informs us that his visual patrol showed no
trace of the supernova to mag 16.0 on Apr. 15.55 UT and to mag 15.5
on Apr. 24.55 UT (during the total lunar eclipse).
Visual magnitude estimates by R. McNaught, Coonabarabran,
N.S.W.: June 3.43 UT, 13.7; 5.42, 13.9; 9.43, 13.8; 11.42, 13.9;
13.53, 13.9; 14.58, 14.2; 15.37, 14.7; 16.37, 14.5; 24.35, 14.8;
29.44, 14.6; July 6.37, 14.3; 7.46, 14.3; 12.45, 14.7; 14.42, 14.8.
1986 September 15 (4254) Daniel W. E. Green
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