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IAUC 6702: SATURN VI (TITAN); BL Lac; C/1997 N1

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                                                 Circular No. 6702
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/cfa/ps/cbat.html
Phone 617-495-7244/7440/7444 (for emergency use only)


SATURN VI (TITAN)
     A. Marten and T. Hidayat, Observatoire de Paris-Meudon (OPM);
R. Moreno and G. Paubert, Institut de Radioastronomie Millimetrique
(IRAM); B. Bezard and D. Gautier, OPM; H. Matthews, Joint Astronomy
Centre, Hilo; and T. Owen, University of Hawaii, report the
detection of the isotope HC**15N of hydrogen cyanide on Saturn VI
(Titan):  "The (3-2) transition of HC**15N centered at 258.157 GHz
was observed with the IRAM 30-m radiotelescope at Granada on July
4-7.  The emission line contrast recorded at a spectral resolution
of 312 kHz represents a signal-to-noise ratio of 18 after 460 min
of integration time on Titan.  Using a second heterodyne receiver
at 3-mm wavelength, the HCN(1-0) transition at 88.63 GHz was
simultaneously observed during the four days of observations.  The
signal-to-noise ratio at the peak of the line is about 48 at 1-MHz
resolution.  This latter measurement is in excellent agreement with
the previous ones reported by Hidayat et al. (1997, Icarus 126,
170).  The HC**14N/HC**15N ratio inferred from direct comparison of
the observed spectra with appropriate synthetic calculations is
found to be on the order of 60, within 20 percent.  Assuming that
this value is representative of the **14N/**15N ratio in Titan's
atmosphere, we derive an enrichment of this ratio by a factor of
about 4.5 with respect to the terrestrial value of 272."


BL LACERTAE
     J. Mattox, Boston University, reports:  "CGRO, XTE, and ASCA
observations are now either underway or planned in response to the
major optical outburst of BL Lac (IAUC 6693, 6700).  Observations
at other wavelengths are obviously of interest.  A Web page to make
plans and results rapidly available to other observers during this
outburst has been established at
http://bu-ast.bu.edu/~mattox/multiwavelength/bl_lac.html and will
be mirrored for easier access in Asia at
http://www.astro.isas.ac.jp/~mattox/multiwavelength/bl_lac.html."


COMET C/1997 N1 (TABUR)
     Visual m_1 estimates:  July 9.81 UT, 10.4 (D. A. J. Seargent,
The Entrance, N.S.W., 25x100 binoculars); 11.91, 10.3 (A. Pearce,
Subiaco, W. Australia, 0.2-m reflector); 14.91, 10.0 (Pearce);
16.91, 9.8 (Pearce).

                      (C) Copyright 1997 CBAT
1997 July 19                   (6702)            Daniel W. E. Green

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