Central Bureau for Astronomical Telegrams
IAUC 3690: Occn BY URANUS AND ITS RINGS; SN IN NGC 4490
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Circular No. 3690
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 617-864-5758
OCCULTATION BY URANUS AND ITS RINGS
The occultation on Apr. 22 of star No. 14 (Klemola et al. 1981,
A.J. 86, 138) by Uranus and its rings was observed at 2 um with the
1-m and 3.6-m telescopes at the European Southern Observatory by P.
Bouchet, A. Brahic, C. Perrier and B. Sicardy. The observed data
for the occultations by the nine well-established rings are:
Ring Pre-immersion Width Depth Post-emersion Width Depth Error
epsilon 1h33m26s34 4s95 0.87 3h00m42s17 2s6 0.95 0s03
delta 1 36 29.41 0.3 0.45 2 58 05.53 0.4 0.48 0.03
gamma 1 37 08.01 0.4 0.60 2 57 26.51 0.35 0.58 0.03
eta 1 37 34.1 - - 2 57 01.1 0.3 0.16 0.1
beta 1 39 03.45 0.4 0.51 2 55 34.42 0.6 0.34 0.03
alpha 1 39 57.04 0.35 0.51 2 54 39.17 0.45 0.60 0.03
4 1 42 01.7 - 0.15 2 54 37.6 0.35 0.22 0.1
5 1 42 21.0 0.35 0.26 2 52 12.1 0.35 0.26 0.1
6 1 42 46.8 - 0.17 2 51 55.6 0.25 0.12 0.1
The UT times of pre-immersion and post-emersion occultations
correspond to the middle of each event, and the +/- error applies in each
case. Observations extended from 0h53m to 11h17m UT (the latter
time corresponding to the star's crossing the orbit of Uranus IV).
Wide components are suspected in the region of the known rings.
An isolated event was observed simultaneously (within 0s.02) by both
telescopes at 4h37m13s.44 UT. The occultation by Uranus (and its
atmosphere) lasted from 1h58m50s to 2h36m45s UT.
SUPERNOVA IN NGC 4490
C. Aikman, Dominion Astrophysical Observatory, reports that
photographs of this object (cf. IAUC 3689) by J. Newton in Victoria
with his 0.41-m telescope on dry-ice-cooled emulsion yield the
following magnitude estimates by comparison with the Palomar Sky
Survey prints as calibrated by the magnitude-diameter relations of
King and Raff (1977, P.A.S.P. 89, 120): Mar. 29.24 UT, red magnitude
14.8, Ektachrome 400; Apr. 21.21, red magnitude 14.5, Ektachrome
400; Apr. 22.21, mpv = 16.1, Tri-X. The Ektachrome observations
are by comparison to the Sky Survey E print, the Tri-X observation
by comparison to the O print. The estimates are by Aikman.
It should be noted that the first observation precedes the Apr. 15
discovery observation by 17 days.
1982 April 28 (3690) Brian G. Marsden
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