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IAUC 3784: Occn BY URANUS II (UMBRIEL) ON 1983 Mar. 25; SN IN Anon GALAXY; TY Psc

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IAUC number

                                                  Circular No. 3784
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 617-864-5758

     D. Mink, Massachusetts Institute of Technology, informs us
that the prediction for the occultation of Hyd -21 64352 (V ~ 10)
by Uranus II (Umbriel) on March 25 (Mink and Klemola 1982, A.J.
87, 1881) has been updated using an improved position for the star
(R.A. = 16h27m33s03, Decl. = -21deg38'03".7, equinox 1950.0), derived
from observations at the Perth Observatory of the occultation of the
same star by Uranus' epsilon ring on March 3.  Timings of the March 3
event, forwarded by R. Millis, were used in conjunction with the
ring-orbit model of R. French to correct the star position relative
to Uranus.  Recent astrometry by A. R. Klemola with the Lick
double astrograph confirms this correction.  The uncertainty in
the revised prediction, due almost entirely to that in the ephemeris
of Umbriel, is on the order of 0".1.  The diameter of 1110 km
given for Umbriel by Brown and Cruikshank leads to a maximum duration
of ~ 3 min.  The predicted track now runs from Christmas Island
through Samoa, Fiji and New Caledonia, with the northern and
southern limits crossing the east coast of Australia near
Maryborough, Q, and Newcastle, NSW: the central line then passes near
Port Pirie, SA, and Albany, WA.  Predicted local circumstances:
Fiji, mid-occultation 16h15m27s UT, duration 155 s: Siding Spring,
16h22m47s, 153 s: Perth, 16h28m21s, 129 s.

     J. Maza, Department of Astronomy, University of Chile,
telexes that L. E. Gonzalez at Cerro El Roble has found a supernova
2" east and 12" north of the nucleus of on anonymous galaxy at
R.A. = 3h25m5, Decl. = -55deg15' (equinox 1950.0).  Photographic
magnitude estimates are: Feb. 15, 17.5; Mar. 10, 19.5.

     J. Mattei, AAVSO, informs us that the observation of this
star on IAUC 3770 refers to a short, normal outburst of the type
that occurs every 25-50 days; another one (to mag 12.4, according
to E. Mayer, Barberton, OH) occurred on Feb. 20/21.  In contrast,
the superoutbursts, such as the one mentioned on IAUC 3740 and
3747, occur approximately every 370 days.

1983 March 17                  (3784)              Brian G. Marsden

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