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IAUC 3464: NO Occn BY PLUTO ON 1980 Apr. 6; SN IN NGC 3733; LSI +61 303

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IAUC number

                                                  Circular No. 3464
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

     A. R. Kiemola, Lick Observatory; and J. L. Elliot, Massachusetts
Institute of Technology, inform us that there will probably
be no occultation of the mag ~ 12 star at R.A. = 13h40m45s.1, Decl. =
+8o34'48" (equinox 1950.0) by Pluto on Apr. 6 (cf. IAU Comm. 20
Occultation Bull. Nos. 10 and 15).  At Cape Town the star is expected
to pass 0".85 from the center of Pluto (in p.a. ~ 30o) on
Apr. 6d23h49m.3 UT.  According to Harrington and Christy (1980, A.J.
85, 168) the probable satellite 1978 P 1 will be at greatest
northern elongation (separation ~ 0".9) on Apr. 7d01h UT; an
occultation by 1978 P 1 is not particularly likely, but this object may
be only 0".1-0".2 from the star around Apr. 6d23h37m UT.

     R. Kirshner, University of Michigan, reports that spectrophotometry
by C. Canizares, G. Kriss and M. Johns at McGraw-Hill Observatory
on Mar. 22 showed this object (cf. IAUC 3462) to be a
supernova of type I, at mv ~ 15.5 and near maximum.

LSI +61 303
     A. R. Taylor and P. C. Gregory, Physics Department, University
of British Columbia, report that the radio emission of this object
(cf. IAUC 3170, 3180) varies in a periodic fashion with a period of
26.45 +/- 0.05 days, based on observations over two years at N.R.A.O.
(5 GHz) and A.R.O. (10 GHz).  At phase 0.3 (1978 Feb. 21) the radio
emission at both 5 and 10 GHz is ~ 15 mJy.  Maximum occurs at phase
0.65 and is typically 200 mJy.

     Radial-velocity measurements by J. B. Hutchings and D. Crampton,
Dominion Astrophysical Observatory, of H and He I absorptions in the
optical spectrum indicate an orbital amplitude of K = 15 +/- 4 km/s if
the period is 26.45 days.  This yields a mass function of 0.0093,
which implies secondary masses between 1.0 and 1.9 Msol for primary
masses of 10-20 Msol and inclination > 60o.  The phase of maximum
positive velocity coincides with the phase of radio minimum.  The
general appearance of the spectrum has not changed appreciably over two

1980 March 31                  (3464)              Brian G. Marsden

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