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IAUC 2841: HD 77581; 1975h; JUPITER XIII

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                                                  Circular No. 2841
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Cable Address: SATELLITES, NEWYORK
Western Union: RAPID SATELLITE CAMBMASS


HD 77581
     J. A. van Paradijs, G. Hammerschlag-Hensberge, E. P. J. van
den Heuvel, F. J. Zuiderwijk and R. J. Takens, Astronomical Institute,
University of Amsterdam; and C. De Loore, Free University of
Brussels, write: "We have analyzed 33 blue plates (dispersions 12
and 20 A/mm) taken of HD 77581 = Vela X-1 at the European Southern
Observatory between Apr. 1973 and June 1975.  Radial-velocity
measurements of lines of O II, Si III, Si IV, N II and N III reveal
the following orbital elements: P = 8d.96, K = 22.4 +/- 2.0 km/s, e =
0.16 +/- 0.10, a sin i = (2.72 +/- 0.24) x 10**6 km, Peri. = 357o +/- 32o,
f(M) = 0.010 Msol.  The values for e and Peri. are in excellent agreement with
those derived from the Doppler shift in the x-ray pulses of Vela
X-1 by Rappaport and McClintock (IAUC 2833).  Combining our further
orbital elements with theirs, we obtain: Mopt/Mx = 11.0, Mx sin**3 i
= 1.71 Msol, Mopt sin**3 i = 20.4 Msol.  From the light curve analysis of
HD 77581 by Avni and Bahcall we know that i = 74o-90o.  This results
in Mx = 1.7-2.0 Msol and Mopt = 20-23 Msol."


COMET KOBAYASHI-BERGER-MILON (1975h)
     The following precise positions have been reported:

     1975 UT             R. A. (1950) Decl.       Observer
     July 22.95539    18 12 57.28   +52 01 52.1   Codina
          22.97414    18 12 22.15   +52 05 23.8     "
     Aug. 14.44633    11 58 17.15   +44 34 03.3   Kurosaki
          14.47133    11 58 10.40   +44 32 56.5     "

J. M. Codina (Barcelona Observatory).  Computer: N. Torras.
T. Kurosaki (Utsunomiya).  20-cm f/6.2 reflector.  From Nihondaira
   Obs. Circ. No. 688 (with correction).


JUPITER XIII
     The following semiaccurate position has been derived from a 2-hr
exposure by P. J. Shelus with the McDonald Observatory's 208-cm
reflector.  Measurer: R. I. Abbot.  Communicated by J. Mulholland.

     1975 UT             R. A. (1950) Decl.
     Sept. 1.41458     1 30 16.9    + 8 08 05


1975 September 25              (2841)              Brian G. Marsden

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