Central Bureau for Astronomical Telegrams
IAUC 4273: 1982i; LSI +65 010
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Circular No. 4273
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 617-495-7244/7440/7444
PERIODIC COMET HALLEY (1982i)
Z. Sekanina, Jet Propulsion Laboratory, California Institute
of Technology, writes: "The approximation of P/Halley's nucleus by
a torque-free rigid spheroid, which is homogeneous and has axial
ratios of 1.9:1.0:1.0, reconciles the two reported recurrence
periods as follows. The 2.2-day period (IAUC 4151; also Sekanina
1986, Adv. Space Res. 5, No. 12, 307) is the precession period of
the long axis about a fixed direction. The 7.4-day period (Millis
and Schleicher 1986, Nature, in press) is identified with the
rotation period about this axis. The moments of inertia require that
the precession angle (the semiamplitude of the precessional motion)
be 77 deg, implying a 26 deg full-amplitude wobble for what had
been interpreted as the 'spin axis'. This model offers attractive
explanations for various aspects of the observed phenomena (
including the jet evolution) that had been rather puzzling, but it
involves an element of instability (a prolate spheroid). The
possibility was investigated that the 7.4-day period is a composite
of the 2.2-day period and an intrinsic period of rotation about
the long axis, but no satisfactory solution was found. A more
detailed study is being submitted to Nature."
LSI +65 010
E. Faverey, M. H. van Kerkwyk and E. P. J. van den Heuvel,
Astronomical Institute, University of Amsterdam, telex: "Reticon
spectra (dispersion 6 nm/mm, wavelength range 380-540 nm) obtained
with the Calar Alto 1.2-m telescope show that strong Balmer
absorption lines suddenly appeared in the spectrum of LSI +65 010 (2S
0114+650, spectral type B0IIIe) from Nov. 4 onwards. During Oct.
31-Nov. 3, the same lines were weak, as usual (cf. Crampton et al.
1985, Ap.J. 299, 839), with central depths not exceeding 15
percent at our resolution. On Nov. 4.91, 5.08, 5.10 and 5.89 UT
the relative central depths were larger than 30 percent, and the
equivalent widths had increased by a factor of ~ 3 with respect to
those of the previous week. As this strongly suggests that the Be
component of this x-ray binary has entered a mass-ejection (shell)
phase, x-ray astronomers are urged to observe this source, for an
increase of the x-ray intensity of the neutron-star component is
expected. Photometric observations are also needed."
1986 November 17 (4273) Brian G. Marsden
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