Central Bureau for Astronomical Telegrams
IAUC 3358: SS 433
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Read IAUC 3359
Circular No. 3358
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
SS 433
P. G. Martin, Institute of Astronomy, University of Cambridge;
and P. G. Murdin and D. H. Clark, Royal Greenwich Obseryatory,
report: "Following identification of the moving emission features and
velocity-shifted Balmer and He I lines (Liebert et al. 1979, Nature
in press) and announcement of a 160-day periodicity (Margon et al.,
IAUC 3345), we have reanalyzed spectrograms obtained with the
Anglo-Australian Telescope on 1978 June 29, 30, and July 13, 14, 15 and
17 (Clark and Murdin 1978, Nature 276, 44). We find emission
systems consistent with this general picture. The July spectra are
particularly interesting since they were at a previously unobserved
phase that corresponds to 1979 June 1 in the current cycle. In
units of the rest wavelength, the red and blue systems occur at
1.076 and 0.989 (1978 July 15), the mean wavelength being offset to
1.033, which is typical of all phases. These data, together with
extensive previous results (see also Mammano et al., paper submitted
to Astron. Astrophys.), suggest a reliable ephemeris that
should be useful for identifying the features in the coming months.
Underlying this ephemeris might be a model with the following
characteristics. The emission arises in two opposing jets (Fabian and
Rees 1978, Monthly Notices Roy. Astron. Soc. 187, 13P), flowing
away from a central neutron star at a quasisteady velocity 0.25 c.
The latter property accounts for the constant offset in mean
wavelength (cf. Milgrom, preprint). Variable Doppler shifts result
from steady precession of the jet axis, which in a period of 160
days sweeps out a cone of opening angle 21o.5, centered on
inclination 79o.1 relative to the line of sight. Phase phi = 0, when the
axis is least tilted to the line of sight (57o.6), would have
occurred most recently near 1979 Apr. 22. In numerical terms, the
ephemeris for relative wavelengths is then 1.033 [1 +/- (0.044 +
0.09 cos 2 pi phi)], which approximates the data from parts of three
cycles well. Observations of the following interesting phenomena
will be important in refining this ephemeris/model. Near phases
0.33 and 0.67 (1979 June 14 and Aug. 7), the red and blue systems
should blend together near relative wavelength 1.033. Between
these phases the maximum excursions to the blue and red should be
0.985 and 1.081, near phase 0.5 (1979 July 11)."
Corrigendum. The report by E. F. Milone on IAUC 3354 should
conclude: "that of theta Lyr (K0II and E(B-V) ~ 0.17; Milone 1976,
Astrophys. J. Suppl. 31, 93)."
1979 May 11 (3358) Brian G. Marsden
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