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IAUC 3416: W50 AND SS 433; PKS 2155 AND Cyg X-2

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IAUC number

                                                  Circular No. 3416
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

W50 AND SS 433
     W. Zealey, Royal Observatory, Edinburgh; M. Dopita, Mt. Stromlo
and Siding Spring Observatories; and D. Malin, Anglo-Australian
Observatory, communicate: "Following our independent discovery of
the optical filaments in W50 (cf. IAUC 3393, 3400) we obtained
high-resolution red spectra of them with the IPCS on the
Anglo-Australian Telescope.  Confirming the results of Murdin and Clark
(IAUC 3400), we find strong forbidden lines of nitrogen, sulphur
and oxygen.  The radial velocities lie in the range +126 to +70
km/s (local standard of rest); velocity dispersions are 50 to 90
km/s.  These features are similar to those seen in some Herbig-Haro
objects and indicate excitation by low-velocity shocks.  Except
possibly for nitrogen, abundances could be normal.  From these
spectra and from morphological considerations we have derived
mass-loss rates for the relativistic jets of SS 433 in the range 2 x
10**-6 to 4 x 10**-7 Msol/yr and a lifetime of the order of 2 x 10**4 yr.
This is consistent with models involving black holes with
super-critical accretion disks (cf., e.g., Martin and Rees 1979, M.N.
189, 19P).  Using the theory of Jaroszynski et al. (A. & Ap. in
press), we find for the black hole a mass estimate in the range 8
to 1.5 Msol.  If the compact companion is a neutron star, accretion
rates required to maintain the jets are of the order of 2 x 10**21
g/s, and if maintained for the lifetime of the system such rates
would probably have already induced the collapse to a black hole."

     L. Maraschi, E. G. Tanzi and A. Treves, University of Milan,
communicate that the x-ray emitting BL Lac object PKS 2155 was
observed with IUE at Vuspa on Oct. 13 and 14 in a bright phase, B =
13.  The ultraviolet fluxes were 1.2 x 10**-15 J m**-2 s**-1 nm**-1 at 150
nm and 7 x 10**16 J m**-2 s**-1 nm**-1 at 250 nm.  They urge observations
at other wavelengths.  Treves, Maraschi and Tanzi also report that
IUE observations of Cyg X-2 showed a variation in extreme ultraviolet
flux by a factor of five within three days.  On Oct. 12.7 UT,
corresponding to orbital phase 0.3 (Cowley et al. 1979, Ap. J. 231,
539), the 150-nm flux was 5 x 10**-17 J m**-2 s**-1 nm**-1, while on Oct.
15.7 UT, at phase 0.6, it was 1 x 10**-17 J m**-2 s**-1 nm**-1.  Several
emission lines were observed at both phases that can be attributed
to N V, Si IV, He II, N III and C III.  C IV was not apparent.

1979 October 25                (3416)              Brian G. Marsden

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