3,113 research outputs found
SS 433: The accretion disk revealed in H alpha
{The Galactic microquasar SS 433 is very luminous and ejects opposite jets at
approximately one quarter the speed of light. It is regarded as a
super-Eddington accretor but until recently there were no observations of
accretion.} % aims heading (mandatory) {To present an analysis of spectroscopic
optical data obtained before and during a major flare, which yield in H
unambiguous evidence for the accretion disk.} % methods heading (mandatory)
{Published high resolution spectra, taken with a 3.6-m telescope almost nightly
over 0.4 of a precession cycle, are analysed.} % results heading (mandatory)
{Optical spectra taken almost nightly in August and September 2004 revealed a
period of quiescence followed by activity which culminated in the accretion
disk of SS433 becoming visible. The visible material in the accretion disk
orbited the compact object at greater than 500 km s, implying that the
mass of the compact object is less than 37 . Evidence that an
accretion stream joins the disk at over 700 km s suggests that the mass
is considerably below this upper limit. The accretion disk clearly orbits the
centre of mass of the binary system with the compact object, sharing its speed
of approximately 175 km s. The mass of the companion lies between 20 and
30 and it probably does not fill its Roche lobe.}Comment: 6 pages, 3 figures. This version to appear in A&A is a little more
detailed than the origina
The mass of SS 433: a conflict resolved?
The Galactic microquasar SS\,433 is very luminous and launches
oppositely-directed jets of cool hydrogen at a quarter of the speed of light.
Observations of emission lines from the circumbinary disk imply a system mass
exceeding 40 . The most recent attempts to establish a mass via
observation of absorption lines in the spectrum of the companion imply a system
mass of no more than 20 . Aims. To examine these conflicting data and
present a possible resolution of this conflict. Methods. Interpretation of data
through the application of simple trigonometry to the configuration of the SS
433 system. Results. The absorption spectra which, attributed to the atmosphere
of the companion, yield an orbital speed of 60 km s could well be
attributable to absorption of light from the companion in material of the
circumbinary disk. Then the absorption spectra predict an orbital speed for the
circumbinary disk material of 240 km s, in agreement with the
emission line data. Conclusions. If continuum light from the companion is
absorbed in passage through the circumbinary disk material rather than in the
atmosphere of the companion itself, the periodic Doppler shifts in the
absorption spectra are entirely consistent with observations of the
circumbinary disk and a system mass exceeding 40 . The striking
consistency implies that the compact object is a rather massive stellar black
hole.Comment: This is a sequel to my article on the circumbinary disk of SS 433.
arXiv:1004.0119v1 [astro-ph.GA]. The second version is 4 pages and has been
augmented by 2 figures. The discussion has been somewhat extended to
highlight the conditions necessary for this suggestion to appl
More on the circumbinary disk of SS 433
Certain lines in spectra of the Galactic microquasar SS 433, in particular
the brilliant H alpha line, have been interpreted as emission from a
circumbinary disk. In this interpretation the orbital speed of the glowing
material is in excess of 200 km/s and the mass of the binary system in excess
of 40 solar masses. A very simple model of excitation of disk material is in
remarkable agreement with the observations, yet it seems that the very
existence of a circumbinary disk is regarded as controversial.
Published spectra, taken almost nightly over two orbital periods of the
binary system, show H alpha and He I lines; these were analysed as
superpositions of Gaussian components. A model in which the excitation of any
given patch of putative circumbinary material is proportional to the inverse
square of its instantaneous distance from the compact object was constructed
and compared with observations.
The new model provides an excellent description of the observations. The
variation of the H alpha and He I spectra with orbital phase are described
quantitatively provided the radius of the emitting ring is not much greater
than the radius of the closest stable circumbinary orbit.
The new analysis has greatly strengthened the case for a circumbinary disk
orbiting the SS 433 system with a speed of over 200 km/s and presents supposed
alternative explanations with major difficulties. If the circumbinary disk
scenario is essentially correct, the mass of the binary system must exceed 40
solar masses and the compact object must be a rather massive black hole. The
case is so strong that this possibility should be taken seriously.Comment: 7 pages, 7 figures. The second version has two additional figures and
an extended discussion. To appear in A &
SS 433: The wiggle of the wind
The Balmer H alpha emission line in the stationary spectrum of SS 433 has a
component originating in the wind above the accretion disk. The Doppler motion
of this line is a blurred representation of the motion of the compact object
accreting. I show how this may be understood in terms of emission lasting over
a few days, like radiation from the jet bolides.Comment: 4 pages, 3 figures. A coda to my circumbinary disk studies. To appear
in A&
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