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$\alpha$ 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$^{-1}$, implying that the mass of the compact object is less than 37 $M_\odot$. Evidence that an accretion stream joins the disk at over 700 km s$^{-1}$ 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$^{-1}$. The mass of the companion lies between 20 and 30 $M_\odot$ 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 $M_\odot$. 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 $M_\odot$. 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 $\sim$ 60 km s$^{-1}$ 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 $\sim$ 240 km s$^{-1}$, 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 $\sim$ 40 $M_\odot$. 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&