Interpretation of observations of the circumbinary disk of SS 433

Context. The Galactic microquasar SS 433 is possessed of a circumbinary disk most clearly seen in the brilliant Balmer H alpha emission line. The orbital speed of the glowing material is an important determinant of the mass of the binary system. The circumbinary disk may be fed through the L2 point and in turn may feed a very extended radio feature known as the ruff. Aims. To present an analysis of spectroscopic optical data from H alpha and He I spectral lines which reveal the circumbinary disk. To use comparisons of the rather different signals to better understand the disk and improve estimates of the rotational speed of the inner rim. To present a simple model which naturally explains some apparently bizarre spectral variations with orbital phase. Methods. Published spectra, taken almost nightly over two orbital periods of the binary system, are analysed. H alpha and He I lines are analysed as superpositions of Gaussian components and a simple model constructed. Results. The data are understood in terms of a hot spot, generated by proximity of the compact object, rotating round the inner circumbinary disk with a period of 13 days. The glowing material fades with time, quite slowly for the H alpha source but more rapidly for the He I spectral lines. The orbital speed of the inner rim is approximately 250 km/s. Conclusions. The mass of the binary system must exceed 40 solar masses and the compact object must be a rather massive stellar black hole. The corollary is that the orbital speed of the companion must exceed 130 km/s.Comment: Article; 6 pages, 8 figures. The new version of 28 July 2010, to appear in A&A, is 8 pages and 8 figures. The principal addition is some discussion of the behaviour of a gas stream from the L2 point. I also have added a note about the possibility that absorption lines taken as indicating an orbital speed of 60 km/s for the companion might have their origin in the circumbinary dis

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&

Ultraluminous X-ray sources with flat-topped noise and QPO

We analyzed the X-ray power density spectra of five ultraluminous X-ray sources (ULXs) NGC5408 X-1, NGC6946 X-1, M82 X-1, NGC1313 X-1 and IC342 X-1 that are the only ULXs which display both flat-topped noise (FTN) and quasi-periodic oscillations (QPO). We studied the QPO frequencies, fractional root-mean-square (rms) variability, X-ray luminosity and spectral hardness. We found that the level of FTN is anti-correlated with the QPO frequency. As the frequency of the QPO and brightness of the sources increase, their fractional variability decreases. We propose a simple interpretation using the spherizarion radius, viscosity time and $\alpha$-parameter as basic properties of these systems. The main physical driver of the observed variability is the mass accretion rate which varies >3 between different observations of the same source. As the accretion rate decreases the spherization radius reduces and the FTN plus the QPO move toward higher frequencies resulting in a decrease of the fractional rms variability. We also propose that in all ULXs when the accretion rate is low enough (but still super-Eddington) the QPO and FTN disappear. Assuming that the maximum X-ray luminosity depends only on the black hole (BH) mass and not on the accretion rate (not considering the effects of either the inclination of the super-Eddington disc nor geometrical beaming of radiation) we estimate that all the ULXs have about similar BH masses, with the exception of M82 X-1, which might be 10 times more massive.Comment: 15 pages, 7 figures, accepted for publication in MNRA

A non-perturbative proof of Bertrand's theorem

We discuss an alternative non-perturbative proof of Bertrand's theorem that leads in a concise way directly to the two allowed fields: the newtonian and the isotropic harmonic oscillator central fields.Comment: Latex file plus one eps figur

Search for LBV Candidates in the M33 Galaxy

A total of 185 luminous blue variable (LBV) candidates with V < 18.5 and B-V < 0.35 are selected based on the photometrical Survey of Local Group Galaxies made by P. Massey et al. 2006. The candidates were selected using aperture photometry of H-alpha images. The primary selection criterion is that the prospective candidate should be a blue star with H-aplha emission. In order not to miss appreciably reddened LBV candidates, we compose an additional list of 25 presumably reddened (0.35 < B-V < 1.2, V < 18.5) emission star candidates. A comparison with the list of known variables in the M33 galaxy showed 29% of our selected candidates to be photometrically variable. We also find our list to agree well with the lists of emission-line objects obtained in earlier papers using different methods.Comment: 6 figure

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 &

SS433's accretion disc, wind and jets: before, during and after a major flare

The Galactic microquasar SS433 occasionally exhibits a major flare when the intensity of its emission increases significantly and rapidly. We present an analysis of high-resolution, almost-nightly optical spectra obtained before, during and after a major flare, whose complex emission lines are deconstructed into single gaussians and demonstrate the different modes of mass loss in the SS433 system. During our monitoring, an initial period of quiescence was followed by increased activity which culminated in a radio flare. In the transition period the accretion disc of SS433 became visible in H-alpha and HeI emission lines and remained so until the observations were terminated; the line-of-sight velocity of the centre of the disc lines during this time behaved as though the binary orbit has significant eccentricity rather than being circular, consistent with three recent lines of evidence. After the accretion disc appeared its rotation speed increased steadily from 500 to 700 km/s. The launch speed of the jets first decreased then suddenly increased. At the same time as the jet launch speed increased, the wind from the accretion disc doubled in speed. Two days afterwards, the radio flux exhibited a flare. These data suggest that a massive ejection of material from the companion star loaded the accretion disc and the system responded with mass loss via different modes that together comprise the flare phenomena. We find that archival data reveal similar behaviour, in that when the measured jet launch speed exceeds 0.29c this is invariably simultaneous with, or a few days before, a radio flare. Thus we surmise that a major flare consists of the overloading of the accretion disc, resulting in the speeding up of the H-alpha rotation disc lines, followed by enhanced mass loss not just via its famous jets at higher-than-usual speeds but also directly from its accretion disc's wind.Comment: Accepted by MNRA