arXiv subjects

M. G. Bowler

Publications and source records attributed to M. G. Bowler.

11 recordsLinked to original sources

arXiv2021

SS 433: flares in H alpha, GRAVITY observations & L2 ejection

Abstract The microquasar SS 433 exhibits in H alpha intermittent flares, Doppler shifted to both the red and the blue. The mean remembers the orbital phase of the compact object. I show that the flares are not intermittent sightings of an accretion disk; rather, plasma must be expelled through the L2 point, thus remembering the phase of the orbit as it invades the space beyond the system. That space has been mapped with GRAVITY observations of a similar flare, revealing a strong rotation component.

astro-ph.GA↗

arXiv2020

SS 433: C II emission from the disk photosphere

The Galactic microquasar SS 433 is a member of a binary system but there is a lack of data on the orbital velocities of the components. The emission lines of the C II doublet at 7231 and 7236 Angstrom have been tracked nightly over two orbital cycles. The spectra are adequate to establish that these lines are eclipsed by the companion and hence to extract a measure of the orbital velocity of the compact object; the lines are formed in the disk photosphere. This velocity is 176 plus/minus 13 km/s. Could XSHOOTER do better?

astro-ph.SR↗

arXiv2020

W50 morphology and the dynamics of SS 433 formation

The jets of SS 433 have punched through the supernova remnant from the explosion forming the compact object. The precessing jets collimate before reaching beyond the shell, some 40 pc downstream, just the region of origin of TeV gamma radiation. Collimation could be effected by ambient pressure in the SNR cavity; I investigate conditions under which W50 morphology and the origins of TeV gamma radiation can be explained in terms of collimation, with associated shocks, induced by ambient pressure. I consider the age of the SNR and hence the present ambient pressure. The cavity is now ~ 10^5 years after the supernova; with lower pressure, collimation and associated shocks would occur ~40 pc downstream, just the origin of TeV gamma radiation. Modelling of evolution of binary systems indicates that Roche lobe overflow and initiation of the jets is recent. Collimation would still occur ~40 pc downstream, but the cone angle of the precession must then have increased with time - driven by the Roche lobe overflow. The morphology of W50 and the site of the origin of TeV gamma radiation are readily explained in terms of collimation of the jets by internal SNR pressure.

astro-ph.HE↗

arXiv2017

The accretion disk of SS 433?

I discuss two points concerning recent Brackett series spectra of SS 433. The first is that outbursts to red and blue episodic in the Balmer series are now shown to be episodic in the far infrared Brackett series. The second point is that while in quiet times the Brackett profiles are characteristic of a disk rotating at ~ 200 km/s, such a disk is not the accretion disk and it should not be claimed that these profiles require a compact object mass less than 2.2 solar masses.

astro-ph.SR↗

arXiv2015

SS 433: Stationary lines and primary eclipses

Some stationary lines in the emission spectra of SS 433 are eclipsed, but most are not. Lines attributed to a circumbinary disk are not eclipsed, but double in relative intensity during primary eclipse. A C II doublet is eclipsed and Doppler shifts over two periods yield an orbital speed of 176 +/- 13 km/s.

astro-ph.SR↗

arXiv2012

Of priors and prejudice

If species abundance distributions are dominated by the simple processes of individuals in a community giving birth and death independently, the result is a log series distribution. I calculate this in a number of different ways, using both master equations and also the combinatoric methods of elementary statistical mechanics. Considerable light is shed on the nature and role of 'priors' in the language of MaxEnt.

q-bio.PE↗

arXiv2011

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.

astro-ph.GA↗

arXiv2011

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.

astro-ph.GA↗

arXiv2010

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.

astro-ph.GA↗

arXiv2010

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.

astro-ph.GA↗

arXiv2009

Apsidal advance in SS 433?

Context. The Galactic microquasar SS 433 launches oppositely directed jets at speeds approximately a quarter of the speed of light. Both the speed and direction of the jets exhibit small fluctuations. A component of the speed variation has 13 day periodicity and the orbital phase at which its maximum speed occurs has advanced approximately 90 degrees in 25 years. Aims. To examine the possibility that these variations are associated with a mildly eccentric orbit and conditions necessary to achieve this apsidal advance. Methods. The advance of the orbital phase for maximum speed is taken to be advance of the apses of the putative elliptical orbit. It is compared with calculations of the effects of tides induced in the companion and also with gravitational perturbations from the circumbinary disc. These calculations are made in the light of recent results on the SS 433 system. Results. The 13 day periodicity in the speed of the jets of SS 433 might be attributed to a mildly elliptical orbit, through periodic approaches of the donor and the compact object. Advance of the apses of such an elliptical orbit due to tidal effects induced in a normal companion looks to be to small; if caused by the circumbinary disc the mass of the inner regions of that disc is ~ 0.15 solar masses.

astro-ph.GA↗