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&

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

Near-Infrared Spectroscopy of 2M0441+2301 AabBab: A Quadruple System Spanning the Stellar to Planetary Mass Regimes

We present Keck/NIRC2 and OSIRIS near-infrared imaging and spectroscopy of 2M0441+2301 AabBab, a young (1--3 Myr) hierarchical quadruple system comprising a low-mass star, two brown dwarfs, and a planetary-mass companion in Taurus. All four components show spectroscopic signs of low surface gravity, and both 2M0441+2301 Aa and Ab possess Pa$\beta$ emission indicating they each harbor accretion subdisks. Astrometry spanning 2008--2014 reveals orbital motion in both the Aab (0.23" separation) and Bab (0.095" separation) pairs, although the implied orbital periods of $>$300 years means dynamical masses will not be possible in the near future. The faintest component (2M0441+2301 Bb) has an angular $H$-band shape, strong molecular absorption (VO, CO, H$_2$O, and FeH), and shallow alkali lines, confirming its young age, late spectral type (L1 $\pm$ 1), and low temperature ($\approx$1800~K). With individual masses of 200$^{+100}_{-50}$ Mjup, 35 $\pm$ 5 Mjup, 19 $\pm$ 3 Mjup, and 9.8 $\pm$ 1.8 Mjup, 2M0441+2301 AabBab is the lowest-mass quadruple system known. Its hierarchical orbital architecture and mass ratios imply that it formed from the collapse and fragmentation of a molecular cloud core, demonstrating that planetary-mass companions can originate from a stellar-like pathway analogous to higher-mass quadruple star systems as first speculated by Todorov et al. More generally, cloud fragmentation may be an important formation pathway for the massive exoplanets that are now regularly being imaged on wide orbits.Comment: Added an additional mention of an already cited reference, upon indirect reques

On the intersection conjecture for infinite trees of matroids

Using a new technique, we prove a rich family of special cases of the matroid intersection conjecture. Roughly, we prove the conjecture for pairs of tame matroids which have a common decomposition by 2-separations into finite parts