Jet propulsion of wind ejecta from a major flare in the black hole microquasar SS433

We present direct evidence, from Adaptive-Optics near-infra-red imaging, of the jets in the Galactic microquasar SS433 interacting with enhanced wind-outflow off the accretion disc that surrounds the black hole in this system. Radiant quantities of gas are transported significant distances away from the black hole approximately perpendicular to the accretion disc from which the wind emanates. We suggest that the material that comprised the resulting "bow-tie" structure is associated with a major flare that the system exhibited ten months prior to the observations. During this flare, excess matter was expelled by the accretion disc as an enhanced wind, which in turn is "snow-ploughed", or propelled, out by the much faster jets that move at approximately a quarter of the speed of light. Successive instances of such bow-ties may be responsible for the large-scale X-ray cones observed across the W50 nebula by ROSAT.Comment: Accepted by ApJ Let

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.Comment: 2 pages, no figures To appear in A & A. No significant changes from original version poste

How revealing is revealed preference?

This lecture address the following two key criticisms of the empirical application of revealed preference theory: When the RP conditions do not reject, they do not provide precise predictions; and when they do reject, they do not help characterize the nature of irrationality or the degree/direction of changing tastes. Recent developments in the application of RP theory are shown to have rendered these criticisms unfounded. A powerful test of rationality is available that also provides a natural characterization of changing tastes. Tight bounds on demand responses and on the welfare costs of relative price and tax changes are also available and are shown to work well in practice

Radio-loud and radio-quiet quasars: one population, different epochs of observation

I bring together evidence for the rapidity with which quasars' radio synchrotron lobe emission fades and for the intermittency with which jet plasma is ejected from individual quasars and radio galaxies and affirm the picture presented by Nipoti et al (2005) that the radio-loudness of quasars is a function of the epoch at which they are observed. I briefly illustrate this account with examples of successive episodes of jet activity where the axis along which jet plasma is launched appears to have precessed. A new model for the weak core radio emission from radio-quiet quasars, that is not any kind of jet ejecta, is also briefly described.Comment: Invited talk at Alaska meeting on "Extragalactic Jets: theory and observation from radio to gamma-ray". Editors: Travis Rector and David De Youn

Sigurd Lewerentz: Church of St Peter, Klippan, 1963–66

This modest building questions basic assumptions about processes and finishes, about the nature of brickwork and the detailing of window frames – and provides a powerful space for worship

Improving revealed preference bounds on demand responses

There are three key dimensions by which revealed preference bounds on consumer demand responses can be improved. The first relates to the improvements that arise from using expansion paths for given relative prices, E-bounds. The second concerns the addition of new price information. Thirdly, there are improvements due to assuming separability. Our previous research has examined the first two cases. In this article, we show how to impose separability assumptions within a fully nonparametric analysis and distinguish between weak and homothetic separability. We also apply these ideas to the analysis of demand responses using United Kingdom household level data

Working with the given

In this essay the author suggests that although the resulting architectural style may be ambiguous, a dialogue with an existing place can be creative, rewarding and appropriate