A precise measurement of the magnetic field in the corona of the black hole binary V404 Cygni

Observations of binary stars containing an accreting black hole or neutron star often show x-ray emission extending to high energies (>10 kilo­–electron volts), which is ascribed to an accretion disk corona of energetic particles akin to those seen in the solar corona. Despite their ubiquity, the physical conditions in accretion disk coronae remain poorly constrained. Using simultaneous infrared, optical, x-ray, and radio observations of the Galactic black hole system V404 Cygni, showing a rapid synchrotron cooling event in its 2015 outburst, we present a precise 461 ± 12 gauss magnetic field measurement in the corona. This measurement is substantially lower than previous estimates for such systems, providing constraints on physical models of accretion physics in black hole and neutron star binary systems. This article has a correction. Please see: http://science.sciencemag.org/content/360/6386/eaat927

Erratum for the Report “A precise measurement of the magnetic field in the corona of the black hole binary V404 Cygni”

In the Report “A precise measurement of the magnetic field in the corona of the black hole binary V404 Cygni,” a calculation error led to values of the magnetic field that were about 14 times too high. The mathematical expressions given in the Report were correct, but the code used to calculate the numerical values included an extraneous factor, which led to incorrect results. The magnetic fields calculated from the observations at different wavelengths were all scaled by the same factor, so after this is removed they remain consistent with each other. The corrected value of the magnetic field is lower than previously calculated, making the field in V404 Cygni even more unlike those estimated for other systems. However, the lower magnetic field is no longer consistent with the value predicted from the equipartition model. The text, materials and methods, Table S1, and Figure S3 have been updated to reflect the corrected magnetic field values and to state that the system was not in equipartition. No other results or conclusions of the study were affected. The authors thank J. Malzac (Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse) for alerting them to this error

KRYPTON OVERLAYERS ON GRAPHITE : LOW ENERGY ELECTRON DIFFRACTION AND AUGER ELECTRON SPECTROSCOPY MEASUREMENTS

La diffraction d'électrons lents et la spectroscopie des électrons Auger ont été utilisées pour étudier l'adsorption de krypton sur la face (0001) du graphite. Les pressions et températures de changement d'état des phases bidimensionnelles à p 10-4 torr.Low energy electron diffraction and Auger electron spectroscopy were used to study the adsorption of krypton on the (0001) plane of graphite. The pressures and temperatures for two dimensional phase transitions at p 10-4 torr

Can Parameter Instability Explain the Meese-Rogoff Puzzle?

The empirical literature on nominal exchange rates shows that the current exchange rate is often a better predictor of future exchange rates than a linear combination of macroeconomic fundamentals. This result is behind the famous Meese-Rogoff puzzle. In this paper we evaluate whether parameter instability can account for this puzzle. We consider a theoretical reduced-form relationship between the exchange rate and fundamentals in which parameters are either constant or time varying. We calibrate the model to data for exchange rates and fundamentals and conduct the exact same Meese-Rogoff exercise with data generated by the model. Our main finding is that the Impact of time-varying parameters on the prediction performance either is very small or goes in the wrong direction. To help interpret the findings, we derive theoretical results on the impact of time-varying parameters on the out-of-sample forecasting performance of the model. We conclude that it is not time-varying parameters, but rather small sample estimation bias, that explains the Meese-Rogoff puzzle

How does UK-based foreign exchange dealers think their market operates?

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