Application of the Thermal Wind Model to Absorption Features in the Black Hole X-ray Binary H 1743-322

Abstract: High inclination black hole X-ray binaries exhibit blueshifted ionized absorption lines from disk winds, whose launching mechanism is still in debate. The lines are predominantly observed in the high/soft state and disappear in the low/hard state, anti-correlated with the jet. We have tested if the thermal winds, which are driven by the irradiation of the outer disk by the X-rays from the inner disk, can explain these observed properties or whether we need a magnetic switch between jet and wind. We use analytic thermal-radiative wind models to predict the column density, ionisation parameter and velocity of the wind given the broadband continuum shape and luminosity determined from RXTE monitoring. We use these to simulate the detailed photo-ionised absorption features predicted at epochs where there are Chandra high resolution spectra. These include low/hard, high/soft and very high states. The model was found to well reproduce the observed lines in the high/soft state, and also successfully predicts their disappearance in the low/hard state. However, the simplest version of the thermal wind model also predicts that there should be strong features observed in the very high state, which are not seen in the data. Nonetheless, we show this is consistent with thermal winds when we include self-shielding by the irradiated inner disk atmosphere. These results indicate that the evolution of observed wind properties in different states during outbursts in H 1743-322 can be explained by the thermal wind model and does not require magnetic driving.