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arXiv · 2308.08962

The heart of Sakurai's Object revealed by ALMA

Daniel Tafoya·Peter A. M. van Hoof·Jesus A. Toala·Griet Van de Steene·Suzanna Randall·Ramlal Unnikrishnan·Stefan Kimeswenger·Marcin Hajduk·Daniela Barria·Albert Zijlstra
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Abstract

We present high angular-resolution observations of Sakurai's object using the Atacama Large Millimeter Array, shedding new light on its morpho-kinematical structure. The millimetre continuum emission, observed at an angular resolution of 20 milliarcsec (corresponding to 70 AU), reveals a bright compact central component whose spectral index indicates that it composed of amorphous carbon dust. Based on these findings, we conclude that this emission traces the previously suggested dust disc observed in mid-infrared observations. Therefore, our observations provide the first direct imaging of such a disc. The H$^{12}$CN($J$=4$\rightarrow$3) line emission, observed at an angular resolution of 300 milliarcsec (corresponding to 1000 AU), displays bipolar structure with a north-south velocity gradient. From the position-velocity diagram of this emission we identify the presence of an expanding disc and a bipolar molecular outflow. The inclination of the disc is determined to be $i$=72$^\circ$. The derived values for the de-projected expansion velocity and the radius of the disc are $v_{\rm exp}$=53 km s$^{-1}$ and $R$=277 AU, respectively. On the other hand, the de-projected expansion velocity of the bipolar outflow detected in the H$^{12}$CN($J$=4$\rightarrow$3) emission of approximately 1000 km s$^{-1}$. We propose that the molecular outflow has an hourglass morphology with an opening angle of around 60$^{\circ}$. Our observations unambiguously show that an equatorial disc and bipolar outflows formed in Sakurai's object in less than 30 years after the born-again event occurred, providing important constraints for future modelling efforts of this phenomenon.

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Daniel Tafoya, Peter A. M. van Hoof, Jesus A. Toala, Griet Van de Steene, Suzanna Randall, Ramlal Unnikrishnan, Stefan Kimeswenger, Marcin Hajduk, Daniela Barria, Albert Zijlstra. 2023-08-17. The heart of Sakurai's Object revealed by ALMA. https://arxiv.org/abs/2308.08962

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