ALMA imaging of the nascent planetary nebula IRAS 15103-5754

Jose F. Gomez, Gilles Niccolini, Olga Suarez, Luis F. Miranda, J. Ricardo Rizzo, Lucero Uscanga, James A. Green, Itziar de Gregorio-Monsalvo. 2018. ALMA imaging of the nascent planetary nebula IRAS 15103–5754. Monthly Notices of the Royal Astronomical Society 480, 4, 4991-5009 DOI: 10.1093/mnras/sty2193

We present continuum and molecular-line (CO, (CO)-O-18, HCO+) observations carried out with the Atacama Large Millimeter/submillimeter Array toward the ‘water fountain’ star IRAS 15103-5754, an object that could be the youngest planetary nebula (PN) known. We detect two continuum sources, separated by 0.39 +/- 0.03 arcsec. The emission from the brighter source seems to arise mainly from ionized gas, thus confirming the PN nature of the object. The molecular-line emission is dominated by a circumstellar torus with a diameter of similar or equal to 0.6 arcsec (2000 au) and expanding at similar or equal to 23 km s(-1). We see at least two gas outflows. The highest-velocity outflow (deprojected velocities up to 250 km s(-1)), traced by the CO lines, shows a biconical morphology, whose axis is misaligned similar or equal to 14 degrees with respect to the symmetry axis of the torus, and with a different central velocity (by similar or equal to 8 km s(-1)). An additional high-density outflow (traced by HCO+) is oriented nearly perpendicular to the torus. We speculate that IRAS 15103-5754 was a triple stellar system that went through a common envelope phase, and one of the components was ejected in this process. A subsequent low-collimation wind from the remaining binary stripped out gas from the torus, creating the conical outflow. The high velocity of the outflow suggests that the momentum transfer from the wind is extremely efficient, or that we are witnessing a very energetic mass-loss event.

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