First Images of the Molecular Gas around a Born-again Star Revealed by ALMA

DOI: 
10.3847/2041-8213/ac4a5b
Publication date: 
20/01/2022
Main author: 
Tafoya D.
IAA authors: 
Guerrero, Martín A.
Authors: 
Tafoya, Daniel;Toalá, Jesús A.;Unnikrishnan, Ramlal;Vlemmings, Wouter H.T.;Guerrero, Martín A.;Kimeswenger, Stefan;Van Hoof, Peter A.M.;Zapata, Luis A.;Trevio-Morales, Sandra P.;Rodríguez-González, Janis B.
Journal: 
Astrophysical Journal Letters
Publication type: 
Article
Volume: 
925.0
Pages: 
L4
Number: 
L4
Abstract: 
Born-again stars allow probing stellar evolution in human timescales and provide the most promising path for the formation of hydrogen-deficient post-asymptotic giant branch objects, but their cold and molecular components remain poorly explored. Here we present ALMA observations of V 605 Aql that unveil for the first time the spatio-kinematic distribution of the molecular material associated with a born-again star. Both the continuum and molecular line emission exhibit a clumpy ring-like structure with a total extent of ≈1″ in diameter. The bulk of the molecular emission is interpreted as being produced in a radially expanding disk-like structure with an expansion velocity ∼ 90 km s-1 and an inclination i ≈ 60 with respect to the line of sight. The observations also reveal a compact high-velocity component, ∼ 280 km s-1, that is aligned perpendicularly to the expanding disk. This component is interpreted as a bipolar outflow with a kinematical age τ ≲ 20 yr, which could either be material that is currently being ejected from V 605 Aql, or is being dragged from the inner parts of the disk by a stellar wind. The dust mass of the disk is in the range M dust ∼ 0.2-8 10-3 M o˙, depending on the dust absorption coefficient. The mass of the CO is M CO ≈ 1.1 10-5 M o˙, which is more than three orders of magnitude larger than the mass of the other detected molecules. We estimate a 12C/13C ratio of 5.6 0.6, which is consistent with the single stellar evolution scenario in which the star experienced a very late thermal pulse instead of a nova-like event as previously suggested.
Database: 
SCOPUS
ADS
URL: 
https://ui.adsabs.harvard.edu/#abs/2022ApJ...925L...4T/abstract
ADS Bibcode: 
2022ApJ...925L...4T