Clues to PPN Chemical Evolution: The Unique Molecular Environment of V510 Pup

TL;DR

This study uses archival ACA spectral line data to map the gas-phase molecular inventory of the binary post-AGB system V510 Pup and to link chemical makeup with kinematic structure. It detects 16 molecules, including both O-rich and C-rich species, and shows that they occupy distinct velocity components, revealing spatially separated chemical reservoirs. LTE modeling indicates CV is O-rich and cooler, while MV is C-rich and slightly warmer, consistent with acetylene-rich C-rich material in MV and oxygen-rich material in CV. The findings imply a layered evolutionary history where an older O-rich equatorial waist coexists with a later fast C-rich outflow, likely shaped by binary interactions, and call for higher-resolution follow-up to map the reservoirs in detail and constrain their dynamics.

Abstract

V510 Pup (IRAS 08005-2356) is a binary post-AGB system with a fast molecular outflow that has been noted for its puzzling mixture of carbon- and oxygen-rich features in the optical and infrared. To explore this chemical dichotomy and relate it to the kinematics of the source, we present an ACA spectral line survey detailing fourteen newly detected molecules in this pre-planetary nebula. The simultaneous presence of CN/C2H/HC3N and SO/SO2 support the previous conclusion of mixed chemistry, and their line profiles indicate that the C- and O-rich material trace distinct velocity structures in the outflow. This evidence suggests that V510 Pup could harbor a dense O-rich central waist from an earlier stage of evolution, which persisted after a fast C-rich molecular outflow formed. By studying the gas phase composition of this unique source, we aim to reveal new insights into the interplay between dynamics and chemistry in rapidly evolving post-AGB systems.

Figures (4)

• Figure 1: Emission line profiles of various molecules measured by the ACA toward V510 Pup. The central velocity (CV), medium-velocity (MV), and high-velocity (HV) components are defined in the left panel. Species that are typically associated with O- and C-rich evolved stellar outflows are shown in the middle and right panels, respectively. Spectra were extracted from an aperture with diameter 10" centered on the position of the post-AGB star. Some transitions are scaled for comparison.
• Figure 2: Comparison of integrated molecular line brightness (relative to ^13CO) for SO (red) and HC3N (blue) among a sample of nearby PPNe. For V510 Pup, the O-rich central and C-rich medium velocity components are labeled CV and MV, respectively. Hatched regions denote upper limits, while solid regions indicate detected transitions. Data for sources other than V510 Pup adapted from Olofsson2019, GallardoCava2022, and Pardo2004.
• Figure 3: Examples of LTE emission line fits for SO (left panels) and HC3N (right panels). ACA spectrum shown in black, while colored lines represent fitted molsim simulation. For SO, a narrow (magenta dashed) and wide (green dashed) gaussian were needed to reproduce the shape of the CV component. For HC3N, one component was used, centered on the red-shifted side of the MV region.
• Figure 4: Diagram of the circumstellar environment of V510 Pup as suggested by our ACA analysis of its millimeter spectrum. Includes major morphological structures and their velocities, as well as the observed chemistry in each region. Proposed components include a carbon-rich bipolar outflow (red and blue), and a slowly expanding oxygen-rich equatorial waist surrounding the central binary (brown).