Remodel the Envelope Around the 21 micrometer PPN IRAS 07134+1005

TL;DR

This paper refines the understanding of the envelope structure and mass-loss rate of the 21 micrometer PPN IRAS 07134+1005 by constructing a detailed radiative transfer model based on CO J=3-2 observations.

Contribution

It introduces a new radiative transfer model with a two-component structure that better fits observational data and provides a more accurate superwind mass-loss rate estimate.

Findings

CO emission is slightly further from the center than mid-IR emission.

The superwind mass-loss rate is approximately 1.8 x 10^-5 solar masses per year.

The model includes an inner ellipsoidal superwind and an outer AGB wind.

Abstract

Recently, the CO J=3-2 observational result of the envelope of the 21 micrometer PPN IRAS 07134+1005 has been reported. Assuming that the CO J=3-2 line was optically thin, the mass-loss rate of the superwind in this PPN was found to be at least 2 orders of magnitude lower than the typical range. In order to obtain a more accurate mass-loss rate, we reexamine this data and construct a radiative transfer model to compare with the data. Also, in order to better resolve the superwind, we adopt a different weighting on the data to obtain maps at higher resolution. Our result shows that the CO J=3-2 emission is located slightly further away from the central source than the mid-IR emission, probably because that the material is cooler in the outer part and thus better traced by the CO emission. At lower resolution, however, the CO emission appeared to be spatially coincident with the mid-IR emission. Our model has two components, an inner ellipsoidal shell-like superwind with an equatorial density enhancement and an outer spheroidal AGB wind. The thick torus in previous model could be considered as the dense equatorial part of our ellipsoidal superwind. With radiative transfer, our model reproduces more observed features than previous model and obtains an averaged superwind mass-loss rate of ~ 1.8 x 10^-5 solar mass per year, which is typical for a superwind. The mass-loss rate in the equatorial plane is 3 x 10^-5 solar mass per year, also the same as that derived before from modeling CO J=1-0 emission.