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Title: PHOTOCHEMISTRY IN THE INNER LAYERS OF CLUMPY CIRCUMSTELLAR ENVELOPES: FORMATION OF WATER IN C-RICH OBJECTS AND OF C-BEARING MOLECULES IN O-RICH OBJECTS

Abstract

A mechanism based on the penetration of interstellar ultraviolet photons into the inner layers of clumpy circumstellar envelopes (CSEs) around asymptotic giant branch stars is proposed to explain the non-equilibrium chemistry observed in such objects. We show through a simple modeling approach that in CSEs with a certain degree of clumpiness or with moderately low mass loss rates (a few 10{sup -7} M {sub sun} yr{sup -1}) a photochemistry can take place in the warm and dense inner layers, inducing important changes in the chemical composition. In carbon-rich objects water vapor and ammonia would be formed with abundances of 10{sup -8}-10{sup -6} relative to H{sub 2}, while in oxygen-rich envelopes ammonia and carbon-bearing molecules such as HCN and CS would form with abundances of 10{sup -9}-10{sup -7} relative to H{sub 2}. The proposed mechanism would explain the recent observation of warm water vapor in the carbon-rich envelope IRC+10216 with the Herschel Space Observatory and predict that H{sub 2}O should be detectable in other carbon-rich objects.

Authors:
 [1];  [2];  [3]
  1. LUTH, Observatoire de Paris-Meudon, 5 Place Jules Janssen, 92190 Meudon (France)
  2. Departamento de Astrofisica, Centro de AstrobiologIa, CSIC-INTA, Ctra. de Torrejon a Ajalvir km 4, Torrejon de Ardoz, 28850 Madrid (Spain)
  3. Institut de Radioastronomie Millimetrique, 300 rue de la Piscine, 38406 Saint Martin d'Heres (France)
Publication Date:
OSTI Identifier:
21452645
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal Letters
Additional Journal Information:
Journal Volume: 724; Journal Issue: 2; Other Information: DOI: 10.1088/2041-8205/724/2/L133; Journal ID: ISSN 2041-8205
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AMMONIA; ASTROPHYSICS; CARBON; CHEMICAL COMPOSITION; HYDROGEN; PHOTOCHEMISTRY; PHOTONS; STARS; ULTRAVIOLET RADIATION; WATER VAPOR; BOSONS; CHEMISTRY; ELECTROMAGNETIC RADIATION; ELEMENTARY PARTICLES; ELEMENTS; FLUIDS; GASES; HYDRIDES; HYDROGEN COMPOUNDS; MASSLESS PARTICLES; NITROGEN COMPOUNDS; NITROGEN HYDRIDES; NONMETALS; PHYSICS; RADIATIONS; VAPORS

Citation Formats

Agundez, Marcelino, Cernicharo, Jose, and Guelin, Michel. PHOTOCHEMISTRY IN THE INNER LAYERS OF CLUMPY CIRCUMSTELLAR ENVELOPES: FORMATION OF WATER IN C-RICH OBJECTS AND OF C-BEARING MOLECULES IN O-RICH OBJECTS. United States: N. p., 2010. Web. doi:10.1088/2041-8205/724/2/L133.
Agundez, Marcelino, Cernicharo, Jose, & Guelin, Michel. PHOTOCHEMISTRY IN THE INNER LAYERS OF CLUMPY CIRCUMSTELLAR ENVELOPES: FORMATION OF WATER IN C-RICH OBJECTS AND OF C-BEARING MOLECULES IN O-RICH OBJECTS. United States. https://doi.org/10.1088/2041-8205/724/2/L133
Agundez, Marcelino, Cernicharo, Jose, and Guelin, Michel. 2010. "PHOTOCHEMISTRY IN THE INNER LAYERS OF CLUMPY CIRCUMSTELLAR ENVELOPES: FORMATION OF WATER IN C-RICH OBJECTS AND OF C-BEARING MOLECULES IN O-RICH OBJECTS". United States. https://doi.org/10.1088/2041-8205/724/2/L133.
@article{osti_21452645,
title = {PHOTOCHEMISTRY IN THE INNER LAYERS OF CLUMPY CIRCUMSTELLAR ENVELOPES: FORMATION OF WATER IN C-RICH OBJECTS AND OF C-BEARING MOLECULES IN O-RICH OBJECTS},
author = {Agundez, Marcelino and Cernicharo, Jose and Guelin, Michel},
abstractNote = {A mechanism based on the penetration of interstellar ultraviolet photons into the inner layers of clumpy circumstellar envelopes (CSEs) around asymptotic giant branch stars is proposed to explain the non-equilibrium chemistry observed in such objects. We show through a simple modeling approach that in CSEs with a certain degree of clumpiness or with moderately low mass loss rates (a few 10{sup -7} M {sub sun} yr{sup -1}) a photochemistry can take place in the warm and dense inner layers, inducing important changes in the chemical composition. In carbon-rich objects water vapor and ammonia would be formed with abundances of 10{sup -8}-10{sup -6} relative to H{sub 2}, while in oxygen-rich envelopes ammonia and carbon-bearing molecules such as HCN and CS would form with abundances of 10{sup -9}-10{sup -7} relative to H{sub 2}. The proposed mechanism would explain the recent observation of warm water vapor in the carbon-rich envelope IRC+10216 with the Herschel Space Observatory and predict that H{sub 2}O should be detectable in other carbon-rich objects.},
doi = {10.1088/2041-8205/724/2/L133},
url = {https://www.osti.gov/biblio/21452645}, journal = {Astrophysical Journal Letters},
issn = {2041-8205},
number = 2,
volume = 724,
place = {United States},
year = {Wed Dec 01 00:00:00 EST 2010},
month = {Wed Dec 01 00:00:00 EST 2010}
}