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Title: ON IRON MONOXIDE NANOPARTICLES AS A CARRIER OF THE MYSTERIOUS 21 μm EMISSION FEATURE IN POST-ASYMPTOTIC GIANT BRANCH STARS

Abstract

A prominent mysterious emission feature peaking at ∼20.1 μm—historically known as the '21 μm' feature—is seen in over two dozen Galactic and Magellanic Cloud carbon-rich, post-asymptotic giant branch (post-AGB) stars. The nature of its carrier remains unknown since the first detection of the 21 μm feature in 1989. Over a dozen materials have been suggested as possible carrier candidates. However, none of them has been accepted: they either require too much material (compared to what is available in the circumstellar shells around these post-AGB stars), or exhibit additional emission features that are not seen in these 21 μm sources. Recently, iron monoxide (FeO) nanoparticles seem to be a promising carrier candidate as Fe is an abundant element and FeO emits exclusively at ∼21 μm. In this work, using the proto-typical protoplanetary nebula HD 56126 as a test case, we examine FeO nanoparticles as a carrier for the 21 μm feature by modeling their infrared emission, with FeO being stochastically heated by single stellar photons. We find that FeO emits too broad a 21 μm feature to explain that observed and the Fe abundance required to be locked up in FeO exceeds what is available in HD 56126. We therefore concludemore » that FeO nanoparticles are not likely to be responsible for the 21 μm feature.« less

Authors:
;  [1]
  1. Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211 (United States)
Publication Date:
OSTI Identifier:
22270613
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 777; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; ASYMPTOTIC SOLUTIONS; CARBON; COMPARATIVE EVALUATIONS; COSMIC DUST; ELEMENT ABUNDANCE; GIANT STARS; IRON; IRON OXIDES; MAGELLANIC CLOUDS; NANOSTRUCTURES; NEBULAE; PARTICLES; PHOTONS; PROTOPLANETS; STOCHASTIC PROCESSES

Citation Formats

Li, Aigen, Jiang, B. W., and Liu, J. M., E-mail: lia@missouri.edu, E-mail: bjiang@bnu.edu.cn. ON IRON MONOXIDE NANOPARTICLES AS A CARRIER OF THE MYSTERIOUS 21 μm EMISSION FEATURE IN POST-ASYMPTOTIC GIANT BRANCH STARS. United States: N. p., 2013. Web. doi:10.1088/0004-637X/777/2/111.
Li, Aigen, Jiang, B. W., & Liu, J. M., E-mail: lia@missouri.edu, E-mail: bjiang@bnu.edu.cn. ON IRON MONOXIDE NANOPARTICLES AS A CARRIER OF THE MYSTERIOUS 21 μm EMISSION FEATURE IN POST-ASYMPTOTIC GIANT BRANCH STARS. United States. https://doi.org/10.1088/0004-637X/777/2/111
Li, Aigen, Jiang, B. W., and Liu, J. M., E-mail: lia@missouri.edu, E-mail: bjiang@bnu.edu.cn. 2013. "ON IRON MONOXIDE NANOPARTICLES AS A CARRIER OF THE MYSTERIOUS 21 μm EMISSION FEATURE IN POST-ASYMPTOTIC GIANT BRANCH STARS". United States. https://doi.org/10.1088/0004-637X/777/2/111.
@article{osti_22270613,
title = {ON IRON MONOXIDE NANOPARTICLES AS A CARRIER OF THE MYSTERIOUS 21 μm EMISSION FEATURE IN POST-ASYMPTOTIC GIANT BRANCH STARS},
author = {Li, Aigen and Jiang, B. W. and Liu, J. M., E-mail: lia@missouri.edu, E-mail: bjiang@bnu.edu.cn},
abstractNote = {A prominent mysterious emission feature peaking at ∼20.1 μm—historically known as the '21 μm' feature—is seen in over two dozen Galactic and Magellanic Cloud carbon-rich, post-asymptotic giant branch (post-AGB) stars. The nature of its carrier remains unknown since the first detection of the 21 μm feature in 1989. Over a dozen materials have been suggested as possible carrier candidates. However, none of them has been accepted: they either require too much material (compared to what is available in the circumstellar shells around these post-AGB stars), or exhibit additional emission features that are not seen in these 21 μm sources. Recently, iron monoxide (FeO) nanoparticles seem to be a promising carrier candidate as Fe is an abundant element and FeO emits exclusively at ∼21 μm. In this work, using the proto-typical protoplanetary nebula HD 56126 as a test case, we examine FeO nanoparticles as a carrier for the 21 μm feature by modeling their infrared emission, with FeO being stochastically heated by single stellar photons. We find that FeO emits too broad a 21 μm feature to explain that observed and the Fe abundance required to be locked up in FeO exceeds what is available in HD 56126. We therefore conclude that FeO nanoparticles are not likely to be responsible for the 21 μm feature.},
doi = {10.1088/0004-637X/777/2/111},
url = {https://www.osti.gov/biblio/22270613}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 777,
place = {United States},
year = {Sun Nov 10 00:00:00 EST 2013},
month = {Sun Nov 10 00:00:00 EST 2013}
}