IDENTIFICATION OF THREE NEW PROTOPLANETARY NEBULAE EXHIBITING THE UNIDENTIFIED FEATURE AT 21 {mu}m

Journal Article · Sat Sep 10 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/738/2/121; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21584895

Cerrigone, Luciano ^[1]; Hora, Joseph L; Hart, Alexa; Fazio, Giovanni ^[2]; Umana, Grazia; Trigilio, Corrado ^[3]

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1. Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn (Germany)
2. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
3. INAF, Osservatorio Astrofisico di Catania, via Santa Sofia 78, 95123 Catania (Italy)

Among its great findings, the Infrared Astronomical Satellite mission showed the existence of an unidentified mid-IR feature around 21 {mu}m. Since its discovery, this feature has been detected in all C-rich protoplanetary nebulae (PPNe) of intermediate spectral type (F-G) and-weakly-in a few PNe and asymptotic giant branch (AGB) stars, but the nature of its carriers remains unknown. In this paper, we show the detection of this feature in the spectra of three new stars transiting from the AGB to the PN stage obtained with the Spitzer Space Telescope. Following a recent suggestion, we try to model the spectral energy distributions of our targets with amorphous carbon and FeO, which might be responsible for the unidentified feature. The fit thus obtained is not completely satisfactory, since the shape of the feature is not well matched. In an attempt to relate the unidentified feature to other dust features, we retrieved mid-IR spectra of all 21 {mu}m sources currently known from Infrared Space Observatory and Spitzer online archives and noticed a correlation between the flux emitted in the 21 {mu}m feature and that emitted at 7 and 11 {mu}m (polycyclic aromatic hydrocarbon bands and hydrogenated amorphous carbon broad emission). Such a correlation may point to a common nature of the carriers.

• OSTI ID: 21584895
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 738; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
AROMATICS
CARBON
CHALCOGENIDES
ELEMENTS
EMISSION
ENERGY SPECTRA
GIANT STARS
HYDROCARBONS
INFRARED SPECTRA
IRON COMPOUNDS
IRON OXIDES
NEBULAE
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLANETARY NEBULAE
POLYCYCLIC AROMATIC HYDROCARBONS
PROTOPLANETS
SPECTRA
STARS
TRANSITION ELEMENT COMPOUNDS