J/ApJ/866/L1 Dust models & IR spectroscopy obs. of AGB stars (Sargent, 2018)
Alumina polymorphism in the circumstellar dust shells of asymptotic giant branch
stars.
Sargent B.A.
<Astrophys. J., 866, L1 (2018)>
=2018ApJ...866L...1S 2018ApJ...866L...1S
ADC_Keywords: Spectra, infrared; Stars, giant; Models; Interstellar medium
Keywords: circumstellar matter ; infrared: stars
Abstract:
Many emission features remain unidentified in the infrared spectra of
asymptotic giant branch (AGB) stars. In particular, features at ∼11,
20, 28, and 32µm have been noted in mid-infrared spectra of
oxygen-rich AGB stars. Here, I present models of dust excess emission
in 36 spectra of 24 AGB stars from the Short Wavelength Spectrometer
on board the Infrared Space Observatory and the Infrared Spectrograph
on the Spitzer Space Telescope. The models include opacities of grains
composed of mixtures of various polymorphs of alumina obtained by
preparing bayerite and boehmite at high temperatures, and these dust
components provide satisfactory fits to the 11, 20, 28, and 32µm
features. Though not a direct conclusion from this study, the presence
of grains of the various polymorphs of aluminas in circumstellar dust
shells around AGB stars suggests that corundum may have a role in
giving rise to the 13µm feature.
Description:
The spectra analyzed in this study come both from the Spitzer Space
Telescope Infrared Spectrograph (IRS) and from the Infrared Space
Observatory (ISO) Short Wavelength Spectrometer (SWS). My sample of
spectra were chosen from among previous studies of AGB stars (see
Table 1) for their relatively prominent 11, 20, 28, and 32um emission
features.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
sample.dat 16 24 List of the stars; table added by CDS
table1.dat 197 72 Sample information and dust model parameters
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+AS/146/437 : IR spectra of oxygen-rich evolved stars (Speck+, 2000)
J/A+A/442/281 : Late-type giants BVRIJHKL & Teff calib. (Kucinskas+, 2005)
J/A+A/483/661 : Refractive index for silicon carbide (SiC) (Pitman+, 2008)
J/ApJ/693/L81 : Extinction in star-forming regions (McClure, 2009)
J/ApJS/193/23 : Fundamental stellar parameters in 47 Tucanae (McDonald+, 2011)
J/A+A/553/A81 : Refraction of corundum, spinel, α-quartz (Zeidler+, 2013)
J/ApJ/811/45 : Infrared spectral properties of M giants (Sloan+, 2015)
J/A+A/592/A42 : A study of dust nucleation in Mira. Part I. (Kaminski+, 2016)
Byte-by-byte Description of file: sample.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- ID Target identifier
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- ID Target identifier
18 A1 --- r_ID [abcdef] Flag on ID (1)
20- 23 F4.2 kpc Dist [0.1/7.8]? Distance (2)
25 A1 --- f_Dist [ghij] Flag on Dist (3)
27- 31 F5.3 mag Av [0.01/1.6]? V band extinction (4)
33 A1 --- f_Av [ghij] Flag on Av (3)
35- 45 A11 --- Inst Spitzer/IRS or ISO/SWS instrument
47- 54 I8 --- AOR Spitzer AOR or ISO AOT data identifier
56- 77 A22 --- ModScl Module scalars (5)
79- 82 I4 K Temp [56/1400] Model dust temperature
84- 93 E10.2 g/cm2 AmEn [0/3.5e-14] Amorphous Enstatite mass weight (6)
95-104 E10.2 g/cm2 e_AmEn [1.5e-22/1.4e-14] Uncertainty in AmEn
106-114 E9.2 g/cm2 Cor [0/1.2e-13] Corundum mass weight (6)
116-124 E9.2 g/cm2 e_Cor [3e-23/1.4e-13] Uncertainty in Cor
126-135 E10.2 g/cm2 Bayer [0/1.2e-14] "Bayerite 1273K" mass weight (6)(7)
137-145 E9.2 g/cm2 e_Bayer [5.8e-23/8.5e-16] Uncertainty in Bayer
147-156 E10.2 g/cm2 AmAl [0/2.4e-14] Amorphous Alumina mass weight (6)
158-165 E8.2 g/cm2 e_AmAl [9.5e-23/5.5e-15] Uncertainty in AmAl
167-176 E10.2 g/cm2 Boe [0/3.8e-14] "Boehmite 1173K" mass weight (6)(7)
178-186 E9.2 g/cm2 e_Boe [7.3e-23/2.2e-15] Uncertainty in Boe
188-197 F10.5 --- Chi2 [0.8/1704]? Model Χ2/degrees of freedom
value determined over 8.0<λ<37um
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Note (1): Flag as follows:
a = Sources from Smolders+ (2012A&A...540A..72S 2012A&A...540A..72S);
b = Sources from Sloan+ (2003ApJ...594..483S 2003ApJ...594..483S);
c = Source from McDonald+ (2011MNRAS.417...20M 2011MNRAS.417...20M);
d = Sources from Lebzelter+ (2006ApJ...653L.145L 2006ApJ...653L.145L);
e = Sources from Sloan+ (2010ApJ...719.1274S 2010ApJ...719.1274S);
f = Source from Olofsson+ (2009A&A...507..327O 2009A&A...507..327O).
Note (2): From parallaxes reported by GAIA DR2
(Gaia Collaboration 2016A&A...595A...2G 2016A&A...595A...2G ; Arenou+ 2018A&A...616A..17A 2018A&A...616A..17A
Gaia Collaboration 2018A&A...616A...1G 2018A&A...616A...1G and Luri+ 2018A&A...616A...9L 2018A&A...616A...9L).
Note (3): Flag as follows:
g = Leid 33062 belongs to ω Cen. For this cluster, I assume the same
as McDonald+ (2011MNRAS.417...20M 2011MNRAS.417...20M); namely, the distance is 5kpc, and
E(B-V)=0.12. AV=3.1*RV is assumed (Mathis 1990ARA&A..28...37M 1990ARA&A..28...37M).
h = For NGC 104 (47 Tuc), I assume the same as
McDonald+ (2011, J/ApJS/193/23); namely, the distance is 4.6kpc, and
E(B-V)=0.04. AV=3.1*RV is assumed (Mathis 1990ARA&A..28...37M 1990ARA&A..28...37M).
i = For NGC 5927, I assume 7.8kpc and E(B-V)=0.46
(Sloan+ 2010ApJ...719.1274S 2010ApJ...719.1274S) and Av=3.1*E(B-V)
(Mathis 1990ARA&A..28...37M 1990ARA&A..28...37M).
j = For NGC 6352, I assume 5.9kpc and E(B-V)=0.21
(Sloan+ 2010ApJ...719.1274S 2010ApJ...719.1274S) and Av=3.1*E(B-V)
(Mathis 1990ARA&A..28...37M 1990ARA&A..28...37M).
Note (4): Determined (unless otherwise indicated) from Drimmel+
(2003A&A...409..205D 2003A&A...409..205D), assuming the distance, Dist.
Note (5): Scalars applied to raw reduced Spitzer-IRS spectra from individual
modules, with the entries in the following order:
Short-Low/Long-Low/Short-High/Long-High (DL Cha is a special case,
where the Spitzer-IRS spectrum was appended to the ISO-SWS spectrum
(AOT 62804032) at the shortest wavelength of its Spitzer-IRS
Short-High spectrum).
Note (6): Mass weights equal to mass divided by the square of Earth-target
distance and its uncertainty for all dust species at the temperature
specified in the "Temp" column. One dust model is completely specified
by two adjacent rows (with the same AOR).
Note (7): The "Bayerite 1273K" and "Boehmite 1173K" are included in quotes
because the samples no longer contain bayerite or boehmite,
respectively, as noted in Section 3 of the text, but were obtained by
heating these minerals at these temperatures.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 09-Oct-2019