J/MNRAS/440/631 IR photometry of LMC O-rich evolved stars (Jones+, 2014)
Modelling the alumina abundance of oxygen-rich evolved stars in the
Large Magellanic Cloud.
Jones O.C., Kemper F., Srinivasan S., McDonald I., Sloan G.C.,
Zijlstra A.A.
<Mon. Not. R. Astron. Soc., 440, 631-651 (2014)>
=2014MNRAS.440..631J 2014MNRAS.440..631J
ADC_Keywords: Magellanic Clouds ; Stars, giant ; Photometry, infrared ;
Stars, supergiant ; Mass loss
Keywords: radiative transfer - stars: AGB and post-AGB - circumstellar matter -
dust, extinction - Magellanic Clouds - infrared: stars
Abstract:
In order to determine the composition of the dust in the circumstellar
envelopes of oxygen-rich asymptotic giant branch (AGB) stars, we have
computed a grid of MODUST radiative-transfer models for a range of
dust compositions, mass-loss rates, dust-shell inner radii and stellar
parameters. We compare the resulting colours with the observed
oxygen-rich AGB stars from the SAGE-Spec Large Magellanic Cloud (LMC)
sample, finding good overall agreement for stars with a mid-infrared
excess. We use these models to fit a sample of 37 O-rich AGB stars in
the LMC with optically thin circumstellar envelopes, for which
5-35µm Spitzer infrared spectrograph (IRS) spectra and
broad-band photometry from the optical to the mid-infrared are
available. From the modelling, we find mass-loss rates in the range
∼8x10-8-5x10-6M☉/yr, and we show that a grain mixture
consisting primarily of amorphous silicates, with contributions from
amorphous alumina and metallic iron, provides a good fit to the
observed spectra. Furthermore, we show from dust models that the
AKARI [11]-[15] versus [3.2]-[7] colour-colour diagram is able to
determine the fractional abundance of alumina in O-rich AGB stars.
Description:
To determine the relative contributions of alumina dust from the
spectra of O-rich AGB stars in the LMC, radiative transfer modelling
is required to calculate detailed spectra of circumstellar dust
shells. In this paper, we use the one-dimensional radiative transfer
code MODUST (Bouwman et al., 2000A&A...360..213B 2000A&A...360..213B, 2001A&A...375..950B 2001A&A...375..950B;
Kemper et al., 2001A&A...369..132K 2001A&A...369..132K) to evaluate the emergent spectrum
from a central star surrounded by a spherically symmetric dust shell.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 85 38 The best-fitting model results for the spectra
and photometry of the O-AGB sample
tablea1.dat 111 158 Spectral classification and photometric catalogue
of all the O-rich sources used in this study
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See also:
II/305 : SAGE LMC and SMC IRAC Source Catalog (IPAC 2009)
J/PASP/122/683 : SAGE-Spec Spitzer legacy program (Kemper+, 2010)
J/MNRAS/411/1597 : LMC point source classification in SAGE-Spec (Woods+, 2011)
J/MNRAS/427/3209 : Galactic and SMC O-AGBs and RSGs stars (Jones+, 2012)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 F8.5 deg RAdeg Right ascension (J2000)
11- 20 F10.6 deg DEdeg Declination sign (J2000)
22- 25 I4 --- SSID SAGE-Spec identification
26 A1 --- n_SSID [*] Note (1)
28- 29 A2 --- SpType MK spectral type
31- 36 F6.2 mag Mbol Bolometric magnitude
38- 41 F4.2 mag e_Mbol rms uncertainty on Mbol
43- 46 F4.1 --- Rin Dust shell inner radius (in stellar radii)
48- 50 F3.1 --- e_Rin rms uncertainty on Rin (in stellar radii)
52- 59 E8.3 Msun/yr dM/dt Mass-loss rate
61- 68 E8.3 Msun/yr e_dM/dt rms uncertainty on dM/dt
70- 71 I2 % Alx Fractional abundance of alumina
73- 74 I2 % e_Alx rms uncertainty on Alx
76- 80 F5.1 --- rchi2 RBest-fit model chi2/data point
82- 85 F4.1 --- rchi2NoA ? Best-fit model without an alumina dust
component chi2/data point
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Note (1): * indicates the best fit obtained without a metallic iron component.
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- SSID [1/4814] SSID identification number
(SAGE-Spec designation)
6- 10 A5 --- SpC Spectroscopic classification: O-AGB or RSG (2)
12- 16 F5.2 mag Jmag 2MASS J magnitude (1)
18- 22 F5.2 mag Hmag 2MASS H magnitude (1)
24- 28 F5.2 mag Kmag 2MASS K magnitude (1)
30- 34 F5.2 mag [3.6] ?=- IRAC 3.6um magnitude (1)
36- 40 F5.2 mag [4.5] IRAC 4.5um magnitude (1)
42- 46 F5.2 mag [5.8] IRAC 5.8um magnitude (1)
48- 52 F5.2 mag [8.0] IRAC 8.0um magnitude (1)
54- 58 F5.2 mag [24] ?=- MIPS 24um magnitude (1)
60- 64 F5.2 mag W1mag ?=- WISE W1 magnitude (1)
66- 70 F5.2 mag W2mag ?=- WISE W2 magnitude (1)
72- 76 F5.2 mag W3mag ?=- WISE W3 magnitude (1)
78- 82 F5.2 mag W4mag ?=- WISE W4 magnitude (1)
84- 88 F5.2 mag N3mag ?=- AKARI N3 (3.27um) magnitude (1)
90- 94 F5.2 mag S7mag ?=- AKARI S7 (7.31um) magnitude (1)
96-100 F5.2 mag S11mag ?=- AKARI S11 (10.95um) magnitude (1)
102-106 F5.2 mag L15mag ?=- AKARI L15 (16.16um) magnitude (1)
108-111 F4.2 mag L24mag ?=- AKARI L24 (23.35um) magnitude (1)
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Note (1): Magnitudes have not been corrected for reddening.
Note (2): classes are:
O-AGB = Oxy-gen-rich Asymptotic Giant Branch
RSG = Red SuperGiant
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History:
* 16-Apr-2015: table1a, from electronic version of the journal
* 01-Dec-2015: table2 added, from Olivia Charlotte Jones,
ojones(at)stsci.edu
(End) Olivia Charlotte Jones [STScI], Patricia Vannier [CDS] 19-Jan-2015