J/A+A/565/A109 Herschel/PACS spectra of 48 evolved stars (Blommaert+, 2014)
Herschel/PACS observations of the 69µm band of crystalline olivine around
evolved stars.
Blommaert J.A.D.L., de Vries B.L., Waters, L.B.F.M., Waelkens, C.,
Min M., Van Winckel H., Molster F., Decin L., Groenewegen, M.A.T.,
Barlow, M., Garcia-Lario, P., Kerschbaum F., Posch T., Royer P.,
Ueta T., Vandenbussche B., Van de Steene G., van Hoof P.
<Astron. Astrophys. 565, A109 (2014)>
=2014A&A...565A.109B 2014A&A...565A.109B
ADC_Keywords: Stars, late-type ; Spectra, infrared ; Mass loss
Keywords: stars: AGB and post-AGB - circumstellar matter -
stars: winds, outflows - stars: evolution - dust, extinction
Abstract:
We present 48 Herschel/PACS spectra of evolved stars in the wavelength
range of 67-72um. This wavelength range covers the 69mu band of
crystalline olivine (Mg2-2xFe(2x)SiO4). The width and wavelength
position of this band are sensitive to the temperature and composition
of the crystalline olivine. Our sample covers a wide range of objects:
from high mass-loss rate AGB stars (OH/IR stars,
dM/dt≥10-5M☉/yr), through post-AGB stars with and without
circumbinary disks, to planetary nebulae and even a few massive
evolved stars. The goal of this study is to exploit the spectral
properties of the 69um band to determine the composition and
temperature of the crystalline olivine. Since the objects cover a
range of evolutionary phases, we study the physical and chemical
properties in this range of physical environments.
We fit the 69um band and use its width and position to probe the
composition and temperature of the crystalline olivine. For 27 sources
in the sample, we detected the 69um band of crystalline olivine
(Mg2-2xFe(2x)SiO4). The 69um band shows that all the sources
produce pure forsterite grains containing no iron in their lattice
structure. The temperature of the crystalline olivine as indicated by
the 69um band, shows that on average the temperature of the
crystalline olivine is highest in the group of OH/IR stars and the
post-AGB stars with confirmed Keplerian disks. The temperature is
lower for the other post-AGB stars and lowest for the planetary
nebulae. A couple of the detected 69um bands are broader than those of
pure magnesium-rich crystalline olivine, which we show can be due to a
temperature gradient in the circumstellar environment of these stars.
The disk sources in our sample with crystalline olivine are very
diverse. They show either no 69um band, a moderately strong band, or a
very strong band, together with a temperature for the crystalline
olivine in their disk that is either very warm (∼600K), moderately
warm (∼200K), or cold (∼120K), respectively.
Description:
Herschel/PACS spectra of the 67-72 micron range of 48 evolved stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
sources.dat 80 48 List of studied sources
sp/* . 47 Individual spectra
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Byte-by-byte Description of file: sources.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Name Source name
16 A1 --- n_Name [*] Note for NGC 6720 (1)
17- 26 A10 --- IRAS IRAS name (HHMMs+DDMM, B1950)
29- 30 I2 h RAh Right ascension (J2000)
32- 33 I2 min RAm Right ascension (J2000)
35- 39 F5.2 s RAs Right ascension (J2000)
41 A1 --- DE- Declination sign (J2000)
42- 43 I2 deg DEd Declination (J2000)
45- 46 I2 arcmin DEm Declination (J2000)
48- 51 F4.1 arcsec DEs Declination (J2000)
54- 65 A12 --- Type Source Type (AGB, PN, Symbiotic, etc)
67- 80 A14 --- FileName Name of the spectrum file in subdirectory sp
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Note (1): For NGC 6720, both the ISO-SWS and our Herschel-PACS spectrum may
have missed the presence of crystalline silicates because the dusty
ring structure of NGC 6720 (>45", van Hoof et al. 2010A&A...518L.137V 2010A&A...518L.137V)
falls mostly outside the field-of-view of both apertures (50"x50").
So there is no spectrum.
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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1- 5 F5.2 um lambda [67/72] Wavelength λ
8- 14 F7.2 Jy Flux [14/1114] Flux density
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Acknowledgements:
Joris Blommaert, jorisb(at)ster.kuleuven.be
(End) Patricia Vannier [CDS] 04-May-2014