C2D Spitzer-IRS spectra of disks around T Tauri stars

Olofsson, J.; Augereau, J.-C.; Dishoeck, E. F. van; Merın, Bruno; Lahuis, F.; Kessler-Silacci, J. E.; Dullemond, C. P.; Oliveira, I.; Blake, G. A.; Boogert, A. C. A.; Brown, J. M.; Evans, Neal J.; Geers, V. C.; Knez, C.; Monin, J.; Pontoppidan, K. M.

doi:10.1051/0004-6361/200912062

Cited by 101 publications

(159 citation statements)

References 76 publications

(162 reference statements)

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“…For the targets where we detected a 69 μm band, and those with marginal Spitzer detections, we carefully re-reduced the Spitzer spectra, using the same data reduction approach as Juhász et al (2010), but with the latest calibration version (S18.18.0). Our re-processed spectra only marginally differ from those reported by Juhász et al (2010) and Olofsson et al (2009). However, we report the detection of forsterite bands between ∼19 to 33 μm in the Spitzer spectrum of HD 141569, not reported by Juhász et al (2010).…”

Section: Comparison To Spitzer Irs Datacontrasting

confidence: 83%

“…Bouwman et al 2003;Meeus et al 2001) for intermediate-mass Herbig Ae/Be stars and later with much improved sensitivity provided by Spitzer for disks around brown dwarfs/low-mass stars (e.g. Pascucci et al 2009), T Tauri stars (Bouwman et al 2008;Kessler-Silacci et al 2006;Olofsson et al 2009;Furlan et al 2009;Watson et al 2009) and Herbig Ae/Be stars (Juhász et al 2010). Regions closer to the mid-plane can only be probed by observations at (sub)-millimetre wavelengths where the disks become optically thin.…”

Section: Introductionmentioning

confidence: 99%

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The 69μm forsterite band in spectra of protoplanetary disks. Results from theHerschelDIGIT programme

Sturm

Bouwman

Henning

et al. 2013

A&A

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Context. We have analysed far-infrared spectra of 32 circumstellar disks around Herbig Ae/Be and T Tauri stars obtained within the Herschel key programme Dust, Ice and Gas in Time (DIGIT). The spectra were taken with the Photodetector Array Camera and Spectrometer (PACS) on board the Herschel Space Observatory. In this paper we focus on the detection and analysis of the 69 μm emission band of the crystalline silicate forsterite. Aims. This work aims at providing an overview of the 69 μm forsterite bands present in the DIGIT sample. We use characteristics of the emission band (peak position and FWHM) to derive the dust temperature and to constrain the iron content of the crystalline silicates. With this information, constraints can be placed on the spatial distribution of the forsterite in the disk and the formation history of the crystalline grains. Methods. The 69 μm forsterite emission feature is analysed in terms of position and shape to derive the temperature and composition of the dust by comparison to laboratory spectra of that band. The PACS spectra are combined with existing Spitzer IRS spectra and we compare the presence and strength of the 69 μm band to the forsterite bands at shorter wavelengths. Results. A total of 32 disk sources have been observed. Out of these 32, 8 sources show a 69 μm emission feature that can be attributed to forsterite. With the exception of the T Tauri star AS 205, all of the detections are for disks associated with Herbig Ae/Be stars. Most of the forsterite grains that give rise to the 69 μm bands are found to be warm (∼100-200 K) and iron-poor (less than ∼2% iron). AB Aur is the only source where the emission cannot be fitted with iron-free forsterite requiring approximately 3-4% of iron. Conclusions. Our findings support the hypothesis that the forsterite grains form through an equilibrium condensation process at high temperatures. The large width of the emission band in some sources may indicate the presence of forsterite reservoirs at different temperatures. The connection between the strength of the 69 and 33 μm bands shows that at least part of the emission in these two bands originates fom the same dust grains. We further find that any model that can explain the PACS and the Spitzer IRS observations must take the effects of a wavelength dependent optical depth into account. We find weak indications of a correlation of the detection rate of the 69 μm band with the spectral type of the host stars in our sample. However, the sample size is too small to obtain a definitive result.

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Section: Comparison To Spitzer Irs Datacontrasting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

The 69μm forsterite band in spectra of protoplanetary disks. Results from theHerschelDIGIT programme

Sturm

Bouwman

Henning

et al. 2013

A&A

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“…As part of the "Core to Disks" (c2d) Legacy survey (Evans et al 2003), more than a hundred T Tauri stars were spectroscopically observed, to confirm or invalidate some of the predictions concerning dust processing and grain dynamics in protoplanetary disks. In Kessler-Silacci et al (2006, and Olofsson et al (2009), we showed that most of the objects display silicate emission features arising from within 10 AU from the star. This allowed both a classical study of grain coagulation and a comprehensive statistical analysis of dust crystallization in planet forming regions of disks around young solar analogs.…”

Section: Introductionmentioning

confidence: 81%

C2D Spitzer-IRS spectra of disks around T Tauri stars

Olofsson¹,

Augereau²,

Dishoeck

et al. 2010

A&A

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Context. Dust particles evolve in size and lattice structure in protoplanetary disks, due to coagulation, fragmentation and crystallization, and are radially and vertically mixed in disks due to turbulent diffusion and wind/radiation pressure forces. Aims. This paper aims at determining the mineralogical composition and size distribution of the dust grains in planet forming regions of disks around a statistical sample of 58 T Tauri stars observed with Spitzer/IRS as part of the Cores to Disks (c2d) Legacy Program. Methods. We present a spectral decomposition model, named "B2C", that reproduces the IRS spectra over the full spectral range (5-35 μm). The model assumes two dust populations: a warm component responsible for the 10 μm emission arising from the disk inner regions ( 1 AU) and a colder component responsible for the 20-30 μm emission, arising from more distant regions ( 10 AU). The fitting strategy relies on a random exploration of parameter space coupled with a Bayesian inference method. Results. We show evidence for a significant size distribution flattening in the atmospheres of disks compared to the typical MRN distribution, providing an explanation for the usual flat, boxy 10 μm feature profile generally observed in T Tauri star spectra. We reexamine the crystallinity paradox, observationally identified by Olofsson et al. (2009, A&A, 507, 327), and we find a simultaneous enrichment of the crystallinity in both the warm and cold regions, while grain sizes in both components are uncorrelated. We show that flat disks tend to have larger grains than flared disk. Finally our modeling results do not show evidence for any correlations between the crystallinity and either the star spectral type, or the X-ray luminosity (for a subset of the sample). Conclusions. The size distribution flattening may suggests that grain coagulation is a slightly more effective process than fragmentation (helped by turbulent diffusion) in disk atmospheres, and that this imbalance may last over most of the T Tauri phase. This result may also point toward small grain depletion via strong stellar winds or radiation pressure in the upper layers of disk. The non negligible cold crystallinity fractions suggests efficient radial mixing processes in order to distribute crystalline grains at large distances from the central object, along with possible nebular shocks in outer regions of disks that can thermally anneal amorphous grains.

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“…Kemper et al (2004) infer from the observed stellar extinction that Mg/(Mg+Fe) ∼ 0.5, whereas Min et al (2007) conclude that Mg/(Mg + Fe) ∼ 0.9. Silicates with a high magnesium fraction of Mg/(Mg + Fe) ∼ 0.8 have been found in environments that show silicates with a crystalline structure, for example around evolved stars (Molster et al 2002a,b,c;de Vries et al 2010), in comets, (Wooden et al 1999;Messenger et al 2005) and in disks around T Tauri stars (Olofsson et al 2009). Therefore, our samples have ratios of Mg/(Mg+Fe) that vary between 0.5 and 0.9.…”

Section: The Samplesmentioning

confidence: 99%

Absorption and scattering by interstellar dust in the silicon K-edge of GX 5-1

Zeegers

Costantini

Vries

et al. 2017

A&A

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Context. We study the absorption and scattering of X-ray radiation by interstellar dust particles, which allows us to access the physical and chemical properties of dust. The interstellar dust composition is not well understood, especially on the densest sight lines of the Galactic Plane. X-rays provide a powerful tool in this study. Aims. We present newly acquired laboratory measurements of silicate compounds taken at the Soleil synchrotron facility in Paris using the Lucia beamline. The dust absorption profiles resulting from this campaign were used in this pilot study to model the absorption by interstellar dust along the line of sight of the low-mass X-ray binary (LMXB) GX 5-1. Methods. The measured laboratory cross-sections were adapted for astrophysical data analysis and the resulting extinction profiles of the Si K-edge were implemented in the SPEX spectral fitting program. We derive the properties of the interstellar dust along the line of sight by fitting the Si K-edge seen in absorption in the spectrum of GX 5-1. Results. We measured the hydrogen column density towards GX 5-1 to be 3.40 ± 0.1 × 10 22 cm −2 . The best fit of the silicon edge in the spectrum of GX 5-1 is obtained by a mixture of olivine and pyroxene. In this study, our modeling is limited to Si absorption by silicates with different Mg:Fe ratios. We obtained an abundance of silicon in dust of 4.0 ± 0.3 × 10 −5 per H atom and a lower limit for total abundance, considering both gas and dust, of > 4.4 × 10 −5 per H atom, which leads to a gas to dust ratio of > 0.22. Furthermore, an enhanced scattering feature in the Si K-edge may suggest the presence of large particles along the line of sight.

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C2D Spitzer-IRS spectra of disks around T Tauri stars

Cited by 101 publications

References 76 publications

The 69μm forsterite band in spectra of protoplanetary disks. Results from theHerschelDIGIT programme

The 69μm forsterite band in spectra of protoplanetary disks. Results from theHerschelDIGIT programme

C2D Spitzer-IRS spectra of disks around T Tauri stars

Absorption and scattering by interstellar dust in the silicon K-edge of GX 5-1

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