Mg-Rich Silicate Crystals in Comet Hale–Bopp: ISM Relics or Solar Nebula Condensates?

Wooden, D. H.; Butner, H. M.; Harker, David; Woodward, C. E.

doi:10.1006/icar.1999.6240

Cited by 79 publications

(52 citation statements)

References 51 publications

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“…The similarity of these spectral features to those seen in comet C/1995 O1 (Hale-Bopp; e.g., Wooden et al 2000) suggests that this circumstellar material may represent debris from either cometary or asteroidal material located within the habitable zones of the stars. Dramatically, observations with the Infrared Spectrometer (IRS) on the Spitzer Space Telescope (Houck et al 2004) revealed a bright spectrum of features due to hot (400 K) silicate grains around the nearby (12.6 pc), mature (2 Gyr) K0 V star, HD 69830 (Beichman et al 2005b).…”

Section: Introductionmentioning

confidence: 59%

EXPLORATIONS BEYOND THE SNOW LINE:SPITZER/IRS SPECTRA OF DEBRIS DISKS AROUND SOLAR-TYPE STARS

Lawler

Beichman

Bryden

et al. 2009

ApJ

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We have observed 152 nearby solar-type stars with the Infrared Spectrometer (IRS) on the Spitzer Space Telescope. Including stars that met our criteria but were observed in other surveys, we get an overall success rate for finding excesses in the long-wavelength IRS band (30-34 μm) of 11.8% ± 2.4%. The success rate for excesses in the shortwavelength band (8.5-12 μm) is ∼1% including sources from other surveys. For stars with no excess at 8.5-12 μm, the IRS data set 3σ limits of around 1000 times the level of zodiacal emission present in our solar system, while at 30-34 μm data set limits of around 100 times the level of our solar system. Two stars (HD 40136 and HD 10647) show weak evidence for spectral features; the excess emission in the other systems is featureless. If the emitting material consists of large (10 μm) grains as implied by the lack of spectral features, we find that these grains are typically located at or beyond the snow line, ∼1-35 AU from the host stars, with an average distance of 14 ± 6 AU; however, smaller grains could be located at significantly greater distances from the host stars. These distances correspond to dust temperatures in the range ∼50-450 K. Several of the disks are well modeled by a single dust temperature, possibly indicative of a ring-like structure. However, a single dust temperature does not match the data for other disks in the sample, implying a distribution of temperatures within these disks. For most stars with excesses, we detect an excess at both IRS and Multiband Imaging Photometer for Spitzer (MIPS) wavelengths. Only three stars in this sample show a MIPS 70 μm excess with no IRS excess, implying that very cold dust is rare around solar-type stars.

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Section: Introductionmentioning

confidence: 59%

EXPLORATIONS BEYOND THE SNOW LINE:SPITZER/IRS SPECTRA OF DEBRIS DISKS AROUND SOLAR-TYPE STARS

Lawler

Beichman

Bryden

et al. 2009

ApJ

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“…Similar results were found studying other solar system bodies, for exemple, comet Hale-Bopp. Spectroscopic studies of this object (Wooden et al 1999;Wooden et al 2000) revealed the presence of crystalline olivine, crystalline ortho-pyroxene and crystalline clino-pyroxene, in significant quantities.…”

Section: On the Similarities With Solar System Objectsmentioning

confidence: 98%

C2D Spitzer-IRS spectra of disks around T Tauri stars

Olofsson¹,

Augereau²,

Dishoeck

et al. 2009

A&A

102

148

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Aims. Dust grains in the planet-forming regions around young stars are expected to be heavily processed due to coagulation, fragmentation, and crystallization. This paper focuses on the crystalline silicate dust grains in protoplanetary disks for a statistically significant number of TTauri stars (96). Methods. As part of the cores to disks (c2d) legacy program, we obtained more than a hundred Spitzer/IRS spectra of TTauri stars, over a spectral range of 5−35 μm where many silicate amorphous and crystalline solid-state features are present. At these wavelengths, observations probe the upper layers of accretion disks up to distances of a dozen AU from the central object.Results. More than 3/4 of our objects show at least one crystalline silicate emission feature that can be essentially attributed to Mg-rich silicates. The Fe-rich crystalline silicates are largely absent in the c2d IRS spectra. The strength and detection frequency of the crystalline features seen at λ > 20 μm correlate with each other, while they are largely uncorrelated with the observational properties of the amorphous silicate 10 μm feature. This supports the idea that the IRS spectra essentially probe two independent disk regions: a warm zone (≤1 AU) emitting at λ ∼ 10 μm and a much colder region emitting at λ > 20 μm (≤10 AU). We identify a crystallinity paradox, as the long-wavelength (λ > 20 μm) crystalline silicate features are detected 3.5 times more frequently (∼55% vs. ∼15%) than the crystalline features arising from much warmer disk regions (λ ∼ 10 μm). This suggests that the disk has an inhomogeneous dust composition within ∼10 AU. The analysis of the shape and strength of both the amorphous 10 μm feature and the crystalline feature around 23 μm provides evidence for the prevalence of μm-sized (amorphous and crystalline) grains in upper layers of disks. Conclusions. The abundant crystalline silicates found far from their presumed formation regions suggest efficient outward radial transport mechanisms in the disks around TTauri stars. The presence of μm-sized grains in disk atmospheres, despite the short timescales for settling to the midplane, suggests efficient (turbulent) vertical diffusion, probably accompanied by grain-grain fragmentation to balance the expected efficient growth. In this scenario, the depletion of submicron-sized grains in the upper layers of the disks points toward removal mechanisms such as stellar winds or radiation pressure.

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“…4.1, we discussed some effects of the mixing processes during the primeval stages of a solar/stellar nebula. The detection of silicate bands in comets (Hanner et al 1994) indicates that crystalline forms can exist in these outer disk bodies (Bouwman et al 2000;Wooden et al 2000). Since these crystals can only be formed at the relatively high disk temperatures existing near the star, it has been proposed that a large-scale mixing occurred during the early disk epochs, transporting material from the inner to the outer regions of the disk.…”

Section: The Link Between Migration and Stellar Abundancesmentioning

confidence: 99%

Distribution of refractory and volatile elements in CoRoT exoplanet host stars

Chavero

Reza

Domingos³

et al. 2010

A&A

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The relative distribution of abundances of refractory, intermediate, and volatile elements in stars with planets can be an important tool for investigating the internal migration of a giant planet. This migration can lead to the accretion of planetesimals and the selective enrichment of the star with these elements. We report on a spectroscopic determination of the atmospheric parameters and chemical abundances of the parent stars in transiting planets . Adding data for CoRoT-3 and CoRoT-5 from the literature, we find a flat distribution of the relative abundances as a function of their condensation temperatures. For CoRoT-2, the relatively high lithium abundance and intensity of its Li i resonance line permit us to propose an age of 120 Myr, making this star one of the youngest stars with planets to date. We introduce a new methodology to investigate a relation between the abundances of these stars and the internal migration of their planets. By simulating the internal migration of a planet in a disk formed only by planetesimals, we are able, for the first time, to separate the stellar fractions of refractory, intermediate, and volatile rich planetesimals accreting onto the central star. Intermediate and volatile element fractions enriching the star are similar and much larger than those of pure refractory ones. This result is opposite to what has been considered in the literature for the accreting self-enrichment processes of stars with planets. We also show that these results are highly dependent on the model adopted for the disk distribution regions in terms of refractory, intermediate, and also volatile elements and other parameters considered. We note however, that this self-enrichment mechanism is only efficient during the first 20-30 Myr or later in the lifetime of the disk when the surface convection layers of the central star for the first time attain its minimum size configuration.

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Mg-Rich Silicate Crystals in Comet Hale–Bopp: ISM Relics or Solar Nebula Condensates?

Cited by 79 publications

References 51 publications

EXPLORATIONS BEYOND THE SNOW LINE:SPITZER/IRS SPECTRA OF DEBRIS DISKS AROUND SOLAR-TYPE STARS

EXPLORATIONS BEYOND THE SNOW LINE:SPITZER/IRS SPECTRA OF DEBRIS DISKS AROUND SOLAR-TYPE STARS

C2D Spitzer-IRS spectra of disks around T Tauri stars

Distribution of refractory and volatile elements in CoRoT exoplanet host stars

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