Abundant Circumstellar Silica Dust and SiO Gas Created by a Giant Hypervelocity Collision in the ~12 Myr HD172555 System

Abstract

The fine dust detected by IR emission around the nearby Beta Pic analogue star HD172555 is very peculiar. The dust mineralogy is composed primarily of highly refractory, non-equilibrium materials, with approximately three-quarters of the Si atoms in silica (SiO2) species. Tektite and obsidian lab thermal emission spectra (non-equilibrium glassy silicas found in impact and magmatic systems) are required to fit the data. The best-fit model size distribution for the observed fine dust is dn/da = a-3.95 +/- 0.10. This steep a size distribution, with abundant micron-sized particles, argues for a fresh source of material within the last 0.1 Myr. The location of the dust with respect to the star is at 5.8 +/- 0.6 AU (equivalent to 1.9 +/- 0.2 AU from the Sun), within the terrestrial planet formation region but at the outer edge of any possible terrestrial habitability zone. The mass of fine dust is 4 x 10^19 - 2 x 10^20 kg, equivalent to a 150 - 200 km radius asteroid. Significant emission features centered at 4 and 8 um due to fluorescing SiO gas are also found. Roughly 10^22 kg of SiO gas, formed by vaporizing silicate rock, is also present in the system, and a separate population of very large, cool grains, massing 10^21 - 10^22 kg and equivalent to the largest sized asteroid currently found in the Solar System's main asteroid belt, dominates the solid circumstellar material by mass. The makeup of the observed dust and gas, and the noted lack of a dense circumstellar gas disk, strong primary x-ray activity, or an extended disk of Beta-meteroids argues that the source of the observed circumstellar materials is a giant hypervelocity (> 10 km sec^-1) impact between large rocky planetesimals, similar to the ones which formed the Moon and which stripped the surface crustal material off of Mercury's surface.

48 Pages, 8 Figures, 4 Tables Accepted for Publication in the Astrophysical Journal 13-Jun-2009 References, Figures Updated 16-Jun-2009

References in corpus (13)

• Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era
• Debris Disk Evolution Around A Stars
• Equilibration in the Aftermath of the Lunar-Forming Giant Impact
• Transience of hot dust around sun-like stars
• Spitzer IRS Spectroscopy of IRAS-Discovered Debris Disks
• Nearby debris disk systems with high fractional luminosity reconsidered
• The Carbon-Rich Gas in the Beta Pictoris Circumstellar Disk
• Carbon Deficiency in Externally-Polluted White Dwarfs: Evidence for Accretion of Asteroids
• On the Nature of the Dust in the Debris Disk Around HD69830
• X-ray and Infrared Observations of Two Externally-Polluted White Dwarfs
• Warm dust in the terrestrial planet zone of a sun-like Pleiad: collisions between planetary embryos?
• Circumstellar Dust Created by Terrestrial Planet Formation in HD 113766
• Dust Processing in Disks around T Tauri Stars

Cited by in corpus (33)

• A perspective from extinct radionuclides on a Young Stellar Object: The Sun and its accretion disk
• ALMA observations of the $\eta$ Corvi debris disc: inward scattering of CO-rich exocomets by a chain of 3-30 M${}_{\oplus }$ planets?
• Five steps in the evolution from protoplanetary to debris disk
• A near-infrared interferometric survey of debris-disc stars. IV. An unbiased sample of 92 southern stars observed in H-band with VLTI/PIONIER
• Gas and dust in the Beta Pictoris Moving Group as seen by the Herschel Space Observatory
• Planetesimal driven migration as an explanation for observations of high levels of warm, exozodiacal dust
• Variability of the Infrared Excess of Extreme Debris Disks
• Planetary Collisions outside the Solar System: Time Domain Characterization of Extreme Debris Disks
• Solar System Physics for Exoplanet Research
• Peter Pan Disks: Long-lived Accretion Disks Around Young M Stars
• A Deep Spitzer Survey of Circumstellar Disks in the Young Double Cluster, h and chi Persei
• Is there more than meets the eye? Presence and role of submicron grains in debris discs
• Herschel Observations of Dusty Debris Disks
• Probing the Terrestrial Regions of Planetary Systems: Warm Debris Disks with Emission Features
• Carbon monoxide gas produced by a giant impact in the inner region of a young system
• Mid-infrared Studies of HD 113766 and HD 172555: Assessing Variability in the Terrestrial Zone of Young Exoplanetary Systems
• Dust from collisions: A way to probe the composition of exo-planets?
• Habitable planet formation around low-mass stars: Rapid accretion, rapid debris removal and the essential contribution of external giants
• Dynamical avenues for Mercury's origin I: The lone survivor of a primordial generation of short-period proto-planets
• Extrasolar Kuiper Belts
• Hint of an exocomet transit in the CHEOPS lightcurve of HD 172555
• On the Silicate Crystallinities of Oxygen-Rich Evolved Stars and Their Mass Loss Rates
• Mid-infrared spectra of differentiated meteorites (achondrites): Comparison with astronomical observations of dust in protoplanetary and debris disks
• Polarimetric and radiative transfer modelling of HD 172555
• A catalog of collected debris disks: properties, classifications and correlations between disks and stars/planets
• RW Aur A : SpeX Spectral Evidence for Differentiated Planetesimal Formation, Migration and Destruction in an 3 Myr Old Excited CTTS System
• Abundant sub-micron grains revealed in newly discovered extreme debris discs
• Discovery of Volatile Gas in the Giant Impact Disk around the 150-Myr old HD 23514
• V488 Per revisited: no strong mid-infrared emission features and no evidence for stellar/sub-stellar companions
• Discovery of carbon monoxide emission from five debris disks around young A-type stars
• A retrospective analysis of mid-infrared observations of the Comet D/Shoemaker-Levy 9 and Wesley impacts on Jupiter
• Diversity of Exoplanets
• Re-accretion of Giant Impact Ejecta Can Drive Significant Atmospheric Erosion on Terrestrial Planets