Multi-Epoch Observations of Hd 69830: High-Resolution Spectroscopy and Limits to Variability

Abstract

The main-sequence solar-type star HD69830 has an unusually large amount of dusty debris orbiting close to three planets found via the radial velocity technique. In order to explore the dynamical interaction between the dust and planets, we have performed multi-epoch photometry and spectroscopy of the system over several orbits of the outer dust. We find no evidence for changes in either the dust amount or its composition, with upper limits of 5-7% (1 σ per spectral element) on the variability of the dust spectrum over 1 year, 3.3% (1 σ) on the broad-band disk emission over 4 years, and 33% (1 σ) on the broad-band disk emission over 24 years. Detailed modeling of the spectrum of the emitting dust arXiv:1108.4704v1 [astro-ph.GA] 23 Aug 2011 -2indicates that the dust is located outside of the orbits of the three planets and has a composition similar to main-belt, C-type asteroids asteroids in our solar system. Additionally, we find no evidence for a wide variety of gas species associated with the dust. Our new higher SNR spectra do not confirm our previously claimed detection of H 2 O ice leading to a firm conclusion that the debris can be associated with the break-up of one or more C-type asteroids formed in the dry, inner regions of the protoplanetary disk of the HD69830 system. The modeling of the spectral energy distribution and high spatial resolution observations in the mid-infrared are consistent with a ∼ 1 AU location for the emitting material.

Transient dust in warm debris disks

“…This is why we prefer to use less dust species but focus on those that have been intensively studied in laboratory experiments, and have a good coverage of their optical data. Finally, Beichman et al (2011) mentioned that no gas lines could be convincingly detected in their data.…”

“…(1) Chen et al (2005); (2) Chen et al (2006); (3) Lisse et al (2008); (4) Beichman et al (2005); (5) Lisse et al (2007); (6) Beichman et al (2011); (7) Weinberger (2008); (8) Zuckerman et al (2008); (9) Weinberger et al (2011); (10) Melis et al (2010); (11) Moór et al (2009); (12) Koerner et al (2000); (13) Prato et al (2001); (14) Furlan et al (2007); (15) Verrier & Evans (2008); (16) Gorlova et al (2007); (17) Naylor & Jeffries (2006).…”

“…sion features, have been observed numerous times in disks around young Class II objects (e.g., Bouwman et al 2001Bouwman et al , 2008Juhász et al 2010;Oliveira et al 2011;Olofsson et al 2009Olofsson et al , 2010Sargent et al 2009b), and disks around evolved Class III objects (e.g., Beichman et al 2011;Lisse et al 2007Lisse et al , 2008Lisse et al , 2009Weinberger et al 2011). Amorphous grains of olivine (Mg 2x Fe 2(1−x) SiO 4 ) and pyroxene (Mg 2x Fe 2(1−x) Si 2 O 6 ) stoichiometries are also the dominant species in the interstellar medium (∼98%, Kemper et al 2005;Min et al 2007).…”

“…In a recent study, Beichman et al (2011) investigated the time variability of the dust around HD 69830. With new spectroscopic observations and using the model from Lisse et al (2007), they performed a similar mineralogical analysis.…”

“…Sulfides (Fe 90 Mg 10 S), for which an upper limit were found in the 2007 analysis, was detected in the latest best-fit model. According to Beichman et al (2011), the most significant difference between the two models is that water ice was no longer needed to reproduce the spectrum, therefore they concluded that the debris disk is really dry. Based on the main mineralogical markers from both analyses, the authors stated that the dust has not evolved significantly in time, but instead that the aforementioned differences arise from a higher signal-to-noise ratio (S/R hereafter) of the new observations and a better data calibration for the IRS spectra.…”