Circumstellar material in the Vega inner system revealed by CHARA/FLUOR

Absil, Olivier; Folco, E. Di; Mérand, A.; Augereau, J.-C.; Foresto, V. Coudé du; Aufdenberg, J. P.; Kervella, P.; Ridgway, Stephen T.; Berger, David H.; Brummelaar, Theo A. ten; Sturmann, J.; Sturmann, L.; Turner, N.; McAlister, Harold A.

doi:10.1051/0004-6361:20054522

Cited by 152 publications

(255 citation statements)

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“…We only calculated the emission spectrum of the dust and ignored the (viewing-angle-dependent) contribution of scattered light, since thermal emission was found to dominate scattered light at the wavelengths in which hot exozodiacal dust is detected (Absil et al 2006). For the analytical dust distributions, we assumed the dust has a black-body temperature (Eq.…”

Section: Comparison With Observationsmentioning

confidence: 99%

“…The dust can be studied by observing its infrared and (sub-)millimeter emission, as well as the stellar radiation it scatters, and is usually found at large distances from the star (tens of AUs, Carpenter et al 2009). Recently, interferometric observations have found excess nearinfrared (NIR) emission emanating from the innermost parts of several debris disks, which has been interpreted as thermal emission from hot (>1000 K) dust (Ciardi et al 2001;Absil et al 2006Absil et al , 2008Absil et al , 2009di Folco et al 2007;Akeson et al 2009;Defrère et al 2011Defrère et al , 2012 Table 1 for an overview). This material is known as hot exozodiacal dust.…”

Section: Introductionmentioning

confidence: 99%

“…A possible transportation mechanism is Poynting-Robertson (P-R) drag (see, e.g., Burns et al 1979). Because P-R drag acts on a timescale that is much longer than that of collisions, it is sometimes not favored as a possible mechanism for maintaining exozodiacal dust (e.g., Absil et al 2006). However, as long as there are no mechanisms that prevent inward migration, a small amount of dust is always transported to the innermost part of the disk (Wyatt 2005), where it produces a NIR signal.…”

Section: Introductionmentioning

confidence: 99%

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Near-infrared emission from sublimating dust in collisionally active debris disks

Lieshout

Dominik

Kama

et al. 2014

A&A

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Context. Hot exozodiacal dust is thought to be responsible for excess near-infrared (NIR) emission emanating from the innermost parts of some debris disks. The origin of this dust, however, is still a matter of debate. Aims. We test whether hot exozodiacal dust can be supplied from an exterior parent belt by Poynting-Robertson (P-R) drag, paying special attention to the pile-up of dust that occurs owing to the interplay of P-R drag and dust sublimation. Specifically, we investigate whether pile-ups still occur when collisions are taken into account, and if they can explain the observed NIR excess. Methods. We computed the steady-state distribution of dust in the inner disk by solving the continuity equation. First, we derived an analytical solution under a number of simplifying assumptions. Second, we developed a numerical debris disk model that for the first time treats the complex interaction of collisions, P-R drag, and sublimation in a self-consistent way. From the resulting dust distributions, we generated thermal emission spectra and compare these to observed excess NIR fluxes. Results. We confirm that P-R drag always supplies a small amount of dust to the sublimation zone, but find that a fully consistent treatment yields a maximum amount of dust that is about 7 times lower than that given by analytical estimates. The NIR excess due to this material is much less ( < ∼ 10 −3 for A-type stars with parent belts at > ∼ 1 AU) than the values derived from interferometric observations (∼10 −2 ). Pile-up of dust still occurs when collisions are considered, but its effect on the NIR flux is insignificant. Finally, the cross-section in the innermost regions is clearly dominated by barely bound grains.

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Section: Comparison With Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Near-infrared emission from sublimating dust in collisionally active debris disks

Lieshout

Dominik

Kama

et al. 2014

A&A

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“…For β UMi, we have used the Johnson K-band magnitude of −1.39 , yielding a magnitude of −1.45 in the Selby system. Zeropoints are calculated using the Kurucz theoretical spectrum of Vega (Cohen et al 1992), taking into account the observed near-IR excess of Vega (Absil et al 2006). For the Selby photometric system we obtain a zeropoint of 4.0517 × 10 −10 W/m 2 /μm.…”

Section: Comparison Between Sed and Theoretical Predictionsmentioning

confidence: 99%

Structure of the outer layers of cool standard stars

Dehaes

Bauwens

Decin

et al. 2011

A&A

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Context. Among late-type red giants, an interesting change occurs in the structure of the outer atmospheric layers as one moves to later spectral types in the Hertzsprung-Russell diagram: a chromosphere is always present, but the coronal emission diminishes and a cool massive wind steps in. Aims. Where most studies have focussed on short-wavelength observations, this article explores the influence of the chromosphere and the wind on long-wavelength photometric measurements. The goal of this study is to assess wether a set of standard near-infrared calibration sources are fiducial calibrators in the far-infrared, beyond 50 μm. Methods. The observational spectral energy distributions were compared with the theoretical model predictions for a sample of nine K-and M-giants. The discrepancies found are explained using basic models for flux emission originating in a chromosphere or an ionised wind. Results. For seven out of nine sample stars, a clear flux excess is detected at (sub)millimetre and/or centimetre wavelengths, while only observational upper limits are obtained for the other two. The precise start of the excess depends upon the star under consideration. For six sources the flux excess starts beyond 210 μm and they can be considered as fiducial calibrators for Herschel/PACS (60-210 μm). Out of this sample, four sources show no flux excess in the Herschel/SPIRE wavelength range (200-670 μm) and are good calibration sources for this instrument as well. The flux at wavelengths shorter than ∼1 mm is most likely dominated by an optically thick chromosphere, where an optically thick ionised wind is the main flux contributor at longer wavelengths. Conclusions. Although the optical to mid-infrared spectrum of the studied K-and M-type infrared standard stars is represented well by a radiative equilibrium atmospheric model, a chromosphere and/or ionised stellar wind at higher altitudes dominates the spectrum in the (sub)millimetre and centimetre wavelength ranges. The presence of a flux excess has implications on the role of the stars as fiducial spectrophotometric calibrators in these wavelength ranges.

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“…Their observations have revealed a wide variety of inferred dust masses, disk extents, and even disk morphologies (e.g., Wyatt 2008, and references therein). For example, dust has been detected from well within one AU (Beichman et al 2005;Absil et al 2006), out to hundreds of AU (e.g., Su et al 2005). While the former cases seem to be rare (Wyatt et al 2007), the latter are more commonly reported, corresponding to significantly higher detection rates at longer wavelengths.…”

Section: Introductionmentioning

confidence: 99%

Modelling the huge,Herschel-resolved debris ring around HD 207129

Löhne

Augereau

Ertel

et al. 2012

A&A

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Debris disks, which are inferred from the observed infrared excess to be ensembles of dust, rocks, and probably planetesimals, are common features of stellar systems. As the mechanisms of their formation and evolution are linked to those of planetary bodies, they provide valuable information. The few well-resolved debris disks are even more valuable because they can serve as modelling benchmarks and help resolve degeneracies in modelling aspects such as typical grain sizes and distances. Here, we present an analysis of the HD 207129 debris disk, based on its well-covered spectral energy distribution and Herschel/PACS images obtained in the framework of the DUNES (DUst around NEarby Stars) programme. We use an empirical power-law approach to the distribution of dust and we then model the production and removal of dust by means of collisions, direct radiation pressure, and drag forces. The resulting best-fit model contains a total of nearly 10 −2 Earth masses in dust, with typical grain sizes in the planetesimal belt ranging from 4 to 7 µm. We constrain the dynamical excitation to be low, which results in very long collisional lifetimes and a drag that notably fills the inner gap, especially at 70 µm. The radial distribution stretches from well within 100 AU in an unusual, outward-rising slope towards a rather sharp outer edge at about 170-190 AU. The inner edge is therefore smoother than that reported for Fomalhaut, but the contribution from the extended halo of barely bound grains is similarly small. Both slowly self-stirring and planetary perturbations could potentially have formed and shaped this disk.

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Circumstellar material in the Vega inner system revealed by CHARA/FLUOR

Cited by 152 publications

References 58 publications

Near-infrared emission from sublimating dust in collisionally active debris disks

Near-infrared emission from sublimating dust in collisionally active debris disks

Structure of the outer layers of cool standard stars

Modelling the huge,Herschel-resolved debris ring around HD 207129

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