Hot circumstellar material resolved around<i>β</i> Pic with VLTI/PIONIER

Defrère, Denis; Lebreton, J.; Bouquin, J.-B. Le; Lagrange, Anne-Marie; Absil, Olivier; Augereau, J.-C.; Berger, J.‐P.; Folco, E. Di; Ertel, S.; Kluska, J.; Montagnier, G.; Millan-Gabet, R.; Traub, W.; Zins, G.

doi:10.1051/0004-6361/201220287

Cited by 44 publications

(74 citation statements)

References 27 publications

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“…Alternative sources of continuum emission, such as free-free emission from a stellar wind, mass-loss events or hot gas, have been discussed e.g. in Paper II, Absil et al (2008) and Defrère et al (2012) and can be considered unsatisfying explanations: emission by very hot dust is the most convincing explanation to date. In the solar system, nanometer-sized particles are detected with the STEREO and Ulysse spacecrafts (Meyer-Vernet et al 2009;Krüger et al 2010, respectively), with an increase in the particle flux in the inner solar system.…”

Section: Discussionmentioning

confidence: 99%

An interferometric study of the Fomalhaut inner debris disk

Lebreton

Lieshout

Augereau

et al. 2013

A&A

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111

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Context. Debris disks are thought to be extrasolar analogs to the solar system planetesimal belts. The star Fomalhaut harbors a cold debris belt at 140 AU comparable to the Edgeworth-Kuiper belt, as well as evidence of a warm dust component, unresolved by singledish telescopes, which is suspected of being a bright analog to the solar system's zodiacal dust. Aims. Interferometric observations obtained with the VLTI/VINCI instrument and the Keck Interferometer Nuller have identified nearand mid-infrared excesses attributed respectively to hot and warm exozodiacal dust residing in the inner few AU of the Fomalhaut environment. We aim to characterize the properties of this double inner dust belt and to unveil its origin. Methods. We performed parametric modeling of the exozodiacal disk ("exozodi") using the GRaTeR radiative transfer code to reproduce the interferometric data, complemented by mid-to far-infrared photometric measurements from Spitzer and Herschel . A detailed treatment of sublimation temperatures was introduced to explore the hot population at the size-dependent sublimation rim. We then used an analytical approach to successively testing several source mechanisms for the dust and suspected parent bodies. Results. A good fit to the multiwavelength data is found by two distinct dust populations: (1) a population of very small (0.01 to 0.5 μm), hence unbound, hot dust grains confined in a narrow region (∼0.1-0.3 AU) at the sublimation rim of carbonaceous material; (2) a population of bound grains at ∼2 AU that is protected from sublimation and has a higher mass despite its fainter flux level. We propose that the hot dust is produced by the release of small carbon grains following the disruption of dust aggregates that originate in the warm component. A mechanism, such as gas braking, is required to further confine the small grains for a long enough time. In situ dust production could hardly be ensured for the age of the star, so we conclude that the observed amount of dust is triggered by intense dynamical activity. Conclusions. Fomalhaut may be representative of exozodis that are currently being surveyed at near and mid-infrared wavelengths worldwide. We propose a framework for reconciling the "hot exozodi phenomenon" with theoretical constraints: the hot component of Fomalhaut is likely the "tip of the iceberg" since it could originate in the more massive, but fainter, warm dust component residing near the ice line. This inner disk exhibits interesting morphology and can be considered a prime target for future exoplanet research.

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Section: Discussionmentioning

confidence: 99%

An interferometric study of the Fomalhaut inner debris disk

Lebreton

Lieshout

Augereau

et al. 2013

A&A

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111

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“…These very accurate instruments are pushed to their limits by such observations in terms of both statistical accuracy and ability to calibrate the data obtained. Until now, only two detections could be confirmed from repeated observations: Vega (Absil et al 2006;Defrère et al 2011) and β Pic (Defrère et al 2012;Ertel et al 2014). …”

Section: Introductionmentioning

confidence: 92%

“…It is generally attributed to the presence of hot circumstellar dust. The detections have been made using near-IR interferometry mostly employing the instruments Fiber Linked Unit for Optical Recombination (FLUOR) Resolution Astronomy (CHARA) array (e.g., Absil et al 2006Absil et al , 2013 and Precision Integrated Optics Near Infrared ExpeRiment (PIONIER) at the Very Large Telescope Interferometer (VLTI; Defrère et al 2012;Ertel et al 2014). These very accurate instruments are pushed to their limits by such observations in terms of both statistical accuracy and ability to calibrate the data obtained.…”

Section: Introductionmentioning

confidence: 99%

A near-infrared interferometric survey of debris-disc stars

Ertel¹,

Defrère²,

Absil³

et al. 2016

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Context. Extended circumstellar emission has been detected within a few 100 milli-arcsec around > ∼ 10% of nearby main sequence stars using near-infrared interferometry. Follow-up observations using other techniques, should they yield similar results or non-detections, can provide strong constraints on the origin of the emission. They can also reveal the variability of the phenomenon. Aims. We aim to demonstrate the persistence of the phenomenon over the timescale of a few years and to search for variability of our previously detected excesses. Methods. Using Very Large Telescope Interferometer (VLTI)/Precision Integrated Optics Near Infrared ExpeRiment (PIONIER) in H band we have carried out multi-epoch observations of the stars for which a near-infrared excess was previously detected using the same observation technique and instrument. The detection rates and distribution of the excesses from our original survey and the follow-up observations are compared statistically. A search for variability of the excesses in our time series is carried out based on the level of the broadband excesses. Results. In 12 of 16 follow-up observations, an excess is re-detected with a significance of >2σ, and in 7 of 16 follow-up observations significant excess (>3σ) is re-detected. We statistically demonstrate with very high confidence that the phenomenon persists for the majority of the systems. We also present the first detection of potential variability in two sources. Conclusions. We conclude that the phenomenon responsible for the excesses persists over the timescale of a few years for the majority of the systems. However, we also find that variability intrinsic to a target can cause it to have no significant excess at the time of a specific observation.

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“…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%

“…(b) For the outer belt distance (r 0 in our models) we list literature estimates of the radial distance to (the inner edge of) "cold" and "warm" outer belts, derived from SED fitting and/or resolved imaging. (c) The NIR excess of β Pic contains a significant contribution from stellar light scattered by the outer belt (Defrère et al 2012). (d) The debris disk around β Pic is seen edge-on, making it hard to determine the parent belt location.…”

Section: Introductionmentioning

confidence: 99%

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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Hot circumstellar material resolved aroundβ Pic with VLTI/PIONIER

Cited by 44 publications

References 27 publications

An interferometric study of the Fomalhaut inner debris disk

An interferometric study of the Fomalhaut inner debris disk

A near-infrared interferometric survey of debris-disc stars

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

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