A near-infrared interferometric survey of debris-disc stars

Nuñez, Paul D.; Scott, Nicholas J.; Mennesson, Bertrand; Absil, Olivier; Augereau, J.-C.; Bryden, G.; Brummelaar, T. ten; Foresto, V. Coudé du; Ridgway, Stephen T.; Sturmann, J.; Sturmann, L.; Turner, Neal; Turner, N.

doi:10.1051/0004-6361/201730859

Cited by 24 publications

(26 citation statements)

References 54 publications

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“…It may indeed be possible that Altair's atmosphere is more metallic than its interior, as a possible consequence of a recent accretion of metals from a residual disc or planetoids. This idea is comforted by the fact that Nuñez et al (2017) found an extended, weak IR excess (a few % in K band) for Altair, which suggests the presence of a tenuous circumstellar material (possibly from a debris disc) within a few AU of the star.…”

Section: Massmentioning

confidence: 99%

A realistic two-dimensional model of Altair

Bouchaud

Souza

Rieutord

et al. 2020

A&A

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Context. Fast rotation is responsible for important changes in the structure and evolution of stars and the way we see them. Optical long baseline interferometry (OLBI) now allows for the study of its effects on the stellar surface, mainly gravity darkening and flattening. Aims. We aim to determine the fundamental parameters of the fast-rotating star Altair, in particular its evolutionary stage (represented here by the core hydrogen mass fraction X c ), mass, and differential rotation, using state-of-the-art stellar interior and atmosphere models together with interferometric (ESO-VLTI), spectroscopic, and asteroseismic observations. Methods. We use ESTER two-dimensional stellar models to produce the relevant surface parameters needed to create intensity maps from atmosphere models. Interferometric and spectroscopic observables are computed from these intensity maps and several stellar parameters are then adjusted using the publicly available MCMC algorithm Emcee. Results. We determined Altair's equatorial radius to be R eq = 2.008 ± 0.006 R , the position angle PA = 301.1 ± 0.3 • , the inclination i = 50.7 ± 1.2 • , and the equatorial angular velocity Ω = 0.74 ± 0.01 times the Keplerian angular velocity at equator. This angular velocity leads to a flattening of ε = 0.220 ± 0.003. We also deduce from the spectroscopically derived v sin i 243 km s −1 , a true equatorial velocity of ∼ 314 km s −1 corresponding to a rotation period of 7h46m (∼3 cycles/day). The data also impose a strong correlation between mass, metallicity, hydrogen abundance, and core evolution. Thanks to asteroseismic data, and provided our frequencies identification is correct, we constrain the mass of Altair to 1.86±0.03 M and further deduce its metallicity Z = 0.019 and its core hydrogen mass fraction X c = 0.71, assuming an initial solar hydrogen mass fraction X = 0.739. These values suggest that Altair is a young star ∼100 Myrs old. Finally, the 2D ESTER model also gives the internal differential rotation of Altair, showing that its core rotates approximately 50% faster than the envelope, while the surface differential rotation does not exceed 6%.

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Section: Massmentioning

confidence: 99%

A realistic two-dimensional model of Altair

Bouchaud

Souza

Rieutord

et al. 2020

A&A

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“…In fact, this is the case for the zodiacal cloud, much of which is replenished from dust that originates from comets that disintegrate as they pass through the inner Solar System (Nesvorný et al 2010). Based on the NIR excess measured in nearby stars using interferometry, it has been estimated that ∼ 10 − 30% of AFGK-type stars have exozodi levels above 1% of the stellar flux (Absil et al 2013;Ertel et al 2014), with a tentative correlation with the existence of an outer reservoir of cold dust for FGK-type stars (Nuñez et al 2017). On the other hand, MIR excess are less commonly detected (e.g.…”

Section: Introductionmentioning

confidence: 99%

Scattering of exocomets by a planet chain: exozodi levels and the delivery of cometary material to inner planets

Marino

Bonsor

Wyatt

et al. 2018

Monthly Notices of the Royal Astronomical Society

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Exocomets scattered by planets have been invoked to explain observations in multiple contexts, including the frequently found near-and mid-infrared excess around nearby stars arising from exozodiacal dust. Here we investigate how the process of inward scattering of comets originating in an outer belt, is affected by the architecture of a planetary system, to determine whether this could lead to observable exozodi levels or deliver volatiles to inner planets. Using N-body simulations, we model systems with different planet mass and orbital spacing distributions in the 1-50 AU region. We find that tightly packed (∆a p < 20R H,m ) low mass planets are the most efficient at delivering material to exozodi regions (5-7% of scattered exocomets end up within 0.5 AU at some point), although the exozodi levels do not vary by more than a factor of ∼ 7 for the architectures studied here. We suggest that emission from scattered dusty material in between the planets could provide a potential test for this delivery mechanism. We show that the surface density of scattered material can vary by two orders of magnitude (being highest for systems of low mass planets with medium spacing), whilst the exozodi delivery rate stays roughly constant, and that future instruments such as JWST could detect it. In fact for η Corvi, the current Herschel upper limit rules out the scattering scenario by a chain of 30 M ⊕ planets. Finally, we show that exocomets could be efficient at delivering cometary material to inner planets (0.1-1% of scattered comets are accreted per inner planet). Overall, the best systems at delivering comets to inner planets are the ones that have low mass outer planets and medium spacing (∼ 20R H,m ).

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“…Interferometry is required to spatially resolve the thermal dust emission in the infrared and thus disentangle it from the host star. This has been done successfully for the hot dust using optical long baseline interferometry in the near-infrared (Absil et al 2006(Absil et al , 2013Defrère et al 2012b;Ertel et al 2014aErtel et al , 2016Nuñez et al 2017). In the mid infrared where HZ dust is the brightest, nulling interferometry (Bracewell & MacPhie 1979;Hinz et al 1998Hinz et al , 2000 has been used to suppress the bright, unresolved star light and detect the faint, extended dust emission (Stock et al 2010;Millan-Gabet et al 2011;Mennesson et al 2014;Ertel et al 2018b).…”

mentioning

confidence: 99%

The HOSTS Survey for Exozodiacal Dust: Observational Results from the Complete Survey

Ertel

Defrère

Hinz

et al. 2020

Self Cite

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The Large Binocular Telescope Interferometer (LBTI) enables nulling interferometric observations across the N band (8 to 13 µm) to suppress a star's bright light and probe for faint circumstellar emission. We present and statistically analyze the results from the LBTI/HOSTS (Hunt for Observable Signatures of Terrestrial Systems) survey for exozodiacal dust. By comparing our measurements to model predictions based on the Solar zodiacal dust in the N band, we estimate a 1 σ median sensitivity of 23 zodis for early type stars and 48 zodis for Sun-like stars, where 1 zodi is the surface density of habitable zone (HZ) dust in the Solar system. Of the 38 stars observed, 10 show significant excess. A clear correlation of our detections with the presence of cold dust in the systems was found, but none with the stellar spectral type or age. The majority of Sun-like stars have relatively low HZ dust levels (best-fit median: 3 zodis, 1 σ upper limit: 9 zodis, 95% confidence: 27 zodis based on our N band measurements), while ∼20% are significantly more dusty. The Solar system's HZ dust content is consistent with being typical. Our median HZ dust level would not be a major limitation to the direct imaging search for Earth-like exoplanets, but more precise constraints are still required, in particular

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A near-infrared interferometric survey of debris-disc stars

Cited by 24 publications

References 54 publications

A realistic two-dimensional model of Altair

A realistic two-dimensional model of Altair

Scattering of exocomets by a planet chain: exozodi levels and the delivery of cometary material to inner planets

The HOSTS Survey for Exozodiacal Dust: Observational Results from the Complete Survey

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