Engineering topics

Arbo, P.

Publications and source records attributed to Arbo, P..

4 records

DOE OSTI2021

The HOSTS Survey: Evidence for an Extended Dust Disk and Constraints on the Presence of Giant Planets in the Habitable Zone of β Leo

The young (50–400 Myr) A3V star β Leo is a primary target to study the formation history and evolution of extrasolar planetary systems as one of the few stars with known hot (∼1600 K), warm (∼600 K), and cold (∼120 K) dust belt components. In this paper, we present deep mid-infrared measurements of the warm dust brightness obtained with the Large Binocular Telescope Interferometer (LBTI) as part of its exozodiacal dust survey (HOSTS). The measured excess is 0.47% ± 0.050% within the central 1.5 au, rising to 0.81% ± 0.026% within 4.5 au, outside the habitable zone of β Leo. This dust level is 50 ± 10 times greater than in the solar system’s zodiacal cloud. Poynting–Robertson drag on the cold dust detected by Spitzer, and Herschel underpredicts the dust present in the habitable zone of β Leo, suggesting an additional delivery mechanism (e.g., comets) or an additional belt at ∼5.5 au. A model of these dust components is provided that implies the absence of planets more than a few Saturn masses between ∼5 au and the outer belt at ∼40 au. We also observationally constrain giant planets with the LBTI imaging channel at 3.8 μm wavelength. Assuming an age of 50 Myr, any planet in the system between approximately 5–50 au must be less than a few Jupiter masses, consistent with our dust model. Taken together, these observations showcase the deep contrasts and detection capabilities attainable by the LBTI for both warm exozodiacal dust and giant exoplanets in or near the habitable zone of nearby stars.

47 OTHER INSTRUMENTATION↗

DOE OSTI2020

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

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/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 1σ median sensitivity of 23 zodis times the solar system dust surface density in its habitable zone (HZ; 23 zodis) for early-type stars and 48 zodis for Sun-like stars, where 1 zodi is the surface density of 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, 1σ 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 to evaluate the impact of exozodiacal dust for the spectroscopic characterization of imaged exo-Earth candidates.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS2018

The HOSTS Survey-Exozodiacal Dust Measurements for 30 Stars

The Hunt for Observable Signatures of Terrestrial Systems survey searches for dust near the habitable zones (HZs) around nearby, bright main-sequence stars. We use nulling interferometry in the N band to suppress the bright stellar light and to probe for low levels of HZ dust around the 30 stars observed so far. Our overall detection rate is 18%, including four new detections, among which are the first three around Sun-like stars and the first two around stars without any previously known circumstellar dust. The inferred occurrence rates are comparable for early-type and Sun-like stars, but decrease from 60(sup +16)(sub -21)% for stars with previously detected cold dust to 8(sup +10)(sub -3)% for stars without such excess, confirming earlier results at higher sensitivity. For completed observations on individual stars, our sensitivity is five to ten times better than previous results. Assuming a lognormal excess luminosity function, we put upper limits on the median HZ dust level of 13 zodis (95% confidence) for a sample of stars without cold dust and of 26 zodis when focusing on Sun-like stars without cold dust. However, our data suggest that a more complex luminosity function may be more appropriate. For stars without detectable Large Binocular Telescope Interferometer (LBTI) excess, our upper limits are almost reduced by a factor of two, demonstrating the strength of LBTI target vetting for future exo-Earth imaging missions. Our statistics are limited so far, and extending the survey is critical to informing the design of future exo-Earth imaging surveys.

The Hunt for Observable Signatures of Terrestrial ↗

NASA NTRS2016

Nulling Data Reduction and On-Sky Performance of the Large Binocular Telescope Interferometer

The Large Binocular Telescope Interferometer (LBTI) is a versatile instrument designed for high angular resolution and high-contrast infrared imaging (1.5-13 micrometers). In this paper, we focus on the mid-infrared (8-13 micrometers) nulling mode and present its theory of operation, data reduction, and on-sky performance as of the end of the commissioning phase in 2015 March. With an interferometric baseline of 14.4 m, the LBTI nuller is specifically tuned to resolve the habitable zone of nearby main-sequence stars, where warm exozodiacal dust emission peaks. Measuring the exozodi luminosity function of nearby main-sequence stars is a key milestone to prepare for future exo-Earth direct imaging instruments. Thanks to recent progress in wavefront control and phase stabilization, as well as in data reduction techniques, the LBTI demonstrated in 2015 February a calibrated null accuracy of 0.05% over a 3 hr long observing sequence on the bright nearby A3V star Beta Leo. This is equivalent to an exozodiacal disk density of 15-30 zodi for a Sun-like star located at 10 pc, depending on the adopted disk model. This result sets a new record for high-contrast mid-infrared interferometric imaging and opens a new window on the study of planetary systems.

circumstellar matter aEuro" techniques: interferom↗