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41 result(s) for "Guillet, Bruno"
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Light curves and colours of the ejecta from Dimorphos after the DART impact
On 26 September 2022, the Double Asteroid Redirection Test (DART) spacecraft struck Dimorphos, a satellite of the asteroid 65803 Didymos 1 . Because it is a binary system, it is possible to determine how much the orbit of the satellite changed, as part of a test of what is necessary to deflect an asteroid that might threaten Earth with an impact. In nominal cases, pre-impact predictions of the orbital period reduction ranged from roughly 8.8 to 17 min (refs. 2 , 3 ). Here we report optical observations of Dimorphos before, during and after the impact, from a network of citizen scientists’ telescopes across the world. We find a maximum brightening of 2.29 ± 0.14 mag on impact. Didymos fades back to its pre-impact brightness over the course of 23.7 ± 0.7 days. We estimate lower limits on the mass contained in the ejecta, which was 0.3–0.5% Dimorphos’s mass depending on the dust size. We also observe a reddening of the ejecta on impact. Optical observations of Dimorphos, a satellite of the asteroid 65803 Didymos, before, during and after the impact of the DART spacecraft, from a network of citizen science telescopes across the world are reported.
A hot-Jupiter progenitor on a super-eccentric retrograde orbit
Giant exoplanets orbiting close to their host stars are unlikely to have formed in their present configurations 1 . These ‘hot Jupiter’ planets are instead thought to have migrated inward from beyond the ice line and several viable migration channels have been proposed, including eccentricity excitation through angular-momentum exchange with a third body followed by tidally driven orbital circularization 2 , 3 . The discovery of the extremely eccentric ( e  = 0.93) giant exoplanet HD 80606 b (ref.  4 ) provided observational evidence that hot Jupiters may have formed through this high-eccentricity tidal-migration pathway 5 . However, no similar hot-Jupiter progenitors have been found and simulations predict that one factor affecting the efficacy of this mechanism is exoplanet mass, as low-mass planets are more likely to be tidally disrupted during periastron passage 6 – 8 . Here we present spectroscopic and photometric observations of TIC 241249530 b, a high-mass, transiting warm Jupiter with an extreme orbital eccentricity of e  = 0.94. The orbit of TIC 241249530 b is consistent with a history of eccentricity oscillations and a future tidal circularization trajectory. Our analysis of the mass and eccentricity distributions of the transiting-warm-Jupiter population further reveals a correlation between high mass and high eccentricity. The spectroscopic and photometric observations of a high-mass, transiting warm Jupiter, TIC 241249530 b, with an orbital eccentricity of 0.94, provide evidence that hot Jupiters may have formed by means of a high-eccentricity tidal-migration pathway.
The Unistellar Exoplanet Campaign: Citizen Science Results and Inherent Education Opportunities
This paper presents early results from and prospects for exoplanet science using a citizen science private/public partnership observer network managed by the SETI Institute in collaboration with Unistellar. The network launched in 2020 January and includes 163 citizen scientist observers across 21 countries. These observers can access a citizen science mentoring service developed by the SETI Institute and are also equipped with Unistellar Enhanced Vision Telescopes. Unistellar technology and the campaign’s associated photometric reduction pipeline enable each telescope to readily obtain and communicate light curves to observers with signal-to-noise ratio suitable for publication in research journals. Citizen astronomers of the Unistellar Exoplanet (UE) Campaign routinely measure transit depths of ≳1% and contribute their results to the exoplanet research community. The match of the detection system, targets, and scientific and educational goals is robust. Results to date include 281 transit detections out of 651 processed observations. In addition to this campaign’s capability to contribute to the professional field of exoplanet research, UE endeavors to drive improved science, technology, engineering, and mathematics education outcomes by engaging students and teachers as participants in science investigations, that is, learning science by doing science.
La sub( 0.7)Sr sub( 0.3)MnO sub( 3) Thin Films for Magnetic and Temperature Sensors at Room Temperature
In this paper, the potentialities of the manganese oxide La sub( 0.7)Sr sub( 0.3)MnO sub( 3) (LSMO) for the realization of sensitive room temperature thermometers and magnetic sensors are discussed. LSMO exhibits both a large change of the resistance versus temperature at its metal-to-insulator transition (about 330 K) and low field magnetoresistive effects at room temperature. The sensor performances are described in terms of signal-to-noise ratio in the 1 Hz - 100 kHz frequency range. It is shown that due to the very low 1/f noise level, LSMO based sensors can exhibit competitive performances at room temperature.
Properties of Ultra-Thin NbN Films for Membrane-Type THz HEB
Various buffer layers have been investigated in order to improve the crystalline quality of NbN ultra-thin films. The structural properties, the thickness, the surface morphology of 5–10 nm NbN films have been studied by different techniques. Uncertainty on thickness measurements in this range and the relation between NbN film quality and gain bandwidth are discussed in the framework of their use in Hot Electron Bolometers (HEB).
La0.7Sr0.3MnO3 Thin Films for Magnetic and Temperature Sensors at Room Temperature
In this paper, the potentialities of the manganese oxide La0.7Sr0.3MnO3 (LSMO) for the realization of sensitive room temperature thermometers and magnetic sensors are discussed. LSMO exhibits both a large change of the resistance versus temperature at its metal-to-insulator transition (about 330 K) and low field magnetoresistive effects at room temperature. The sensor performances are described in terms of signal-to-noise ratio in the 1 Hz - 100 kHz frequency range. It is shown that due to the very low 1/f noise level, LSMO based sensors can exhibit competitive performances at room temperature.
La^sub 0.7^Sr^sub 0.3^MnO^sub 3^ Thin Films for Magnetic and Temperature Sensors at Room Temperature
In this paper, the potentialities of the manganese oxide La^sub 0.7^Sr^sub 0.3^MnO^sub 3^ (LSMO) for the realization of sensitive room temperature thermometers and magnetic sensors are discussed. LSMO exhibits both a large change of the resistance versus temperature at its metal-to-insulator transition (about 330 K) and low field magnetoresistive effects at room temperature. The sensor performances are described in terms of signal-to-noise ratio in the 1 Hz - 100 kHz frequency range. It is shown that due to the very low 1/f noise level, LSMO based sensors can exhibit competitive performances at room temperature. [PUBLICATION ABSTRACT]
Giant Outer Transiting Exoplanet Mass (GOT 'EM) Survey. VI: Confirmation of a Long-Period Giant Planet Discovered with a Single TESS Transit
We report the discovery and confirmation of TOI-4465 b, a \\(1.25^{+0.08}_{-0.07}~R_{J}\\), \\(5.89\\pm0.26~M_{J}\\) giant planet orbiting a G dwarf star at \\(d\\simeq\\) 122 pc. The planet was detected as a single-transit event in data from Sector 40 of the Transiting Exoplanet Survey Satellite (TESS) mission. Radial velocity (RV) observations of TOI-4465 showed a planetary signal with an orbital period of \\(\\sim\\)102 days, and an orbital eccentricity of \\(e=0.24\\pm0.01\\). TESS re-observed TOI-4465 in Sector 53 and Sector 80, but did not detect another transit of TOI-4465 b, as the planet was not expected to transit during these observations based on the RV period. A global ground-based photometry campaign was initiated to observe another transit of TOI-4465 b after the RV period determination. The \\(\\sim\\)12 hour-long transit event was captured from multiple sites around the world, and included observations from 24 citizen scientists, confirming the orbital period as \\(\\sim\\)102 days. TOI-4465 b is a relatively dense (\\(3.73\\pm0.53~\\rm{g/cm^3}\\)), temperate (375-478 K) giant planet. Based on giant planet structure models, TOI-4465 b appears to be enriched in heavy elements at a level consistent with late-stage accretion of icy planetesimals. Additionally, we explore TOI-4465 b's potential for atmospheric characterization, and obliquity measurement. Increasing the number of long-period planets by confirming single-transit events is crucial for understanding the frequency and demographics of planet populations in the outer regions of planetary systems.
Light Curves and Colors of the Ejecta from Dimorphos after the DART Impact
On 26 September 2022 the Double Asteroid Redirection Test (DART) spacecraft impacted Dimorphos, a satellite of the asteroid 65803 Didymos. Because it is a binary system, it is possible to determine how much the orbit of the satellite changed, as part of a test of what is necessary to deflect an asteroid that might threaten Earth with an impact. In nominal cases, pre-impact predictions of the orbital period reduction ranged from ~8.8 - 17.2 minutes. Here we report optical observations of Dimorphos before, during and after the impact, from a network of citizen science telescopes across the world. We find a maximum brightening of 2.29 \\(\\pm\\) 0.14 mag upon impact. Didymos fades back to its pre-impact brightness over the course of 23.7 \\(\\pm\\) 0.7 days. We estimate lower limits on the mass contained in the ejecta, which was 0.3 - 0.5% Dimorphos' mass depending on the dust size. We also observe a reddening of the ejecta upon impact.