Mathieu C.

The time of large-scale astronomical surveys is now upon us. These huge spectral, astrometric and photometric surveys are providing us astronomers with the richest datasets to date, to better characterise the stars contained within the Milky Way like never before. With almost every star being orbited by at least one exoplanet across our galaxy, these large scale surveys can help better inform us in characterising confirmed and potential planet-hosting stars. We've been able to utilise GALAH's… Show more

The time of large-scale astronomical surveys is now upon us. These huge spectral, astrometric and photometric surveys are providing us astronomers with the richest datasets to date, to better characterise the stars contained within the Milky Way like never before. With almost every star being orbited by at least one exoplanet across our galaxy, these large scale surveys can help better inform us in characterising confirmed and potential planet-hosting stars. We've been able to utilise GALAH's last two data releases (DR2 and DR3), along with GAIA DR2 and EDR3 to better characterise over 125 exoplanet hosts and 250 candidate hosting stars, as well as 45,000 stars currently being observed by TESS. This poster also shows how GALAH's chemical abundances can help inform exoplanetary scientists on what types of planets TESS will likely uncover, and some trends in planetary populations with different chemical abundances. Show less

Short-orbit gas giant planet formation/evolution mechanisms are still not well understood. One promising pathway to discriminate between mechanisms is to constrain the occurrence rate of these peculiar exoplanets at the earliest stage of the system's life. However, a major limitation when studying newly born stars is stellar activity. This cocktail of phenomena triggered by fast rotation, strong magnetic fields, and complex internal dynamics, especially present in very young stars, compromises… Show more

Short-orbit gas giant planet formation/evolution mechanisms are still not well understood. One promising pathway to discriminate between mechanisms is to constrain the occurrence rate of these peculiar exoplanets at the earliest stage of the system's life. However, a major limitation when studying newly born stars is stellar activity. This cocktail of phenomena triggered by fast rotation, strong magnetic fields, and complex internal dynamics, especially present in very young stars, compromises our ability to detect exoplanets. In this paper, we investigated the limitations of such detections in the context of already acquired data solely using radial velocity data acquired with a non-stabilized spectrograph. We employed two strategies: Doppler Imaging and Gaussian Processes and could confidently detect hot Jupiters with a semi-amplitude of 100 m s-1 buried in the stellar activity. We also showed the advantages of the Gaussian Process approach in this case. This study serves as a proof of concept to identify potential candidates for follow-up observations or even discover such planets in legacy data sets available to the community. Show less

An unprecedented number of exoplanets are being discovered by the Transiting Exoplanet Survey Satellite (TESS). Determining the orbital parameters of these exoplanets, and especially their mass and radius, will depend heavily upon the measured physical characteristics of their host stars. We have cross-matched spectroscopic, photometric, and astrometric data from GALAH Data Release 2, the TESS Input Catalog and Gaia Data Release 2, to create a curated, self-consistent catalogue of physical and… Show more

An unprecedented number of exoplanets are being discovered by the Transiting Exoplanet Survey Satellite (TESS). Determining the orbital parameters of these exoplanets, and especially their mass and radius, will depend heavily upon the measured physical characteristics of their host stars. We have cross-matched spectroscopic, photometric, and astrometric data from GALAH Data Release 2, the TESS Input Catalog and Gaia Data Release 2, to create a curated, self-consistent catalogue of physical and chemical properties for 47 285 stars. Using these data, we have derived isochrone masses and radii that are precise to within 5 per cent. We have revised the parameters of three confirmed, and twelve candidate, TESS planetary systems. These results cast doubt on whether CTOI-20125677 is indeed a planetary system, since the revised planetary radii are now comparable to stellar sizes. Our GALAH-TESS catalogue contains abundances for up to 23 elements. We have specifically analysed the molar ratios for C/O, Mg/Si, Fe/Si, and Fe/Mg, to assist in determining the composition and structure of planets with Rp < 4R⊕. From these ratios, 36 per cent fall within 2 σ sigma of the Sun/Earth values, suggesting that these stars may host rocky exoplanets with geological compositions similar to planets found within our own Solar system. Show less

We report the discovery of a warm sub-Saturn, TOI-257b (HD 19916b), based on data from NASA's Transiting Exoplanet Survey Satellite (TESS). The transit signal was detected by TESS and confirmed to be of planetary origin based on radial velocity observations. An analysis of the TESS photometry, the MINERVA-Australis, FEROS, and HARPS radial velocities, and the asteroseismic data of the stellar oscillations reveals that TOI-257b has a mass of MP = 0.138 ± 0.023 MJ (43.9 ± 7.3 M⊕ ), a radius… Show more

We report the discovery of a warm sub-Saturn, TOI-257b (HD 19916b), based on data from NASA's Transiting Exoplanet Survey Satellite (TESS). The transit signal was detected by TESS and confirmed to be of planetary origin based on radial velocity observations. An analysis of the TESS photometry, the MINERVA-Australis, FEROS, and HARPS radial velocities, and the asteroseismic data of the stellar oscillations reveals that TOI-257b has a mass of MP = 0.138 ± 0.023 MJ (43.9 ± 7.3 M⊕ ), a radius of RP = 0.639 ± 0.013 RJ (7.16 ± 0.15 R⊕ ), bulk density of 0.65+0.12−0.11 (cgs), and period 18.38818+0.00085−0.00084 days . TOI-257b orbits a bright (V = 7.612 mag) somewhat evolved late F-type star with M* = 1.390 ± 0.046 Msun , R* = 1.888 ± 0.033 Rsun , Teff = 6075 ± 90 K , and vsin i = 11.3 ± 0.5 km s-1. Additionally, we find hints for a second non-transiting sub-Saturn mass planet on a ∼71 day orbit using the radial velocity data. This system joins the ranks of a small number of exoplanet host stars (∼100) that have been characterized with asteroseismology. Warm sub-Saturns are rare in the known sample of exoplanets, and thus the discovery of TOI-257b is important in the context of future work studying the formation and migration history of similar planetary systems. Show less

The MINERVA-Australis telescope array is a facility dedicated to the follow-up, confirmation, characterization, and mass measurement of planets orbiting bright stars discovered by the Transiting Exoplanet Survey Satellite (TESS)—a category in which it is almost unique in the Southern Hemisphere. It is located at the University of Southern Queensland’s Mount Kent Observatory near Toowoomba, Australia. Its flexible design enables multiple 0.7 m robotic telescopes to be used both in combination… Show more

The MINERVA-Australis telescope array is a facility dedicated to the follow-up, confirmation, characterization, and mass measurement of planets orbiting bright stars discovered by the Transiting Exoplanet Survey Satellite (TESS)—a category in which it is almost unique in the Southern Hemisphere. It is located at the University of Southern Queensland’s Mount Kent Observatory near Toowoomba, Australia. Its flexible design enables multiple 0.7 m robotic telescopes to be used both in combination, and independently, for high-resolution spectroscopy and precision photometry of TESS transit planet candidates. MINERVA-Australis also enables complementary studies of exoplanet spin-orbit alignments via Doppler observations of the Rossiter-McLaughlin effect, radial velocity searches for nontransiting planets, planet searches using transit timing variations, and ephemeris refinement for TESS planets. In this first paper, we describe the design, photometric instrumentation, software, and science goals of MINERVA-Australis, and note key differences from its Northern Hemisphere counterpart, the MINERVA array. We use recent transit observations of four planets, WASP-2b, WASP-44b, WASP-45b, and HD 189733b, to demonstrate the photometric capabilities of MINERVA-Australis. Show less