ORCID Profile
0000-0002-2072-6541
Current Organisation
University of Kansas
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Publisher: American Astronomical Society
Date: 17-10-2022
Abstract: We report observations of the recently discovered warm Neptune TOI-674 b (5.25 R ⊕ , 23.6 M ⊕ ) with the Hubble Space Telescope’s Wide Field Camera 3 instrument. TOI-674 b is in the Neptune desert, an observed paucity of Neptune-size exoplanets at short orbital periods. Planets in the desert are thought to have complex evolutionary histories due to photoevaporative mass loss or orbital migration, making identifying the constituents of their atmospheres critical to understanding their origins. We obtained near-infrared transmission spectroscopy of the planet’s atmosphere with the G141 grism. After extracting, detrending, and fitting the spectral light curves to measure the planet’s transmission spectrum, we used the petitRADTRANS atmospheric spectral synthesis code to perform retrievals on the planet’s atmosphere to identify which absorbers are present. These results show moderate evidence for increased absorption at 1.4 μ m due to water vapor at 2.9 σ (Bayes factor = 15.8), as well as weak evidence for the presence of clouds at 2.2 σ (Bayes factor = 4.0). TOI-674 b is a strong candidate for further study to refine the water abundance, which is poorly constrained by our data. We also incorporated new TESS short-cadence optical photometry, as well as Spitzer/IRAC data, and refit the transit parameters for the planet. We find the planet to have the following transit parameters: R p / R * = 0.1135 ± 0.0006, T 0 = 2458544.523792 ± 0.000452 BJD, and P = 1.977198 ± 0.00007 day. These measurements refine the planet radius estimate and improve the orbital ephemerides for future transit spectroscopy observations of this highly intriguing warm Neptune.
Publisher: IOP Publishing
Date: 04-2022
Abstract: NASA’s TESS mission yields light curves for tens of millions of stars spread across the entire sky, a data set that will be a challenge to fully exploit without help from citizen scientists. To address this, we launched a new citizen science project, called “Planet Patrol”, designed to analyze TESS data on exoplanet and eclipsing binary candidates. The project will also serve to benchmark different data reduction pipelines and help analyze unusual light curves that might defeat automated algorithms. The first stage of the project ran on the Zooniverse platform between 2020 September and November and involved more than 5500 registered volunteers. The Planet Patrol citizen scientists produced nearly 400,000 classifications of difference images used for photocenter analysis of about 1000 planet candidates from TESS. The results were incorporated into the photocenter module of the Discovery And Vetting of Exoplanets (DAVE) pipeline to improve its reliability. Specifically, the classifications indicated that all per-transit difference images are appropriate for photocenter analysis for about 40% of the planet candidates, and the corresponding measurements are sound. In contrast, the volunteers found that all per-transit difference images are dominated by astrophysical contamination and/or systematic effects for about 10% of the planet candidates. This indicated that the corresponding photocenter measurements are unreliable. Finally, the fraction of images appropriate for photocenter analysis varies between 0 and 1 for half the candidates. Removing the images classified as poor from DAVE’s analysis of most of these candidates helped reduce the corresponding photocenter uncertainty by up to ∼30%. We plan to implement the output from another module of DAVE, designed for lightcurve vetting, into a second stage of the Planet Patrol project.
Publisher: American Astronomical Society
Date: 09-2023
Publisher: American Astronomical Society
Date: 27-06-2019
Publisher: American Astronomical Society
Date: 09-2022
Abstract: In recent years, the discovery of increasing numbers of rocky, terrestrial exoplanets orbiting nearby stars has drawn increased attention to the possibility of studying these planets’ atmospheric and surface properties. This is especially true for planets orbiting M dwarfs, whose properties can best be studied with existing observatories. In particular, the minerological composition of these planets and the extent to which they can retain their atmospheres in the face of intense stellar irradiation both remain unresolved. Here, we report the detection of the secondary eclipse of the terrestrial exoplanet GJ 1252b, obtained via 10 eclipse observations using the Spitzer Space Telescope’s IRAC2 4.5 μ m channel. We measure an eclipse depth of 149 − 32 + 25 ppm, corresponding to a dayside brightness temperature of 1410 − 125 + 91 K. This measurement is consistent with the prediction for a bare rock surface. Comparing the eclipse measurement to a large suite of simulated planetary spectra indicates that GJ 1252b has a surface pressure of ≲10 bar, i.e., substantially thinner than the atmosphere of Venus. Assuming energy-limited escape, even a 100 bar atmosphere would be lost in Myr, far shorter than our gyrochronological age estimate of 3.9 ± 0.4 Gyr. The expected mass loss could be overcome by mantle outgassing, but only if the mantle’s carbon content were % by mass—over two orders of magnitude greater than that found in Earth. We therefore conclude that GJ 1252b has no significant atmosphere. Model spectra with granitoid or feldspathic surface composition, but with no atmosphere, are disfavored at σ . The eclipse occurs just +1.4 − 1.0 + 2.8 minutes after orbital phase 0.5, indicating e cos ω = +0.0025 − 0.0018 + 0.0049 , consistent with a circular orbit. Tidal heating is therefore likely to be negligible with regard to GJ 1252b’s global energy budget. Finally, we also analyze additional, unpublished TESS transit photometry of GJ 1252b, which improves the precision of the transit ephemeris by a factor of 10, provides a more precise planetary radius of 1.180 ± 0.078 R ⊕ , and rules out any transit-timing variations with litudes ≳1 minute.
Publisher: American Astronomical Society
Date: 06-2023
Abstract: We present the first elemental abundance measurements of the K dwarf (K7V) exoplanet-host star WASP-107 using high-resolution ( R ≃45,000), near-infrared ( H - and K -band) spectra taken from Gemini-S/IGRINS. We use the previously determined physical parameters of the star from the literature and infer the abundances of 15 elements—C, N, O, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, and Ni, all with precision 0.1 dex—based on model fitting using MARCS model atmospheres and the Turbospectrum spectral synthesis code. Our results show near-solar abundances and a carbon-to-oxygen ratio (C/O) of 0.50 ± 0.10, which is consistent with the solar value of 0.54 ± 0.09. The orbiting planet, WASP-107b, is a super-Neptune with a mass in the Neptune regime (=1.8 M Nep ) and a radius close to Jupiter's (=0.94 R Jup ). This planet is also being targeted by four JWST Cycle 1 programs in transit and eclipse, which should provide highly precise measurements of atmospheric abundances. This will enable us to properly compare the planetary and stellar chemical abundances, which is essential in understanding the formation mechanisms, internal structure, and chemical composition of exoplanets. Our study is a proof-of-concept that will pave the way for such measurements to be made for all of JWST’s cooler exoplanet-host stars.
Location: United States of America
No related grants have been discovered for Jonathan Brande.