ORCID Profile
0000-0001-7576-6703
Current Organisation
University of Cambridge
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Publisher: American Association of Physics Teachers
Date: 18-12-2015
Publisher: Oxford University Press (OUP)
Date: 06-04-2023
Abstract: We present an optical transmission spectrum of the hot Jupiter WASP-101b. We observed three primary transits with Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph, covering a wavelength range from 0.3 to 1 $\\mu$m. The observations suffer from significant systematics that we model using Gaussian Processes. Kernel selection for the Gaussian Processes is performed in a data-driven approach through Bayesian model comparison. We find a flat and featureless transmission spectrum, corroborating a previous measurement obtained with HST/Wide-Field Camera 3 in the 1–1.7 $\\mu$m range. The spectrum is consistent with high-altitude clouds located at less than 100 $\\mu$bar. This cloud layer completely blocks our view into deeper parts of the atmosphere and makes WASP-101b the cloudiest gas giant observed so far. We compute a series of temperature-pressure profiles for WASP-101b and compare these to condensation curves for cloud particles, which match clouds composed of silicates. We also include 13 transits observed with Transiting Exoplanet Survey Satellite and use these to refine system parameters.
Publisher: American Physical Society (APS)
Date: 14-09-2018
Publisher: American Astronomical Society
Date: 15-03-2022
Abstract: Measured spectral shifts due to intrinsic stellar variability (e.g., pulsations, granulation) and activity (e.g., spots, plages) are the largest source of error for extreme-precision radial-velocity (EPRV) exoplanet detection. Several methods are designed to disentangle stellar signals from true center-of-mass shifts due to planets. The Extreme-precision Spectrograph (EXPRES) Stellar Signals Project (ESSP) presents a self-consistent comparison of 22 different methods tested on the same extreme-precision spectroscopic data from EXPRES. Methods derived new activity indicators, constructed models for mapping an indicator to the needed radial-velocity (RV) correction, or separated out shape- and shift-driven RV components. Since no ground truth is known when using real data, relative method performance is assessed using the total and nightly scatter of returned RVs and agreement between the results of different methods. Nearly all submitted methods return a lower RV rms than classic linear decorrelation, but no method is yet consistently reducing the RV rms to sub-meter-per-second levels. There is a concerning lack of agreement between the RVs returned by different methods. These results suggest that continued progress in this field necessitates increased interpretability of methods, high-cadence data to capture stellar signals at all timescales, and continued tests like the ESSP using consistent data sets with more advanced metrics for method performance. Future comparisons should make use of various well-characterized data sets—such as solar data or data with known injected planetary and/or stellar signals—to better understand method performance and whether planetary signals are preserved.
Publisher: IOP Publishing
Date: 30-07-2012
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Vinesh Maguire Rajpaul.