pytransit: fast and easy exoplanet transit modelling in python

Parviainen, H.

doi:10.1093/mnras/stv894

Cited by 183 publications

(112 citation statements)

References 23 publications

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“…We model CLV and RM contributions by simulating the transmission lightcurve of a planet without an atmosphere at the same phases as the data (Section 5.2). We then divide the observed lightcurve by the model, and fit the residuals using the PyTransit package (Parviainen 2015). We estimate limb-darkening coefficients with the LDTk package (Parviainen & Aigrain 2015).…”

Section: Lightcurve Analysismentioning

confidence: 99%

Detection of neutral atomic species in the ultra-hot Jupiter WASP-121b

Cabot

Madhusudhan

Welbanks

et al. 2020

Monthly Notices of the Royal Astronomical Society

106

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The class of ultra-hot Jupiters comprises giant exoplanets undergoing intense irradiation from their host stars. They have proved to be a particularly interesting population for their orbital and atmospheric properties. One such planet, WASP-121 b, is in a highly misaligned orbit close to its Roche limit, and its atmosphere exhibits a thermal inversion. These properties make WASP-121 b an interesting target for additional atmospheric characterization. In this paper, we present analysis of archival high-resolution optical spectra obtained during transits of WASP-121 b. Artifacts from the Rossiter-McLaughlin effect and Center-to-Limb Variation are deemed negligible. However, we discuss scenarios where these effects warrant more careful treatment by modeling the WASP-121 system and varying its properties. We report a new detection of atmospheric absorption from Hα in the planet with a transit depth of 1.87 ± 0.11%. We further confirm a previous detection of the Na I doublet, and report a new detection of Fe I via cross-correlation with a model template. We attribute the Hα absorption to an extended Hydrogen atmosphere, potentially undergoing escape, and the Fe I to equilibrium chemistry at the planetary photosphere. These detections help to constrain the composition and chemical processes in the atmosphere of WASP-121 b.

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Section: Lightcurve Analysismentioning

confidence: 99%

Detection of neutral atomic species in the ultra-hot Jupiter WASP-121b

Cabot

Madhusudhan

Welbanks

et al. 2020

Monthly Notices of the Royal Astronomical Society

106

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“…The analyses were carried out with a custom Python code based on PyTransit v2 5 (Parviainen 2015;Parviainen et al 2019), which includes a physics-based contamination model based on the PHOENIX-calculated stellar spectrum library by Husser et al (2013). The limb darkening computations were carried out with LDTk 6 (Parviainen & Aigrain 2015), and MCMC sampling was carried out with emcee All the code for the analyses presented in this paper is available from GitHub as Python code and Jupyter notebooks from https://github.com/hpparvi/parviainen_2019b_ toi_263.…”

Section: Overviewmentioning

confidence: 99%

MuSCAT2 multicolour validation of TESS candidates: an ultra-short-period substellar object around an M dwarf

Parviainen

Πάλλη

Osorio

et al. 2020

A&A

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Context. We report the discovery of TOI 263.01 (TIC 120916706), a transiting substellar object (R = 0.87 R Jup ) orbiting a faint M3.5 V dwarf (V = 18.97) on a 0.56 d orbit.Aims. We set out to determine the nature of the TESS planet candidate TOI 263.01 using ground-based multicolour transit photometry. The host star is faint, which makes RV confirmation challenging, but the large transit depth makes the candidate suitable for validation through multicolour photometry.Methods. Our analysis combines three transits observed simultaneously in r , i , and z s bands using the MuSCAT2 multicolour imager, three LCOGT-observed transit light curves in g , r , and i bands, a TESS light curve from Sector 3, and a low-resolution spectrum for stellar characterisation observed with the ALFOSC spectrograph. We model the light curves with PyTransit using a transit model that includes a physics-based light contamination component that allows us to estimate the contamination from unresolved sources from the multicolour photometry. This allows us to derive the true planet-star radius ratio marginalised over the contamination allowed by the photometry, and, combined with the stellar radius, gives us a reliable estimate of the object's absolute radius. Results. The ground-based photometry strongly excludes contamination from unresolved sources with a significant colour difference to TOI 263. Further, contamination from sources of same stellar type as the host is constrained to levels where the true radius ratio posterior has a median of 0.217 and a 99 percentile of 0.286. The median and maximum radius ratios correspond to absolute planet radii of 0.87 and 1.41 R Jup , respectively, which confirms the substellar nature of the planet candidate. The object is either a giant planet or a brown dwarf (BD) located deep inside the socalled "brown dwarf desert". Both possibilities offer a challenge to current planet/BD formation models and makes TOI 263.01 an object deserving of in-depth follow-up studies.

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“…All observations covered from 2 to 3.2 hours around the expected midtransit time, and were carried simultaneously in the r , i , and z passbands with a common exposure time of 10 seconds. The photometry was done with the MuSCAT2 pipeline based on PyTransit (Parviainen 2015) and LDTk (Parviainen & Aigrain 2015).…”

Section: Photometrymentioning

confidence: 99%

Radial velocity confirmation of K2-100b: a young, highly irradiated, and low-density transiting hot Neptune

Barragán

Aigrain

Kubyshkina

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We present a detailed analysis of HARPS-N radial velocity observations of K2-100, a young and active star in the Praesepe cluster, which hosts a transiting planet with a period of 1.7 days. We model the activity-induced radial velocity variations of the host star with a multi-dimensional Gaussian Process framework and detect a planetary signal of 10.6 ± 3.0 m s −1 which matches the transit ephemeris, and translates to a planet mass of 21.8 ± 6.2 M ⊕ . We perform a suite of validation tests to confirm that our detected signal is genuine. This is the first mass measurement for a transiting planet in a young open cluster. The relatively low density of the planet, 2.04 +0.66 −0.61 g cm −3 , implies that K2-100b retains a significant volatile envelope. We estimate that the planet is losing its atmosphere at a rate of 10 11 − 10 12 g s −1 due to the high level of radiation it receives from its host star.

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pytransit: fast and easy exoplanet transit modelling in python

Cited by 183 publications

References 23 publications

Detection of neutral atomic species in the ultra-hot Jupiter WASP-121b

Detection of neutral atomic species in the ultra-hot Jupiter WASP-121b

MuSCAT2 multicolour validation of TESS candidates: an ultra-short-period substellar object around an M dwarf

Radial velocity confirmation of K2-100b: a young, highly irradiated, and low-density transiting hot Neptune

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