Dealing With δ-Scuti Variables: Transit Light Curve Analysis of Planets Orbiting Rapidly Rotating, Seismically Active A/F Stars

Ahlers, John P.; Barnes, Jason W.; Myers, Samuel A.

doi:10.3847/1538-3881/ab27c4

Cited by 13 publications

(9 citation statements)

References 72 publications

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“…This facilitates a measurement of Ψ on the basis of time-series photometry alone, making it a powerful tool to study the history of planets orbiting early-type stars. Due to the high photometric precision required, studies have been limited until recently to planets and low-mass stellar companions orbiting a handful of the brightest stars in the Kepler field (Barnes et al 2011(Barnes et al , 2015Szabó et al 2011Szabó et al , 2020Masuda 2015;Zhou & Huang 2013;Ahlers et al 2014Ahlers et al , 2015Ahlers et al , 2019Howarth & Morello 2017;Herman et al 2018). Observations from the Transiting Exoplanet Survey Satellite (TESS; Ricker et al 2015) have the benefit of observing many more of the systems producing the most pronounced gravity darkening signatures than Kepler.…”

Section: Introductionmentioning

confidence: 99%

Spi-OPS: Spitzer and CHEOPS confirm the near-polar orbit of MASCARA-1 b and reveal a hint of dayside reflection

Hooton

Hoyer

Kitzmann³

et al. 2022

A&A

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Context. The light curves of tidally locked hot Jupiters transiting fast-rotating, early-type stars are a rich source of information about both the planet and star, with full-phase coverage enabling a detailed atmospheric characterisation of the planet. Although it is possible to determine the true spin–orbit angle Ψ – a notoriously difficult parameter to measure – from any transit asymmetry resulting from gravity darkening induced by the stellar rotation, the correlations that exist between the transit parameters have led to large disagreements in published values of Ψ for some systems. Aims. We aimed to study these phenomena in the light curves of the ultra-hot Jupiter MASCARA-1 b, which is characteristically similar to well-studied contemporaries such as KELT-9 b and WASP-33 b. Methods. We obtained optical CHaracterising ExOPlanet Satellite (CHEOPS) transit and occultation light curves of MASCARA-1 b, and analysed them jointly with a Spitzer/IRAC 4.5 μm full-phase curve to model the asymmetric transits, occultations, and phase-dependent flux modulation. For the latter, we employed a novel physics-driven approach to jointly fit the phase modulation by generating a single 2D temperature map and integrating it over the two bandpasses as a function of phase to account for the differing planet–star flux contrasts. The reflected light component was modelled using the general ab initio solution for a semi-infinite atmosphere. Results. When fitting the CHEOPS and Spitzer transits together, the degeneracies are greatly diminished and return results consistent with previously published Doppler tomography. Placing priors informed by the tomography achieves even better precision, allowing a determination of Ψ = 72.1−2.4+2.5 deg. From the occultations and phase variations, we derived dayside and nightside temperatures of 3062−68+66 K and 1720 ± 330 K, respectively.Our retrieval suggests that the dayside emission spectrum closely follows that of a blackbody. As the CHEOPS occultation is too deep to be attributed to blackbody flux alone, we could separately derive geometric albedo Ag = 0.171−0.068+0.066 and spherical albedo As = 0.266−0.100+0.097 from the CHEOPS data, and Bond albedoAB = 0.057−0.101+0.083 from the Spitzer phase curve.Although small, the Ag and As indicate that MASCARA-1 b is more reflective than most other ultra-hot Jupiters, where H− absorption is expected to dominate. Conclusions. Where possible, priors informed by Doppler tomography should be used when fitting transits of fast-rotating stars, though multi-colour photometry may also unlock an accurate measurement of Ψ. Our approach to modelling the phase variations at different wavelengths provides a template for how to separate thermal emission from reflected light in spectrally resolved James Webb Space Telescope phase curve data.

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Section: Introductionmentioning

confidence: 99%

Spi-OPS: Spitzer and CHEOPS confirm the near-polar orbit of MASCARA-1 b and reveal a hint of dayside reflection

Hooton

Hoyer

Kitzmann³

et al. 2022

A&A

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“…This work marks one of only a handful to account for gravity darkening in an exoplanet analysis (Barnes et al 2011;Szabó et al 2011Szabó et al , 2020Zhou & Huang 2013;Ahlers et al 2014Ahlers et al , 2015Ahlers et al , 2019Ahlers et al , 2020Barnes et al 2015;Masuda 2015). In Section 2 we describe the gravity-darkening technique we use to measure KELT-9 b's alignment angle.…”

Section: Introductionmentioning

confidence: 99%

KELT-9 b’s Asymmetric TESS Transit Caused by Rapid Stellar Rotation and Spin–Orbit Misalignment

Ahlers

Johnson

Stassun

et al. 2020

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KELT-9 b is an ultra-hot Jupiter transiting a rapidly rotating, oblate early-A-type star in a polar orbit. We model the effect of rapid stellar rotation on KELT-9 b's transit light curve using photometry from the Transiting Exoplanet Survey Satellite to constrain the planet's true spin-orbit angle and to explore how KELT-9 b may be influenced by stellar gravity darkening. We constrain the host star's equatorial radius to be 1.089±0.017 times as large as its polar radius and its local surface brightness to vary by ∼38% between its hot poles and cooler equator. We model the stellar oblateness and surface brightness gradient and find that it causes the transit light curve to lack the usual symmetry around the time of minimum light. We take advantage of the light-curve asymmetry to constrain KELT-9 b's true spin-orbit angle (- +  87 11 10), agreeing with Gaudi et al. that KELT-9 b is in a nearly polar orbit. We also apply a gravity-darkening correction to the spectral energy distribution model from Gaudi et al. and find that accounting for rapid rotation gives a better fit to available spectroscopy and yields a more reliable estimate for the star's polar effective temperature.

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“…We show the full normalized light curve in Figure 1. We phase-fold the light curve on MASCARA-4 b's orbital period and re-bin at 120 seconds to reduce computation time, following previous gravity-darkening works (Barnes et al 2011;Ahlers et al 2014Ahlers et al , 2015Masuda 2015;Barnes et al 2015;Ahlers et al 2019).…”

Section: Data Processingmentioning

confidence: 99%

“…Dorval et al (2019) previously measured the planet's projected obliquity to be 247.5 •+1.5 • −1.7 • via Doppler tomography. We apply the gravity-darkening technique (Barnes 2009; Barnes et al 2011;Ahlers et al 2014Ahlers et al , 2015Masuda 2015;Barnes et al 2015;Ahlers et al 2019;Zhou et al 2019) to TESS photometry to further constrain the planet's orbit geometry and measure its true spin-orbit angle. Our results match previous observations that close-in giant planets around high-mass stars commonly have misaligned orbits (e.g., Winn et al 2010;Schlaufman 2010).…”

Section: Introductionmentioning

confidence: 99%

Gravity-darkening Analysis of the Misaligned Hot Jupiter MASCARA-4 b

Ahlers

Kruse

Colón

et al. 2020

ApJ

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MASCARA-4 b is a hot Jupiter in a highly-misaligned orbit around a rapidly-rotating A3V star that was observed for 54 days by the Transiting Exoplanet Survey Satellite (TESS ). We perform two analyses of MASCARA-4 b using a stellar gravity-darkened model. First, we measure MASCARA-4 b's misaligned orbital configuration by modeling its TESS photometric light curve. We take advantage of the asymmetry in MASCARA-4 b's transit due to its host star's gravity-darkened surface to measure MASCARA-4 b's true spin-orbit angle to be 104 •+7 • −13 • . We also detect a ∼ 4σ secondary eclipse at 0.491 ± 0.007 orbital phase, proving that the orbit is slightly eccentric. Second, we model MASCARA-4 b's insolation including gravity-darkening and find that the planet's received XUV flux varies by 4% throughout its orbit. MASCARA-4 b's short-period, polar orbit suggests that the planet likely underwent dramatic orbital evolution to end up in its present-day configuration and that it receives a varying stellar irradiance that perpetually forces the planet out of thermal equilibrium. These findings make MASCARA-4 b an excellent target for follow-up characterization to better understand orbital evolution and current-day of planets around high-mass stars.

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Dealing With δ-Scuti Variables: Transit Light Curve Analysis of Planets Orbiting Rapidly Rotating, Seismically Active A/F Stars

Cited by 13 publications

References 72 publications

Spi-OPS: Spitzer and CHEOPS confirm the near-polar orbit of MASCARA-1 b and reveal a hint of dayside reflection

Spi-OPS: Spitzer and CHEOPS confirm the near-polar orbit of MASCARA-1 b and reveal a hint of dayside reflection

KELT-9 b’s Asymmetric TESS Transit Caused by Rapid Stellar Rotation and Spin–Orbit Misalignment

Gravity-darkening Analysis of the Misaligned Hot Jupiter MASCARA-4 b

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