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

Abstract

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.

A First Look at CRIRES+: Performance Assessment and Exoplanet Spectroscopy

“…Likewise, using the H 2 O signal, we obtain K p = 197.8 ± 3.5 and 194.9 ± 3.0 km s −1 , respectively. These values are somewhat different from 204.2 ± 0.2 km s −1 , as calculated using parameters from Hooton et al (2022). Our detection of emission features of CO and H 2 O requires the presence of a temperature inversion in the dayside atmosphere of MASCARA-1 b.…”

“…To demonstrate the on-sky performance of CRIRES+ for exoplanet atmospheric characterization, we conduct a case study of the UHJ MASCARA-1 b (Talens et al 2017;Hooton et al 2022). Previous transmission spectroscopy studies in the optical have found no chemical signatures in the planet's atmosphere (Stangret et al 2022); these studies were made particularly difficult due to the strong Rossiter-McLaughlin effect when searching for key atomic species.…”

“…To further demonstrate the performance and scientific potential of CRIRES+ for atmospheric characterization of exoplanets, we perform a case study of the ultrahot Jupiter (UHJ) MASCARA-1 b observed in thermal emission. MAS-CARA-1 b (also known as HD 201585 b) is one of the hottest known exoplanets, with an equilibrium temperature of 2594 K and orbiting a bright A8 type star (V = 8.3) with a period of 2.15 days (Talens et al 2017;Hooton et al 2022). Here we present the first atmospheric characterization of MASCARA-1 b in search of CO and H 2 O, as well as the potential existence of a temperature inversion.…”

HD 56414 b: A Warm Neptune Transiting an A-type Star

“…Based on the rapid rotational rate of HD 56414, we might expect to see an asymmetrical transit profile due to gravity darkening, which can be modeled to independently measure the true spin-orbit angle (Ψ; Barnes 2009). To test this, we also fit the TESS light curve to a gravity-darkened model following Hooton et al (2022) in which we additionally fit for the stellar inclination (i å ) and sky-projected stellar obliquity (λ). We fixed the stellar polar temperature, stellar equatorial radius, and  v i sin to the median values in Table 1, and fixed the gravitydarkening coefficient β according to Claret (2017).…”

Phase curve and geometric albedo of WASP-43b measured with CHEOPS, TESS, and HST WFC3/UVIS

“…One of the main themes of its science program is the characterization of exoplanet atmospheres (Benz et al 2021). This consists of observations of secondary eclipses of hot Jupiters (e.g., Lendl et al 2020;Hooton et al 2022) across a wide range of temperatures and planetary surface gravities, full or partial phase curves of the most compelling targets (e.g., Deline et al 2022), and detailed observations of ultra-hot super-Earths (e.g., Morris et al 2021).…”