Super-Earths transiting nearby bright stars are key objects that simultaneously allow for accurate measurements of both their mass and radius, providing essential constraints on their internal ...composition. We present here the confirmation, based on Spitzer transit observations, that the super-Earth HD 97658 b transits its host star. HD 97658 is a low-mass (M sub(*) = 0.77 + or - 0.05 M sub(middot in circle)) K1 dwarf, as determined from the Hipparcos parallax and stellar evolution modeling. To constrain the planet parameters, we carry out Bayesian global analyses of Keck-High Resolution Echelle Spectrometer (Keck-HIRES) radial velocities and Microvariability and Oscillations of STars (MOST) and Spitzer photometry. HD 97658 b is a massive (MP = 7.55 super(+0.83) sub(-0.79) M sub(+ in circle))) and large (RP = 2.247 super(+0.098) sub(-0.095) R sub(+ in circle) at 4.5 mum) super-Earth. We investigate the possible internal compositions for HD 97658 b. Our results indicate a large rocky component, of at least 60% by mass, and very little H-He components, at most 2% by mass. We also discuss how future asteroseismic observations can improve the knowledge of the HD 97658 system, in particular by constraining its age. Orbiting a bright host star, HD 97658 b will be a key target for upcoming space missions such as the Transiting Exoplanet Survey Satellite (TESS), the Characterizing Exoplanet Satellite (CHEOPS), the Planetary Transits and Oscillations of stars (PLATO), and the James Webb Space Telescope to characterize thoroughly its structure and atmosphere.
ABSTRACT
CHEOPS (CHaracterising ExOPlanet Satellite) is an ESA S-class mission that observes bright stars at high cadence from low-Earth orbit. The main aim of the mission is to characterize ...exoplanets that transit nearby stars using ultrahigh precision photometry. Here, we report the analysis of transits observed by CHEOPS during its Early Science observing programme for four well-known exoplanets: GJ 436 b, HD 106315 b, HD 97658 b, and GJ 1132 b. The analysis is done using pycheops, an open-source software package we have developed to easily and efficiently analyse CHEOPS light-curve data using state-of-the-art techniques that are fully described herein. We show that the precision of the transit parameters measured using CHEOPS is comparable to that from larger space telescopes such as Spitzer Space Telescope and Kepler. We use the updated planet parameters from our analysis to derive new constraints on the internal structure of these four exoplanets.
We report the discovery by the TESS mission of a super-Earth on a 4.8-days orbit around an inactive M4.5 dwarf (TOI-1680), validated by ground-based facilities. The host star is located 37.14 pc ...away, with a radius of 0.2100 ± 0.0064
R
⊙
, mass of 0.1800 ± 0.0044
M
⊙
, and an effective temperature of 3211 ±100 K. We validated and characterized the planet using TESS data, ground-based multi-wavelength photometry from TRAPPIST, SPECULOOS, and LCO, as well as high-resolution AO observations from Keck/NIRC2 and
Shane.
Our analyses have determined the following parameters for the planet: a radius of 1.466
−0.049
+0.063
R
⊕
and an equilibrium temperature of 404 ± 14 K, assuming no albedo and perfect heat redistribution. Assuming a mass based on mass-radius relations, this planet is a promising target for atmospheric characterization with the
James Webb
Space Telescope (JWST).
The CHEOPS mission Benz, W.; Broeg, C.; Fortier, A. ...
Experimental astronomy,
2021, Letnik:
51, Številka:
1
Journal Article, Web Resource
Recenzirano
Odprti dostop
The CHaracterising ExOPlanet Satellite (CHEOPS) was selected on October 19, 2012, as the first small mission (S-mission) in the ESA Science Programme and successfully launched on December 18, 2019, ...as a secondary passenger on a Soyuz-Fregat rocket from Kourou, French Guiana. CHEOPS is a partnership between ESA and Switzerland with important contributions by ten additional ESA Member States. CHEOPS is the first mission dedicated to search for transits of exoplanets using ultrahigh precision photometry on bright stars already known to host planets. As a follow-up mission, CHEOPS is mainly dedicated to improving, whenever possible, existing radii measurements or provide first accurate measurements for a subset of those planets for which the mass has already been estimated from ground-based spectroscopic surveys. The expected photometric precision will also allow CHEOPS to go beyond measuring only transits and to follow phase curves or to search for exo-moons, for example. Finally, by unveiling transiting exoplanets with high potential for in-depth characterisation, CHEOPS will also provide prime targets for future instruments suited to the spectroscopic characterisation of exoplanetary atmospheres. To reach its science objectives, requirements on the photometric precision and stability have been derived for stars with magnitudes ranging from 6 to 12 in the V band. In particular, CHEOPS shall be able to detect Earth-size planets transiting G5 dwarf stars (stellar radius of 0.9
R
⊙
) in the magnitude range 6 ≤
V
≤ 9 by achieving a photometric precision of 20 ppm in 6 hours of integration time. In the case of K-type stars (stellar radius of 0.7
R
⊙
) of magnitude in the range 9 ≤
V
≤ 12, CHEOPS shall be able to detect transiting Neptune-size planets achieving a photometric precision of 85 ppm in 3 hours of integration time. This precision has to be maintained over continuous periods of observation for up to 48 hours. This precision and stability will be achieved by using a single, frame-transfer, back-illuminated CCD detector at the focal plane assembly of a 33.5 cm diameter, on-axis Ritchey-Chrétien telescope. The nearly 275 kg spacecraft is nadir-locked, with a pointing accuracy of about 1 arcsec rms, and will allow for at least 1 Gbit/day downlink. The sun-synchronous dusk-dawn orbit at 700 km altitude enables having the Sun permanently on the backside of the spacecraft thus minimising Earth stray light. A mission duration of 3.5 years in orbit is foreseen to enable the execution of the science programme. During this period, 20% of the observing time is available to the wider community through yearly ESA call for proposals, as well as through discretionary time approved by ESA’s Director of Science. At the time of this writing, CHEOPS commissioning has been completed and CHEOPS has been shown to fulfill all its requirements. The mission has now started the execution of its science programme.
We present the detection of three exoplanets orbiting the early M dwarf TOI-663 (TIC 54962195; V = 13.7 mag, J = 10.4 mag, R ★ = 0.512 ± 0.015 R ⊙ , M ★ = 0.514 ± 0.012 M ⊙ , d = 64 pc). TOI-663 b, ...c, and d, with respective radii of 2.27 ± 0.10 R ⊕ , 2.26 ± 0.10 R ⊕ , and 1.92 ± 0.13 R ⊕ and masses of 4.45 ± 0.65 M ⊕ , 3.65 ± 0.97 M ⊕ , and <5.2 M ⊕ at 99%, are located just above the radius valley that separates rocky and volatile-rich exoplanets. The planet candidates are identified in two TESS sectors and are validated with ground-based photometric follow-up, precise radial-velocity measurements, and high-resolution imaging. We used the software package juliet to jointly model the photometric and radial-velocity datasets, with Gaussian processes applied to correct for systematics. The three planets discovered in the TOI-663 system are low-mass mini-Neptunes with radii significantly larger than those of rocky analogs, implying that volatiles, such as water, must predominate. In addition to this internal structure analysis, we also performed a dynamical analysis that confirmed the stability of the system. The three exoplanets in the TOI-663 system, similarly to other sub-Neptunes orbiting M dwarfs, have been found to have lower densities than planets of similar sizes orbiting stars of different spectral types.
Context.
Gas giants orbiting close to hot and massive early-type stars can reach dayside temperatures that are comparable to those of the coldest stars. These ‘ultra-hot Jupiters’ have atmospheres ...made of ions and atomic species from molecular dissociation and feature strong day-to-night temperature gradients. Photometric observations at different orbital phases provide insights on the planet’s atmospheric properties.
Aims.
We aim to analyse the photometric observations of WASP-189 acquired with the Characterising Exoplanet Satellite (CHEOPS) to derive constraints on the system architecture and the planetary atmosphere.
Methods.
We implemented a light-curve model suited for an asymmetric transit shape caused by the gravity-darkened photosphere of the fast-rotating host star. We also modelled the reflective and thermal components of the planetary flux, the effect of stellar oblateness and light-travel time on transit-eclipse timings, the stellar activity, and CHEOPS systematics.
Results.
From the asymmetric transit, we measure the size of the ultra-hot Jupiter WASP-189 b, R
p
= 1.600
−0.016
+0.017
R
J
, with a precision of 1%, and the true orbital obliquity of the planetary system, Ψ
p
= 89.6 ± 1.2deg (polar orbit). We detect no significant hotspot offset from the phase curve and obtain an eclipse depth of δ
ecl
= 96.5
−5.0
+4.5
ppm, from which we derive an upper limit on the geometric albedo:
A
g
< 0.48. We also find that the eclipse depth can only be explained by thermal emission alone in the case of extremely inefficient energy redistribution. Finally, we attribute the photometric variability to the stellar rotation, either through superficial inhomogeneities or resonance couplings between the convective core and the radiative envelope.
Conclusions.
Based on the derived system architecture, we predict the eclipse depth in the upcoming Transiting Exoplanet Survey Satellite (TESS) observations to be up to ~165 ppm. High-precision detection of the eclipse in both CHEOPS and TESS passbands might help disentangle reflective and thermal contributions. We also expect the right ascension of the ascending node of the orbit to precess due to the perturbations induced by the stellar quadrupole moment
J
2
(oblateness).
Context.
Refraction deflects photons that pass through atmospheres, which affects transit light curves. Refraction thus provides an avenue to probe physical properties of exoplanet atmospheres and to ...constrain the presence of clouds and hazes. In addition, an effective surface can be imposed by refraction, thereby limiting the pressure levels probed by transmission spectroscopy.
Aims.
The main objective of the paper is to model the effects of refraction on photometric light curves for realistic planets and to explore the dependencies on atmospheric physical parameters. We also explore under which circumstances transmission spectra are significantly affected by refraction. Finally, we search for refraction signatures in photometric residuals in
Kepler
data.
Methods.
We use the model of Hui & Seager (2002, ApJ, 572, 540) to compute deflection angles and refraction transit light curves, allowing us to explore the parameter space of atmospheric properties. The observational search is performed by stacking large samples of transit light curves from
Kepler
.
Results.
We find that out-of-transit refraction shoulders are the most easily observable features, which can reach peak amplitudes of ~10 parts per million (ppm) for planets around Sun-like stars. More typical amplitudes are a few ppm or less for Jovians and at the sub-ppm level for super-Earths. In-transit, ingress, and egress refraction features are challenging to detect because of the short timescales and degeneracies with other transit model parameters. Interestingly, the signal-to-noise ratio of any refraction residuals for planets orbiting Sun-like hosts are expected to be similar for planets orbiting red dwarfs and ultra-cool stars. We also find that the maximum depth probed by transmission spectroscopy is not limited by refraction for weakly lensing planets, but that the incidence of refraction can vary significantly for strongly lensing planets. We find no signs of refraction features in the stacked
Kepler
light curves, which is in agreement with our model predictions.
Context . Multiwavelength photometry of the secondary eclipses of extrasolar planets is able to disentangle the reflected and thermally emitted light radiated from the planetary dayside. Based on ...this, we can measure the planetary geometric albedo A g , which is an indicator of the presence of clouds in the atmosphere, and the recirculation efficiency ϵ , which quantifies the energy transport within the atmosphere. Aims . We measure A g and ϵ for the planet WASP-178 b, a highly irradiated giant planet with an estimated equilibrium temperature of 2450 K. Methods . We analyzed archival spectra and the light curves collected by CHEOPS and TESS to characterize the host WASP-178, refine the ephemeris of the system, and measure the eclipse depth in the passbands of the two telescopes. Results . We measured a marginally significant eclipse depth of 70 ± 40 ppm in the TESS passband, and a statistically significant depth of 70 ± 20 ppm in the CHEOPS passband. Conclusions . Combining the eclipse-depth measurement in the CHEOPS ( λ eff = 6300 Å) and TESS ( λ eff = 8000 Å) passbands, we constrained the dayside brightness temperature of WASP-178 b in the 2250–2800 K interval. The geometric albedo 0.1< A g <0.35 generally supports the picture that giant planets are poorly reflective, while the recirculation efficiency ϵ >0.7 makes WASP-178 b an interesting laboratory for testing the current heat-recirculation models.
Since 1998, a planet-search program around main sequence stars within 50 pc in the southern hemisphere has been carried out with the CORALIE echelle spectrograph at La Silla Observatory. With an ...observing time span of more than 14 years, the CORALIE survey is now able to unveil Jovian planets on Jupiter's period domain. This growing period-interval coverage is important for building formation and migration models since observational constraints are still weak fir periods beyond the ice line. Long-term, precise Doppler measurements with the CORALIE echelle spectrograph, together with a few additional observations made with the HARPS spectrograph on the ESO 3.6m telescope, reveal radial velocity signatures of massive planetary companions on long-period orbits. In this paper we present seven new planets orbiting HD27631, HD98649, HD 106515A, HD166724, HD196067, HD219077, and HD220689, together with the CORALIE orbital parameters for three already known planets around HD10647, HD30562, and HD86226. Finally, the hosts of these long period planets show no metallicity excess.
Context.
Ultra-short period planets undergo strong tidal interactions with their host star which lead to planet deformation and orbital tidal decay.
Aims.
WASP-103b is the exoplanet with the highest ...expected deformation signature in its transit light curve and one of the shortest expected spiral-in times. Measuring the tidal deformation of the planet would allow us to estimate the second degree fluid Love number and gain insight into the planet’s internal structure. Moreover, measuring the tidal decay timescale would allow us to estimate the stellar tidal quality factor, which is key to constraining stellar physics.
Methods.
We obtained 12 transit light curves of WASP-103b with the CHaracterising ExOplanet Satellite (CHEOPS) to estimate the tidal deformation and tidal decay of this extreme system. We modelled the high-precision CHEOPS transit light curves together with systematic instrumental noise using multi-dimensional Gaussian process regression informed by a set of instrumental parameters. To model the tidal deformation, we used a parametrisation model which allowed us to determine the second degree fluid Love number of the planet. We combined our light curves with previously observed transits of WASP-103b with the
Hubble
Space Telescope (HST) and
Spitzer
to increase the signal-to-noise of the light curve and better distinguish the minute signal expected from the planetary deformation.
Results.
We estimate the radial Love number of WASP-103b to be h
f
= 1.59
−0.53
+0.45
. This is the first time that the tidal deformation is directly detected (at 3
σ
) from the transit light curve of an exoplanet. Combining the transit times derived from CHEOPS, HST, and
Spitzer
light curves with the other transit times available in the literature, we find no significant orbital period variation for WASP-103b. However, the data show a hint of an orbital period increase instead of a decrease, as is expected for tidal decay. This could be either due to a visual companion star if this star is bound, the Applegate effect, or a statistical artefact.
Conclusions.
The estimated Love number of WASP-103b is similar to Jupiter’s. This will allow us to constrain the internal structure and composition of WASP-103b, which could provide clues on the inflation of hot Jupiters. Future observations with
James Webb
Space Telescope can better constrain the radial Love number of WASP-103b due to their high signal-to-noise and the smaller signature of limb darkening in the infrared. A longer time baseline is needed to constrain the tidal decay in this system.
PDF
