With the continuous improvement in the precision of exoplanet observations, it has become feasible to probe for subtle effects that can enable a more comprehensive characterization of exoplanets. A ...notable example is the tidal deformation of ultra-hot Jupiters by their host stars, whose detection can provide valuable insights into the planetary interior structure. In this work we extend previous research on modeling deformation in transit light curves by proposing a straightforward approach to account for tidal deformation in phase curve observations. The planetary shape is modeled as a function of the second fluid Love number for radial deformation
h
2
f
. For a planet in hydrostatic equilibrium,
h
2
f
provides constraints on the interior structure of the planet. We show that the effect of tidal deformation manifests across the full orbit of the planet as its projected area varies with phase, thereby allowing us to better probe the planet’s shape in phase curves than in transits. Comparing the effects and detectability of deformation by different space-based instruments (JWST, HST, PLATO, CHEOPS, and TESS), we find that the effect of deformation is more prominent in infrared observations where the phase curve amplitude is the largest. A single JWST phase curve observation of a deformed planet, such as WASP-12 b, can allow up to a 17
σ
measurement of
h
2
f
compared to 4
σ
from transit-only observation. This high-precision
h
2
f
measurement can constrain the core mass of the planet to within 19% of the total mass, thus providing unprecedented constraints on the interior structure. Due to the lower phase curve amplitudes in the optical, the other instruments provide ≤ 4
σ
precision on
h
2
f
depending on the number of phase curves observed. We also find that detecting deformation from infrared phase curves is less affected by uncertainty in limb darkening, unlike detection in transits. Finally, the assumption of sphericity when analyzing the phase curve of deformed planets can lead to biases in several system parameters (radius, dayside and nightside temperatures, and hotspot offset, among others), thereby significantly limiting their accurate characterization.
ABSTRACT
We set out to look at the overlap between CHaracterizing ExOPlanets Satellite (CHEOPS) sky coverage and Transiting Exoplanet Survey Satellite (TESS) primary mission monotransits to determine ...what fraction of TESS monotransits may be observed by CHEOPS. We carry out a simulation of TESS transits based on the stellar population in TICv8 in the primary TESS mission. We then select the monotransiting candidates and determine their CHEOPS observing potential. We find that TESS will discover approximately 433 monotransits during its primary mission. Using a baseline observing efficiency of 40 per cent, we then find that 387 of these (∼89 per cent) will be observable by CHEOPS with an average observing time of ∼60 d yr−1. Based on the individual observing times and orbital periods of each system, we predict that CHEOPS could observe additional transits for approximately 302 of the 433 TESS primary mission monotransits (∼70 per cent). Given that CHEOPS will require some estimate of period before observing a target, we estimate that up to 250 (∼58 per cent) TESS primary mission monotransits could have solved periods prior to CHEOPS observations using a combination of photometry and spectroscopy.
Aims.
We investigate the atmospheric composition of the long-period (
P
orb
= 10 days) eccentric exo-Saturn WASP-117b. WASP-117b could be similar in atmospheric temperature and chemistry to ...WASP-107b. In mass and radius, WASP-117b is similar to WASP-39b, which allows a comparative study of these planets.
Methods.
We analyzed a near-infrared transmission spectrum of WASP-117b taken with the
Hubble
Space Telescope (HST) WFC3 G141, which was reduced with two independent pipelines. High-resolution measurements were taken with VLT/ESPRESSO in the optical.
Results.
We report the robust (3
σ
) detection of a water spectral feature. In a 1D atmosphere model with isothermal temperature, uniform cloud deck, and equilibrium chemistry, the Bayesian evidence of a retrieval analysis of the transmission spectrum indicates a preference for a high atmospheric metallicity Fe/H = 2.58
−0.37
+0.26
and clear skies. The data are also consistent with a lower metallicity composition Fe/H < 1.75 and a cloud deck between 10
−2.2
and 10
−5.1
bar, but with weaker Bayesian preference. We retrieve a low CH
4
abundance of <10
−4
volume fraction within 1
σ
and <2 × 10
−1
volume fraction within 3
σ
. We cannot constrain the equilibrium temperature between theoretically imposed limits of 700 and 1000 K. Further observations are needed to confirm quenching of CH
4
with
K
zz
≥ 10
8
cm
2
s
−1
. We report indications of Na and K in the VLT/ESPRESSO high-resolution spectrum with substantial Bayesian evidence in combination with HST data.
We report the discovery of two hot-Jupiter planets, each orbiting one of the stars of a wide binary system. WASP-94A (2MASS 20550794–3408079) is an F8 type star hosting a transiting planet with a ...radius of 1.72 ± 0.06 RJup, a mass of 0.452 ± 0.034 MJup, and an orbital period of 3.95 days. The Rossiter-McLaughlin effect is clearly detected, and the measured projected spin-orbit angle indicates that the planet occupies a retrograde orbit. WASP-94B (2MASS 20550915–3408078) is an F9 stellar companion at an angular separation of 15′′ (projected separation 2700 au), hosting a gas giant with a minimum mass of 0.618 ± 0.028 MJup with a period of 2.008 days, detected by Doppler measurements. The orbital planes of the two planets are inclined relative to each other, indicating that at least one of them is inclined relative to the plane of the stellar binary. These hot Jupiters in a binary system bring new insights into the formation of close-in giant planets and the role of stellar multiplicity.
Massive companions in close orbits around G dwarfs are thought to undergo rapid orbital decay due to runaway tidal dissipation. We report here the discovery of WASP-128b, a brown dwarf discovered by ...the WASP survey transiting a G0V host on a 2.2 d orbit, where the measured stellar rotation rate places the companion in a regime where tidal interaction is dominated by dynamical tides. Under the assumption of dynamical equilibrium, we derive a value of the stellar tidal quality factor log {Q_\star ^' }} = {6.96 ± 0.19}. A combined analysis of ground-based photometry and high-resolution spectroscopy reveals a mass and radius of the host, MSUB⋆/SUB = 1.16 ± 0.04MSUB⊙/SUB, RSUB⋆/SUB = 1.16 ± 0.02RSUB⊙/SUB, and for the companion, MSUBb/SUB = 37.5 ± 0.8Mj, RSUBb/SUB = 0.94 ± 0.02Rj, placing WASP-128b in the driest parts of the brown dwarf desert, and suggesting a mild inflation for its age. We estimate a remaining lifetime for WASP-128b similar to that of some ultra-short period massive hot Jupiters, and note it may be a propitious candidate for measuring orbital decay and testing tidal theories.
ABSTRACT We report the discovery of three new transiting hot Jupiters by WASP-South together with the TRAPPIST photometer and the Euler/CORALIE spectrograph. WASP-74b orbits a star of V = 9.7, making ...it one of the brighter systems accessible to southern telescopes. It is a 0.95MJup planet with a moderately bloated radius of 1.5 in a 2 day orbit around a slightly evolved F9 star. WASP-83b is a Saturn-mass planet at 0.3 with a radius of 1.0 . It is in a 5 day orbit around a fainter (V = 12.9) G8 star. WASP-89b is a 6 MJup planet in a 3 day orbit with an eccentricity of e = 0.2. It is thus similar to massive, eccentric planets such as XO-3b and HAT-P-2b, except that those planets orbit F stars whereas WASP-89 is a K star. The V = 13.1 host star is magnetically active, showing a rotation period of 20.2 days, while star spots are visible in the transits. There are indications that the planet's orbit is aligned with the stellar spin. WASP-89 is a good target for an extensive study of transits of star spots.
WASP-80b has a dayside within the T-dwarf range Triaud, Amaury H. M. J; Gillon, Michaël; Ehrenreich, David ...
Monthly notices of the Royal Astronomical Society,
07/2015, Letnik:
450, Številka:
3
Journal Article, Web Resource
Recenzirano
Odprti dostop
WASP-80b is a missing link in the study of exoatmospheres. It falls between the warm Neptunes and the hot Jupiters and is amenable for characterization, thanks to its host star's properties. We ...observed the planet through transit and during occultation with Warm Spitzer. Combining our mid-infrared transits with optical time series, we find that the planet presents a transmission spectrum indistinguishable from a horizontal line. In emission, WASP-80b is the intrinsically faintest planet whose dayside flux has been detected in both the 3.6 and 4.5 μm Spitzer channels. The depths of the occultations reveal that WASP-80b is as bright and as red as a T4 dwarf, but that its temperature is cooler. If planets go through the equivalent of an L–T transition, our results would imply that this happens at cooler temperatures than for brown dwarfs. Placing WASP-80b's dayside into a colour–magnitude diagram, it falls exactly at the junction between a blackbody model and the T-dwarf sequence; we cannot discern which of those two interpretations is the more likely. WASP-80b's flux density is as low as GJ 436b at 3.6 μm; the planet's dayside is also fainter, but bluer than HD 189733Ab's nightside (in the 3.6 and 4.5Spitzer bands). Flux measurements on other planets with similar equilibrium temperatures are required to establish whether irradiated gas giants, such as brown dwarfs, transition between two spectral classes. An eventual detection of methane absorption in transmission would also help lift that degeneracy. We obtained a second series of high-resolution spectra during transit, using HARPS. We reanalyse the Rossiter–McLaughlin effect. The data now favour an aligned orbital solution and a stellar rotation nearly three times slower than stellar line broadening implies. A contribution to stellar line broadening, maybe macroturbulence, is likely to have been underestimated for cool stars, whose rotations have therefore been systematically overestimated.
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.
Planets around stars in the solar neighbourhood will be prime targets for characterisation with upcoming large space- and ground-based facilities. Since large-scale exoplanet searches will ...not be feasible with such telescopes, it is crucial to use currently available data and instruments to find possible target planets before next-generation facilities come online.
Aims.
We aim to detect new extrasolar planets around stars in the solar neighbourhood via blind radial velocity (RV) searching with ESPRESSO. Our target sample consists of nearby stars (
d
< 11 pc) with few (<10) or no previous RV measurements.
Methods.
We used 31 radial velocity measurements obtained with ESPRESSO at the VLT between December 2020 and February 2022 of the nearby M dwarf star (
M
★
= 0.21
M
⊙
,
d
= 10.23 pc) L 363-38 to derive the orbital parameters of the newly discovered planet. In addition, we used TESS photometry and archival VLT/NaCo high-contrast imaging data to put further constraints on the orbit inclination and the possible planetary system architecture around L 363-38.
Results.
We present the detection of a new extrasolar planet orbiting the nearby M dwarf star L 363-38. L 363-38 b is a planet with a minimum mass of
m
p
sin(
i
) = 4.67 ± 0.43
M
⊕
orbiting its star with a period of
P
= 8.781 ± 0.007 days, corresponding to a semi-major axis of
a
= 0.048 ± 0.006 AU, which is smaller than the inner edge of the habitable zone. We further estimate a minimum radius of
r
p
sin(
i
) ≈ 1.55–2.75
R
⊕
and an equilibrium temperature of
T
eq
≈ 330 K.
Conclusions.
With this study, we further demonstrate the potential of the state-of-the-art spectrograph ESPRESSO in detecting and investigating planetary systems around nearby M dwarf stars, which were inaccessible to previous instruments such HARPS.
Context.
Ultra-hot Jupiters (UHJs), rendering the hottest planetary atmospheres, offer great opportunities of detailed characterisation with high-resolution spectroscopy. MASCARA-4 b is a recently ...discovered close-in gas giant belonging to this category.
Aims.
We aim to characterise MASCARA-4 b, search for chemical species in its atmosphere, and put these in the context of the growing knowledge on the atmospheric properties of UHJs.
Methods.
In order to refine system and planet parameters, we carried out radial velocity measurements and transit photometry with the CORALIE spectrograph and EulerCam at the Swiss 1.2 m Euler telescope. We observed two transits of MASCARA-4 b with the high-resolution spectrograph ESPRESSO at ESO’s Very Large Telescope. We searched for atomic, ionic, and molecular species via individual absorption lines and cross-correlation techniques. These results are compared to literature studies on UHJs characterised to date.
Results.
With CORALIE and EulerCam observations, we update the mass of MASCARA-4 b (
M
p
= 1.675 ± 0.241
M
Jup
) as well as other system and planet parameters. In the transmission spectrum derived from ESPRESSO observations, we resolve excess absorption by H
α
, H
β
, NaI D1&D2, CaII H&K, and a few strong lines of MgI, FeI, and FeII. We also present the cross-correlation detection of Mg I, CaI, Cr I, Fe I, and Fe II. The absorption strength of Fe II significantly exceeds the prediction from a hydrostatic atmospheric model, as commonly observed in other UHJs. We attribute this to the presence of Fe II in the exosphere due to hydrodynamic outflows. This is further supported by the positive correlation of absorption strengths of Fe II with the Hα line, which is expected to probe the extended upper atmosphere and the mass loss process. Comparing transmission signatures of various species in the UHJ population allows us to disentangle the hydrostatic regime (as traced via the absorption by Mg I and Fe I) from the exospheres (as probed by Hα and Fe II) of the strongly irradiated atmospheres.
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