Aims
. We report the discovery and characterisation of the transiting mini-Neptune HD 207496 b (TOI-1099) as part of a large programme that aims to characterise naked core planets.
Methods
. We ...obtained HARPS spectroscopic observations, one ground-based transit, and high-resolution imaging which we combined with the TESS photometry to confirm and characterise the TESS candidate and its host star.
Results
. The host star is an active early K dwarf with a mass of 0.80 ± 0.04
M
⊙
, a radius of 0.769 ± 0.026
R
⊙
, and a
G
magnitude of 8. We found that the host star is young, ~0.52 Gyr, allowing us to gain insight into planetary evolution. We derived a planetary mass of 6.1 ± 1.6
M
⊕
, a planetary radius of 2.25 ± 0.12
R
⊕
, and a planetary density of
ρ
p
= 3.27
−0.91
+0.97
g cm
−3
.
Conclusions
. From internal structure modelling of the planet, we conclude that the planet has either a water-rich envelope, a gas-rich envelope, or a mixture of both. We have performed evaporation modelling of the planet. If we assume the planet has a gas-rich envelope, we find that the planet has lost a significant fraction of its envelope and its radius has shrunk. Furthermore, we estimate it will lose all its remaining gaseous envelope in ~0.52 Gyr. Otherwise, the planet could have already lost all its primordial gas and is now a bare ocean planet. Further observations of its possible atmosphere and/or mass-loss rate would allow us to distinguish between these two hypotheses. Such observations would determine if the planet remains above the radius gap or if it will shrink and be below the gap.
ABSTRACT
We present the results of a spectroscopic campaign on eclipsing binaries with long orbital period (P = 20–75 d) carried out with the CHIRON spectrograph. Physical and orbital solutions for ...seven systems were derived from the V band, and I band ASAS, WASP, and TESS photometry, while radial velocities were calculated from high-quality optical spectra using a two-dimensional cross-correlation technique. The atmospheric parameters of the stars have been determined from the separated spectra. Most of our targets are composed of evolved stars (subgiants or red giants) but two systems show components in different phases of evolution and one possible merger. For four binaries, the masses and radii of the components were obtained with precision better than $3{{\ \rm per\ cent}}$. These objects provide very valuable information on stellar evolution.
We present a fast and efficient hybrid algorithm for selecting exoplanetary candidates from wide-field transit surveys. Our method is based on the widely used SysRem and Box Least-Squares (BLS) ...algorithms. Patterns of systematic error that are common to all stars on the frame are mapped and eliminated using the SysRem algorithm. The remaining systematic errors caused by spatially localized flat-fielding and other errors are quantified using a boxcar-smoothing method. We show that the dimensions of the search-parameter space can be reduced greatly by carrying out an initial BLS search on a coarse grid of reduced dimensions, followed by Newton–Raphson refinement of the transit parameters in the vicinity of the most significant solutions. We illustrate the method's operation by applying it to data from one field of the SuperWASP survey, comprising 2300 observations of 7840 stars brighter than V= 13.0. We identify 11 likely transit candidates. We reject stars that exhibit significant ellipsoidal variations caused indicative of a stellar-mass companion. We use colours and proper motions from the Two Micron All Sky Survey and USNO-B1.0 surveys to estimate the stellar parameters and the companion radius. We find that two stars showing unambiguous transit signals pass all these tests, and so qualify for detailed high-resolution spectroscopic follow-up.
We report the discovery of WASP-8b, a transiting planet of 2.25 ± 0.08 MJup on a strongly inclined eccentric 8.15-day orbit, moving in a retrograde direction to the rotation of its late-G host star. ...Evidence is found that the star is in a multiple stellar system with two other companions. The dynamical complexity of the system indicates that it may have experienced secular interactions such as the Kozai mechanism or a formation that differs from the “classical” disc-migration theory.
We have made a detailed spectral analysis of 11 Wide Angle Search for Planets (WASP) planet host stars using high signal-to-noise ratio (S/N) HARPS spectra. Our line list was carefully selected from ...the spectra of the Sun and Procyon, and we made a critical evaluation of the atomic data. The spectral lines were measured using equivalent widths. The procedures were tested on the Sun and Procyon prior to be being used on the WASP stars. The effective temperature (T
eff), surface gravity (log g), microturbulent velocity (v
mic) and metallicity were determined for all the stars. We show that abundances derived from high S/N spectra are likely to be higher than those obtained from low S/N spectra, as noise can cause the equivalent width to be underestimated. We also show that there is a limit to the accuracy of stellar parameters that can be achieved, despite using high S/N spectra, and the average uncertainty in T
eff, log g, v
mic and metallicity is 83 K, 0.11 dex, 0.11 km s−1 and 0.10 dex, respectively.
ABSTRACT
We report the discovery of a planetary system orbiting TOI-763(aka CD-39 7945), a V = 10.2, high proper motion G-type dwarf star that was photometrically monitored by the TESS space mission ...in Sector 10. We obtain and model the stellar spectrum and find an object slightly smaller than the Sun, and somewhat older, but with a similar metallicity. Two planet candidates were found in the light curve to be transiting the star. Combining TESS transit photometry with HARPS high-precision radial velocity (RV) follow-up measurements confirm the planetary nature of these transit signals. We determine masses, radii, and bulk densities of these two planets. A third planet candidate was discovered serendipitously in the RV data. The inner transiting planet, TOI-763 b, has an orbital period of Pb = 5.6 d, a mass of Mb = 9.8 ± 0.8 M⊕, and a radius of Rb = 2.37 ± 0.10 R⊕. The second transiting planet, TOI-763 c, has an orbital period of Pc = 12.3 d, a mass of Mc = 9.3 ± 1.0 M⊕, and a radius of Rc = 2.87 ± 0.11 R⊕. We find the outermost planet candidate to orbit the star with a period of ∼48 d. If confirmed as a planet, it would have a minimum mass of Md = 9.5 ± 1.6 M⊕. We investigated the TESS light curve in order to search for a mono transit by planet d without success. We discuss the importance and implications of this planetary system in terms of the geometrical arrangements of planets orbiting G-type stars.
We report the discovery of a hot Jupiter on a 3.28-day orbit around a 1.08
M
⊙
G0 star that is the secondary component in a loose binary system. Based on follow-up radial velocity observations of ...TOI-858 B with CORALIE on the Swiss 1.2 m telescope and CHIRON on the 1.5 m telescope at the Cerro Tololo Inter-American Observatory (CTIO), we measured the planet mass to be 1.10
−0.07
+0.08
M
J
. Two transits were further observed with CORALIE to determine the alignment of TOI-858 B b with respect to its host star. Analysis of the Rossiter-McLaughlin signal from the planet shows that the sky-projected obliquity is
λ
= 99.3
−3.7
+3.8°
. Numerical simulations show that the neighbour star TOI-858 A is too distant to have trapped the planet in a Kozai–Lidov resonance, suggesting a different dynamical evolution or a primordial origin to explain this misalignment. The 1.15
M
⊙
primary F9 star of the system (TYC 8501-01597-1, at
ρ
~11″) was also observed with CORALIE in order to provide upper limits for the presence of aplanetary companion orbiting that star.
We report the discovery of two new transiting planets from the WASP survey. WASP-42 b is a 0.500 ± 0.035 MJ planet orbiting a K1 star at a separation of 0.0548 ± 0.0017 AU with a period of ...4.9816872 ± 7.3 × 10-6 days. The radius of WASP-42 b is 1.080 ± 0.057 RJ while its equilibrium temperature is Teq = 995 ± 34 K. We detect some evidence for a small but non-zero eccentricity of e = 0.060 ± 0.013. WASP-49 b is a 0.378 ± 0.027 MJ planet around an old G6 star. It has a period of 2.7817387 ± 5.6 × 10-6 days and a separation of 0.0379 ± 0.0011 AU. This planet is slightly bloated, having a radius of 1.115 ± 0.047 RJ and an equilibrium temperature of Teq = 1369 ± 39 K. Both planets have been followed up photometrically, and in total we have obtained 5 full and one partial transit light curves of WASP-42 and 4 full and one partial light curves of WASP-49 using the Euler-Swiss, TRAPPIST and Faulkes South telescopes.
We report the discovery and tomographic detection of WASP-174b, a planet with a near-grazing transit on a 4.23-d orbit around a V= 11.9, F6V star with Fe/H = 0.09 ± 0.09. The planet is in a ...moderately misaligned orbit with a sky-projected spin-orbit angle of λ = 31° ± 1°. This is in agreement with the known tendency for orbits around hotter stars to be misaligned. Owing to the grazing transit, the planet's radius is uncertain with a possible range of 0.8-1.8 RSUBJup/SUB. The planet's mass has an upper limit of 1.3 MSUBJup/SUB. WASP-174 is the faintest hot-Jupiter system so far confirmed by tomographic means.
Context. AI Phe is a double-lined, detached eclipsing binary, in which a K-type sub-giant star totally eclipses its main-sequence companion every 24.6 days. This configuration makes AI Phe ideal for ...testing stellar evolutionary models. Difficulties in obtaining a complete lightcurve mean the precision of existing radii measurements could be improved. Aims. Our aim is to improve the precision of the radius measurements for the stars in AI Phe using high-precision photometry from the Wide Angle Search for Planets (WASP), and use these improved radius measurements together with estimates of the masses, temperatures and composition of the stars to place constraints on the mixing length, helium abundance and age of the system. Methods. A best-fit ebop model is used to obtain lightcurve parameters, with their standard errors calculated using a prayer-bead algorithm. These were combined with previously published spectroscopic orbit results, to obtain masses and radii. A Bayesian method is used to estimate the age of the system for model grids with different mixing lengths and helium abundances. Results. The radii are found to be R1 = 1.835 ± 0.014 R⊙, R2 = 2.912 ± 0.014 R⊙ and the masses M1 = 1.1973 ± 0.0037 M⊙, M2 = 1.2473 ± 0.0039 M⊙. From the best-fit stellar models we infer a mixing length of 1.78, a helium abundance of YAI = 0.26 +0.02-0.01 and an age of 4.39 ± 0.32 Gyr. Times of primary minimum show the period of AI Phe is not constant. Currently, there are insufficient data to determine the cause of this variation. Conclusions. Improved precision in the masses and radii have improved the age estimate, and allowed the mixing length and helium abundance to be constrained. The eccentricity is now the largest source of uncertainty in calculating the masses. Further work is needed to characterise the orbit of AI Phe. Obtaining more binaries with parameters measured to a similar level of precision would allow us to test for relationships between helium abundance and mixing length.
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