ABSTRACT
We report on the discovery and validation of TOI 813 b (TIC 55525572 b), a transiting exoplanet identified by citizen scientists in data from NASA’s Transiting Exoplanet Survey Satellite ...(TESS) and the first planet discovered by the Planet Hunters TESS project. The host star is a bright (V = 10.3 mag) subgiant ($R_\star =1.94\, R_\odot$, $M_\star =1.32\, M_\odot$). It was observed almost continuously by TESS during its first year of operations, during which time four individual transit events were detected. The candidate passed all the standard light curve-based vetting checks, and ground-based follow-up spectroscopy and speckle imaging enabled us to place an upper limit of $2\, M_{\rm Jup}$ (99 per cent confidence) on the mass of the companion, and to statistically validate its planetary nature. Detailed modelling of the transits yields a period of $83.8911 _{ - 0.0031 } ^ { + 0.0027 }$ d, a planet radius of 6.71 ± 0.38 R⊕ and a semimajor axis of $0.423 _{ - 0.037 } ^ { + 0.031 }$ AU. The planet’s orbital period combined with the evolved nature of the host star places this object in a relatively underexplored region of parameter space. We estimate that TOI 813 b induces a reflex motion in its host star with a semi-amplitude of ∼6 m s−1, making this a promising system to measure the mass of a relatively long-period transiting planet.
The Solar Twin Planet Search Maia, M Tucci; Ramirez, I; Melendez, J ...
Astronomy and astrophysics (Berlin),
6/2016, Volume:
590
Journal Article
Peer reviewed
Context. Solar twins are stars with similar stellar (surface) parameters to the Sun that can have a wide range of ages. This provides an opportunity to analyze the variation of their chemical ...abundances with age. Nissen (2015, A&A, 579, A52) recently suggested that the abundances of the s-process element Y and the alpha-element Mg could be used to estimate stellar ages. Aims. This paper aims to determine with high precision the Y, Mg, and Fe abundances for a sample of 88 solar twins that span a broad age range (0.3-10.0 Gyr) and investigate their use for estimating ages. Methods. We obtained high-quality Magellan Inamori Kyocera Echelle (MIKE) spectra and determined Y and Mg abundances using equivalent widths and a line-by-line differential method within a 1D LTE framework. Stellar parameters and iron abundances were measured in Paper I of this series for all stars, but a few (three) required a small revision. Results. The Y/Mg ratio shows a strong correlation with age. It has a slope of ?0.041 + or - 0.001 dex/Gyr and a significance of 41sigma. This is in excellent agreement with the relation first proposed by Nissen (2015). We found some outliers that turned out to be binaries where mass transfer may have enhanced the yttrium abundance. Given a precise measurement of Y/Mg with typical error of 0.02 dex in solar twins, our formula can be used to determine a stellar age with ~0.8 Gyr precision in the 0 to 10 Gyr range.
ABSTRACT
This work aims to examine in detail the depletion of lithium in solar twins to better constrain stellar evolution models and investigate its possible connection with exoplanets. We employ ...spectral synthesis in the region of the asymmetric 6707.75 Å Li I line for a sample of 77 stars plus the Sun. As in previous works based on a smaller sample of solar twins, we find a strong correlation between Li depletion and stellar age. In addition, for the first time we show that the Sun has the lowest Li abundance in comparison with solar twins at similar age (4.6 ± 0.5 Gyr). We compare the lithium content with the condensation temperature slope for a subsample of the best solar twins and determine that the most lithium-depleted stars also have fewer refractory elements. We speculate whether the low lithium content in the Sun might be related to the particular configuration of our Solar system.
The detection of planets around very low-mass stars with the radial velocity (RV) method is hampered by the fact that these stars are very faint at optical wavelengths where the most high-precision ...spectrometers operate. We investigate the precision that can be achieved in RV measurements of low mass stars in the near-infrared (NIR) Y-, J-, and H-bands, and we compare it to the precision achievable in the optical assuming comparable telescope and instrument efficiencies. For early-M stars, RV measurements in the NIR offer no or only marginal advantage in comparison with optical measurements. Although they emit more flux in the NIR, the richness of spectral features in the optical outweighs the flux difference. We find that NIR measurement can be as precise as optical measurements in stars of spectral type {approx}M4, and from there the NIR gains in precision toward cooler objects. We studied potential calibration strategies in the NIR finding that a stable spectrograph with a ThAr calibration can offer enough wavelength stability for m s{sup -1} precision. Furthermore, we simulate the wavelength-dependent influence of activity (cool spots) on RV measurements from optical to NIR wavelengths. Our spot simulations reveal that the RV jitter does not decrease as dramatically toward longer wavelengths as often thought. The jitter strongly depends on the details of the spots, i.e., on spot temperature and the spectral appearance of the spot. At low temperature contrast ({approx}200 K), the jitter shows a decrease toward the NIR up to a factor of 10, but it decreases substantially less for larger temperature contrasts. Forthcoming NIR spectrographs will allow the search for planets with a particular advantage in mid- and late-M stars. Activity will remain an issue, but simultaneous observations at optical and NIR wavelengths can provide strong constraints on spot properties in active stars.
We present the complete optical transmission spectrum of the hot Jupiter WASP-4b from 440 to 940 nm at R ∼ 400-1500 obtained with the Gemini Multi-Object Spectrometers (GMOS); this is the first ...result from a comparative exoplanetology survey program of close-in gas giants conducted with GMOS. WASP-4b has an equilibrium temperature of 1700 K and is favorable to study in transmission due to its large scale height (370 km). We derive the transmission spectrum of WASP-4b using four transits observed with the MOS technique. We demonstrate repeatable results across multiple epochs with GMOS, and derive a combined transmission spectrum at a precision about twice above photon noise, which is roughly equal to one atmospheric scale height. The transmission spectrum is well fitted with a uniform opacity as a function of wavelength. The uniform opacity and absence of a Rayleigh slope from molecular hydrogen suggest that the atmosphere is dominated by clouds with condensate grain sizes of ∼1 m. This result is consistent with previous observations of hot Jupiters since clouds have been seen in planets with similar equilibrium temperatures to WASP-4b. We describe a custom pipeline that we have written to reduce GMOS time-series data of exoplanet transits, and present a thorough analysis of the dominant noise sources in GMOS, which primarily consist of wavelength- and time-dependent displacements of the spectra on the detector, mainly due to a lack of atmospheric dispersion correction.
Colloidal chemistry holds promise to prepare uniform and size-controllable pre-catalysts; however, it remains a challenge to unveil the atomic-level transition from pre-catalysts to active catalytic ...surfaces under the reaction conditions to enable the mechanistic design of catalysts. Here, we report an ambient-pressure X-ray photoelectron spectroscopy study, coupled with in situ environmental transmission electron microscopy, infrared spectroscopy, and theoretical calculations, to elucidate the surface catalytic sites of colloidal Ni nanoparticles for CO2 hydrogenation. We show that Ni nanoparticles with phosphine ligands exhibit a distinct surface evolution compared with amine-capped ones, owing to the diffusion of P under oxidative (air) or reductive (CO2 + H2) gaseous environments at elevated temperatures. The resulting NiP x surface leads to a substantially improved selectivity for CO production, in contrast to the metallic Ni, which favors CH4. The further elimination of surface metallic Ni sites by designing multi-step P incorporation achieves unit selectivity of CO in high-rate CO2 hydrogenation.
Abstract
We combine Hubble Space Telescope (HST) Fine Guidance Sensor, Hipparcos, and Gaia DR3 astrometric observations of the K0 V star 14 Her with the results of an analysis of extensive ...ground-based radial velocity data to determine perturbation orbits and masses for two previously known companions, 14 Her b and c. Radial velocities obtained with the Hobby–Eberly Telescope and from the literature now span over 25 years. With these data we obtain improved radial velocity (RV) orbital elements for both the inner companion, 14 Her b and the long-period outer companion, 14 Her c. We also find evidence of an additional RV signal with
P
∼ 3789
d
. We then model astrometry from Hipparcos, HST, and Gaia with RV results to obtain system parallax and proper motion, perturbation periods, inclinations, and sizes due to 14 Her b and c. We find
P
b
= 1767.6 ± 0.2 days, perturbation semimajor axis
α
b
= 1.3 ± 0.1 mas, and inclination
i
b
= 36° ± 3°,
P
c
= 52160 ± 1028 days, perturbation semimajor axis
α
c
= 10.3 ± 0.7 mas, and inclination
i
c
= 82° ± 14°. In agreement with a past investigation, the 14 Her b, c orbits exhibit significant mutual inclination. Assuming a primary mass
M
*
= 0.98 ± 0.04
M
☉
, we obtain companion masses
b
=
8.5
−
0.8
+
1.0
Jup
and
c
=
7.1
−
0.6
+
1.0
Jup
.
A simple cosmological model with only six parameters (matter density, Omega sub(m)h super(2), baryon density, Omega sub(b)h super(2), Hubble constant, H sub(0), amplitude of fluctuations, sigma ...sub(8), optical depth, tau , and a slope for the scalar perturbation spectrum, n sub(s)) fits not only the 3 year WMAP temperature and polarization data, but also small-scale CMB data, light element abundances, large-scale structure observations, and the supernova luminosity/distance relationship. Using WMAP data, only, the best-fit values for cosmological parameters for the power-law flat Lambda cold dark matter ( Lambda CDM) model are ( Omega sub(m)h super(2), Omega sub(b)h super(2),h,n sub(s), tau , sigma sub(8)) = (0.1277 super(+0.0080)-0.0079,0.02229 plus or minus 0.00073,0.732 super(+0.031)-0.032,0.958 plus or minus 0.016,0.089 plus or minus 0.030,0.761 super(+0.049)-0.048). The 3 year data dramatically shrink the allowed volume in mis six-dimensional parameter space. Assuming that the primordial fluctuations are adiabatic with a power-law spectrum, the WMAP data alone require dark matter and favor a spectral index that is significantly less than the Harrison-Zel'dovich-Peebles scale-invariant spectrum (n sub(s) = 1, r = 0). Adding additional data sets improves the constraints on these components and the spectral slope. For power-law models, WMAP data alone puts an improved upper limit on the tensor-to-scalar ratio, r sub(0.002) < 0.65 (95% CL) and the combination of WMAP and the lensing-normalized SDSS galaxy survey implies r sub(0.002) < 0.30 (95% CL). Models that suppress large-scale power through a running spectral index or a large-scale cutoff in the power spectrum are a better fit to the WMAP and small-scale CMB data than the power-law Lambda CDM model; however, the improvement in the fit to the WMAP data is only Delta chi super(2) = 3 for 1 extra degree of freedom. Models with a running-spectral index are consistent with a higher amplitude of gravity waves. In a flat universe, the combination of WMAP and the Supernova Legacy Survey (SNLS) data yields a significant constraint on the equation of state of the dark energy, w = -0.967 super(+0.073)-0.072. If we assume w = -1, then the deviations from the critical density, Omega sub(K) are small: the combination of WMAP and the SNLS data implies Omega sub(k) = -0.011 plus or minus 0.012. The combination of WMAP 3 year data plus the HST Key Project constraint on H sub(0) implies Omega sub(k) = -0.014 plus or minus 0.017 and Omega sub( Lambda ) = 0.716 plus or minus 0.055. Even if we do not include the prior that the universe is flat, by combining WMAP, large-scale structure, and supernova data, we can still put a strong constraint on the dark energy equation of state, w = -1.08 plus or minus 0.12. For a flat universe, the combination of WMAP and other astronomical data yield a constraint on the sum of the neutrino masses, capital sigma m sub( upsilon ) < 0.66 eV (95%CL). Consistent with the predictions of simple inflationary theories, we detect no significant deviations from Gaussianity in the CMB maps using Minkowski functionals, the bispectrum, trispectrum, and a new statistic designed to detect large-scale anisotropies in the fluctuations.
The CoRoT satellite is expected to discover tens of new transiting exoplanets during its mission. For each of these planets there will be a resulting long, continuous sequence of transit times that ...can be used to search for perturbations arising from an additional planet in the system. I report the results from a study of the transit times for CoRoT-1b, which was one of the first planets discovered by CoRoT. Analysis of the pipeline-reduced CoRoT light curve yields a new determination of the physical and orbital parameters of planet and star, along with 35 individual transit times at a typical precision of 36 s. I estimate a planet-to-star radius ratio of $R_{\rm p}/R_{\star} = 0.1433$ ± 0.0010, a ratio of the planet's orbital semimajor axis to the host star radius of $a/R_{\star} = 4.751$ ± 0.045, and an orbital inclination for the planet of $i=83.88\degr$ ± $0.29\degr$. The observed transit times are consistent with CoRoT-1b having a constant period and there is no evidence of an additional planet in the system. I use the observed constancy of the transit times to set limits on the mass of a hypothetical additional planet in a nearby, stable orbit. I ascertain that the most stringent limits (4 $M_{\oplus}$ at 3σ confidence) can be placed on planets residing in a 1:2 mean motion resonance with the transiting planet. In contrast, the data yield less stringent limits on planets near a 1:3 mean motion resonance (5 MJup at 3σ confidence) than in the surrounding parameter space. In addition, I use a simulation to investigate what sensitivity to additional planets could be obtained from the analysis of data measured for a similar system during a CoRoT long run (100 sequential transit times). I find that for such a scenario, planets with masses greater than twice that of Mars (0.2 $M_{\oplus}$) in a 1:2 mean motion resonance would cause high-significance transit time deviations. Therefore, such planets could be detected or ruled out using CoRoT long run data. I conclude that CoRoT data will indeed be very useful for searching for planets with the transit timing method.
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