In this paper, we present observations of two high-resolution transit datasets obtained with ESPRESSO of the bloated sub-Saturn planet WASP-131~b. We have simultaneous photometric observations with ...NGTS and EulerCam. In addition, we utilised photometric lightcurves from {\tess}, WASP, EulerCam and TRAPPIST of multiple transits to fit for the planetary parameters and update the ephemeris. We spatially resolve the stellar surface of WASP-131 utilising the Reloaded Rossiter McLaughlin technique to search for centre-to-limb convective variations, stellar differential rotation, and to determine the star-planet obliquity for the first time. We find WASP-131 is misaligned on a nearly retrograde orbit with a projected obliquity of \(\lambda = 162.4\substack{+1.3 \\ -1.2}^{\circ}\). In addition, we determined a stellar differential rotation shear of \(\alpha = 0.61 \pm 0.06\) and disentangled the stellar inclination (\(i_* = 40.9\substack{+13.3 \\ -8.5}^{\circ}\)) from the projected rotational velocity, resulting in an equatorial velocity of \(v_{\rm{eq}} = 7.7\substack{+1.5 \\ -1.3}\)~km s\(^{-1}\). In turn, we determined the true 3D obliquity of \(\psi = 123.7\substack{+12.8 \\ -8.0}^{\circ}\), meaning the planet is on a perpendicular/polar orbit. Therefore, we explored possible mechanisms for the planetary system's formation and evolution. Finally, we searched for centre-to-limb convective variations where there was a null detection, indicating that centre-to-limb convective variations are not prominent in this star or are hidden within red noise.
We analyse spectroscopic and photometric transits of the hot Jupiters WASP-52b and HAT-P30b obtained with ESPRESSO, Eulercam and NGTS for both targets, and additional TESS data for HAT-P-30. Our goal ...is to update the system parameters and refine our knowledge of the host star surfaces. For WASP-52, the companion planet has occulted starspots in the past, and as such our aim was to use the reloaded Rossiter-McLaughlin technique to directly probe its starspot properties. Unfortunately, we find no evidence for starspot occultations in the datasets herein. Additionally, we searched for stellar surface differential rotation (DR) and any centre-to-limb variation (CLV) due to convection, but return a null detection of both. This is unsurprising for WASP-52, given its relatively cool temperature, high magnetic activity (which leads to lower CLV), and projected obliquity near 0 degrees (meaning the transit chord is less likely to cross several stellar latitudes). For HAT-P-30, this result was more surprising given its hotter effective temperature, lower magnetic field, and high projected obliquity (near 70 degrees). To explore the reasons behind the null DR and CLV detection for HAT-P-30, we simulated a variety of scenarios. We find that either the CLV present on HAT-P-30 is below the solar level or the presence of DR prevents a CLV detection given the precision of the data herein. A careful treatment of both DR and CLV is required, especially for systems with high impact factors, due to potential degeneracies between the two. Future observations and/or a sophisticated treatment of the red noise present in the data (likely due to granulation) is required to refine the DR and CLV for these particular systems; such observations would also present another opportunity to try to examine starspots on WASP-52.
The number of super-Earth and mini-Neptune planet discoveries has increased significantly in the last two decades thanks to transit and radial velocity surveys. When it is possible to apply both ...techniques, we can characterise the internal composition of exoplanets, which in turn provides unique insights on their architecture, formation and evolution. We performed a combined photometric and radial velocity analysis of TOI-238 (TYC 6398-132-1), which has one short-orbit super-Earth planet candidate announced by NASA's TESS team. We aim to confirm its planetary nature using radial velocities taken with the ESPRESSO and HARPS spectrographs, to measure its mass and to detect the presence of other possible planetary companions. We carried out a joint analysis by including Gaussian processes and Keplerian orbits to account for the stellar activity and planetary signals simultaneously. We detected the signal induced by TOI-238 b in the radial velocity time-series, and the presence of a second transiting planet, TOI-238 c, whose signal appears in RV and TESS data. TOI-238 b is a planet with a radius of 1.402\(^{+0.084}_{-0.086}\) R\(_{\oplus}\) and a mass of 3.40\(^{+0.46}_{-0.45}\) M\(_{\oplus}\). It orbits at a separation of 0.02118 \(\pm\) 0.00038 AU of its host star, with an orbital period of 1.2730988 \(\pm\) 0.0000029 days, and has an equilibrium temperature of 1311 \(\pm\) 28 K. TOI-238 c has a radius of 2.18\(\pm\) 0.18 R\(_{\oplus}\) and a mass of 6.7 \(\pm\) 1.1 M\(_{\oplus}\). It orbits at a separation of 0.0749 \(\pm\) 0.0013 AU of its host star, with an orbital period of 8.465652 \(\pm\) 0.000031 days, and has an equilibrium temperature of 696 \(\pm\) 15 K. The mass and radius of planet b are fully consistent with an Earth-like composition, making it likely a rocky super-Earth. Planet c could be a water-rich planet or a rocky planet with a small H-He atmosphere.
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. 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. The host star is an active early K dwarf with a mass of \(0.80 \pm 0.04\,\)M\(_\odot\), a radius of \(0.769 \pm 0.026\,\)R\(_\odot\), and a G magnitude of 8. We found that the host star is young, \(\sim 0.52\,\) Myr, allowing us to gain insight into planetary evolution. We derived a planetary mass of \(6.1 \pm 1.6\,\mathrm{M}_E\),\, a planetary radius of \(2.25 \pm 0.12\,\mathrm{R}_E\),\ and a planetary density of \(\rho_p = 3.27_{-0.91}^{+0.97}\,\mathrm{g.cm^{-3}}\). 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 \(\sim 0.52\,\) 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.
The current architecture of a given multi-planetary system is a key fingerprint of its past formation and dynamical evolution history. Long-term follow-up observations are key to complete their ...picture. In this paper we focus on the confirmation and characterization of the components of the TOI-969 planetary system, where TESS detected a Neptune-size planet candidate in a very close-in orbit around a late K-dwarf star. We use a set of precise radial velocity observations from HARPS, PFS and CORALIE instruments covering more than two years in combination with the TESS photometric light curve and other ground-based follow-up observations to confirm and characterize the components of this planetary system. We find that TOI-969 b is a transiting close-in (\(P_b\sim 1.82\) days) mini-Neptune planet (\(m_b=9.1^{+1.1}_{-1.0}\) M\(_{\oplus}\), \(R_b=2.765^{+0.088}_{-0.097}\) R\(_{\oplus}\)), thus placing it on the {lower boundary} of the hot-Neptune desert (\(T_{\rm eq,b}=941\pm31\) K). The analysis of its internal structure shows that TOI-969 b is a volatile-rich planet, suggesting it underwent an inward migration. The radial velocity model also favors the presence of a second massive body in the system, TOI-969 c, with a long period of \(P_c=1700^{+290}_{-280}\) days and a minimum mass of \(m_{c}\sin{i_c}=11.3^{+1.1}_{-0.9}\) M\(_{\rm Jup}\), and with a highly-eccentric orbit of \(e_c=0.628^{+0.043}_{-0.036}\). The TOI-969 planetary system is one of the few around K-dwarfs known to have this extended configuration going from a very close-in planet to a wide-separation gaseous giant. TOI-969 b has a transmission spectroscopy metric of 93, and it orbits a moderately bright (\(G=11.3\) mag) star, thus becoming an excellent target for atmospheric studies. The architecture of this planetary system can also provide valuable information about migration and formation of planetary systems.
Silvialite, ideally Ca
Al
Si
SO
, is tetragonal, I4/m, Z = 2, with a = 12.160(3), c = 7.560(1) Å, V = 1117.9(8) Å
, c:a = 0.6217:1, ω= 1.583, Ɛ= 1.558 (uniaxial negative), D
= 2.75 g/cm
, D
= 2.769 ...g/cm
and H (Mohs) = 5.5. It is transparent and slightly yellow, has a good {100} cleavage, chonchoidal fracture, white streak and a vitreous lustre. It occurs in upper-mantle garnet-granulite xenoliths hosted by olivine nephelinite, from McBride Province, North Queensland, Australia. The empirical formula, derived from electron-microprobe analysis, is (Na
Ca
)(Al
Si
)O
(SO
)0.57(CO
. Crystal-structure refinement shows disordered carbonate and sulfate groups along the fourfold axis. Silvialite is a primary cumulate phase precipitated from alkali basalt at 900−1000°C and 8−12 kbar under high f
and f
. The name silvialite, currently used in literature to describe the sulfate analogue of meionite, was suggested by Brauns (1914).
Star Clusters Across Cosmic Time Krumholz, Mark R; McKee, Christopher F; Bland-Hawthorn, Joss
Annual review of astronomy and astrophysics,
08/2019, Letnik:
57, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Star clusters stand at the intersection of much of modern astrophysics: the ISM, gravitational dynamics, stellar evolution, and cosmology. Here, we review observations and theoretical models for the ...formation, evolution, and eventual disruption of star clusters. Current literature suggests a picture of this life cycle including the following several phases:
Clusters form in hierarchically structured, accreting molecular clouds that convert gas into stars at a low rate per dynamical time until feedback disperses the gas.
The densest parts of the hierarchy resist gas removal long enough to reach high star-formation efficiency, becoming dynamically relaxed and well mixed. These remain bound after gas removal.
In the first ∼100 Myr after gas removal, clusters disperse moderately fast, through a combination of mass loss and tidal shocks by dense molecular structures in the star-forming environment.
After ∼100 Myr, clusters lose mass via two-body relaxation and shocks by giant molecular clouds, processes that preferentially affect low-mass clusters and cause a turnover in the cluster mass function to appear on ∼1-10-Gyr timescales.
Even after dispersal, some clusters remain coherent and thus detectable in chemical or action space for multiple galactic orbits.
In the next decade, a new generation of space- and adaptive optics-assisted ground-based telescopes will enable us to test and refine this picture.
Superconductivity and charge density waves (CDWs) are competitive, yet coexisting, orders in cuprate superconductors. To understand their microscopic interdependence, a probe capable of discerning ...their interaction on its natural length and time scale is necessary. We use ultrafast resonant soft x-ray scattering to track the transient evolution of CDW correlations in YBa
Cu
O
after the quench of superconductivity by an infrared laser pulse. We observe a nonthermal response of the CDW order characterized by a near doubling of the correlation length within ≈1 picosecond of the superconducting quench. Our results are consistent with a model in which the interaction between superconductivity and CDWs manifests inhomogeneously through disruption of spatial coherence, with superconductivity playing the dominant role in stabilizing CDW topological defects, such as discommensurations.
The concept that superconductivity competes with other orders in cuprate superconductors has become increasingly apparent, but obtaining direct evidence with bulk-sensitive probes is challenging. We ...have used resonant soft x-ray scattering to identify two-dimensional charge fluctuations with an incommensurate periodicity of ∼3.2 lattice units in the copper-oxide planes of the superconductors (Y,Nd)Ba 2 Cu 3 O 6+x , with hole concentrations of 0.09 to 0.13 per planar Cu ion. The intensity and correlation length of the fluctuation signal increase strongly upon cooling down to the superconducting transition temperature (T c ); further cooling below T c abruptly reverses the divergence of the charge correlations. In combination with earlier observations of a large gap in the spin excitation spectrum, these data indicate an incipient charge density wave instability that competes with superconductivity.
We report new constraints on the local escape speed of our Galaxy. Our analysis is based on a sample of high-velocity stars from the RAVE survey and two previously published data sets. We use ...cosmological simulations of disc galaxy formation to motivate our assumptions on the shape of the velocity distribution, allowing for a significantly more precise measurement of the escape velocity compared to previous studies. We find that the escape velocity lies within the range 498 < vesc < 608 km s−1 (90 per cent confidence), with a median likelihood of 544 km s−1. The fact that v2esc is significantly greater than 2v2circ (where vcirc= 220 km s−1 is the local circular velocity) implies that there must be a significant amount of mass exterior to the solar circle, that is, this convincingly demonstrates the presence of a dark halo in the Galaxy. We use our constraints on vesc to determine the mass of the Milky Way halo for three halo profiles. For example, an adiabatically contracted NFW halo model results in a virial mass of 1.42+1.14−0.54× 1012 M⊙ and virial radius of (90 per cent confidence). For this model the circular velocity at the virial radius is 142+31−21 km s−1. Although our halo masses are model dependent, we find that they are in good agreement with each other.
PDF
