370 research outputs found
Study of the impact of the post-MS evolution of the host star on the orbits of close-in planets. I. Sample definition and physical properties
Context: To date, more than 30 planets have been discovered around giant
stars, but only one of them has been found to be orbiting within 0.6 AU from
the host star, in direct contrast to what is observed for FGK dwarfs. This
result suggests that evolved stars destroy/engulf close-in planets during the
red giant phase.
Aims: We are conducting a radial velocity survey of 164 bright G and K giant
stars in the southern hemisphere with the aim of studying the effect of the
host star evolution on the inner structure of planetary systems. In this paper
we present the spectroscopic atmospheric parameters (\Teff, \logg, ,
[Fe/H]) and the physical properties (mass, radius, evolutionary status) of the
program stars. In addition, rotational velocities for all of our targets were
derived.
Methods: We used high resolution and high S/N spectra to measure the
equivalent widths of many Fe{\sc\,i} and Fe{\sc\,ii} lines, which were used to
derive the atmospheric parameters by imposing local thermodynamic and
ionization equilibrium. The effective temperatures and metallicities were used,
along with stellar evolutionary tracks to determine the physical properties and
evolutionary status of each star.
Results: We found that our targets are on average metal rich and they have
masses between \,1.0\,M and 3.5\,M. In addition, we found
that 122 of our targets are ascending the RGB, while 42 of them are on the HB
phase.Comment: Accepted for publication in A&
Phonons in random alloys: the itinerant coherent-potential approximation
We present the itinerant coherent-potential approximation(ICPA), an analytic,
translationally invariant and tractable form of augmented-space-based,
multiple-scattering theory in a single-site approximation for harmonic phonons
in realistic random binary alloys with mass and force-constant disorder.
We provide expressions for quantities needed for comparison with experimental
structure factors such as partial and average spectral functions and derive the
sum rules associated with them. Numerical results are presented for Ni_{55}
Pd_{45} and Ni_{50} Pt_{50} alloys which serve as test cases, the former for
weak force-constant disorder and the latter for strong. We present results on
dispersion curves and disorder-induced widths. Direct comparisons with the
single-site coherent potential approximation(CPA) and experiment are made which
provide insight into the physics of force-constant changes in random alloys.
The CPA accounts well for the weak force-constant disorder case but fails for
strong force-constant disorder where the ICPA succeeds.Comment: 19 pages, 12 eps figures, uses RevTex
GLIDA: GPCRâligand database for chemical genomics drug discoveryâdatabase and tools update
G-protein coupled receptors (GPCRs) represent one of the most important families of drug targets in pharmaceutical development. GLIDA is a public GPCR-related Chemical Genomics database that is primarily focused on the integration of information between GPCRs and their ligands. It provides interaction data between GPCRs and their ligands, along with chemical information on the ligands, as well as biological information regarding GPCRs. These data are connected with each other in a relational database, allowing users in the field of Chemical Genomics research to easily retrieve such information from either biological or chemical starting points. GLIDA includes a variety of similarity search functions for the GPCRs and for their ligands. Thus, GLIDA can provide correlation maps linking the searched homologous GPCRs (or ligands) with their ligands (or GPCRs). By analyzing the correlation patterns between GPCRs and ligands, we can gain more detailed knowledge about their conserved molecular recognition patterns and improve drug design efforts by focusing on inferred candidates for GPCR-specific drugs. This article provides a summary of the GLIDA database and user facilities, and describes recent improvements to database design, data contents, ligand classification programs, similarity search options and graphical interfaces. GLIDA is publicly available at http://pharminfo.pharm.kyoto-u.ac.jp/services/glida/. We hope that it will prove very useful for Chemical Genomics research and GPCR-related drug discovery
British HIV Association guidelines for the management of tuberculosis in adults living with HIV 2019
The overall purpose of these guidelines is to help physicians manage adults with tuberculosis (TB)/human immunodeficiency virus (HIV) coâinfection. Recommendations for the treatment of TB in HIVâpositive adults are similar to those in HIVânegative adults. Of note, the term âHIVâ refers to HIVâ1 throughout these guidelines
TESS Discovery Of Twin Planets Near 2:1 Resonance Around Early M Dwarf TOI 4342
With data from the Transiting Exoplanet Survey Satellite (TESS), we showcase improvements to the MIT Quick Look Pipeline (QLP) through the discovery and validation of a multiplanet system around M dwarf TOI 4342 (Tmag = 11.032, Mâ = 0.63 Mâ, Râ = 0.60 Râ, Teff = 3900 K, d = 61.54 pc). With updates to QLP, including a new multiplanet search, as well as faster cadence data from TESS\u27s First Extended Mission, we discovered two sub-Neptunes (Rb = 2.266 (+0.038)/(-0.038) Râ and Rc = 2.415 (+0.043)/(-0.040) Râ; Pb = 5.538 days and Pc = 10.689 days) and validated them with ground-based photometry, spectra, and speckle imaging. Both planets notably have high transmission spectroscopy metrics of 36 and 32, making TOI 4342 one of the best systems for comparative atmospheric studies. This system demonstrates how improvements to QLP, along with faster cadence full-frame images, can lead to the discovery of new multiplanet systems
Opposing effects of attention and consciousness on afterimages
The brain's ability to handle sensory information is influenced by both selective attention and consciousness. There is no consensus on the exact relationship between these two processes and whether they are distinct. So far, no experiment has simultaneously manipulated both. We carried out a full factorial 2 Ă 2 study of the simultaneous influences of attention and consciousness (as assayed by visibility) on perception, correcting for possible concurrent changes in attention and consciousness. We investigated the duration of afterimages for all four combinations of high versus low attention and visible versus invisible. We show that selective attention and visual consciousness have opposite effects: paying attention to the grating decreases the duration of its afterimage, whereas consciously seeing the grating increases the afterimage duration. These findings provide clear evidence for distinctive influences of selective attention and consciousness on visual perception
The Spatial and Temporal Construction of Confidence in the Visual Scene
Human subjects can report many items of a cluttered field a few hundred milliseconds after stimulus presentation. This memory decays rapidly and after a second only 3 or 4 items can be stored in working memory. Here we compared the dynamics of objective performance with a measure of subjective report and we observed that 1) Objective performance beyond explicit subjective reports (blindsight) was significantly more pronounced within a short temporal interval and within specific locations of the visual field which were robust across sessions 2) High confidence errors (false beliefs) were largely confined to a small spatial window neighboring the cue. The size of this window did not change in time 3) Subjective confidence showed a moderate but consistent decrease with time, independent of all other experimental factors. Our study allowed us to asses quantitatively the temporal and spatial access to an objective response and to subjective reports
Mass and density of the transiting hot and rocky super-Earth LHS 1478 b (TOI-1640 b)
One of the main objectives of the Transiting Exoplanet Survey Satellite
({TESS}) mission is the discovery of small rocky planets around relatively
bright nearby stars. Here, we report the discovery and characterization of the
transiting super-Earth planet orbiting LHS~1478 (TOI-1640). The star is an
inactive red dwarf (\,mag and spectral type m3\,V) with mass and
radius estimates of \, and \,,
respectively, and an effective temperature of \,K.It was observed by
\tess in four sectors. These data revealed a transit-like feature with a period
of 1.949 days. We combined the TESS data with three ground-based transit
measurements, 57 radial velocity (RV) measurements from CARMENES, and 13 RV
measurements from IRD, determining that the signal is produced by a planet with
a mass of \, and a radius of
\,. The resulting bulk density of this planet
is 6.67\,g\,cm, which is consistent with a rocky planet with an Fe- and
MgSiO-dominated composition. Although the planet would be too hot to
sustain liquid water on its surface (its equilibrium temperature is about
595\,K, suggesting a Venus-like atmosphere), spectroscopic metrics based
on the capabilities of the forthcoming James Webb Space Telescope and the fact
that the host star is rather inactive indicate that this is one of the most
favorable known rocky exoplanets for atmospheric characterization.Comment: 14 pages, 10 figures, 6 tables, accepted for publication in A&
A super-Earth and a mini-Neptune near the 2:1 MMR straddling the radius valley around the nearby mid-M dwarf TOI-2096
Context. Several planetary formation models have been proposed to explain the observed abundance and variety of compositions of super-Earths and mini-Neptunes. In this context, multitransiting systems orbiting low-mass stars whose planets are close to the radius valley are benchmark systems, which help to elucidate which formation model dominates.Aims. We report the discovery, validation, and initial characterization of one such system, TOI-2096 (TIC 142748283), a two-planet system composed of a super-Earth and a mini-Neptune hosted by a mid-type M dwarf located 48 pc away.Methods. We characterized the host star by combining optical spectra, analyzing its broadband spectral energy distribution, and using evolutionary models for low-mass stars. Then, we derived the planetary properties by modeling the photometric data from TESS and ground-based facilities. In addition, we used archival data, high-resolution imaging, and statistical validation to support our planetary interpretation.Results. We found that the stellar properties of TOI-2096 correspond to a dwarf star of spectral type M4±0.5. It harbors a super-Earth (R = 1.24 ± 0.07 Râ) and a mini-Neptune (R = 1.90 ± 0.09 Râ) in likely slightly eccentric orbits with orbital periods of 3.12 d and 6.39 d, respectively. These orbital periods are close to the first-order 2:1 mean-motion resonance (MMR), a configuration that may lead to measurable transit timing variations (TTVs). We computed the expected TTVs amplitude for each planet and found that they might be measurable with high-precision photometry delivering mid-transit times with accuracies of âČ2 min. Moreover, we conclude that measuring the planetary masses via radial velocities (RVs) could also be possible. Lastly, we found that these planets are among the best in their class to conduct atmospheric studies using the NIRSpec/Prism onboard the James Webb Space Telescope (JWST).Conclusions. The properties of this system make it a suitable candidate for further studies, particularly for mass determination using RVs and/or TTVs, decreasing the scarcity of systems that can be used to test planetary formation models around low-mass stars
- âŠ