20 research outputs found
Three low-mass companions around aged stars discovered by TESS
We report the discovery of three transiting low-mass companions to aged
stars: a brown dwarf (TOI-2336b) and two objects near the hydrogen burning mass
limit (TOI-1608b and TOI-2521b). These three systems were first identified
using data from the Transiting Exoplanet Survey Satellite (TESS). TOI-2336b has
a radius of , a mass of and an orbital
period of 7.71 days. TOI-1608b has a radius of , a mass of
and an orbital period of 2.47 days. TOI-2521b has a radius
of , a mass of and an orbital period of
5.56 days. We found all these low-mass companions are inflated. We fitted a
relation between radius, mass and incident flux using the sample of known
transiting brown dwarfs and low-mass M dwarfs. We found a positive correlation
between the flux and the radius for brown dwarfs and for low-mass stars that is
weaker than the correlation observed for giant planets.Comment: 20 pages, 13 figures; submitted to MNRA
TESS spots a mini-neptune interior to a hot saturn in the TOI-2000 system
Hot jupiters (P 60 ) are almost always found
alone around their stars, but four out of hundreds known have inner companion
planets. These rare companions allow us to constrain the hot jupiter's
formation history by ruling out high-eccentricity tidal migration. Less is
known about inner companions to hot Saturn-mass planets. We report here the
discovery of the TOI-2000 system, which features a hot Saturn-mass planet with
a smaller inner companion. The mini-neptune TOI-2000 b (, ) is in a 3.10-day
orbit, and the hot saturn TOI-2000 c (, ) is in a
9.13-day orbit. Both planets transit their host star TOI-2000 (TIC 371188886, V
= 10.98, TESS magnitude = 10.36), a metal-rich ([Fe/H] =
) G dwarf 174 pc away. TESS observed the two planets
in sectors 9-11 and 36-38, and we followed up with ground-based photometry,
spectroscopy, and speckle imaging. Radial velocities from CHIRON, FEROS, and
HARPS allowed us to confirm both planets by direct mass measurement. In
addition, we demonstrate constraining planetary and stellar parameters with
MIST stellar evolutionary tracks through Hamiltonian Monte Carlo under the PyMC
framework, achieving higher sampling efficiency and shorter run time compared
to traditional Markov chain Monte Carlo. Having the brightest host star in the
V band among similar systems, TOI-2000 b and c are superb candidates for
atmospheric characterization by the JWST, which can potentially distinguish
whether they formed together or TOI-2000 c swept along material during
migration to form TOI-2000 b.Comment: v3 adds RV frequency analysis; 25 pages, 11 figures, 14 tables;
revision submitted to MNRAS; machine-readable tables available as ancillary
files; posterior samples available from Zenodo at
https://doi.org/10.5281/zenodo.7683293 and source code at
https://doi.org/10.5281/zenodo.798826
A massive hot Jupiter orbiting a metal-rich early-M star discovered in the TESS full frame images
Observations and statistical studies have shown that giant planets are rare
around M dwarfs compared with Sun-like stars. The formation mechanism of these
extreme systems remains under debate for decades. With the help of the TESS
mission and ground based follow-up observations, we report the discovery of
TOI-4201b, the most massive and densest hot Jupiter around an M dwarf known so
far with a radius of and a mass of ,
about 5 times heavier than most other giant planets around M dwarfs. It also
has the highest planet-to-star mass ratio () among such
systems. The host star is an early-M dwarf with a mass of $0.61\pm0.02\
M_{\odot}0.63\pm0.02\ R_{\odot}0.52\pm 0.08$ dex). However, interior
structure modeling suggests that its planet TOI-4201b is metal-poor, which
challenges the classical core-accretion correlation of stellar-planet
metallicity, unless the planet is inflated by additional energy sources.
Building on the detection of this planet, we compare the stellar metallicity
distribution of four planetary groups: hot/warm Jupiters around G/M dwarfs. We
find that hot/warm Jupiters show a similar metallicity dependence around G-type
stars. For M dwarf host stars, the occurrence of hot Jupiters shows a much
stronger correlation with iron abundance, while warm Jupiters display a weaker
preference, indicating possible different formation histories.Comment: 21 pages, 11 figures, 4 tables, submitted to A
Reduced fire severity offers near-term buffer to climate-driven declines in conifer resilience across the western United States
Increasing fire severity and warmer, drier postfire conditions are making forests in the western United States (West) vulnerable to ecological transformation. Yet, the relative importance of and interactions between these drivers of forest change remain unresolved, particularly over upcoming decades. Here, we assess how the interactive impacts of changing climate and wildfire activity influenced conifer regeneration after 334 wildfires, using a dataset of postfire conifer regeneration from 10,230 field plots. Our findings highlight declining regeneration capacity across the West over the past four decades for the eight dominant conifer species studied. Postfire regeneration is sensitive to high-severity fire, which limits seed availability, and postfire climate, which influences seedling establishment. In the near-term, projected differences in recruitment probability between low- and high-severity fire scenarios were larger than projected climate change impacts for most species, suggesting that reductions in fire severity, and resultant impacts on seed availability, could partially offset expected climate-driven declines in postfire regeneration. Across 40 to 42% of the study area, we project postfire conifer regeneration to be likely following low-severity but not high-severity fire under future climate scenarios (2031 to 2050). However, increasingly warm, dry climate conditions are projected to eventually outweigh the influence of fire severity and seed availability. The percent of the study area considered unlikely to experience conifer regeneration, regardless of fire severity, increased from 5% in 1981 to 2000 to 26 to 31% by mid-century, highlighting a limited time window over which management actions that reduce fire severity may effectively support postfire conifer regeneration. © 2023 the Author(s)
Antiâinflammatory mechanisms in cancer research: Characterization of a distinct M2âlike macrophage model derived from the THPâ1 cell line
Abstract Aims Macrophages play an essential role in cancer development. Tumorâassociated macrophages (TAMs) have predominantly M2âlike attributes that are associated with tumor progression and poor patient survival. Numerous methods have been reported for differentiating and polarizing macrophages in vitro, but there is no standardized and validated model for creating TAMs. Primary cells show varying cytokine responses depending on their origin and functional studies utilizing these cells may lack generalization and validity. A distinct cell lineâderived TAMâlike M2 subtype is required to investigate the mechanisms mediated by antiâinflammatory TAMs in vitro. Our previous work demonstrated a standardized protocol for creating an M2 subtype derived from a human THPâ1 cell line. The cell expression profile, however, has not been validated. The aim of this study was to characterize and validate the TAMâlike M2 subtype macrophage created based on our protocol to introduce them as a standardized model for cancer research. Methods and results Using qRTâPCR and ELISA, we demonstrated that proinflammatory, antiâinflammatory, and tumorâassociated marker expression changed during THPâ1âderived marcrophage development in vitro, mimicking a TAMârelated profile (e.g., TNFα, ILâ1ÎČ). The antiâinflammatory marker ILâ8/CXCL8, however, is most highly expressed in young M0 macrophages. Flow cytometry showed increased expression of CD206 in the final TAMâlike M2 macrophage. Singleâcell RNAâsequencing analysis of primary human monocytes and colon cancer tissue macrophages demonstrated that cell lineâderived M2 macrophages resembled a TAMârelated gene profile. Conclusions The THPâ1âderived M2 macrophage based on a standardized cell line model represents a distinct antiâinflammatory TAMâlike phenotype with an M2a subtype profile. This model may provide a basis for in vitro investigation of functional mechanisms in a variety of antiâinflammatory settings, particularly colon cancer development
State and Trait Effects on Individual Differences in Childrenâs Mathematical Development
Substantial longitudinal relations between children's early mathematics achievement and their much later mathematics achievement are firmly established. These findings are seemingly at odds with studies showing that early educational interventions have diminishing effects on children's mathematics achievement across time. We hypothesized that individual differences in children's later mathematical knowledge are more an indicator of stable, underlying characteristics related to mathematics learning throughout development than of direct effects of early mathematical competency on later mathematical competency. We tested this hypothesis in two longitudinal data sets, by simultaneously modeling effects of latent traits (stable characteristics that influence learning across time) and states (e.g., prior knowledge) on children's mathematics achievement over time. Latent trait effects on children's mathematical development were substantially larger than state effects. Approximately 60% of the variance in trait mathematics achievement was accounted for by commonly used control variables, such as working memory, but residual trait effects remained larger than state effects. Implications for research and practice are discussed
Similarities and Differences between Frozen-Hydrated, Rigor ActoâS1 Complexes of Insect Flight and Chicken Skeletal Muscles
HIP 33609 b: An Eccentric Brown Dwarf Transiting a V = 7.3 Rapidly Rotating B Star
We present the discovery and characterization of HIP 33609 b, a transiting warm brown dwarf orbiting a late B star, discovered by NASA's Transiting Exoplanet Survey Satellite as TOI-588 b. HIP 33609 b is a large ( R _b = R _J ) brown dwarf on a highly eccentric ( e = ) orbit with a 39 days period. The host star is a bright ( V = 7.3 mag), T _eff = 10,400 K star with a mass of M _* = M _â and radius of R _* = R _â , making it the hottest transiting brown dwarf host star discovered to date. We obtained radial velocity measurements from the CHIRON spectrograph confirming the companion's mass of M _b = M _J as well as the host star's rotation rate ( km s ^â1 ). We also present the discovery of a new comoving group of stars, designated as MELANGE-6, and determine that HIP 33609 is a member. We use a combination of rotation periods and isochrone models fit to the cluster members to estimate an age of 150 ± 25 Myr. With a measured mass, radius, and age, HIP 33609 b becomes a benchmark for substellar evolutionary models
TOI-4562b: A Highly Eccentric Temperate Jupiter Analog Orbiting a Young Field Star
We report the discovery of TOI-4562b (TIC-349576261), a Jovian planet orbiting a young F7V-type star, younger than the Praesepe/Hyades clusters (<700 Myr). This planet stands out because of its unusually long orbital period for transiting planets with known masses ( P _orb = 225.11781 days) and because it has a substantial eccentricity ( e = 0.76 ). The location of TOI-4562 near the southern continuous viewing zone of TESS allowed observations throughout 25 sectors, enabling an unambiguous period measurement from TESS alone. Alongside the four available TESS transits, we performed follow-up photometry using the South African Astronomical Observatory node of the Las Cumbres Observatory and spectroscopy with the CHIRON spectrograph on the 1.5 m SMARTS telescope. We measure a radius of R _J and a mass of 2.30 M _J for TOI-4562b. The radius of the planet is consistent with contraction models describing the early evolution of the size of giant planets. We detect tentative transit timing variations at the âŒ20 minutes level from five transit events, favoring the presence of a companion that could explain the dynamical history of this system if confirmed by future follow-up observations. With its current orbital configuration, tidal timescales are too long for TOI-4562b to become a hot Jupiter via high-eccentricity migration though it is not excluded that interactions with the possible companion could modify TOI-4562bâs eccentricity and trigger circularization. The characterization of more such young systems is essential to set constraints on models describing giant-planet evolution
The daily association between affect and alcohol use: A meta-analysis of individual participant data
Influential psychological theories hypothesize that people consume alcohol in response to the experience of both negative and positive emotions. Despite two decades of daily diary and ecological momentary assessment research, it remains unclear whether people consume more alcohol on days they experience higher negative and positive affect in everyday life. In this preregistered meta-analysis, we synthesized the evidence for these daily associations between affect and alcohol use. We included individual participant data from 69 studies (N = 12,394), which used daily and momentary surveys to assess affect and the number of alcoholic drinks consumed. Results indicate that people are not more likely to drink on days they experience high negative affect, but are more likely to drink and drink heavily on days high in positive affect. People self-reporting a motivational tendency to drink-to-cope and drink-to-enhance consumed more alcohol, but not on days they experienced higher negative and positive affect. Results were robust across different operationalizations of affect, study designs, study populations, and individual characteristics. These findings challenge the long-held belief that people drink more alcohol following increases in negative affect. Integrating these findings under different theoretical models and limitations of this field of research, we collectively propose an agenda for future research to explore open questions surrounding affect and alcohol use