7,977 research outputs found
The Penn State - Toru\'n Centre for Astronomy Planet Search stars IV. Dwarfs and the complete sample
Our knowledge of the intrinsic parameters of exoplanets is as precise as our
determinations of their stellar hosts parameters. In the case of radial
velocity searches for planets, stellar masses appear to be crucial. But before
estimating stellar masses properly, detailed spectroscopic analysis is
essential. With this paper we conclude a general spectroscopic description of
the Pennsylvania-Torun Planet Search (PTPS) sample of stars. We aim at a
detailed description of basic parameters of stars representing the complete
PTPS sample. We present atmospheric and physical parameters for dwarf stars
observed within the PTPS along with updated physical parameters for the
remaining stars from this sample after the first Gaia data release. We used
high resolution (R=60 000) and high signal-to-noise-ratio (S/N=150-250) spectra
from the Hobby-Eberly Telescope and its High Resolution Spectrograph. Stellar
atmospheric parameters were determined through a strictly spectroscopic local
thermodynamic equilibrium analysis (LTE) of the equivalent widths of FeI and
FeII lines. Stellar masses, ages, and luminosities were estimated through a
Bayesian analysis of theoretical isochrones. We present , log ,
[Fe/H], micrturbulence velocities, absolute radial velocities, and rotational
velocities for 156 stars from the dwarf sample of PTPS. For most of these stars
these are the first determinations. We refine the definition of PTPS subsamples
of stars (giants, subgiants, and dwarfs) and update the luminosity classes for
all PTPS stars. Using available Gaia and Hipparcos parallaxes, we redetermine
the stellar parameters (masses, radii, luminosities, and ages) for 451 PTPS
stars. The complete PTPS sample of 885 stars is composed of 132 dwarfs, 238
subgiants, and 515 giants, of which the vast majority are of roughly solar
mass.Comment: 11 pages, 10 figures, Accepted for publication in Astronomy &
Astrophysic
Three red giants with substellar-mass companions
We present three giant stars from the ongoing Penn State-Toru\'n Planet
Search with the Hobby-Eberly Telescope, which exhibit radial velocity
variations that point to a presence of planetary --mass companions around them.
BD+49 828 is a K0 giant with a = minimum mass companion in
AU (d),
orbit. HD 95127, a log/=,
, K0 giant has a = minimum mass companion in
AU (d), orbit.
Finally, HD 216536, is a K0 giant with a minimum mass companion in
AU (d),
orbit. Both, HD 95127 b and HD 216536 b in their
compact orbits, are very close to the engulfment zone and hence prone to
ingestion in the near future. BD+49 828 b is among the longest period planets
detected with the radial velocity technique until now and it will remain
unaffected by stellar evolution up to a very late stage of its host. We discuss
general properties of planetary systems around evolved stars and planet
survivability using existing data on exoplanets in more detail.Comment: 47 pages, 11 figures. Accepted by Ap
TAPAS IV. TYC 3667-1280-1 b - the most massive red giant star hosting a warm Jupiter
We present the latest result of the TAPAS project that is devoted to intense
monitoring of planetary candidates that are identified within the
PennState-Toru\'n planet search.
We aim to detect planetary systems around evolved stars to be able to build
sound statistics on the frequency and intrinsic nature of these systems, and to
deliver in-depth studies of selected planetary systems with evidence of
star-planet interaction processes.
The paper is based on precise radial velocity measurements: 13 epochs
collected over 1920 days with the Hobby-Eberly Telescope and its
High-Resolution Spectrograph, and 22 epochs of ultra-precise HARPS-N data
collected over 961 days.
We present a warm-Jupiter (, 0.4)
companion with an orbital period of 26.468 days in a circular () orbit
around a giant evolved (, ) star
with . This is the most massive and oldest star
found to be hosting a close-in giant planet. Its proximity to its host
() means that the planet has a probability of
transits; this calls for photometric follow-up study.
This massive warm Jupiter with a near circular orbit around an evolved
massive star can help set constraints on general migration mechanisms for warm
Jupiters and, given its high equilibrium temperature, can help test energy
deposition models in hot Jupiters.Comment: 5 pages, 3 figures, accepted by A&
TAPAS - Tracking Advanced Planetary Systems with HARPS-N. II. Super Li-rich giant HD 107028
Lithium rich giant stars are rare objects. For some of them, Li enrichment
exceeds abundance of this element found in solar system meteorites, suggesting
that these stars have gone through a Li enhancement process. We identified a Li
rich giant HD 107028 with A(Li) > 3.3 in a sample of evolved stars observed
within the PennState Torun Planet Search. In this work we study different
enhancement scenarios and we try to identify the one responsible for Li
enrichment for HD 107028. We collected high resolution spectra with three
different instruments, covering different spectral ranges. We determine stellar
parameters and abundances of selected elements with both equivalent width
measurements and analysis, and spectral synthesis. We also collected multi
epoch high precision radial velocities in an attempt to detect a companion.
Collected data show that HD 107028 is a star at the base of Red Giant Branch.
Except for high Li abundance, we have not identified any other anomalies in its
chemical composition, and there is no indication of a low mass or stellar
companion. We exclude Li production at the Luminosity Function Bump on RGB, as
the effective temperature and luminosity suggest that the evolutionary state is
much earlier than RGB Bump. We also cannot confirm the Li enhancement by
contamination, as we do not observe any anomalies that are associated with this
scenario. After evaluating various scenarios of Li enhancement we conclude that
the Li-overabundance of HD 107028 originates from Main Sequence evolution, and
may be caused by diffusion process.Comment: Accepted for publication in A&
Tracking Advanced Planetary Systems (TAPAS) with HARPS-N. III. HD 5583 and BD+15 2375 - two cool giants with warm companions
Evolved stars are crucial pieces to understand the dependency of the planet
formation mechanism on the stellar mass and to explore deeper the mechanism
involved in star-planet interactions. Over the past ten years, we have
monitored about 1000 evolved stars for radial velocity variations in search for
low-mass companions under the Penn State - Torun Centre for Astronomy Planet
Search program with the Hobby-Eberly Telescope. Selected prospective candidates
that required higher RV precision measurements have been followed with HARPS-N
at the 3.6 m Telescopio Nazionale Galileo under the TAPAS project.
We aim to detect planetary systems around evolved stars to be able to build
sound statistics on the frequency and intrinsic nature of these systems, and to
deliver in-depth studies of selected planetary systems with evidence of
star-planet interaction processes. For HD 5583 we obtained 14 epochs of precise
RV measurements collected over 2313 days with the Hobby-Eberly Telescope (HET),
and 22 epochs of ultra-precise HARPS-N data collected over 976 days. For BD+15
2375 we collected 24 epochs of HET data over 3286 days and 25 epochs of HARPS-S
data over 902 days.
We report the discovery of two planetary mass objects orbiting two evolved
Red Giant stars: HD~5583 has a m sin i = 5.78 M companion at 0.529~AU in
a nearly circular orbit (e=0.076), the closest companion to a giant star
detected with the RV technique, and BD+15~2735 that with a m sin i= 1.06
M holds the record of the lightest planet found so far orbiting an
evolved star (in a circular e=0.001, 0.576~AU orbit). These are the third and
fourth planets found within the TAPAS project, a HARPS-N monitoring of evolved
planetary systems identified with the Hobby-Eberly Telescope.Comment: 9 pages, 6 figures. Accepted by Astronomy and Astrophysic
Influence of Hydrodynamic Interactions on the Kinetics of Colloidal Particle's Adsorption
The kinetics of irreversible adsorption of spherical particles onto a flat
surface is theoretically studied. Previous models, in which hydrodynamic
interactions were disregarded, predicted a power-law behavior for
the time dependence of the coverage of the surface near saturation.
Experiments, however, are in agreement with a power-law behavior of the form
. We outline that, when hydrodynamic interactions are considered, the
assymptotic behavior is found to be compatible with the experimental results in
a wide region near saturation.Comment: 4 pages, 1 figures, Phys. Rev. Lett. (in press
Species-dependent responses of crop plants to polystyrene microplastics
Abstract: Only recently there has been a strong focus on the impacts of microplastics on terrestrial crop plants. This study aims to examine and compare the effects of microplastics on two monocotyledonous (barley, Hordeum vulgare and wheat, Triticum aestivum), and two dicotyledonous (carrot, Daucus carota and lettuce, Lactuca sativa) plant species through two complimentary experiments. First, we investigated the effects of low, medium, and high (103, 105, 107 particles per mL) concentrations of 500 nm polystyrene microplastics (PS-MPs) on seed germination and early development. We found species-dependent effects on the early development, with microplastics only significantly affecting lettuce and carrot. When acutely exposed during germination, PS-MPs significantly delayed the germination of lettuce by 24%, as well as promoted the shoot growth of carrot by 71% and decreased its biomass by 26%. No effect was recorded on monocot species. Secondly, we performed a chronic (21 d) hydroponic experiment on lettuce and wheat. We observed that PS-MPs significantly reduced the shoot growth of lettuce by up to 35% and increased its biomass by up to 64%, while no record was reported on wheat. In addition, stress level indicators and defence mechanisms were significantly up-regulated in both lettuce and wheat seedlings. Overall, this study shows that PS-MPs affect plant development: impacts were recorded on both germination and growth for dicots, and responses identified by biochemical markers of stress were increased in both lettuce and wheat. This highlights species-dependent effects as the four crops were grown under identical conditions to allow direct comparison. For future research, our study emphasizes the need to focus on crop specific effects, while also working towards knowledge of plastic-induced impacts at environmentally relevant conditions
Helicobacter suis infection alters glycosylation and decreases the pathogen growth inhibiting effect and binding avidity of gastric mucins
Helicobacter suis is the most prevalent non-Helicobacter pylori Helicobacter species in the human stomach and is associated with chronic gastritis, peptic ulcer disease, and gastric mucosa-associated lymphoid tissue (MALT) lymphoma. H. suis colonizes the gastric mucosa of 60-95% of pigs at slaughter age, and is associated with chronic gastritis, decreased weight gain, and ulcers. Here, we show that experimental H. suis infection changes the mucin composition and glycosylation, decreasing the amount of H. suis-binding glycan structures in the pig gastric mucus niche. Similarly, the H. suis-binding ability of mucins from H. pylori-infected humans is lower than that of noninfected individuals. Furthermore, the H. suis growth-inhibiting effect of mucins from both noninfected humans and pigs is replaced by a growth-enhancing effect by mucins from infected individuals/pigs. Thus, Helicobacter spp. infections impair the mucus barrier by decreasing the H. suis-binding ability of the mucins and by decreasing the antiprolific activity that mucins can have on H. suis. Inhibition of these mucus-based defenses creates a more stable and inhabitable niche for H. suis. This is likely of importance for long-term colonization and outcome of infection, and reversing these impairments may have therapeutic benefits
Effects of bee density and sublethal imidacloprid exposure on cluster temperatures of caged honey bees
International audienceAbstractSurvivorship, syrup consumption, and cluster temperatures of honey bees were kept in hoarding cages with different numbers of bees. Cages with either 50, 100, 150, or 200 bees each were monitored over 4–6 weeks in incubators with 12h/12h 30° C/15° C temperature cycles to induce clustering. Survivorship and syrup consumption rates per bee were not different among the bee density groups, but cluster temperatures were. Cluster temperatures ranged from 0.45°C above incubator temperature in the 50 bee cages to 4.05° C in the 200 bee cages over the 1st 7 days, with each additional bee adding on average 0.02° C to cluster temperature. In another set of experiments, cages were established with about 200 bees each, and imidacloprid added to the syrup at 0, 5, 20, and 100 ppb. Imidacloprid in the syrup did not affect bee survivorship but it did reduce syrup consumption per bee, with bees fed 100 ppb imidacloprid syrup consuming on average 631 mg per bee over 28 days while average consumption among the other groups ranged from 853 to 914 mg. Cluster temperature was affected by imidacloprid treatment: bees fed 5 ppb imidacloprid syrup had higher cluster temperatures over the 1st 10 days, 4.17° C above incubator temperature, than either bees fed 100 ppb syrup or control (2.35 and 3.19° C, respectively)
Root presence modifies the long-term decomposition dynamics of fungal necromass and the associated microbial communities in a boreal forest
Recent studies have highlighted that dead fungal mycelium represents an important fraction of soil carbon (C) and nitrogen (N) inputs and stocks. Consequently, identifying the microbial communities and the ecological factors that govern the decomposition of fungal necromass will provide critical insight into how fungal organic matter (OM) affects forest soil C and nutrient cycles. Here, we examined the microbial communities colonising fungal necromass during a multiyear decomposition experiment in a boreal forest, which included incubation bags with different mesh sizes to manipulate both plant root and microbial decomposer group access. Necromass-associated bacterial and fungal communities were taxonomically and functionally rich throughout the 30 months of incubation, with increasing abundances of oligotrophic bacteria and root-associated fungi (i.e., ectomycorrhizal, ericoid mycorrhizal and endophytic fungi) in the late stages of decomposition in the mesh bags to which they had access. Necromass-associated beta-glucosidase activity was highest at 6 months, while leucine aminopeptidase peptidase was highest at 18 months. Based on an asymptotic decomposition model, root presence was associated with an initial faster rate of fungal necromass decomposition, but resulted in higher amounts of fungal necromass retained at later sampling times. Collectively, these results indicate that microbial community composition and enzyme activities on decomposing fungal necromass remain dynamic years after initial input, and that roots and their associated fungal symbionts result in the slowing of microbial necromass turnover with time.Peer reviewe
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