176 research outputs found
Flares in Open Clusters with K2. I. M45 (Pleiades), M44 (Praesepe) and M67
The presence and strength of a stellar magnetic field and activity is rooted
in a star's fundamental parameters such as mass and age. Can flares serve as an
accurate stellar "clock"?
To explore if we can quantify an activity-age relation in the form of a
flaring-age relation, we measured trends in the flaring rates and energies for
stars with different masses and ages.
We investigated the time-domain photometry provided by Kepler's follow-up
mission K2 and searched for flares in three solar metallicity open clusters
with well-known ages, M45 (0.125 Gyr), M44 (0.63 Gyr), and M67 (4.3 Gyr). We
updated and employed the automated flare finding and analysis pipeline
Appaloosa, originally designed for Kepler. We introduced a synthetic flare
injection and recovery subroutine to ascribe detection and energy recovery
rates for flares in a broad energy range for each light curve. We collected a
sample of 1 761 stars, mostly late-K to mid-M dwarfs and found 751 flare
candidates with energies ranging from erg to
erg, of which 596 belong to M45, 155 to M44, and none to M67.
We find that flaring activity depends both on , and age. But
all flare frequency distributions have similar slopes with , supporting a universal flare generation process. We discuss
implications for the physical conditions under which flares occur, and how the
sample's metallicity and multiplicity affect our results.Comment: 17 pages, 11 figures, appendix. Accepted to A&
Three young planets around the K-dwarf K2-198: High-energy environment, evaporation history and expected future
Planets orbiting young stars are thought to experience atmospheric
evaporation as a result of the host stars' high magnetic activity. We study the
evaporation history and expected future of the three known transiting
exoplanets in the young multiplanet system K2-198. Based on spectroscopic and
photometric measurements, we estimate an age of the K-dwarf host star between
200 and 500 Myr, and calculate the high-energy environment of these planets
using eROSITA X-ray measurements. We find that the innermost planet K2-198c has
likely lost its primordial envelope within the first few tens of Myr regardless
of the age at which the star drops out of the saturated X-ray regime. For the
two outer planets, a range of initial envelope mass fractions is possible,
depending on the not-yet-measured planetary mass and the stars' spin-down
history. Regarding the future of the system, we find that the outermost planet
K2-198b is stable against photoevaporation for a wide range of planetary
masses, while the middle planet K2-198d is only able to retain an atmosphere
for a mass range between ~7 and 18 Earth-masses. Lower-mass planets are too
susceptible to mass loss, and a very thin present-day envelope for higher-mass
planets is easily lost with the estimated mass-loss rates. Our results support
the idea that all three planets started out above the radius valley in the
(sub-)Neptune regime and were then transformed into their current states by
atmospheric evaporation, but also stress the importance of measuring planetary
masses for (young) multiplanet systems before conducting more detailed
photoevaporation simulations
Flaring Latitudes in Ensembles of Low Mass Stars
The distribution of small-scale magnetic fields in stellar photospheres is an
important ingredient in our understanding of the magnetism of low mass stars.
Their spatial distribution connects the field generated in the stellar interior
with the outer corona and the large scale field, and thereby affects the space
weather of planets. Unfortunately, we lack techniques that can locate them on
most low-mass stars. One strategy is to localize field concentrations using the
flares that occur in their vicinity.
We explore a new method that adapts the spot simulation software fleck to
study the modulation of flaring times as a function of active latitude. We use
empirical relations to construct flare light curves similar to those available
from Kepler and the Transiting Exoplanet Survey Satellite (TESS), search them
for flares, and use the waiting times between flares to determine the location
of active latitudes.
We find that the mean and standard deviation of the waiting time distribution
provide a unique diagnostic of flaring latitudes as a function of the number of
active regions. Latitudes are best recovered when stars have three or less
active regions that flare repeatedly, and active latitude widths below 20 deg;
when either increases, the information about the active latitude location is
gradually lost. We demonstrate our technique on a sample of flaring G dwarfs
observed with the Kepler satellite, and furthermore suggest that combining
ensemble methods for spots and flares could overcome the limitations of each
individual technique for the localization of surface magnetic fields.Comment: 15 pages, 10 figures. Accepted to MNRAS. Repository with source code:
https://github.com/ekaterinailin/flare-locations-ensembles-science Repository
with data: https://zenodo.org/record/799692
Flares in Open Clusters with K2. II. Pleiades, Hyades, Praesepe, Ruprecht 147, and M67
Flares, energetic eruptions on the surfaces of stars, are an unmistakable
manifestation of magnetically driven emission. Their occurrence rates and
energy distributions trace stellar characteristics such as mass and age. But
before flares can be used to constrain stellar properties, the flaring-age-mass
relation requires proper calibration. This work sets out to quantify flaring
activity of independently age-dated main sequence stars for a broad range of
spectral types using optical light curves obtained by the Kepler satellite.
Drawing from the complete K2 archive, we searched 3435 day long light
curves of 2111 open cluster members for flares using the open-source software
packages K2SC to remove instrumental and astrophysical variability from K2
light curves, and AltaiPony to search and characterize the flare candidates. We
confirmed a total of 3844 flares on high probability open cluster members with
ages from zero age main sequence (Pleiades) to 3.6 Gyr (M67). We extended the
mass range probed in the first study of this series to span from Sun-like stars
to mid-M dwarfs. We added the Hyades (690 Myr) to the sample as a comparison
cluster to Praesepe (750 Myr), the 2.6 Gyr old Ruprecht 147, and several
hundred light curves from the late K2 Campaigns in the remaining clusters. The
flare energy distribution was similar in the entire parameter space, following
a power law relation with exponent . The flaring rates
declined with age, and declined faster for higher mass stars. We found evidence
that a rapid decline in flaring activity occurred in M1-M2 dwarfs around
Hyades/Praesepe age, when these stars spun down to rotation periods of about 10
days, while higher mass stars had already transitioned to lower flaring rates,
and lower mass stars still resided in the saturated activity regime. (abridged)Comment: 27 pages, 13 figures. Accepted to A&
Multidifferential study of identified charged hadron distributions in -tagged jets in proton-proton collisions at 13 TeV
Jet fragmentation functions are measured for the first time in proton-proton
collisions for charged pions, kaons, and protons within jets recoiling against
a boson. The charged-hadron distributions are studied longitudinally and
transversely to the jet direction for jets with transverse momentum 20 GeV and in the pseudorapidity range . The
data sample was collected with the LHCb experiment at a center-of-mass energy
of 13 TeV, corresponding to an integrated luminosity of 1.64 fb. Triple
differential distributions as a function of the hadron longitudinal momentum
fraction, hadron transverse momentum, and jet transverse momentum are also
measured for the first time. This helps constrain transverse-momentum-dependent
fragmentation functions. Differences in the shapes and magnitudes of the
measured distributions for the different hadron species provide insights into
the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any
supplementary material and additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb
public pages
Change in H+ Transport across Thylakoid Membrane as Potential Mechanism of 14.3 Hz Magnetic Field Impact on Photosynthetic Light Reactions in Seedlings of Wheat (Triticum aestivum L.)
Natural and artificial extremely low-frequency magnetic fields (ELFMFs) are important factors influencing physiological processes in living organisms including terrestrial plants. Earlier, it was experimentally shown that short-term and long-term treatments by ELFMFs with Schumann resonance frequencies (7.8, 14.3, and 20.8 Hz) influenced parameters of photosynthetic light reactions in wheat leaves. The current work is devoted to an analysis of potential ways of this ELFMF influence on the light reactions. Only a short-term wheat treatment by 14.3 Hz ELFMF was used in the analysis. First, it was experimentally shown that ELFMF-induced changes (an increase in the effective quantum yield of photosystem II, a decrease in the non-photochemical quenching of chlorophyll fluorescence, a decrease in time of changes in these parameters, etc.) were observed under the action of ELFMF with widely ranging magnitudes (from 3 to 180 ”T). In contrast, the potential quantum yield of photosystem II and time of relaxation of the energy-dependent component of the non-photochemical quenching were not significantly influenced by ELFMF. Second, it was shown that the ELFMF treatment decreased the proton gradient across the thylakoid membrane. In contrast, the H+ conductivity increased under this treatment. Third, an analysis of the simplest mathematical model of an H+ transport across the thylakoid membrane, which was developed in this work, showed that changes in H+ fluxes related to activities of the photosynthetic electron transport chain and the H+-ATP synthase were not likely a mechanism of the ELFMF influence. In contrast, changes induced by an increase in an additional H+ flux (probably, through the proton leakage and/or through the H+/Ca2+ antiporter activity in the thylakoid membrane) were in good accordance with experimental results. Thus, we hypothesized that this increase is the mechanism of the 14.3 Hz ELFMF influence (and, maybe, influences of other low frequencies) on photosynthetic light reactions in wheat
Influence of Magnetic Field with Schumann Resonance Frequencies on Photosynthetic Light Reactions in Wheat and Pea
Photosynthesis is an important target of action of numerous environmental factors; in particular, stressors can strongly affect photosynthetic light reactions. Considering relations of photosynthetic light reactions to electron and proton transport, it can be supposed that extremely low frequency magnetic field (ELFMF) may influence these reactions; however, this problem has been weakly investigated. In this paper, we experimentally tested a hypothesis about the potential influence of ELFMF of 18 ”T intensity with Schumann resonance frequencies (7.8, 14.3, and 20.8 Hz) on photosynthetic light reactions in wheat and pea seedlings. It was shown that ELFMF decreased non-photochemical quenching in wheat and weakly influenced quantum yield of photosystem II at short-term treatment; in contrast, the changes in potential and effective quantum yields of photosystem II were observed mainly under chronic action of ELFMF. It is interesting that both short-term and chronic treatment decreased the time periods for 50% activation of quantum yield and non-photochemical quenching under illumination. Influence of ELFMF on pea was not observed at both short-term and chronic treatment. Thus, we showed that ELFMF with Schumann resonance frequencies could influence photosynthetic light processes; however, this effect depends on plant species (wheat or pea) and type of treatment (short-term or chronic)
Influence of Magnetic Field with Schumann Resonance Frequencies on Photosynthetic Light Reactions in Wheat and Pea
Photosynthesis is an important target of action of numerous environmental factors; in particular, stressors can strongly affect photosynthetic light reactions. Considering relations of photosynthetic light reactions to electron and proton transport, it can be supposed that extremely low frequency magnetic field (ELFMF) may influence these reactions; however, this problem has been weakly investigated. In this paper, we experimentally tested a hypothesis about the potential influence of ELFMF of 18 µT intensity with Schumann resonance frequencies (7.8, 14.3, and 20.8 Hz) on photosynthetic light reactions in wheat and pea seedlings. It was shown that ELFMF decreased non-photochemical quenching in wheat and weakly influenced quantum yield of photosystem II at short-term treatment; in contrast, the changes in potential and effective quantum yields of photosystem II were observed mainly under chronic action of ELFMF. It is interesting that both short-term and chronic treatment decreased the time periods for 50% activation of quantum yield and non-photochemical quenching under illumination. Influence of ELFMF on pea was not observed at both short-term and chronic treatment. Thus, we showed that ELFMF with Schumann resonance frequencies could influence photosynthetic light processes; however, this effect depends on plant species (wheat or pea) and type of treatment (short-term or chronic)
Influence of Schumann Range Electromagnetic Fields on Components of Plant Redox Metabolism in Wheat and Peas
The Schumann Resonances (ScR) are Extremely Low Frequency (ELF) electromagnetic resonances in the Earth-ionosphere cavity excited by global lightning discharges. ScR are the part of electromagnetic field (EMF) of Earth. The influence of ScR on biological systems is still insufficiently understood. The purpose of the study is to characterize the possible role of the plant cell redox metabolism regulating system in the Schumann Resonances EMF perception. Activity of catalase and superoxide dismutase, their isoenzyme structure, content of malondialdehyde, composition of polar lipids in leaf extracts of wheat and pea plants treated with short-time (30 min) and long-time (18 days) ELF EMF with a frequency of 7.8 Hz, 14.3 Hz, 20.8 Hz have been investigated. Short-time exposure ELF EMF caused more pronounced bio effects than long-time exposure. Wheat catalase turned out to be the most sensitive parameter to magnetic fields. It is assumed that the change in the activity of wheat catalase after a short-term ELF EMF may be associated with the ability of this enzyme to perceive the action of a weak EMF through calcium calmodulin and/or cryptochromic signaling systems
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Focus of the IPCC Assessment Reports Has Shifted to Lower Temperatures
Funder: Templeton World Charity FoundationAbstract: We focus on how different global temperature increases represented in IPCC reports have shifted over time. While the first four assessment reports had a roughly equal focus on temperatures above and below 2°C, the more recent fifth and sixth assessment reports have a considerably stronger focus on warming below 2°C. This is concerning as warming above 2°C is more likely given current emissions trajectories and is more influential on climate risk assessments
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