Flaring Activity Research Articles

Avalanches and the Distribution of Reconnection Events in Magnetized Circumstellar Disks

Cosmic rays produced by young stellar objects can potentially alter the ionization structure, heating budget, chemical composition, and accretion activity in circumstellar disks. The inner edges of these disks are truncated by strong magnetic fields, which can reconnect and produce flaring activity that accelerates cosmic radiation. The resulting cosmic rays can provide a source of ionization and produce spallation reactions that alter the composition of planetesimals. These reconnection and particle acceleration processes are analogous to the physical processes that produce flaring in and the heating of stellar coronae. Flaring events on the surface of the Sun exhibit a power-law distribution of energy, reminiscent of those measured for earthquakes and avalanches. Numerical lattice reconnection models are capable of reproducing the observed power-law behavior of solar flares under the paradigm of self-organized criticality. One interpretation of these experiments is that the solar corona maintains a nonlinear attractor—or “critical”—state by balancing energy input via braided magnetic fields and output via reconnection events. Motivated by these results, we generalize the lattice reconnection formalism for applications in the truncation region of magnetized disks. Our numerical experiments demonstrate that these nonlinear dynamical systems are capable of both attaining and maintaining criticality in the presence of Keplerian shear and other complications. The resulting power-law spectrum of flare energies in the equilibrium attractor state is found to be nearly universal in magnetized disks. This finding indicates that magnetic reconnection and flaring in the inner regions of circumstellar disks occur in a manner similar to the activity on stellar surfaces. These results, in turn, have ramifications for the spallation-driven injection of radionuclides in planetesimals, disk ionization, and the subsequent planetary formation process.

Mass Accretion, Spectral, and Photometric Properties of T Tauri Stars in Taurus Based on TESS and LAMOST

We present the analysis of 16 classical T Tauri stars (CTTSs) using LAMOST and TESS data, investigating spectral properties, photometric variations, and mass accretion rates. All 16 stars exhibit emissions in Hα lines, from which the average mass accretion rate of 1.76 × 10−9 M ⊙ yr−1 is derived. Two of the stars, DL Tau and Haro 6-13, show mass accretion bursts simultaneously in TESS, ASAS-SN, and/or the ZTF survey. Based on these observations, we find that the mass accretion rates of DL Tau and Haro 6-13 reach their maxima of 2.5 × 10−8 M ⊙ yr−1 and 2 × 10−10 M ⊙ yr−1, respectively, during the TESS observation. We detect 13 flares among these stars. The flare frequency distribution shows that the CTTSs’ flare activity is not only dominated by strong flares with high energy but also much more active than those of solar-type and young low-mass stars. By comparing the variability classes reported in the literature, we find that the transition timescale between different classes of variability in CTTSs, such as from stochastic (S) to bursting (B) or from quasi-periodic symmetric to quasi-periodic dipping, may range from 1.6 to 4 yr. We observe no significant correlation between inclination and mass accretion rates derived from the emission indicators. This suggests that inner disk properties may be more important than those of outer disks. Finally, we find a relatively significant positive correlation between the asymmetric metric M and the cold disk inclination compared to the literature. A weak negative correlation between the periodicity metric Q value and inclination has also been found.

Further evidence of the link between activity and metallicity using the flaring properties of stars in the Kepler field

ABSTRACT The magnetic activity level of low-mass stars is known to vary as a function of the physical properties of the star. Many studies have shown that the stellar mass and rotation are both important parameters that determine magnetic activity levels. In contrast, the impact of a star’s chemical composition on magnetic activity has received comparatively little attention. Data sets for traditional activity proxies, e.g. X-ray emission or calcium emission, are not large enough to search for metallicity trends in a statistically meaningful way. Recently, studies have used the photometric variability amplitude as a proxy for magnetic activity to investigate the role of metallicity because it can be relatively easily measured for large samples of stars. These studies find that magnetic activity and metallicity are positively correlated. In this work, we investigate the link between activity and metallicity further by studying the flaring properties of stars in the Kepler field. Similar to the photometric variability, we find that flaring activity is stronger in more metal-rich stars for a fixed mass and rotation period. This result adds to a growing body of evidence that magnetic field generation is correlated with metallicity.

The complex spectral behavior of the newly discovered neutron star X-ray binary Swift J1858.6-0814

ABSTRACT We report on the NuSTAR observation of the newly discovered neutron star X-ray binary Swift J1858.6-0814 taken on 23rd March 2019. The light curve of the source exhibits several large flares during some time intervals of this observation. The source is softer in the high-intensity interval where the large flaring activity mainly occurs. We perform time-resolved spectroscopy on the source by extracting spectra for two different intensity intervals. The source was observed with a 3 − 79keV luminosity of ∼9.68 × 1036 ergs/s and ∼4.78 × 1036 ergs/s for high and low-intensity interval, respectively assuming a distance of 15 kpc. We find a large value of the absorbing column density ($\rm {N_{H}}\sim 1.1\times 10^{23}$ cm−2), and it appears to be uncorrelated with the observed flux of the source. Each spectrum shows evidence of Fe Kα emission in the 5 − 7keV energy band, an absorption edge around ∼7 − 8keV, and a broad Compton hump above 15keV, indicating the presence of a reflection spectrum. The observed features are well explained by the contribution of a relativistic reflection model and a partially covering absorption model. From the best-fit spectral model, we found an inner disc radius to be $4.87_{-0.96}^{+1.63}\,\,R_{ISCO}$ (for the high-intensity interval) and $5.68_{-2.78}^{+9.54}\,\,R_{ISCO}$ (for the low-intensity interval), indicating a significant disc truncation. The disk inclination is found to be relatively low, i < 330. We further place an upper limit on this source’s magnetic field strength considering the disc is truncated at the magnetospheric radius.

Complete X-ray census of M dwarfs in the solar neighborhood

Context. X-ray emission is the most sensitive diagnostic of magnetic activity in M dwarfs and, hence, of the dynamo in low-mass stars. Moreover it is crucial for quantifying the influence of the stellar irradiation on the evolution of planet atmospheres. Aims. We have embarked in a systematic study of the X-ray emission in a volume-limited sample of M dwarf stars to explore the full range of activity levels present in their coronae. We look to obtain a better understanding of the conditions in their outer atmospheres and their possible impact on the circumstellar environment. Methods. Based on a recent catalog of Gaia objects within 10 pc from the Sun, we identified all its stars with spectral types between M0 and M4 and we carried out a systematic search for X-ray measurements of this sample. To this end, we used both archival data from ROSAT, XMM-Newton, and the ROentgen Survey with an Imaging Telescope Array (eROSITA) on board the Russian Spektrum-Roentgen-Gamma mission, as well as our own dedicated XMM-Newton observations. To make inferences on the properties of the M dwarf corona, we compared the range of their observed X-ray emission levels to the flux radiated by the Sun from different types of magnetic structures: coronal holes, background corona, active regions, and cores of active regions. In this work, we focus on the properties of stars with the faintest X-ray emission. Results. At the current state of our project, with more than 90% of the 10 pc M dwarf sample observed in the X-ray, there is only one star that has had no detections: GJ 745 A. With an upper limit luminosity of log Lx (erg s−1) < 25.4 and an X-ray surface flux of log FX,SURF (erg cm−2 s−1) < 3.6, GJ 745 A defines the lower boundary of the X-ray emission level for M dwarfs. Together with its proper motion companion (GJ 745 B), it is the only star in this volume-complete sample located in the range of X-ray surface flux that corresponds to the faintest solar coronal structures, namely: coronal holes. The fact that the ultra-low X-ray emission level of GJ 745 B (log Lx (erg s−1) = 25.6 and log FX,SURF (erg cm−2 s−1) = 3.8) is entirely attributed to flaring activity indicates that while its corona is dominated by “holes,” at least one magnetically active structure is present. This structure determines the total X-ray brightness and the coronal temperature of the star.

Quantification of Gas Flaring from Satellite Imagery: A Comparison of Two Methods for SLSTR and BIROS Imagery.

Gas flaring is an environmental problem of local, regional and global concerns. Gas flares emit pollutants and greenhouse gases, yet knowledge about the source strength is limited due to disparate reporting approaches in different geographies, whenever and wherever those are considered. Remote sensing has bridged the gap but uncertainties remain. There are numerous sensors which provide measurements over flaring-active regions in wavelengths that are suitable for the observation of gas flares and the retrieval of flaring activity. However, their use for operational monitoring has been limited. Besides several potential sensors, there are also different approaches to conduct the retrievals. In the current paper, we compare two retrieval approaches over an offshore flaring area during an extended period of time. Our results show that retrieved activities are consistent between methods although discrepancies may originate for individual flares at the highly temporal scale, which are traced back to the variable nature of flaring. The presented results are helpful for the estimation of flaring activity from different sources and will be useful in a future integration of diverse sensors and methodologies into a single monitoring scheme.

Large-scale structures in the stellar wind of fast-rotating stars spawned by the presence of Earth-like planets

ABSTRACT Forming planets around young, fast-rotating solar-like stars are exposed to an intense X-ray/extreme ultraviolet radiation field and strongly magnetized stellar winds, as a consequence of the high magnetic activity of these stars. Under these conditions, Earth-like exoplanets may experience a rapid loss of their primordial hydrogen atmospheres, resulting in atmosphereless rocky obstacles for the stellar winds. The interaction of stellar winds with those planets leads to the formation of potentially observable structures due to the formation of large-scale magnetic field and density disturbances in the vicinity of these planets, such as bow shocks, induced magnetospheres, and comet-like tails. In this work, we study the interaction between the stellar winds of active, fast-rotating solar-like stars in the superfast-magnetosonic regime with Earth-like, unmagnetized, tenuous atmosphere, planetary obstacles through numerical three-dimensional simulations using the pluto magnetohydrodynamical code. The properties of AB Doradus, a nearby young star with a small rotation period (0.51 d) and a strong flaring activity, have been used to parametrize this early wind state. Bow shock and induced magnetosphere formation are characterized through the Alfvénic Mach number MA of the wind, for different stellar wind configurations. Large bow shocks, up to an extension of ∼7.0 planetary radii, are found for low-MA winds. The general increase of density, temperature, and magnetic field in these large-scale structures formed around planets may result in potentially detectable spectral signatures.

Efficacy of subtenon steroid injection alone or in combination with topical steroid in the management of trematode-induced anterior granulomatous uveitis

Background Presumed trematode-induced uveitis is a newly recognized cause of intraocular granulomatous inflammation in children, usually presenting with single or multiple pearl-like white nodules in the anterior chamber (AC) with or without subconjunctival lesions or corneal opacities. Objective The aim of this study was to evaluate the efficacy of subtenon steroid injection alone or in combination with topical steroid in the management of trematode-induced anterior granulomatous uveitis. Patients and methods This is a prospective comparative study, that included the children who presented with AC granulomas at the Uveitis Unit at Tanta Ophthalmology Hospital, Tanta, Egypt. The patients were divided into two groups: Group A, who received subtenon steroid injection only, and Group B, who received both subtenon steroid injection and topical steroid eye drops. The basic demographic data, visual acuity (VA), granuloma site and size, and AC activity (cells and flare) were recorded and analyzed. A systemic work-up, including stool and urine analysis, full blood count, chest X-ray, and schistosomiasis titer, was performed. The patients were followed up on the first day, at 2 weeks, 1, and 3 months Results The study included 30 eyes of 30 patients. The mean age of the patients was 13.4±2.42 years, and 87% of the patients were males. Group B patients demonstrated statistically significant better improvement in VA, AC activity, and granuloma site and size compared to Group A patients (P<0.001). The granuloma in group A did not change in size and continued to exhibit AC activity. Conclusion The combination of subtenon and topical steroid was found to be more effective in the treatment of granuloma than the subtenon injection alone.

Magnetar Flare-driven Bumpy Declining Light Curves in Hydrogen-poor Superluminous Supernovae

Recent observations indicate that hydrogen-poor superluminous supernovae (SLSNe-I) often display bumpy declining light curves. However, the cause of these undulations remains unclear. In this paper, we have improved the magnetar model, which includes flare activities. We present a systematic analysis of a well-observed SLSN-I sample with bumpy light curves in their late phase. These SLSNe-I were identified from multiple transient surveys, such as the Pan-STARRS1 Medium Deep Survey and the Zwicky Transient Facility. Our study provides a set of magnetar-powered model light curve fits for five SLSNe-I, which accurately reproduce the observed light curves using reasonable physical parameters. By extracting the essential characteristics of both the explosions and central engines, these fits provide valuable insights into investigating their potential association with gamma-ray burst engines. We found that the SLSN flares tend to be the dim and long extension of GRB flares in the peak luminosity versus peak time plane. Conducting large-scale, high-cadence surveys in the near future could enhance our comprehension of both SLSN undulating light curve properties and their potential relationship with GRBs by modeling their light curve characteristics.

Analysis of the Solar Flare Index for Solar Cycles 18 – 24: Extremely Deep Gnevyshev Gap in the Chromosphere

We study the solar flare index (SFI) for the Solar Cycles 18 – 24. We find that SFI has deeper Gnevyshev gap (GG) in its first principal component than other atmospheric parameters. The GG is extremely clear especially in the even cycles.The GG of the SFI appears about a half year later as a drop in the interplanetary magnetic field near the Earth and in the geomagnetic Ap-index. The instantaneous response of the magnetic field to solar flares, however, shows about two to three days after the eruption as a high, sharp peak in the cross-correlation of the SFI and Ap-index and as a lower peak in SFI vs. IMF B cross-correlation. We confirm these rapid responses using superposed-epoch analysis.The most active flare cycles during 1944 – 2020 are Cycles 19 and 21. Cycle 18 has very strong SFI days as many as Cycle 22, but it has the least nonzero SFI days in the whole interval. Interestingly, Cycle 20 can be compared to Cycles 23 and 24 in its low flare activity, although it is located between the most active SFI cycles.

Deep neural networks of solar flare forecasting for complex active regions

Solar flare forecasting is one of major components of operational space weather forecasting. Complex active regions (ARs) are the main source producing major flares, but only a few studies are carried out to establish flare forecasting models for these ARs. In this study, four deep learning models, called Complex Active Region Flare Forecasting Model (CARFFM)-1, −2, −3, and −4, are established. They take AR longitudinal magnetic fields, AR vector magnetic fields, AR longitudinal magnetic fields and the total unsigned magnetic flux in the neutral line region, AR vector magnetic fields and the total unsigned magnetic flux in the neutral region as input, respectively. These four models can predict the production of M-class or above flares in the complex ARs for the next 48 h. Through comparing the performance of the models, CARFFM-4 has the best forecasting ability, which has the most abundant input information. It is suggested that more valuable and rich input can improve the model performance.

Gas flaring-induced impacts on aquatic resources in the Niger Delta Region, Nigeria

The Niger Delta is the Nigerian oil and gas province. About 10 – 40% of produced associated gas is underutilized and is flared into the environment. Gas flaring is the burning of natural gas and petroleum hydrocarbons in flare stacks by upstream oil companies in oil fields during operations. Flaring operations have adverse impacts on the environmental components and its aquatic resources. This paper reviewed the impacts of gas flaring on aquatic resources in the Niger Delta Region of Nigeria. The study revealed the induced thermal impacts on the aquatic environment to include alteration of ionic components, pH, temperature, conductivity, heavy metal concentration especially in rain water which could cause death of aquatic biota. Water toxicity from acid rain and heating from flare stacks had also caused some fish species to become extinct. Exposure to harmful air pollutants generated during incomplete combustion of gas had been linked to a variety of health hazards such as: cancer, neurological, reproductive and developmental consequences. It also affects vegetation leading to decrease in growth and productivity probably due to changes in soil quality parameters in the aquatic environment. Climate change has an impact on both physical and biological habitats, influencing biodiversity both directly and indirectly via interactions with other environmental factors. It is recommended that strict government legislations on how gas production projects may be conducted should be introduced and monitored. Regulatory agencies must fulfil their responsibilities of enforcing laws and regulregulations to check gas flaring activities in order to protect the aquatic resources of the Niger Delta Region.

X-ray polarization evidence for a 200-year-old flare of Sgr A.

The centre of the Milky Way Galaxy hosts a black hole with a solar mass of about 4 million (Sagittarius A* (Sgr A)) that is very quiescent at present with a luminosity many orders of magnitude below those of active galactic nuclei1. Reflection of X-rays from Sgr A* by dense gas in the Galactic Centre region offers a means to study its past flaring activity on timescales of hundreds and thousands of years2. The shape of the X-ray continuum and the strong fluorescent iron line observed from giant molecular clouds in the vicinity of Sgr A* are consistent with the reflection scenario3-5. If this interpretation is correct, the reflected continuum emission should be polarized6. Here we report observations of polarized X-ray emission in the direction of the molecular clouds in the Galactic Centre using the Imaging X-ray Polarimetry Explorer. We measure a polarization degree of 31% ± 11%, and a polarization angle of -48° ± 11°. The polarization angle is consistent with Sgr A* being the primary source of the emission, and the polarization degree implies that some 200 years ago, the X-ray luminosity of Sgr A* was briefly comparable to that of a Seyfert galaxy.

Chromospheric thermodynamic conditions from inversions of complex Mg II h & k profiles observed in flares

The flare activity of the Sun has been studied for decades, using both space- and ground-based telescopes. The former have mainly focused on the corona, while the latter have mostly been used to investigate the conditions in the chromosphere and photosphere. The Interface Region Imaging Spectrograph (IRIS) instrument has served as a gateway between these two cases, given its capability to observe quasi-simultaneously the corona, the transition region, and the chromosphere using different spectral lines in the near- and far-ultraviolet ranges. IRIS thus provides unique diagnostics to investigate the thermodynamics of flares in the solar atmosphere. In particular, the Mg II h&k and the Mg II UV triplet lines provide key information about the thermodynamics of low to upper chromosphere, while the C II 1334 & 1335 Å lines cover the upper-chromosphere and low transition region. The Mg II h&k and the Mg II UV triplet lines show a peculiar, pointy shape before and during the flare activity. The physical interpretation, i.e., the physical conditions in the chromosphere, that can explain these profiles has remained elusive. In this paper, we show the results of a non-LTE inversion of such peculiar profiles. To better constrain the atmospheric conditions, the Mg II h&k and the Mg II UV triplet lines are simultaneously inverted with the C II 1334 & 1335 Å lines. This combined inversion leads to more accurate derived thermodynamic parameters, especially the temperature and the turbulent motions (micro-turbulence velocity). We use an iterative process that looks for the best fit between the observed profile and a synthetic profile obtained by considering non-local thermodynamic equilibrium and partial frequency redistribution of the radiation due to scattered photons. This method is computationally rather expensive (≈6 CPU-hour/profile). Therefore, we use the k-means clustering technique to identify representative profiles and associated representative model atmospheres. By inverting the representative profiles with the most advanced inversion code (STiC), in addition to recover the main physical parameters, we are able to conclude that these unique, pointy profiles are associated with a large gradient in the line-of-sight velocity along the optical depth in the high chromosphere.

The first photometric, period variation, and flare activity studies of TIC 24233294: Reviewing with the latest results of well-studied late-type active binaries

In the current study, we present the first photometric, period variation, and flaring activity investigations of TIC 24233294. Additionally, we also review and report the flaring activity of five well-studied eclipsing binaries BX Tri, V405 And, GJ 3236, Thor 42, and GU Boo. Using the Transiting Exoplanet Survey Satellite (TESS) data, continuous variations in the light curves of binaries TIC 24233294, and BX Tri are analysed and presented. The primary and secondary components of all the six binaries in the study are M-type dwarfs. All these binaries are observed to be in detached/semi-detached configuration. Photometric analysis on TIC 24233294 and BX Tri was carried out using the Wilson–Devinney program. The long-term orbital period changes are analyzed and presented, on the basis of photometric solutions and the evolutionary status of the binary systems in the study. Flares are observed to be common in stars with outer convection zones. We identified flares on all binaries in the study and calculated their characteristic parameters like amplitudes, frequency, duration, and energies. Many superflares and few hyperflares were identified in the list of flares detected within the energy range of 1033-1037 erg. The flare events in the binaries could be related to the strong tidal interactions between the components of the binaries and fully/deeper convective interiors.

EI Eridani: A star under the influence

Context. Homogeneous photometric time series spanning decades provide a unique opportunity to study the long-term cyclic behavior of active spotted stars such as our target EI Eridani. In addition, with ultraprecise space photometry data, it is possible to investigate the accompanying flare activity in detail. However, the rotation period of ≈2 days for EI Eri makes it impossible to achieve time-resolved surface images from a single ground-based observing site. Therefore, for this purpose, spectroscopic data from a multi-site observing campaign are needed. Aims. We use our photometric time series of more than 40 yr to analyze the long-term behavior of EI Eri. We investigate flare activity using photometric data obtained with the Transiting Exoplanet Survey Satellite (TESS). The MUlti-SIte Continuous Spectroscopy (MUSICOS) campaign in 1998 was designed to achieve high-resolution, multi-wavelength spectroscopic observations from many sites around the globe, which meant that uninterrupted phase coverage of EI Eri became available. We use these data to reconstruct successive surface-temperature maps of the star in order to study the changes of starspots on a very short timescale. Methods. We used long-term seasonal period analysis of our photometric time series to study changes in the rotational period. We also applied short-term Fourier-transform to look for activity cycle-like changes. We also studied the phase and frequency distribution of hand-selected flares. We applied our multi-line Doppler imaging code to reconstruct four consecutive Doppler images. These images were also used to measure surface differential rotation with our cross-correlation technique. In addition, we carried out tests to demonstrate how Doppler imaging is affected by the fact that the data came from several different instruments with different spectral resolutions. Results. Seasonal period analysis of the light curve reveals a smooth, significant change in period, possibly indicating the evolution of active latitudes. Temperature curves from B − V and V − I show slight differences, indicating the activity of EI Eri is spot dominated. Short-term Fourier transform reveals smoothly changing cycles of between 4.5 and 5.5 yr and of between 8.9 and 11.6 yr. The time-resolved spotted surface of EI Eri from Doppler imaging enabled us to follow the evolution of the different surface features. Cross-correlating the consecutive Doppler maps reveals surface shear of α = 0.036 ± 0.007. Our tests validate our approach and show that the surface-temperature distribution is adequately reconstructed by our method. The tests also indicate how accurately the cross-correlation method can reproduce the surface shear as a function of the spectral resolution.

Analysis of the Possibilities of Short-Term Prediction of Geomagnetic Perturbations from Observations of Coronal Mass Ejections at the BSA LPI Radio Telescope

From April 2021 to October 2022, in the monitoring data obtained daily at the Big Scanning Antenna radio telescope (BSA LPI), 11 events were identified for which X-ray flares in the solar corona were followed by magnetic storms on Earth. Interplanetary scintillation monitoring data were considered together with data on solar flare activity and a simple kinematic model of ejection propagation. Based on the estimated ejection velocity between the Sun and the probed region, under the assumption of a constant velocity, the time of arrival of the ejection to the Earth was calculated. Of the 11 events considered, 7 are associated with solitary flares followed by a coronal mass ejection (CME) and 4 are more complex and possibly associated with corotating perturbations or a superposition of corotating and flare perturbations. For the entire set of events, the average time of the real onset of a magnetic storm after the time predicted by the model was 3.6 h and the average time between the onset of scintillation enhancement and the onset of a magnetic storm was 20.1 h. For events associated with solitary flares, the magnetic storm began, on average, 0.8 hours after the predicted time and 15.6 hours after the onset of scintillation enhancement. The delay of magnetic storms with respect to the predicted time is apparently related to the deceleration of the ejection between the probed region of the solar wind and the Earth’s orbit.

Leukemia Cutis as the Presenting Sign of Acute Myeloid Leukemia in an HIV+ patient

Leukemia Cutis (LC) is a rare extramedullary cutaneous manifestation of leukemia that varies in terms of clinical presentation, leukemia type, and timing of presentation in relation to systemic leukemia. LC typically presents following diagnosis of systemic leukemia and during an active flare or relapse. An estimated 3.7% of patients with Acute Myeloid Leukemia (AML) develop LC. A 61-year-old male with poorly controlled HIV presented with a rash that began one month prior on his cheek as a red papule, which he believed was an ingrown hair. On exam, pink and yellow firm papules and nodules covered his entire body surface except the groin and axilla. One nodule held a peau d’orange appearance. The rash was overall asymptomatic, and he reported only increased fatigue. His CD4 count and viral load were 136 and 330,000 respectively. One punch biopsy revealed negative cultures for fungus, bacteria, and acid-fast bacilli. Two biopsies sent for pathologic evaluation revealed AML of the skin. Bone marrow biopsy confirmed AML. Clinically the presentation of LC is nonspecific, and systemic symptoms rarely appear in conjunction with LC. High clinical suspicion and histopathologic examination are necessary for diagnosis of LC.

Extracellular vesicles in systemic juvenile idiopathic arthritis.

Systemic juvenile idiopathic arthritis is a chronic pediatric inflammatory disease of unknown etiology, characterized by fever, rash, hepatosplenomegaly, serositis, and arthritis. We hypothesized that intercellular communication, mediated by extracellular vesicles, contributes to systemic juvenile idiopathic arthritis pathogenesis and that the number and cellular sources of extracellular vesicles would differ between inactive and active states of systemic juvenile idiopathic arthritis and healthy controls. We evaluated plasma from healthy pediatric controls and patients with systemic juvenile idiopathic arthritis with active systemic flare or inactive disease. We isolated extracellular vesicles by size exclusion chromatography and determined total extracellular vesicle abundance and size distribution using microfluidic resistive pulse sensing. Cell-specific extracellular vesicle subpopulations were measured by nanoscale flow cytometry. Isolated extracellular vesicles were validated using a variety of ways, including nanotracking and cryo-electron microscopy. Extracellular vesicle protein content was analyzed in pooled samples using mass spectrometry. Total extracellular vesicle concentration did not significantly differ between controls and patients with systemic juvenile idiopathic arthritis. Extracellular vesicles with diameters <200 nm were the most abundant, including the majority of cell-specific extracellular vesicle subpopulations. Patients with systemic juvenile idiopathic arthritis had significantly higher levels of extracellular vesicles from activated platelets, intermediate monocytes, and chronically activated endothelial cells, with the latter significantly more elevated in active systemic juvenile idiopathic arthritis relative to inactive disease and controls. Protein analysis of isolated extracellular vesicles from active patients showed a proinflammatory profile, uniquely expressing heat shock protein 47, a stress-inducible protein. Our findings indicate that multiple cell types contribute to altered extracellular vesicle profiles in systemic juvenile idiopathic arthritis. The extracellular vesicle differences between systemic juvenile idiopathic arthritis disease states and healthy controls implicate extracellular vesicle-mediated cellular crosstalk as a potential driver of systemic juvenile idiopathic arthritis disease activity.

Flare activity behaviour of low mass eclipsing binary KOI-7234

Flare activity behaviour of low mass eclipsing binary KOI-7234