arXiv subjects

Rachel A. Osten

Publications and source records attributed to Rachel A. Osten.

At least 19 recordsLinked to original sources

arXiv2026

Broadband 12-26 GHz Radio Radiation Reveals Evidence for Micro-flares on AU Mic

We present sequential 12-18 and 18-26 GHz radio-band ($Ku$, $K$) VLA observations of the 22 Myr dM1e star AU Mic. We detect two flares and two marginal events over a total of 3 contiguous hours on source, resulting in a radio flare rate of $\sim$1 flare hour$^{-1}$. While this rate is consistent with previous $Ku$-band observations, both flaring ($<$1 mJy) and quiescent ($\sim$0.4 mJy) flux densities are significantly lower. Furthermore, the quiescent spectral shape here is distinct, allowing for unique constraints on the radio-emitting sources of AU Mic. The time-averaged quiescent spectrum is best described by gyrosynchrotron radiation with a peak around 17 GHz and an optically thin spectral index of $\alpha \approx -0.6$. We estimate that the source regions have magnetic field strengths of $\sim$1 kG and cover a fraction of $<$0.5% of the stellar surface, yet the instantaneous total electron kinetic energies are $\sim$10$^{28}$ erg. The power-law index describing the distribution of electrons with energy derived from the spectral index, $\delta \approx 2$, implies a near-continuous injection of electrons. This could arise from micro-flares that occur over the surface of AU Mic that sustain the radio radiation. One clear flare per band occurs, with decay-to-rise $e$-folding time ratios of $3 - 4$, indicating magnetic trapping of the electrons. The $Ku$-band flare is optically thick during the rise and peak times, indicating a peak frequency above 18 GHz. Together, these quiescent and flaring characteristics suggest that continuous, unresolved micro-flaring and magnetic trapping dominate the non-thermal radio emission of active M-dwarf coronae.

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arXiv2026

ESCAPE: a small explorer mission to study the stellar drivers of exoplanet evolution

The long-term stability of exoplanetary atmospheres depends critically on the extreme-ultraviolet (EUV) photon and high-energy particle fluxes from the host star, which are poorly constrained. To address this key gap in our understanding of atmospheric retention, we present the Extreme-ultraviolet Stellar Characterization for Atmospheric Physics and Evolution (ESCAPE) mission, a NASA Small Explorer concept proposed in 2026. ESCAPE employs extreme- and far-ultraviolet spectroscopy (80 - 1650 Ang) to provide the first comprehensive study of the stellar EUV history and stellar coronal mass ejection (CME) environments that control atmospheric mass-loss and determine the habitability of rocky exoplanets. This paper outlines both the primary science goals of the mission, the breadth of future general observer investigations, and a detailed design study of the mission's instrumentation. The ESCAPE instrument comprises a grazing incidence telescope that feeds multiple diffraction gratings and a photon-counting detector. We describe a demonstration of the Hettrick-Bowyer telescope, etched silicon diffraction gratings, the microchannel plate detector and housing, and gold and zirconium coatings. We present a STOP analysis that verifies ESCAPE's ability to meet its structural integrity, thermal stability, and optical performance requirements throughout the mission environment.

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arXiv2026

Atmospheric Escape Rates from Mars - If it Orbited an Old M-Dwarf Star

Atmospheric escape is an important process that influences the evolution of planetary atmospheres. A variety of physical mechanisms can contribute to escape from an atmosphere, including thermal escape, ion escape, photochemical escape, and sputtering. Here we estimate escape rates via each of these processes for a hypothetical Mars-like exoplanet orbiting Barnard's star (an old, inactive M dwarf star). We place the planet at an orbital distance that receives the same total stellar flux as it does in our solar system. We use the measured stellar extreme ultraviolet (EUV) spectrum and assumptions on the star's magnetic field to determine both the high-energy radiation and the stellar wind environment around the planet. This information is used to model the response of the planet's thermosphere, exosphere and magnetosphere using a variety of models that have been validated against solar system observations. We find overall escape rates that are dominated by thermal processes and elevated by 2-5 orders of magnitude relative to present-day Mars, suggesting that a Mars-like planet orbiting Barnard's star would not retain a significant atmosphere for more than 10's of millions of years. Recently reported planets around Barnard's star should also not have retained significant atmospheres. By extension, Mars-like planets orbiting any M dwarf near the 'Habitable Zone' should not retain atmospheres for extended periods of time.

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arXiv2025

A 7 Day Multiwavelength Flare Campaign on AU Mic. IV: Quiescent Gyrosynchrotron and Gyroresonance Radiation from 12 to 25 GHz

We present an analysis of the radio quiescent data from a multiwavelength campaign of the active M-dwarf flare star AU Mic (dM1e) that occurred in October 2018. Using Ku-band data (12 to 18 GHz) from the Very Large Array and K-band data (17 to 25 GHz) from the Australia Telescope Compact Array, we find that the quiescent spectrum can be decomposed into two components: one falling with frequency and one that remains flat. The flat component has a relatively steady flux density of 0.64 $\pm$ 0.14 mJy. The falling component varies in strength, but exhibits a spectral index of $α$ = $-0.88 \pm 0.10$. The falling component is thus consistent with nonthermal, optically thin gyrosynchrotron radiation with a corresponding power-law index similar to flares from AU Mic. While a flat component may arise from thermal, optically thin free-free emission, the observed flux density and inferred mass-loss rate are both too large compared to previous stellar wind and X-ray emission theory and models, necessitating an alternative explanation. This flat component instead matches well with an optically thick gyroresonance component integrated over multiple source regions such that the composite spectra are reasonably flat. The persistence of these components across the rotational period suggests multiple source regions, which may help explain changes in flux density and persistent high-energy electrons.

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arXiv2025

Radio and Optical Flares on the dMe Flare Star EV Lac

We present the results of a coordinated campaign to observe radio and optical stellar flares from the nearby M dwarf flare star EV~Lac. From a total of 27 hours of radio and 29 hours of optical observations, we examine the correspondence of the action of accelerated electrons of different energies in two distinct regions of the stellar atmosphere. We find that out of 9 optical flares with suitable radio coverage, only four have plausible evidence for a radio response. Optical photometric properties cannot predict which flares will have a radio response. From flares with time-resolved optical spectroscopy available, optical-only flares have similar implied electron distributions, while those with radio responses better correlate with higher low-energy cutoffs. The optical flares with a radio response all exhibit a delay between the optical and radio peaks of $\approx$1-7 minutes, with the optical flare peaking earlier in all cases. This likely indicates multiple loops are involved in the event, and/or the different impacts on electrons trapped in a magnetic loop (producing radio emission), versus those directly precipitating from the loop (producing the optical flare). We also remark on the radio spectral index behavior at early times for the largest radio flare observed in this study, which we interpret as evidence for increased opacity from a chromospheric evaporation front.

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arXiv2025

The Solar Neighborhood. LV. M Dwarf Twin Binaries -- One in Five Twin Sibling Pairs Are Mismatched in Activity and/or Rotation

We report on a study of 36 pairs of `twin' M dwarfs in wide binaries and assess how similarly the stars behave. Stars in each twin pair have BP, RP, $J$, $H$, and $K_s$ differing by $<$0.10 mag, mass estimates matching within $<$3%, and presumably the same age and composition. We utilize short- and long-term photometry, multi-epoch spectroscopy, and archival data to measure rotation periods, photometric activity levels, and H$α$ equivalent widths for many systems. Speckle imaging, radial velocities, and long-term astrometry are used to identify unresolved companions, yielding three systems with unseen components. Among the 33 remaining twin systems, numerous remarkable pairs show nearly identical rotation rates and activity levels between their twin components, including cases throughout the lower main sequence and across a broad range of rotation-activity parameter space. In contrast, mismatches with $>$25% differences exist in rotation period for $21\%_{-7\%}^{+14\%}$ of twin pairs, in rotation amplitude for $67\%_{-15\%}^{+10\%}$ of pairs, in multi-year photometric variability for $33\%_{-9\%}^{+12\%}$ of pairs, and in H$α$ activity for $21\%_{-6\%}^{+9\%}$ of pairs, with fully convective systems generally mismatched more often. Thus, roughly one out of five M dwarf twin sets does not match in rotation and/or activity despite otherwise identical fundamental parameters. Furthermore, we compile three key systems showing larger relative active/inactive H$α$ mismatches. We propose the various mismatches likely stem from factors such as dynamo stochasticity, activity cycles, formative disk aspects, and/or star-planet interactions, depending on the system. These well-vetted twins offer ripe targets for many future investigations.

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arXiv2025

A Seven-Day Multi-Wavelength Flare Campaign on AU Mic III: Quiescent and Flaring Properties of the X-ray Spectra and Chromospheric lines

We present the X-ray quiescent and flaring properties from a unique, 7-day multiwavelength observing campaign on the M1 flare star AU Mic. Combining the XMM-Newton X-ray spectra with the chromospheric line and broadband NUV and optical continuum observations provides a dataset that is one of the most comprehensive to date. We analyze the sample of 38 X-ray flares and study in detail the X-ray flare temperature ($T$) and emission measure (EM) evolutions of three largest flares with the X-ray flare energies of $>10^{33}$ erg. The $T-\mathrm{EM}$ evolution tracks and multi-wavelength emission evolutions of the largest-amplitude Neupert-type flare reveal that the so-called ``Flare H-R diagram" is consistent with thermal coronal flare emission evolution. The two other more gradual and longer duration X-ray flares are interpreted as having larger size scales. None of the 17 H$α$ and H$β$ flares show clear blue/red wing asymmetries, including the ones associated with the potential X-ray dimming event previously reported. The above largest-amplitude Neupert flare shows clear symmetric H$α$ and H$β$ broadenings with roughly $\pm$400 and $\pm$600 km s$^{-1}$, respectively, which are synchronized with the optical/NUV continuum emission evolution. Radiative hydrodynamic modeling results suggest that electron beam heating parameters that have been used to reproduce M-dwarf flare NUV/optical continuum emissions can reproduce these large broadenings of H$α$ and H$β$ lines. These results suggest that these most energetic M-dwarf flares are associated with stronger magnetic field flux densities and larger size scales than solar flares but can be interpreted in terms of the standard flare model.

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arXiv2025

The Variable Radio Emission of V830 Tau and Its Putative Planet

We report on the first moderate-length time-scale observations of a young stellar object (YSO) at microwave frequencies. V830 Tau was monitored over the course of eight days with the JVLA at a frequency range of 4-8 GHz. Previous brief radio observations of this purported planet-hosting star indicated a radio-bright source with sparse evidence of dramatic intensity changes. Our observations confirm variability larger than a factor of five over the 8 days, with closer-spaced data indicating a long-lived flare event spanning multiple days. We discuss a hypothesis that the large, long-duration radio flare may be produced as a result of magnetospheric interaction between the star and its purported planet, using multi-year monitoring of a few active binary systems with the Green Bank Interferometer to augment our discussion. Although we cannot disentangle the effect of the large stellar surface area from any effects of orbital separation, the disputed star-planet system would have a large amount of power generated from stretching and breaking of magnetic fields. If this long-duration flare behavior repeats with additional data on timescales close to the planetary orbital period, microwave signatures of interacting magnetospheres could be a new observational tool to confirm the existence of planets around young, magnetically active stars.

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arXiv2025

The Proxima Centauri Campaign -- First Constraints On Millimeter Flare Rates from ALMA

Proxima Centauri (Cen) has been the subject of many flaring studies due to its proximity and potential to host habitable planets. The discovery of millimeter flares from this M dwarf with ALMA has opened a new window into the flaring process and the space-weather environments of exoplanets like Proxima b. Using a total of ~50 hours of ALMA observations of Proxima Cen at 1.3 mm (233 GHz), we add a new piece to the stellar flaring picture and report the first cumulative flare frequency distribution (FFD) at millimeter wavelengths of any M dwarf. We detect 463 flares ranging from energies 10$^{24}$ erg to 10$^{27}$ erg. The brightest and most energetic flare in our sample reached a flux density of 119 $\pm$ 7 mJy, increasing by a factor of 1000x the quiescent flux, and reaching an energy of 10$^{27}$ erg in the ALMA bandpass, with t$_{1/2}$~16s. From a log-log linear regression fit to the FFD, we obtain a power law index of $α_\mathrm{FFD}$ = 2.92 $\pm$ 0.02, much steeper than $α_\mathrm{FFD}$ values (~2) observed at X-ray to optical wavelengths. If millimeter flare rates are predictive of flare rates at extreme-UV wavelengths, the contribution of small flares to the radiation environment of Proxima b may be much higher than expected based on the shallower power-law slopes observed at optical wavelengths.

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arXiv2025

A 7-Day Multi-Wavelength Flare Campaign on AU Mic. II: Electron Densities and Kinetic Energies from High-Frequency Radio Flares

M dwarfs are the most common type of star in the solar neighborhood, and many exhibit frequent and highly energetic flares. To better understand these events across the electromagnetic spectrum, a campaign observed AU Mic (dM1e) over 7 days from the X-ray to radio regimes. Here, we present high-time-resolution light curves from the Karl G. Jansky Very Large Array (VLA) Ku band (12--18 GHz) and the Australia Telescope Compact Array (ATCA) K band (16--25 GHz), which observe gyrosynchrotron radiation and directly probe the action of accelerated electrons within flaring loops. Observations reveal 16 VLA and 3 ATCA flares of varying shapes and sizes, from a short (30 sec) spiky burst to a long-duration ($\sim$5 hr) decaying exponential. The Ku-band spectral index is found to often evolve during flares. Both rising and falling spectra are observed in the Ku-band, indicating optically thick and thin flares, respectively. Estimations from optically thick radiation indicate higher loop-top magnetic field strengths ($\sim$1 kG) and sustained electron densities ($\sim$10$^{6}$ cm$^{-3}$) than previous observations of large M-dwarf flares. We estimate the total kinetic energies of gyrating electrons in optically thin flares to be between 10$^{32}$ and 10$^{34}$ erg when the local magnetic field strength is between 500 and 700 G. These energies are able to explain the combined radiated energies from multi-wavelength observations. Overall, values are more aligned with modern radiative-hydrodynamic simulations of M-dwarf flares, and future modeling efforts will better constrain findings.

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arXiv2024

Rising Near-Ultraviolet Spectra in Stellar Megaflares

Flares from M-dwarf stars can attain energies up to $10^4$ times larger than solar flares but are generally thought to result from similar processes of magnetic energy release and particle acceleration. Larger heating rates in the low atmosphere are needed to reproduce the shape and strength of the observed continua in stellar flares, which are often simplified to a blackbody model from the optical to the far-ultraviolet (FUV). The near-ultraviolet (NUV) has been woefully undersampled in spectral observations despite this being where the blackbody radiation should peak. We present Hubble Space Telescope NUV spectra in the impulsive phase of a flare with $E_{\rm{TESS}} \approx 7.5 \times 10^{33}$ erg and a flare with $E_{\rm{TESS}} \approx 10^{35}$ erg and the largest NUV flare luminosity observed to date from an M star. The composite NUV spectra are not well represented by a single blackbody that is commonly assumed in the literature. Rather, continuum flux rises toward shorter wavelengths into the FUV, and we calculate that an optical $T=10^4$ K blackbody underestimates the short wavelength NUV flux by a factor of $\approx 6$. We show that rising NUV continuum spectra can be reproduced by collisionally heating the lower atmosphere with beams of $E \gtrsim 10$ MeV protons or $E \gtrsim 500$ keV electrons and flux densities of $10^{13}$ erg cm$^{-2}$ s$^{-1}$. These are much larger than canonical values describing accelerated particles in solar flares.

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arXiv2024

The Solar Neighborhood LII: M Dwarf Twin Binaries -- Presumed Identical Twins Appear Fraternal in Variability, Rotation, H$α$, and X-rays

We present an investigation into the rotation and stellar activity of four fully convective M dwarf `twin' wide binaries. Components in each pair have (1) astrometry confirming they are common-proper-motion binaries, (2) Gaia $BP$, $RP$, and 2MASS $J$, $H$, and $K_s$ magnitudes matching within 0.10 mag, and (3) presumably the same age and composition. We report long-term photometry, rotation periods, multi-epoch H$α$ equivalent widths, X-ray luminosities, time series radial velocities, and speckle observations for all components. Although it might be expected for the twin components to have matching magnetic attributes, this is not the case. Decade-long photometry of GJ 1183 AB indicates consistently higher spot activity on A than B, a trend matched by A appearing 58$\pm$9% stronger in $L_X$ and 26$\pm$9% stronger in H$α$ on average -- this is despite similar rotation periods of A=0.86d and B=0.68d, thereby informing the range in activity for otherwise identical and similarly-rotating M dwarfs. The young $β$ Pic Moving Group member 2MA 0201+0117 AB displays a consistently more active B component that is 3.6$\pm$0.5 times stronger in $L_X$ and 52$\pm$19% stronger in H$α$ on average, with distinct rotation at A=6.01d and B=3.30d. Finally, NLTT 44989 AB displays remarkable differences with implications for spindown evolution -- B has sustained H$α$ emission while A shows absorption, and B is $\geq$39$\pm$4 times stronger in $L_X$, presumably stemming from the surprisingly different rotation periods of A=38d and B=6.55d. The last system, KX Com, has an unresolved radial velocity companion, and is therefore not a twin system.

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arXiv2024

A Multiwavelength Survey of Nearby M dwarfs: Optical and Near-Ultraviolet Flares and Activity with Contemporaneous TESS, Kepler/K2, \textit{Swift}, and HST Observations

We present a comprehensive multiwavelength investigation into flares and activity in nearby M~dwarf stars. We leverage the most extensive contemporaneous dataset obtained through the Transiting Exoplanet Sky Survey (TESS), Kepler/K2, the Neil Gehrels Swift Observatory (\textit{Swift}), and the Hubble Space Telescope (HST), spanning the optical and near-ultraviolet (NUV) regimes. In total, we observed 213 NUV flares on 24 nearby M dwarfs, with $\sim$27\% of them having detected optical counterparts, and found that all optical flares had NUV counterparts. We explore NUV/optical energy fractionation in M dwarf flares. Our findings reveal a slight decrease in the ratio of optical to NUV energies with increasing NUV energies, a trend in agreement with prior investigations on G-K stars' flares at higher energies. Our analysis yields an average NUV fraction of flaring time for M0-M3 dwarfs of 2.1\%, while for M4-M6 dwarfs, it is 5\%. We present an empirical relationship between NUV and optical flare energies and compare to predictions from radiative-hydrodynamic and blackbody models. We conducted a comparison of the flare frequency distribution (FFDs) of NUV and optical flares, revealing the FFDs of both NUV and optical flares exhibit comparable slopes across all spectral subtypes. NUV flares on stars affect the atmospheric chemistry, the radiation environment, and the overall potential to sustain life on any exoplanets they host. We find that early and mid-M dwarfs (M0-M5) have the potential to generate NUV flares capable of initiating abiogenesis.

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arXiv2023

A Seven-Day Multi-Wavelength Flare Campaign on AU Mic I: High-Time Resolution Light Curves and the Thermal Empirical Neupert Effect

We present light curves and flares from a seven day, multi-wavelength observational campaign of AU Mic, a young and active dM1e star with exoplanets and a debris disk. We report on 73 unique flares between the X-ray to optical data. We use high-time resolution NUV photometry and soft X-ray (SXR) data from XMM-Newton to study the empirical Neupert effect, which correlates the gradual and impulsive phase flaring emissions. We find that 65% (30 of 46) flares do not follow the Neupert effect, which is three times more excursions than seen in solar flares, and propose a four part Neupert effect classification (Neupert, Quasi-Neupert, Non-Neupert I & II) to explain the multi-wavelength responses. While the SXR emission generally lags behind the NUV as expected from the chromospheric evaporation flare models, the Neupert effect is more prevalent in larger, more impulsive flares. Preliminary flaring rate analysis with X-ray and U-band data suggests that previously estimated energy ratios hold for a collection of flares observed over the same time period, but not necessarily for an individual, multi-wavelength flare. These results imply that one model cannot explain all stellar flares and care should be taken when extrapolating between wavelength regimes. Future work will expand wavelength coverage using radio data to constrain the nonthermal empirical and theoretical Neupert effects to better refine models and bridge the gap between stellar and solar flare physics.

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arXiv2022

Constraints on Stellar Flare Energy Ratios in the NUV and Optical From a Multiwavelength Study of GALEX and Kepler Flare Stars

We present a multiwavelength study of stellar flares on primarily G-type stars using overlapping time domain surveys in the near ultraviolet (NUV) and optical regimes. The NUV (GALEX) and optical (Kepler) wavelength domains are important for understanding energy fractionations in stellar flares, and for constraining the associated incident radiation on a planetary atmosphere. We follow up on the NUV flare detections presented in Brasseur et al. 2019, using coincident Kepler long (1557 flares) and short (2 flares) cadence light curves. We find no evidence of optical flares at these times, and place limits on the flare energy ratio between the two wavebands. We find that the energy ratio is correlated with GALEX band energy, and extends over a range of about three orders of magnitude in the ratio of the upper limit of Kepler band flare energy to NUV flare energy at the same time for each flare. The two flares with Kepler short cadence data indicate that the true Kepler band energy may be much lower than the long cadence based upper limit. A similar trend appears for the bulk flare energy properties of non-simultaneously observed flares on the same stars. We provide updated models to describe the flare spectral energy distribution from the NUV through the optical including continua and emission lines to improve upon blackbody-only models. The spread of observed energy ratios is much larger than encompassed by these models and suggests new physics is at work. These results call for better understanding of NUV flare physics and provide a cautionary tale about using only optical flare measurements to infer the UV irradiation of close-in planets.

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arXiv2022

First Millimeter Flares Detected from Epsilon Eridani with ALMA

We report the detection of three large millimeter flaring events from the nearby Sun-like, $ε$ Eridani, found in archival ALMA 12m and ACA observations at 1.33 mm taken from 2015 January 17-18 and 2016 October 24-November 23, respectively. This is the first time that flares have been detected from a Sun-like star at millimeter wavelengths. The largest flare among our data was detected in the ALMA observations on 2015 January 17 from 20:09:10.4-21:02:49.3 (UTC) with a peak flux density of 28 $\pm$ 7 mJy and a duration of 9 sec. The peak brightness of the largest flare is $ 3.4 \pm 0.9 \times 10^{14}$ erg s$^{-1}$Hz$^{-1}$, a factor of $>50\times$ times brighter than the star's quiescent luminosity and $>10\times$ brighter than solar flares observed at comparable wavelengths. We find changes in the spectral index (F$_ν\proptoν^α$) at the flare peak, with $α$ = 1.81 $\pm$ 1.94 and a lower limit on the fractional linear polarization $|Q/I| = $ 0.08 $\pm$ 0.12. This positive spectral index is more similar to millimeter solar flares, differing from M dwarf flares also detected at millimeter wavelengths that exhibit steeply negative spectral indices.

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arXiv2022

New Time-Resolved, Multi-Band Flares In The GJ 65 System With gPhoton

Characterizing the distribution of flare properties and occurrence rates is important for understanding habitability of M dwarf exoplanets. The GALEX space telescope observed the GJ 65 system, composed of the active, flaring M stars BL Cet and UV Cet, for 15900 seconds (~4.4 hours) in two ultraviolet bands. The contrast in flux between flares and the photospheres of cool stars is maximized at ultraviolet wavelengths, and GJ 65 is the brightest and nearest flaring M dwarf system with significant GALEX coverage. It therefore represents the best opportunity to measure low energy flares with GALEX. We construct high cadence light curves from calibrated photon events and find 13 new flare events with NUV energies ranging from 10^28.5 - 10^29.5 ergs and recover one previously reported flare with an energy of 10^31 ergs. The newly reported flares are among the smallest M dwarf flares observed in the ultraviolet with sufficient time resolution to discern light curve morphology. The estimated flare frequency at these low energies is consistent with extrapolation from the distributions of higher-energy flares on active M dwarfs measured by other surveys. The largest flare in our sample is bright enough to exceed the local non-linearity threshold of the GALEX detectors, which precludes color analysis. However, we detect quasi-periodic pulsations (QPP) during this flare in both the FUV and NUV bands at a period of ~50 seconds, which we interpret as a modulation of the flare's chromospheric thermal emission through periodic triggering of reconnection by external MHD oscillations in the corona.

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arXiv2021

Simultaneous Multiwavelength Flare Observations of EV Lacertae

We present the first results of our ongoing project conducting simultaneous multiwavelength observations of flares on nearby active M dwarfs. We acquired data of the nearby dM3.5e star EV Lac using 5 different observatories: NASA's Transiting Exoplanet Survey Satellite (TESS), NASA's Neil Gehrels Swift Observatory (\textit{Swift}), NASA's Neutron Interior Composition Explorer (NICER), the University of Hawaii 2.2-m telescope (UH88) and the Las Cumbres Observatory Global Telescope (LCOGT) Network. During the $\sim$25 days of TESS observations, we acquired three simultaneous UV/X-ray observations using \textit{Swift} that total $\sim$18 ks, 21 simultaneous epochs totaling $\sim$98 ks of X-ray data using NICER, one observation ($\sim$ 3 hours) with UH88, and one observation ($\sim$ 3 hours) with LCOGT. We identified 56 flares in the TESS light curve with estimated energies in the range log $E_{\rm T}$ (erg) = (30.5 - 33.2), nine flares in the \textit{Swift} UVM2 light curve with estimated energies in the range log $E_{UV}$ (erg) = (29.3 - 31.1), 14 flares in the NICER light curve with estimated minimum energies in the range log $E_{N}$ (erg) = (30.5 - 32.3), and 1 flare in the LCOGT light curve with log $E_{L}$ (erg) = 31.6. We find that the flare frequency distributions (FFDs) of TESS and NICER flares have comparable slopes, $β_{T}$ = -0.67$\pm$0.09 and $β_{N}$ = -0.65$\pm$0.19, and the FFD of UVOT flares has a shallower slope ($β_{U}$ = -0.38$\pm$0.13). Furthermore, we do not find conclusive evidence for either the first ionization potential (FIP) or the inverse FIP effect during coronal flares on EV Lac.

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