Stellar Flares from the First TESS Data Release: Exploring a New Sample of M Dwarfs

The Astronomical Journal, Год журнала: 2020, Номер 159(2), С. 60 - 60

Опубликована: Янв. 20, 2020

Abstract We perform a study of stellar flares for the 24,809 stars observed with 2 minute cadence during first two months TESS mission. Flares may erode exoplanets’ atmospheres and impact their habitability, but might also trigger genesis life around small stars. provides new sample bright dwarf in our galactic neighborhood, collecting data thousands M dwarfs that host habitable exoplanets. Here, we use an automated search accompanied by visual inspection. Then, public allesfitter code robustly selects appropriate model potentially complex via Bayesian evidence. identify 1228 flaring stars, 673 which are dwarfs. Among 8695 total, largest superflare increased brightness factor 16.1. Bolometric flare energies range from 10 31.0 to 36.9 erg, median 33.1 erg. Furthermore, rate energy as function type rotation period. solidify past findings fast rotating most likely amplitude is independent Finally, link results criteria prebiotic chemistry, atmospheric loss through coronal mass ejections, ozone sterilization. Four exoplanet candidates alerted on , discuss how these effects can life. With upcoming releases, analysis be expanded almost all aiding defining habitability.

Язык: Английский

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Atmospheric escape from the TRAPPIST-1 planets and implications for habitability

Proceedings of the National Academy of Sciences, Год журнала: 2017, Номер 115(2), С. 260 - 265

Опубликована: Дек. 28, 2017

Significance The search for exoplanets has rapidly emerged as one of the most important endeavors in astronomy. This field received a major impetus with recent discovery seven temperate Earth-sized orbiting nearby ultracool dwarf star TRAPPIST-1. One crucial requirements conventional (surface-based) planetary habitability is presence an atmosphere over long timescales. We determine atmospheric escape rates numerically and analytically planets TRAPPIST-1 system show that outer are potentially likely to retain their atmospheres billion-year Our work far-reaching profound implications terrestrial around M dwarfs.

Язык: Английский

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Exoplanet Biosignatures: Future Directions

Astrobiology, Год журнала: 2018, Номер 18(6), С. 779 - 824

Опубликована: Июнь 1, 2018

We introduce a Bayesian method for guiding future directions detection of life on exoplanets. describe empirical and theoretical work necessary to place constraints the relevant likelihoods, including those emerging from better understanding stellar environment, planetary climate geophysics, geochemical cycling, universalities physics chemistry, contingencies evolutionary history, properties as an emergent complex system, mechanisms driving emergence life. provide examples how formalism could guide search strategies, determining observations prioritize or deciding between targeted searches larger lower resolution surveys generate ensemble statistics address methodology constrain prior probability with without positive detection. Key Words: Exoplanets—Biosignatures—Life detection—Bayesian analysis. Astrobiology 18, 779–824. 1. Introduction 2. Setting Stage: What Is Life? Biosignature? 3. Detecting Unknown Biology Worlds: A Framework 3.1. Habitability in framework biosignatures 4. P(data|abiotic) 4.1. Stellar environment 4.2. Climate geophysics 4.2.1. Coupled tectonic–climate models 4.2.2. Community GCM projects generating P(data|life) 4.3. Geochemical 4.3.1. Anticipating unexpected: statistical approaches characterizing atmospheres non-Earth-like worlds 5. 5.1. Black-box living processes 5.1.1. Type classification Seager et al. (2013a) 5.1.1.1. Energy capture (type I) 5.1.1.2. Biomass II) 5.1.1.3. Other uses III) 5.1.1.4. Products modification gases IV) 5.1.2. Alternatives type 5.1.2.1. I, energy 5.1.2.2. II, biomass 5.1.2.3. III, "other uses" 5.1.2.4. IV 5.1.3. When is it appropriate deconstruct black box? 5.2. Life improbable chemistry 5.3. process 5.3.1. coevolution its planet: Earth example 5.3.2. Calculating conditional probabilities biological evolution past biogeochemical states 5.4. Insights universal biology 5.4.1. Network 5.4.2. Universal scaling laws, applicable other worlds? 6. P(life) 6.1. P(emerge): constraining origins 6.2. Biological innovations 7. Example: Atmospheric Oxygen 8. Tuning Search Strategies Based 9. Conclusions Acknowledgments Author Disclosure Statement References Abbreviations Used

Язык: Английский

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Nitrogen Oxide Concentrations in Natural Waters on Early Earth

Geochemistry Geophysics Geosystems, Год журнала: 2019, Номер 20(4), С. 2021 - 2039

Опубликована: Апрель 1, 2019

Abstract A key challenge in origins‐of‐life studies is estimating the abundances of species relevant to chemical pathways proposed have contributed emergence life on early Earth. Dissolved nitrogen oxide anions ( ), particular nitrate ) and nitrite been invoked diverse chemistry, from oligomerization RNA protometabolism. Recent work has calculated supply prebiotic atmosphere ocean reported steady state [ ] be high across all plausible parameter space. These findings rest assumption that stable natural waters unless processed at a hydrothermal vent. Here, we show unstable reducing environment Sinks due ultraviolet photolysis reactions with reduced iron (Fe 2+ suppress by several orders magnitude relative past predictions. For pH = 6.5–8 T 0–50 °C, find it most probable <1μM ocean. On other hand, ponds favorable drainage characteristics may sustained ≥1μM. As modern Earth, Earth should present as , its much greater stability. inform kind chemistries would possible We discuss implications for highlight need further kinetics reduce considerable uncertainties predicting

Язык: Английский

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On the Potential of Silicon as a Building Block for Life

Life, Год журнала: 2020, Номер 10(6), С. 84 - 84

Опубликована: Июнь 10, 2020

Despite more than one hundred years of work on organosilicon chemistry, the basis for plausibility silicon-based life has never been systematically addressed nor objectively reviewed. We provide a comprehensive assessment possibility biochemistry, based review what is known and modeled, even including speculative work. assess whether or not silicon chemistry meets requirements chemical diversity reactivity as compared to carbon. To expand plausible we explore silicon's complexity in diverse solvents found planetary environments, water, cryosolvents, sulfuric acid. In no environment primarily around option. find that water-rich capacity highly limited due ubiquitous silica formation; can likely only be used rare specialized heteroatom. Cryosolvents (e.g., liquid N2) extremely low solubility all molecules, organosilicons. Sulfuric acid, surprisingly, appears able support much larger water.

Язык: Английский

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Discovery of an Extremely Short Duration Flare from Proxima Centauri Using Millimeter through Far-ultraviolet Observations

The Astrophysical Journal Letters, Год журнала: 2021, Номер 911(2), С. L25 - L25

Опубликована: Апрель 1, 2021

Abstract We present the discovery of an extreme flaring event from Proxima Cen by Australian Square Kilometre Array Pathfinder (ASKAP), Atacama Large Millimeter/submillimeter (ALMA), Hubble Space Telescope (HST), Transiting Exoplanet Survey Satellite (TESS), and du Pont that occurred on 2019 May 1. In millimeter FUV, this flare is brightest ever detected, brightening a factor >1000 >14,000 as seen ALMA HST, respectively. The FUV continuum emission trace each other closely during flare, suggesting could serve proxy for stellar flares become powerful new tool to constrain high-energy radiation environment exoplanets. Surprisingly, optical associated with peaks at much lower level time delay. initial burst has extremely short duration, lasting <10 s. Taken together growing sample M dwarf flares, suggests actually common often originates burst-like events.

Язык: Английский

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No Such Thing as a Simple Flare: Substructure and Quasi-periodic Pulsations Observed in a Statistical Sample of 20 s Cadence TESS Flares

The Astrophysical Journal, Год журнала: 2022, Номер 926(2), С. 204 - 204

Опубликована: Фев. 1, 2022

Abstract A 20 s cadence Transiting Exoplanet Survey Satellite monitoring campaign of 226 low-mass flare stars during Cycle 3 recorded 3792 stellar flares ≥10 32 erg. We explore the time-resolved emission and substructure in 440 largest observed at high signal-to-noise, 97% which released energies 33 discover degeneracy present 2 minute between sharply peaked weakly is common, although breaks these degeneracies. better resolve rise phases find 46% large exhibit phase. observe 49 candidate quasi-periodic pulsations (QPP) confirm 17 ≥3 σ . Most our QPPs have periods less than 10 minutes, suggesting short-period optical are common. both decay flares, including a rise-phase QPP from Proxima Cen. that Davenport et al. template provides good fit to most classical cadence, 9% favor Gaussian peaks instead. characterize properties complex finding 17% “peak-bump” morphologies composed large, highly impulsive peak followed by second, more gradual peak. also estimate UVC surface fluences temperate planets one-third 34 erg reach D90 dose Deinococcus radiodurans just absence an atmosphere.

Язык: Английский

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Characterizing the Near-infrared Spectra of Flares from TRAPPIST-1 during JWST Transit Spectroscopy Observations

The Astrophysical Journal, Год журнала: 2023, Номер 959(1), С. 64 - 64

Опубликована: Дек. 1, 2023

Abstract We present the first analysis of JWST near-infrared spectroscopy stellar flares from TRAPPIST-1 during transits rocky exoplanets. Four were observed 0.6–2.8 μ m with Near Infrared Imager and Slitless Spectrograph 0.6–3.5 TRAPPIST-1b, f, g. discover P α Br β line emission characterize flare continuum at wavelengths 1–3.5 for time. Observed lines include H , –P ϵ He i λ 0.7062 m, two Ca ii infrared triplet (IRT) lines, IRT. observe a reversed Paschen decrement γ alongside changes in light-curve shapes these lines. The all four is well described by blackbody an effective temperature below 5300 K, lower than temperatures typically optical wavelengths. 0.6–1 spectra convolved Transiting Exoplanet Survey Satellite (TESS) response, enabling us to measure rate TESS bandpass. find 10 30 erg, large enough impact transit occur 3.6 − 1.3 + 2.1 day −1 ∼10× higher previous predictions K2. amount contamination 2 TRAPPIST-1b f be 500 ± 450 2100 400 ppm, respectively. up 80% can removed, mitigation most 1.0–2.4 m. These results suggest affected may still useful atmospheric characterization efforts.

Язык: Английский

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Modeling Repeated M Dwarf Flaring at an Earth-like Planet in the Habitable Zone: Atmospheric Effects for an Unmagnetized Planet

Astrobiology, Год журнала: 2018, Номер 19(1), С. 64 - 86

Опубликована: Авг. 2, 2018

Understanding the impact of active M-dwarf stars on atmospheric equilibrium and surface conditions a habitable zone Earth-like planet is key to assessing M dwarf habitability. Previous modeling electromagnetic (EM) radiation protons from single large flare an atmosphere indicated that significant long-term reductions in ozone were possible, but recovered. These more realistically exhibit frequent flaring with power-law distribution energies. Here we use coupled 1D photochemical radiative-convective model investigate effects repeated photochemistry UV unprotected by intrinsic magnetic field. We time-resolved spectra obtained for dM3 star AD Leo, combined occurrence frequencies total energies (typically 10$^{30.5}$ 10$^{34}$ erg) 4-year Kepler light curve dM4 GJ1243. Our results show EM-only flares have little effect column depth, multiple proton events can rapidly destroy column. Combining realistic event nominal CME & SEP geometries, find be depleted 94% 10 years, downward trend makes recovery unlikely suggests further destruction. For extreme stellar inputs O3 depletion allows constant 0.1-1 W m$^{-2}$ UV-C at planet's surface, which likely detrimental organic complexity. suggest hosts may comprehensively shields subject magnetically-unprotected planets damage complex structures. However, this does not preclude habitability, as safe haven life could still exist below ocean surface.

Язык: Английский

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Flare Rates, Rotation Periods, and Spectroscopic Activity Indicators of a Volume-complete Sample of Mid- to Late-M Dwarfs within 15 pc

The Astrophysical Journal, Год журнала: 2020, Номер 905(2), С. 107 - 107

Опубликована: Дек. 1, 2020

We present a study of flare rates, rotation periods, and spectroscopic activity indicators 125 single stars within 15 parsecs with masses between 0.1$-$0.3 $M_\odot$ observed during the first year TESS mission, goal elucidating relationship these various magnetically connected phenomena. gathered multi-epoch high resolution spectra each target we measured equivalent widths Helium I D$_3$, $H\alpha$, Calcium infrared triplet line at 8542.09 angstroms. 18 new periods from MEarth photometry 19 photometry. catalog 1392 flares. After correcting for sensitivity, find slope frequency distribution all to have standard value $\alpha$ = 1.98 $\pm$ 0.02. determine R$_{31.5}$, rate flares per day energies above E 3.16$\times$10$^{31}$ ergs in bandpass. that below critical $H\alpha$ EW -0.71 angstroms, log R$_{31.5}$ increases linearly increasing emission; this value, declines rapidly. The divide into two groups: 26% emission, rates typical values -1.30 0.08, Rossby numbers $<$ 0.50. remaining 74% show little no emission exhibit -3.86, majority not showing observations.

Язык: Английский

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