The MUSCLES Treasury Survey. IV. Scaling Relations for Ultraviolet, Ca ii K, and Energetic Particle Fluxes from M Dwarfs

Youngblood, Allison; Loyd, R. O. Parke; Brown, Alexander; Mason, James Paul; Schneider, P. C.; Tilley, Matt; Berta-Thompson, Zachory K.; Buccino, A. P.; Froning, Cynthia S.; Hawley, Suzanne L.; Linsky, Jeffrey L.; Mauas, P. J. D.; Redfield, Seth; Kowalski, Adam F.; Miguel, Yamila; Newton, Elisabeth R.; Rugheimer, Sarah; Segura, Antígona; Roberge, Aki; Vieytes, M.

doi:10.3847/1538-4357/aa76dd

Cited by 104 publications

(123 citation statements)

References 161 publications

(289 reference statements)

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“…The Lyman-α and Si iii lines do not appear redshifted during the flare, as is sometimes the case for chromospheric and transition region lines (e.g. Pillitteri et al 2015, Youngblood et al 2017. We see no sign of the flare in the N v doublet, even though an increase on the order of that in the Si iii line would have been detected.…”

Section: Visit B -September 7/8 2011supporting

confidence: 67%

MOVES III. Simultaneous X-ray and ultraviolet observations unveiling the variable environment of the hot Jupiter HD 189733b

Bourrier

Wheatley

Étangs

et al. 2020

Monthly Notices of the Royal Astronomical Society

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In this third paper of the MOVES (Multiwavelength Observations of an eVaporating Exoplanet and its Star) programme, we combine Hubble Space Telescope far-ultraviolet observations with XMM-Newton/Swift X-ray observations to measure the emission of HD 189733 in various FUV lines, and its soft X-ray spectrum. Based on these measurements we characterise the interstellar medium toward HD 189733 and derive semi-synthetic XUV spectra of the star, which are used to study the evolution of its high-energy emission at five different epochs. Two flares from HD 189733 are observed, but we propose that the long-term variations in its spectral energy distribution have the most important consequences for the environment of HD 189733b. Reduced coronal and wind activity could favour the formation of a dense population of Si 2+ atoms in a bow-shock ahead of the planet, responsible for pre-and in-transit absorption measured in the first two epochs. In-transit absorption signatures are detected in the Lyman-α line in the second, third and fifth epochs, which could arise from the extended planetary thermosphere and a tail of stellar wind protons neutralised via charge-exchange with the planetary exosphere. We propose that increases in the X-ray irradiation of the planet, and decreases in its EUV irradiation causing lower photoionisation rates of neutral hydrogen, favour the detection of these signatures by sustaining larger densities of H 0 atoms in the upper atmosphere and boosting charge-exchanges with the stellar wind. Deeper and broader absorption signatures in the last epoch suggest that the planet entered a different evaporation regime, providing clues as to the link between stellar activity and the structure of the planetary environment.

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Section: Visit B -September 7/8 2011supporting

confidence: 67%

MOVES III. Simultaneous X-ray and ultraviolet observations unveiling the variable environment of the hot Jupiter HD 189733b

Bourrier

Wheatley

Étangs

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…The line cores of Ca II form in the upper chromosphere/lower transition region between 5,000 and 20,000 K while the neighboring emission peaks form at cooler temperatures deeper in the atmosphere between 4,000 and 10,000 K. Since these lines yield information about the temperature structure, before stellar UV spectral observations were available, early semiempirical M dwarf chromosphere models were based on fitting ground-based Ca II K observations (Giampapa et al 1982). More recently, Youngblood et al (2017) found that the equivalent width of the Ca II K line could be used to estimate the stellar surface flux in several ultraviolet emission lines, including Lyα, and developed a scaling relationship to estimate EUV fluxes using time-averaged high resolution Ca II observations. We compare our model spectra to Keck/HIRES observations of Ca II H & K from Vogt (2011) in Figure 4.…”

Section: Visible Spectrummentioning

confidence: 99%

Predicting the Extreme Ultraviolet Radiation Environment of Exoplanets around Low-mass Stars: GJ 832, GJ 176, and GJ 436

Peacock

Barman

Shkolnik

et al. 2019

ApJ

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Correct estimates of stellar extreme ultraviolet (EUV; 100 -1170Å) flux are important for studying the photochemistry and stability of exoplanet atmospheres, as EUV radiation ionizes hydrogen and contributes to the heating, expansion, and potential escape of a planet's upper atmosphere. Contamination from interstellar hydrogen makes observing EUV emission from M stars particularly difficult, and impossible past 100 pc, and necessitates other means to predict the flux in this wavelength regime. We present EUV -infrared (100Å -5.5 µm) synthetic spectra computed with the PHOENIX atmospheric code of three early M dwarf planet hosts: GJ 832 (M1.5 V), GJ 176 (M2.5 V), and GJ 436 (M3.5 V). These one-dimensional semiempirical nonlocal thermodynamic equilibrium models include simple temperature prescriptions for the stellar chromosphere and transition region, from where ultraviolet (UV; 100 -3008Å) fluxes originate. We guide our models with Hubble Space Telescope far-and near-UV spectra and discuss the ability to constrain these models using Galaxy Evolution Explorer UV photometry. Our models closely reproduce the observations and predict the unobservable EUV spectrum at a wavelength resolution of <0.1Å. The temperature profiles that best reproduce the observations for all three stars are described by nearly the same set of parameters, suggesting that early M type stars may have similar thermal structures in their upper atmospheres. With an impending UV observation gap and the scarcity of observed EUV spectra for stars less luminous and more distant than the Sun, upper-atmosphere models such as these are important for providing realistic spectra across short wavelengths and for advancing our understanding of the effects of radiation on planets orbiting M stars.

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“…Additionally, it is important that we learn as much as we can about these planets as we prepare for atmospheric characterization with the James Webb Space Telescope (Deming et al 2009;Morley et al 2017). JWST will provide unique characterization advantages must study the UV irradiation environments of these planets, especially given that individual M stars with the same spectral type can exhibit very different UV properties (e.g., Youngblood et al 2017), and a lifetime of UV flux from the host star can have profound impacts on the composition and evolution of their planetary atmospheres.…”

Section: Introductionmentioning

confidence: 99%

Lyα in the GJ 1132 System: Stellar Emission and Planetary Atmospheric Evolution

Waalkes¹,

Berta-Thompson²,

Bourrier

et al. 2019

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GJ 1132b, which orbits an M dwarf, is one of the few known Earth-sized planets, and at 12 pc away it is one of the closest known transiting planets. Receiving roughly 19x Earth's insolation, this planet is too hot to be habitable but can inform us about the volatile content of rocky planet atmospheres around cool stars. Using Hubble STIS spectra, we search for a transit in the Lyman-α line of neutral hydrogen (Lyα). If we were to observe a deep Lyα absorption signature, that would indicate the presence of a neutral hydrogen envelope flowing from GJ 1132b. On the other hand, ruling out deep absorption from neutral hydrogen may indicate that this planet does not have a detectable amount of hydrogen loss, is not losing hydrogen, or lost hydrogen and other volatiles early in the star's life. We do not detect a transit and determine a 2-σ upper limit on the effective envelope radius of 0.36 R * in the red wing of the Lyα line, which is the only portion of the spectrum we detect after absorption by the ISM. We analyze the Lyα spectrum and stellar variability of GJ1132, which is a slowly-rotating 0.18 solar mass M dwarf with previously uncharacterized UV activity. Our data show stellar variabilities of 5-22%, which is consistent with the M dwarf UV variabilities of up to 41% found by . Understanding the role that UV variability plays in planetary atmospheres is crucial to assess atmospheric evolution and the habitability of cooler rocky exoplanets.

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The MUSCLES Treasury Survey. IV. Scaling Relations for Ultraviolet, Ca ii K, and Energetic Particle Fluxes from M Dwarfs

Cited by 104 publications

References 161 publications

MOVES III. Simultaneous X-ray and ultraviolet observations unveiling the variable environment of the hot Jupiter HD 189733b

MOVES III. Simultaneous X-ray and ultraviolet observations unveiling the variable environment of the hot Jupiter HD 189733b

Predicting the Extreme Ultraviolet Radiation Environment of Exoplanets around Low-mass Stars: GJ 832, GJ 176, and GJ 436

Lyα in the GJ 1132 System: Stellar Emission and Planetary Atmospheric Evolution

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