Far- and Extreme-UV Solar Spectral Irradiance and Radiance from Simplified Atmospheric Physical Models

Fontenla, J. M.; Landi, E.; Snow, M.; Woods, Thomas N.

doi:10.1007/s11207-013-0431-4

Cited by 45 publications

(42 citation statements)

References 34 publications

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“…This might seem surprising for C II, because of its similar formation temperature to Lyα, but Oranje (1986) noted that C II behaves like a transition region line in M dwarfs. Fontenla et al (2016) provide support of C II as a transition region line with their semi-empirical model of GJ 832ʼs atmosphere, which shows that the transition region begins at temperatures ∼2000 K cooler than in the quiet Sun. We find no significant correlation between the chromospheric line Lyα and the transition region emission lines Si III, Si IV, C II, C IV, and He II, but a larger sample size is needed to place a strong constraint on a non-correlation.…”

Section: Comparison With Other Chromospheric and Transition Region Linessupporting

confidence: 63%

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The MUSCLES TREASURY SURVEY. II. INTRINSIC LYα AND EXTREME ULTRAVIOLET SPECTRA OF K AND M DWARFS WITH EXOPLANETS*

Youngblood

Loyd

Linsky

et al. 2016

ApJ

273

289

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The ultraviolet (UV) spectral energy distributions (SEDs) of low-mass (K-and M-type) stars play a critical role in the heating and chemistry of exoplanet atmospheres, but are not observationally well-constrained. Direct observations of the intrinsic flux of the Lyα line (the dominant source of UV photons from low-mass stars) are challenging, as interstellar H I absorbs the entire line core for even the closest stars. To address the existing gap in empirical constraints on the UV flux of K and M dwarfs, the MUSCLES Hubble Space Telescope Treasury Survey has obtained UV observations of 11 nearby M and K dwarfs hosting exoplanets. This paper presents the Lyα and extreme-UV spectral reconstructions for the MUSCLES targets. Most targets are optically inactive, but all exhibit significant UV activity. We use a Markov Chain Monte Carlo technique to correct the observed Lyα profiles for interstellar absorption, and we employ empirical relations to compute the extreme-UV SED from the intrinsic Lyα flux in ∼100 Å bins from 100-1170 Å. The reconstructed Lyα profiles have 300 km s −1 broad cores, while >1% of the total intrinsic Lyα flux is measured in extended wings between 300 and 1200 km s −1 . The Lyα surface flux positively correlates with the Mg II surface flux and negatively correlates with the stellar rotation period. Stars with larger Lyα surface flux also tend to have larger surface flux in ions formed at higher temperatures, but these correlations remain statistically insignificant in our sample of 11 stars. We also present H I column density measurements for 10 new sightlines through the local interstellar medium.

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Section: Comparison With Other Chromospheric and Transition Region Linessupporting

confidence: 63%

“…The Lyα line has not been modeled from first principles for any M dwarf, and semiempirical models provide only a rough fit to the data (Fontenla et al 2016). As discussed in Section 1, no self-reversal of the line core is expected.…”

Section: The Modelmentioning

confidence: 99%

The MUSCLES TREASURY SURVEY. II. INTRINSIC LYα AND EXTREME ULTRAVIOLET SPECTRA OF K AND M DWARFS WITH EXOPLANETS*

Youngblood

Loyd

Linsky

et al. 2016

ApJ

273

289

View full text Add to dashboard Cite

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“…Third, Linsky et al (2014) derive the EUV flux in several 100 Å wide bands on the basis of the Lyα flux. Their relations are based on intrinsic Lyα fluxes, EUVE measurements (<400 Å), and semiempirical models (400 < λ < 912 Å, Fontenla et al 2014). …”

Section: Stellar Euv Emissionmentioning

confidence: 99%

High-energy irradiation and mass loss rates of hot Jupiters in the solar neighborhood

Salz

Schneider

Czesla

et al. 2015

A&A

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Giant gas planets in close proximity to their host stars experience strong irradiation. In extreme cases photoevaporation causes a transonic, planetary wind and the persistent mass loss can possibly affect the planetary evolution. We have identified nine hot Jupiter systems in the vicinity of the Sun, in which expanded planetary atmospheres should be detectable through Lyα transit spectroscopy according to predictions. We use X-ray observations with Chandra and XMM-Newton of seven of these targets to derive the highenergy irradiation level of the planetary atmospheres and the resulting mass loss rates. We further derive improved Lyα luminosity estimates for the host stars including interstellar absorption. According to our estimates WASP-80 b, WASP-77 b, and WASP-43 b experience the strongest mass loss rates, exceeding the mass loss rate of HD 209458 b, where an expanded atmosphere has been confirmed. Furthermore, seven out of nine targets might be amenable to Lyα transit spectroscopy. Finally, we check the possibility of angular momentum transfer from the hot Jupiters to the host stars in the three binary systems among our sample, but find only weak indications for increased stellar rotation periods of WASP-77 and HAT-P-20.

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“…Existing empirical and semi-empirical models include the EUV81 model (Hinteregger & Fukui 1981), the EUVAC model (Richards et al 1994(Richards et al , 2006, the SOLAR2000 model (Tobiska et al 2000;Tobiska 2004), the NRLEUV model (Warren et al 2001;Lean et al 2003;Warren 2005), the FISM (Chamberlin et al 2007), and the empirical model presented in Fontenla et al (2014). Chamberlin et al (2007) compare the first four listed models with TIMED SEE data and determine that the models differ from SEE data by 20-47% in the 35-40 nm band during a rotation in January 2004.…”

Section: Existing Euv Proxies and Modelsmentioning

confidence: 99%

Solar Spectral Proxy Irradiance from GOES (SSPRING): a model for solar EUV irradiance

Suess

Snow

Viereck

et al. 2016

J. Space Weather Space Clim.

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Several currently operating instruments are able to measure the full EUV spectrum at sufficient wavelength resolution for use in upper-atmosphere modeling, the effects of space weather, and modeling satellite drag. However, no missions are planned at present to succeed the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) and Solar Dynamics Observatory (SDO) missions, which currently provide these data sources. To develop a suitable replacement for these measurements, we use two broadband EUV channels on the NOAA GOES satellites, the magnesium core-to-wing ratio (Mg II index) from the SOlar Radiation and Climate Experiment (SORCE) as well as EUV and Mg II time averages to model the EUV spectrum from 0.1 to 105 nm at 5-nm spectral resolution and daily time resolution. A Levenberg-Marquardt least squares fitting algorithm is used to determine a coefficient matrix that best reproduces a reference data set when multiplied by input data. The coefficient matrix is then applied to model data outside of the fitting interval. Three different fitting intervals are tested, with a variable fitting interval utilizing all days of data before the prediction date producing the best results. The correlation between the model results and the observed spectrum is found to be above 95% for the 0.1-50 nm range, and between 74% and 95% for the 50-105 nm range. We also find a favorable comparison between our results and the Flare Irradiance Spectral Model (FISM). These results provide a promising potential source for an empirical EUV spectral model after direct EUV measurements are no longer available, and utilize a similar EUV modeling technique as the upcoming GOES-R satellites.

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Far- and Extreme-UV Solar Spectral Irradiance and Radiance from Simplified Atmospheric Physical Models

Cited by 45 publications

References 34 publications

The MUSCLES TREASURY SURVEY. II. INTRINSIC LYα AND EXTREME ULTRAVIOLET SPECTRA OF K AND M DWARFS WITH EXOPLANETS*

The MUSCLES TREASURY SURVEY. II. INTRINSIC LYα AND EXTREME ULTRAVIOLET SPECTRA OF K AND M DWARFS WITH EXOPLANETS*

High-energy irradiation and mass loss rates of hot Jupiters in the solar neighborhood

Solar Spectral Proxy Irradiance from GOES (SSPRING): a model for solar EUV irradiance

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