J/A+A/644/A67 EUV estimates from CaII H&K activity (Sreejith+, 2020)
Ca II H&K stellar activity parameter:
a proxy for stellar Extreme Ultraviolet Fluxes.
Sreejith A. G., Fossati L., Youngblood A., France K., Ambily S.
<Astron. Astrophys. 644, A67 (2020)>
=2020A&A...644A..67S 2020A&A...644A..67S (SIMBAD/NED BibCode)
ADC_Keywords: Fundamental catalog ; Stars, late-type ; Spectroscopy
Keywords: ultraviolet: stars - stars: chromospheres - planet-star interactions -
stars: late-type - stars: activity -
planets and satellites: atmospheres
Abstract:
Atmospheric escape is an important factor shaping the exoplanet
population and hence drives our understanding of planet formation.
Atmospheric escape from giant planets is driven primarily by the
stellar X-ray and extreme- ultraviolet (EUV) radiation. Furthermore,
EUV and longer wavelength UV radiation power disequilibrium chemistry
in the middle and upper atmosphere. Our understanding of atmospheric
escape and chemistry, therefore, depends on our knowledge of the
stellar UV fluxes. While the far-ultraviolet fluxes can be observed
for some stars, most of the EUV range is unobservable due to the lack
of a space telescope with EUV capabilities and, for the more distant
stars, to interstellar medium absorption. Thus, it becomes essential
to have indirect means for inferring EUV fluxes from features
observable at other wavelengths. We present here analytic functions
for predicting the EUV emission of F, G, K, and M-type stars from the
log R'HK activity parameter that is commonly obtained from
ground-based optical observations of the Ca II H&K lines. The scaling
relations are based on a collection of about 100 nearby stars with
published log R'HK and EUV flux values, where the latter are either
direct measurements or inferences from high-quality far-ultraviolet
(FUV) spectra. The scaling relations presented here return EUV flux
values with an accuracy of about three, which is slightly lower than
that of other similar methods based on FUV or X-ray measurements.
Description:
We have tabulated EUV fluxes in the wavelength range 90-912Å from
logR'HK parameter based on linear scaling relations derived from
France et al., 2018ApJS..239...16F 2018ApJS..239...16F.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 99 95 Stellar parameters and EUV fluxes
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Name Target name
18- 24 A7 --- SpType MK spectral type
26- 30 F5.2 mag Vmag Aparent V magnitude
32- 35 F4.2 mag B-V B-V colour index
37- 40 I4 K Teff Stellar effective temperature
42- 45 F4.2 Rsun Rad Stellar radius
47- 51 F5.2 pc Dist Distance
53- 57 F5.2 [-] logRpHKmean Mean activity index logR'HK
59- 63 F5.2 [-] logRpHKmed Median activity index logR'HK
65- 69 F5.3 [-] logRpHkstddev LogR'HK Standard deviation
71- 72 I2 --- Nobs Number of observations of LogR'HK
74- 80 F7.3 10-10W/m2 Fbol Bolometric flux (10-7erg/s/cm2)
82- 88 F7.2 10-17W/m2 FEUV EUV flux in 90-911Å
(10-14erg/s/cm2)
90- 94 F5.2 [-] log(FEUV/Fbol) Flux ratio, log(FEUV/Fbol)
96- 99 F4.2 [-] e_log(FEUV/Fbol) Error of log(FEUV/Fbol)
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Acknowledgements:
A.G. Sreejith, sreejith.aickara(at)oeaw.ac.at
(End) Patricia Vannier [CDS] 30-Oct-2020