Quest for the origins of the first Americans. E. James Dixon, 1993, University of New Mexico Press, xvi + 154 pp., $24.95 (clothbound)

Donahue, Jack

doi:10.1002/gea.3340080509

Cited by 14 publications

(23 citation statements)

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“…11 also warn that the search for Maunder minimum candidates (e.g. Donahue 1998;Wright 2004) should take into account that coeval stars may have different mean activity levels (∼0.1-0.2 dex in log R ′ HK ) as a function of B −V color. The question remains, can we determine more accurate ages from a activity-rotation-age algorithm compared to the standard activity-age relations?…”

Section: Implications and Tests Of New Gyro-rossby Agesmentioning

confidence: 99%

“…the H-R diagram) in order to populate an activity-age calibration. There are four such R ′ HK vs. age relations in the literature which have been used in agedating field stars: two from Soderblom et al (1991), and one each from Donahue (1993), and Lachaume et al (1999). The activity-age relations from Soderblom et al (1991) include a linear fit to age vs. activity for members of clusters and binaries.…”

Section: Shortcomings Of Previous Activity-age Calibrationsmentioning

confidence: 99%

“…For the Lachaume et al (1999) calibration, the solar R ′ HK value adopted here (-4.91) would imply a solar age of 7.2 Gyr, which is clearly in error. The other two calibrations used the Sun as one of their anchor points, but with slightly different R ′ HK values (for the calibrations of Soderblom et al (1991) and Donahue (1993), one derives ages of 4.1 and 4.0 Gyr, respectively). Soderblom et al (1991) do not advocate extrapolating either of their activity-age relations to the young/active regime (log R ′ HK > -4.4), however Donahue (1993) explicitly fit their activity-age relation to age ∼10 Myr and log R ′ HK ≃ -4.2 (anchoring their fit to data for NGC 2264).…”

Section: Shortcomings Of Previous Activity-age Calibrationsmentioning

confidence: 99%

“…The other two calibrations used the Sun as one of their anchor points, but with slightly different R ′ HK values (for the calibrations of Soderblom et al (1991) and Donahue (1993), one derives ages of 4.1 and 4.0 Gyr, respectively). Soderblom et al (1991) do not advocate extrapolating either of their activity-age relations to the young/active regime (log R ′ HK > -4.4), however Donahue (1993) explicitly fit their activity-age relation to age ∼10 Myr and log R ′ HK ≃ -4.2 (anchoring their fit to data for NGC 2264). Given the observed activity levels in the ∼5-15 Myr Sco-Cen OB association (log R ′ HK ≃ -4.05; §2), neither the fit from Donahue (1993) or extrapolating the two fits from Soderblom et al (1991) estimates an age similar to the isochronal value.…”

Section: Shortcomings Of Previous Activity-age Calibrationsmentioning

confidence: 99%

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Improved Age Estimation for Solar‐Type Dwarfs Using Activity‐Rotation Diagnostics

Mamajek

Hillenbrand

2008

Astrophysical Journal

1,231

157

1,592

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While the strong anti-correlation between chromospheric activity and age has led to the common use of the Ca II H & K emission index (R ′ HK = L HK /L bol ) as an empirical age estimator for solar type dwarfs, existing activity-age relations produce implausible ages at both high and low activity levels. We have compiled R ′ HK data from the literature for young stellar clusters, richly populating for the first time the young end of the activity-age relation. Combining the cluster activity data with modern cluster age estimates, and analyzing the color-dependence of the chromospheric activity age index, we derive an improved activity-age calibration for F7-K2 dwarfs (0.5 < B-V < 0.9 mag). We also present a more fundamentally motivated activity-age calibration that relies on conversion of R ′ HK values through the Rossby number to rotation periods, and then makes use of improved gyrochronology relations. We demonstrate that our new activity-age calibration has typical age precision of ∼0.2 dex for normal solartype dwarfs aged between the Hyades and the Sun (∼0.6-4.5 Gyr). Inferring ages through activity-rotation-age relations accounts for some color-dependent effects, and systematically improves the age estimates (albeit only slightly). We demonstrate that coronal activity as measured through the fractional X-ray luminosity (R X = L X /L bol ) has nearly the same age-and rotation-inferring capability -2as chromospheric activity measured through R ′ HK . As a first application of our calibrations, we provide new activity-derived age estimates for the nearest 100 solar-type field dwarfs (d < 15 pc).

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Section: Implications and Tests Of New Gyro-rossby Agesmentioning

confidence: 99%

Section: Shortcomings Of Previous Activity-age Calibrationsmentioning

confidence: 99%

Section: Shortcomings Of Previous Activity-age Calibrationsmentioning

confidence: 99%

Section: Shortcomings Of Previous Activity-age Calibrationsmentioning

confidence: 99%

See 2 more Smart Citations

Improved Age Estimation for Solar‐Type Dwarfs Using Activity‐Rotation Diagnostics

Mamajek

Hillenbrand

2008

Astrophysical Journal

1,231

157

1,592

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“…Hence, they have not been used as reference stars. Taylor 1994Taylor , 1995, rotational period (P rot ) and v sini (from Donahue 1993;Baliunas et al 1995). The T sp given between brackets are from Hoffleit & Warren (1991) and the values of v sini marked with "*" are from the references given in .…”

Section: The Librarymentioning

confidence: 99%

Library of high and mid-resolution spectra in the Ca ii H & K, H∝, , Hβ, Na i D₁, D₂, and He i D₃ line regions of F, G, K and M field stars

Montes

Martín

Fernández-Figueroa

et al. 1997

Astron. Astrophys. Suppl. Ser.

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Abstract. In this work we present spectroscopic observations centered in the spectral lines most widely used as optical indicators of chromospheric activity (Hα, Hβ, Ca ii H & K, and He i D 3 ) in a sample of F, G, K and M chromospherically inactive stars. The spectra have been obtained with the aim of providing a library of high and mid-resolution spectra to be used in the application of the spectral subtraction technique to obtain the activechromosphere contribution to these lines in chromospherically active single and binary stars. This library can also be used for spectral classification purposes. A digital version with all the spectra is available via ftp and the World Wide Web (WWW) in both ASCII and FITS formats.

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Exoplanet characterisation in the longest known resonant chain: the K2-138 system seen by HARPS

Lopez

Barros

Santerne

et al. 2019

A&A

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The detection of low-mass transiting exoplanets in multiple systems brings new constraints to planetary formation and evolution processes and challenges the current planet formation theories. Nevertheless, only a mere fraction of the small planets detected by Kepler and K2 have precise mass measurements, which are mandatory to constrain their composition. We aim to characterise the planets that orbit the relatively bright star K2-138. This system is dynamically particular as it presents the longest chain known to date of planets close to the 3:2 resonance. We obtained 215 HARPS spectra from which we derived the radial-velocity variations of K2-138. Via a joint Bayesian analysis of both the K2 photometry and HARPS radial-velocities (RVs), we constrained the parameters of the six planets in orbit. The masses of the four inner planets, from b to e, are 3.1, 6.3, 7.9, and 13.0 M ⊕ with a precision of 34%, 20%, 18%, and 15%, respectively. The bulk densities are 4.9, 2.8, 3.2, and 1.8 g cm −3 , ranging from Earth to Neptune-like values. For planets f and g, we report upper limits. Finally, we predict transit timing variations of the order two to six minutes from the masses derived. Given its peculiar dynamics, K2-138 is an ideal target for transit timing variation (TTV) measurements from space with the upcoming CHaracterizing ExOPlanet Satellite (CHEOPS) to study this highly-packed system and compare TTV and RV masses.

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Quest for the origins of the first Americans. E. James Dixon, 1993, University of New Mexico Press, xvi + 154 pp., $24.95 (clothbound)

Cited by 14 publications

References 0 publications

Improved Age Estimation for Solar‐Type Dwarfs Using Activity‐Rotation Diagnostics

Improved Age Estimation for Solar‐Type Dwarfs Using Activity‐Rotation Diagnostics

Library of high and mid-resolution spectra in the Ca ii H & K, H∝, , Hβ, Na i D₁, D₂, and He i D₃ line regions of F, G, K and M field stars

Exoplanet characterisation in the longest known resonant chain: the K2-138 system seen by HARPS

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Quest for the origins of the first Americans. E. James Dixon, 1993, University of New Mexico Press, xvi + 154 pp., $24.95 (clothbound)

Cited by 14 publications

References 0 publications

Improved Age Estimation for Solar‐Type Dwarfs Using Activity‐Rotation Diagnostics

Improved Age Estimation for Solar‐Type Dwarfs Using Activity‐Rotation Diagnostics

Library of high and mid-resolution spectra in the Ca ii H & K, H∝, , Hβ, Na i D1, D2, and He i D3 line regions of F, G, K and M field stars

Exoplanet characterisation in the longest known resonant chain: the K2-138 system seen by HARPS

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Library of high and mid-resolution spectra in the Ca ii H & K, H∝, , Hβ, Na i D₁, D₂, and He i D₃ line regions of F, G, K and M field stars