High-Resolution Optical Observations of Extreme-Ultraviolet–selected Active Late-Type Stars

Christian, D. J.; Mathioudakis, M.

doi:10.1086/339702

Cited by 21 publications

(20 citation statements)

References 29 publications

(37 reference statements)

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“…3 a comparison of log N(Li) derived in this study with other works (Christian & Mathioudakis 2002;Wichmann et al 2000;de Laverny et al 2003;Takeda & Kawanomoto 2005;Jasniewicz et al 1999;Montes et al 2001). As expected, we found only minor differences with respect to other original lithium abundances.…”

Section: Discussion and Resultssupporting

confidence: 87%

“…2, we compare our measurement of the Li EWs with those obtained by other authors for the same stars (Christian & Mathioudakis 2002;Wichmann et al 2000;Gregorio-Hetem & Hetem 2002;de Laverny et al 2003;Takeda & Kawanomoto 2005;Jasniewicz et al 1999;Montes et al 2001). The agreement between the values was good; however, for small EWs, we noted some differences between the samples of other authors and our results.…”

Section: Introductionsupporting

confidence: 80%

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Lithium abundances of nearby young solar-type stars based on optical high-resolution spectroscopy

Xing

2012

A&A

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Context. Lithium has long been recognized as a powerful tool for investigating the internal mixing of low-mass stars. In addition, accurate measurements of lithium abundances in young solar-type stars provide independent and reliable age diagnostics. Aims. To study the relationship between lithium and activity in normal solar type-type stars and determine the effectiveness of lithium and kinematics as activity indicators, we perform a lithium survey of nearby late-type stars. We search for nearby young solar-type stars and investigate the relationship between lithium abundances and X-ray activity by measuring log L x . Methods. On the basis of high-resolution spectroscopic observations, we derived the lithium abundances of 33 young solar-type stars by comparing the measured Li I λ 670.8 nm equivalent widths with the curve of growth calculations in non-LTE (NLTE) conditions. Results. We obtain the lithium abundances of a sample of young solar-type stars. Using the lithium abundance and X-ray luminosity, L x , we investigate the relationship between Li abundance and X-ray activity. We find a clear correlation between lithium abundance (log N(Li)) and X-ray luminosity, log L x , for our sample stars. Conclusions. As the X-ray luminosity, L x , becomes stronger, the lithium abundance decreases in our sample (11 pre-main-sequence, 15 zero-age-main-sequence, and 7 young main-sequence) stars. The results imply that there is a large number of solar-type stars. A correlation appears to exist between Li abundance and age, thus confirming the presence of very active young stars close to the Sun.

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Section: Discussion and Resultssupporting

confidence: 87%

Section: Introductionsupporting

confidence: 80%

Lithium abundances of nearby young solar-type stars based on optical high-resolution spectroscopy

Xing

2012

A&A

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“…But we found only a few measurements of the Ca ii lines for these stars (Stauffer & Hartmann 1986, Rutten 1987, Rutten et al 1989). Instead, we found several measures of the H α EW (Soderblom et al 1991, Hawley et al 1996, Kamper et al 1997, Christian & Mathioudakis 2002, Gizis et al 2002, Pace 2013. Fortunately, there is a relatively tight correlation between the mean Ca ii line mean EW and H α EW in dM3 and dM4 stars.…”

Section: The Rac In M3 Dwarfsmentioning

confidence: 72%

The Rotation–activity Correlations in K and M Dwarfs. II. New Constraints on the Dynamo Mechanisms in Late-K and M Dwarfs before and at the Transition to Complete Convection^∗

Houdebine

Mullan

Bercu

et al. 2017

ApJ

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We study the rotation-activity correlations (RACs) in a sample stars from spectral type dK4 to dM4. We study RACs using chromospheric data and coronal data. We study the Ca ii line surface fluxes-P/ sin i RACs. We fit the RACs with linear homoscedastic and heteroscedastic regression models. We find that these RACs differ substantially from one spectral sub-type to another. For dM3 and dM4 stars, we find that the RACs cannot be described by a simple model, but instead that there may exist two distinct RAC behaviors for the low activity and the high activity stellar sub-samples respectively. Although these results are preliminary and will need confirmation, the data suggest that these distinct RACs may be associated with different dynamo regimes.We also study R'HK as a function of the Rossby number R0. We find that: (i) For dK4 stars, we confirm R'HK as a function of R0 agrees well with previous results for F-G-K stars. (ii) In dK6, dM2, dM3 and dM4 stars, we find that, at a given R0, the values of R'HK lie a factor of 3, 10, 20 and 90 respectively below the F-G-K RAC. Our results suggest a significant decrease in the efficiency of the dynamo mechanism(s) as regards chromospheric heating before and at dM3, i.e. before and at the TTCC.We also show that the ratio of coronal heating to chromospheric heating LX /LHK increases by a factor of 100 between dK4 and dM4 stars.

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“…Therefore, they concluded that Gl 375 was either a fast rotator or a binary. Only recently have Christian & Mathioudakis (2002) obtained a high-resolution optical and IR spectrum of Gl 375, which allowed them to identify the characteristic double features and report the binary nature of this object.…”

Section: Introductionmentioning

confidence: 99%

The spectroscopic binary system Gl 375

Díaz¹,

González

Cincunegui³

et al. 2007

A&A

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Aims. We study the spectroscopic binary system Gl 375 to characterise its orbit and the spectral types and chromospheric activity levels of the components. Methods. We employed medium-resolution echelle spectra obtained at the 2.15 m telescope at the Argentinian observatory CASLEO and photometric observations obtained from the ASAS database. Results. We have separated the composite spectra into those corresponding to both components. The separated spectra allow us to confirm that the spectral types of both components are similar (dMe3.5) and to obtain precise measurements of the orbital period (P = 1.87844 days), minimum masses (M 1 sin 3 i = 0.35 M and M 2 sin 3 i = 0.33 M ), and other orbital parameters. The photometric observations exhibit a sinusoidal variation with the same period as the orbital period. We interpreted this as signs of active regions carried along with rotation in a tidally synchronised system, and studied the evolution of the amplitude of the modulation on longer timescales. Together with the mean magnitude, the modulation exhibits a roughly cyclic variation with a period of around 800 days. This periodicity is also found in the flux of the Ca II K lines of both components, which seem to be in phase.Conclusions. The periodic changes in the three observables are interpreted as a sign of a stellar activity cycle. Both components appear to be in phase, which implies that they are magnetically connected. The measured cycle of ≈2.2 years (≈800 days) is consistent with previous determinations of activity cycles in similar stars.

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High-Resolution Optical Observations of Extreme-Ultraviolet–selected Active Late-Type Stars

Cited by 21 publications

References 29 publications

Lithium abundances of nearby young solar-type stars based on optical high-resolution spectroscopy

Lithium abundances of nearby young solar-type stars based on optical high-resolution spectroscopy

The Rotation–activity Correlations in K and M Dwarfs. II. New Constraints on the Dynamo Mechanisms in Late-K and M Dwarfs before and at the Transition to Complete Convection^∗

The spectroscopic binary system Gl 375

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High-Resolution Optical Observations of Extreme-Ultraviolet–selected Active Late-Type Stars

Cited by 21 publications

References 29 publications

Lithium abundances of nearby young solar-type stars based on optical high-resolution spectroscopy

Lithium abundances of nearby young solar-type stars based on optical high-resolution spectroscopy

The Rotation–activity Correlations in K and M Dwarfs. II. New Constraints on the Dynamo Mechanisms in Late-K and M Dwarfs before and at the Transition to Complete Convection∗

The spectroscopic binary system Gl 375

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Product

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About

The Rotation–activity Correlations in K and M Dwarfs. II. New Constraints on the Dynamo Mechanisms in Late-K and M Dwarfs before and at the Transition to Complete Convection^∗