The Nearest Young Moving Groups

López‐Santiago, J.; Montes, D.; Crespo‐Chacón, I.; Fernández-Figueroa, M. J.

doi:10.1086/503183

Cited by 166 publications

(181 citation statements)

References 33 publications

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“…In their In fact, the stars in the top branch in Fig. 4 (left) are known to be young stars (see López-Santiago et al 2006) and very active M dwarfs. A similar conclusion was already reached by Vaughan & Preston (1980) for G and K stars.…”

Section: Discussionmentioning

confidence: 99%

A high-resolution spectroscopic survey of late-type stars: chromospheric activity, rotation, kinematics, and age

López‐Santiago¹,

Montes²,

Galvez-Ortiz

et al. 2010

A&A

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Aims. We present a compilation of spectroscopic data from a survey of 144 chromospherically active young stars in the solar neighborhood, which may be used to investigate different aspects of its formation and evolution in terms of kinematics and stellar formation history. The data have already been used by us in several studies. With this paper, we make all these data accessible to the scientific community for future studies on different topics. Methods. We performed spectroscopic observations with echelle spectrographs to cover the entirety of the optical spectral range simultaneously. Standard data reduction was performed with the IRAF echelle package. We applied the spectral subtraction technique to reveal chromospheric emission in the stars of the sample. The equivalent width of chromospheric emission lines was measured in the subtracted spectra and then converted to fluxes using equivalent width-flux relationships. Radial and rotational velocities were determined by the cross-correlation technique. Kinematics, equivalent widths of the lithium line λ6707.8 Å and spectral types were also determined. Results. A catalog of spectroscopic data is compiled: radial and rotational velocities, space motion, equivalent widths of optical chromospheric activity indicators from Ca ii H & K to the calcium infrared triplet and the lithium line in λ6708 Å. Fluxes in the chromospheric emission lines and R HK are also determined for each observation of a star in the sample. We used these data to investigate the emission levels of our stars. The study of the Hα emission line revealed two different populations of chromospheric emitters in the sample, clearly separated in the log F Hα /F bol − (V − J) diagram. The dichotomy may be associated with the age of the stars.

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Section: Discussionmentioning

confidence: 99%

A high-resolution spectroscopic survey of late-type stars: chromospheric activity, rotation, kinematics, and age

López‐Santiago¹,

Montes²,

Galvez-Ortiz

et al. 2010

A&A

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“…There are only a few known young star associations and moving groups in the solar neighbourhood and these have welldefined space motions. Using the catalogs of young moving groups (López-Santiago et al 2006;Fernández, priv. comm.…”

Section: Discussionmentioning

confidence: 99%

The effect of activity on stellar temperatures and radii

Morales¹,

Ribas²,

Jordi³

2007

A&A

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156

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Context. Recent analyses of low-mass eclipsing binary stars have unveiled a significant disagreement between the observations and predictions of stellar structure models. Results show that theoretical models underestimate the radii and overestimate the effective temperatures of low-mass stars but yield luminosities that accord with observations. A hypothesis based upon the effects of stellar activity was put forward to explain the discrepancies. Aims. In this paper we study the existence of the same trend in single active stars and provide a consistent scenario to explain systematic differences between active and inactive stars in the H-R diagram reported earlier.Methods. The analysis is done using single field stars of spectral types late-K and M and computing their bolometric magnitudes and temperatures through infrared colours and spectral indices. The properties of the stars in samples of active and inactive stars are compared statistically to reveal systematic differences. Results. After accounting for a number of possible bias effects, active stars are shown to be cooler than inactive stars of similar luminosity therefore implying a larger radius as well, in proportions that are in excellent agreement with those found from eclipsing binaries.Conclusions. The present results generalise the existence of strong radius and temperature dependences on stellar activity to the entire population of low-mass stars, regardless of their membership in close binary systems.

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“…Main properties are detailed at Table 1. In our previous studies (Hernán-Obispo et al 2005, López-Santiago et al 2006, BD+20 1790 shows a high level of stellar activity that is manifested in a plethora of phenomena at different atmospheric layers. We detected strong chromospheric emission, as suggested by all the chromospheric activity indicators being in emission above continuum (from Ca ii H & K to Ca ii infrared triplet).…”

Section: Bd+20 1790 System: Previous Workmentioning

confidence: 87%

“…We compare the activity of this star with a large catalogue of single and binary stars collected and characterized by Montes et al (2001), López-Santiago et al (2006, López-Santiago (2005), Gálvez-Ortiz (2005). BD+20 1790 has a level of activity greater even than the binary systems in the catalogue.…”

Section: Bd+20 1790 System: Previous Workmentioning

confidence: 99%

Analysis of combined radial velocities and activity of BD+20 1790: evidence supporting the existence of a planetary companion

Hernán‐Obispo

Tuomi

Gálvez-Ortiz

et al. 2015

A&A

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Context. In a previous paper we reported a planetary companion to the young and very active K5Ve star BD+20 1790. We found that this star has a high level of stellar activity (log R HK = −3.7) that manifests in a plethora of phenomena (starspots, prominences, plages, large flares). Based on a careful study of these activity features and a deep discussion and analysis of the effects of the stellar activity on the radial velocity measurements, we demonstrated that the presence of a planet provided the best explanation for the radial velocity variations and all the peculiarities of this star. The orbital solution resulted in a close-in massive planet with a period of 7.78 days. However, a paper by Figueira et al. (2010, A&A, 513, L8) questioned the evidence for the planetary companion. Aims. This paper aims to more rigorously assess the nature of the radial velocity measurements with an expanded data set and new methods of analysis. Methods. We have employed Bayesian methods to simultaneously analyse the radial velocity and activity measurements based on a combined data set that includes new and previously published observations. Results. We conclude that the Bayesian analysis and the new activity study support the presence of a planetary companion to BD+20 1790. A new orbital solution is presented, after removing the two main contributions of stellar jitter, one that varies with the photometric period (2.8 days) and another that varies with the synodic period of the star-planet system (4.36 days). We present a new method to determine these jitter components, considering them as second and third signals in the system. A discussion on possible star-planet interaction is included, based on the Bayesian analysis of the activity indices, which indicates that they modulate with the synodic period. We propose two different sources for flare events in this system: one related to the geometry of the system and the relative movement of the star and planet, and a second one purely stochastic source that is related to the evolution of stellar surface active regions. Also, we observe for the first time the magnetic field of the star, from spectropolarimetric data.

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The Nearest Young Moving Groups

Cited by 166 publications

References 33 publications

A high-resolution spectroscopic survey of late-type stars: chromospheric activity, rotation, kinematics, and age

A high-resolution spectroscopic survey of late-type stars: chromospheric activity, rotation, kinematics, and age

The effect of activity on stellar temperatures and radii

Analysis of combined radial velocities and activity of BD+20 1790: evidence supporting the existence of a planetary companion

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