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2821. Chromospheric activity in 4 open clusters
ID:
ivo://CDS.VizieR/J/MNRAS/476/908
Title:
Chromospheric activity in 4 open clusters
Short Name:
J/MNRAS/476/908
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use the LAMOST spectra of member stars in Pleiades, M34, Praesepe, and Hyades to study how chromospheric activity varies as a function of mass and rotation at different age. We measured excess equivalent widths of H{alpha}, H{beta}, and CaII K based on estimated chromospheric contributions from old and inactive field dwarfs, and excess luminosities are obtained by normalizing bolometric luminosity, for more than 700 late-type stars in these open clusters. Results indicate two activity sequences in cool spot coverage and H{alpha} excess emission among GK dwarfs in Pleiades and M dwarfs in Praesepe and Hyades, paralleling with well-known rotation sequences. A weak dependence of chromospheric emission on rotation exists among ultrafast rotators in saturated regime with Rossby number Ro<=0.1. In the unsaturated regime, chromospheric and coronal emission show similar dependence on Ro, but with a shift towards larger Ro, indicating chromospheric emission gets easily saturated than coronal emission, and/or convective turnover time-scales based on X-ray data do not work well with chromospheric emission. More interestingly, our analysis shows fully convective slow rotators obey the rotation-chromospheric activity relation similar to hotter stars, confirming the previous finding. We found correlations among H{alpha}, H{beta}, and CaII K emissions, in which H{alpha} losses are more important than CaII K for cooler and more active stars. In addition, a weak correlation is seen between chromospheric emission and photospheric activity that shows dependence on stellar spectral type and activity level, which provides some clues on how spot configuration varies as a function of mass and activity level.
2822. Chromospheric activity of field stars
ID:
ivo://CDS.VizieR/J/A+A/551/L8
Title:
Chromospheric activity of field stars
Short Name:
J/A+A/551/L8
Date:
21 Oct 2021
Publisher:
CDS
Description:
Compilation of S-index measurements available in the literature cross-correlated with the CDS catalog. The S-index is a measure of the strength of the chromospheric emission in the core of the CaII H and K lines, and it is a proxy for chromospheric activity. Its conversion into logR'HK is also reported, along with temperature, age and metallicity from the CDS.
2823. Chromospheric activity of nearby Sun-like stars
ID:
ivo://CDS.VizieR/J/A+A/641/A110
Title:
Chromospheric activity of nearby Sun-like stars
Short Name:
J/A+A/641/A110
Date:
21 Oct 2021
Publisher:
CDS
Description:
The chromospheric emission in the cores of the CaII H & K lines of late-type dwarfs is a well known indicator of magnetic activity that decreases with increasing stellar age. I use this indicator to investigate the formation history of nearby G- and early K-type stars with origins at galactocentric distances similar to that of the region where the Sun was born. A parent sample of single main-sequence stars with near-solar metallicity and known magnetic activity levels is built from catalogues of stellar atmospheric parameters and chromospheric activity indices. A kinematical approach uses Gaia astrometric data to differentiate thin disc stars from thick disc stars. Measured distributions of R'_HK_ chromospheric activity indices are compared with Monte Carlo simulations based on an empirical model of chromospheric activity evolution. The thin disc includes a significant fraction of Sun-like stars with intermediate activity levels while most early K- and G-type stars from the thick disc are inactive. The chromospheric activity distribution among nearby Sun-like dwarfs from the thin disc can be explained by a combination of an old (>6-7Gyr) star formation event (or events) and a more recent (<3Gyr) burst of star formation. Such an event is not required to account for the R'_HK_ index distributions of nearby thick disc stars. The distribution of magnetic activity among local G- and early K-type stars with a near-solar metallicity bears the imprint of an important star formation event that occurred ~1.9 to 2.6Gyr ago in the thin disc of the Milky Way.
2824. Chromospheric activity of Southern stars
ID:
ivo://CDS.VizieR/J/ApJ/734/70
Title:
Chromospheric activity of Southern stars
Short Name:
J/ApJ/734/70
Date:
21 Oct 2021
Publisher:
CDS
Description:
I present chromospheric-activity measurements of ~670 F, G, K, and M main-sequence stars in the Southern Hemisphere, from ~8000 archival high-resolution echelle spectra taken at Las Campanas Observatory since 2004. These stars were targets from the Old Magellan Planet Search, and are now potential targets for the New Magellan Planet Search that will look for rocky and habitable planets. Activity indices (S values) are derived from CaII H and K line cores and then converted to the Mount Wilson system. From these measurements, chromospheric (log R'_HK_) indices are derived, which are then used as indicators of the level of radial-velocity jitter, age, and rotation periods these stars present.
2825. Chromospherically active binaries
ID:
ivo://CDS.VizieR/J/MNRAS/349/1069
Title:
Chromospherically active binaries
Short Name:
J/MNRAS/349/1069
Date:
21 Oct 2021
Publisher:
CDS
Description:
The kinematics of 237 chromospherically active binaries (CABs) were studied. The sample is heterogeneous with different orbits and physically different components from F to M spectral-type main-sequence stars to G and K giants and supergiants. The computed U, V, W space velocities indicate that the sample is also heterogeneous in velocity space.
2826. Chromospherically Active Binaries
ID:
ivo://CDS.VizieR/V/76
Title:
Chromospherically Active Binaries
Short Name:
V/76
Date:
21 Oct 2021
Publisher:
CDS
Description:
The catalog contains 206 spectroscopic binary systems with at least one late-type component that shows Ca II H and K emission in its spectrum. These systems include the classical RS CVn binaries and BY Dra binaries. The catalog summarizes information on the photometric, spectroscopic, orbital, and physical properties of the systems as well as space motions and positions. Up to 42 "parameters" for each stellar system are listed followed by the appropriate reference to direct interested colleagues to the original papers. A comprehensive selection of further information for each star is given in the individual notes. In addition, the catalog contains a candidate list of 138 stars that have similar characteristics but are not definitely known binaries or have not had Ca II H and K emission observed. This version updates and replaces the 1988 catalog of similar information. (Strassmeier et al., 1988).
2827. Chromospherically Active Binaries. Third version
ID:
ivo://CDS.VizieR/V/128
Title:
Chromospherically Active Binaries. Third version
Short Name:
V/128
Date:
21 Oct 2021
Publisher:
CDS
Description:
Chromospherically Active Binaries (CAB) catalogue have been revised and updated. With 203 new identifications, the number of CAB stars is increased to 409. Catalogue is available in electronic format where each system has various number of lines (sub-orders) with a unique order number. Columns contain data of limited number of selected cross references, comments to explain peculiarities and position of the binarity in case it belongs to a multiple system, classical identifications (RS CVn, BY Dra), brightness and colours, photometric and spectroscopic data, description of emission features (Ca II H&K, H{alpha}, UV, IR), X-Ray luminosity, radio flux, physical quantities and orbital information, where each basic entry are referenced so users can go original sources.
2828. Chromospherically active stars in CoRoT fields
ID:
ivo://CDS.VizieR/J/A+A/469/713
Title:
Chromospherically active stars in CoRoT fields
Short Name:
J/A+A/469/713
Date:
21 Oct 2021
Publisher:
CDS
Description:
In this paper we report the results of the spectroscopic survey we carried out to detect chromospheric activity of late-type stars in the fields of view of the CoRoT space mission. We give an accurate MK classification of all targets, which is valuable information on both the main CoRoT project and additional science programs, by means of cross-correlation with MK standard stars, by using artificial neural networks. The presence or absence of excess H{alpha} emission, determined using spectral subtraction technique, is used to characterize the chromospheric activity level. In most cases our MK classification agrees with the spectral classification reported in the SIMBAD database; however, there are a few stars that are found to have very different MK classes. Our survey reveals that ~7% of late-type stars in our sample indeed possess a very active chromosphere. The measured H{alpha} excess and the presence of the 6708{AA}, Li line allow us to confirm the membership of 5 targets in the young open cluster NGC 2264.
2829. Chromospherically active stars in RAVE. II.
ID:
ivo://CDS.VizieR/J/ApJ/835/61
Title:
Chromospherically active stars in RAVE. II.
Short Name:
J/ApJ/835/61
Date:
21 Oct 2021
Publisher:
CDS
Description:
A large sample of over 38000 chromospherically active candidate solar-like stars and cooler dwarfs from the RAVE survey is addressed in this paper. An improved activity identification with respect to the previous study was introduced to build a catalog of field stars in the solar neighborhood with an excess emission flux in the calcium infrared triplet wavelength region. The central result of this work is the calibration of the age-activity relation for main-sequence dwarfs in a range from a few 10Myr up to a few Gyr. It enabled an order of magnitude age estimation of the entire active sample. Almost 15000 stars are shown to be younger than 1Gyr and ~2000 younger than 100Myr. The young age of the most active stars is confirmed by their position off the main sequence in the J-K versus N_UV_-V diagram showing strong ultraviolet excess, mid-infrared excess in the J-K versus W_1_-W_2_ diagram, and very cool temperatures (J-K>0.7). They overlap with the reference pre-main-sequence RAVE stars often displaying X-ray emission. The activity level increasing with the color reveals their different nature from the solar-like stars and probably represents an underlying dynamo-generating magnetic fields in cool stars. Of the RAVE objects from DR5, 50% are found in the TGAS catalog and supplemented with accurate parallaxes and proper motions by Gaia. This makes the database of a large number of young stars in a combination with RAVE's radial velocities directly useful as a tracer of the very recent large-scale star formation history in the solar neighborhood.
2830. Chromospherically active stars in the Bulge
ID:
ivo://CDS.VizieR/J/AJ/131/1044
Title:
Chromospherically active stars in the Bulge
Short Name:
J/AJ/131/1044
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results from the discovery and study of ~3000 chromospherically active giant and subgiant stars toward the Galactic bulge.

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