The evolution of chromospheric activity of cool giant and subgiant stars

1989 ◽  
Vol 346 ◽  
pp. 303 ◽  
Author(s):  
Theodore Simon ◽  
Stephen A. Drake
Keyword(s):  
Chromospheric Activity ◽  
Subgiant Stars ◽  
Giant And Subgiant Stars

scholarly journals Some Notes on Stars Near K0

1973 ◽  
Vol 50 ◽  
pp. 36-41
Author(s):  
N. G. Roman
Keyword(s):  
Excellent Agreement ◽  
Peculiar Stars ◽  
Subgiant Stars ◽  
Intrinsic Scatter ◽  
Giant And Subgiant Stars

Two hundred giant and subgiant stars near K0 were classified twice by somewhat different techniques. The resulting types were in excellent agreement but a comparison of the assigned types with U, B, V colors indicated both an intrinsic scatter in the colors for stars of similar spectroscopic appearance and a problem in either the luminosity classifications or the standard colors or both. Several peculiar stars and a luminous supergiant were also detected.

scholarly journals On the link between rotation, chromospheric activity and Li abundance in subgiant stars

2003 ◽  
Vol 405 (2) ◽  
pp. 723-731 ◽  
Author(s):  
J. D. do Nascimento ◽  
B. L. Canto Martins ◽  
C. H. F. Melo ◽  
G. Porto de Mello ◽  
J. R. De Medeiros
Keyword(s):  
Chromospheric Activity ◽  
Subgiant Stars

scholarly journals Fundamental stellar parameters of benchmark stars from CHARA interferometry. III. Giant and subgiant stars

2021 ◽  
Author(s):  
I. Karovicova ◽  
T. R. White ◽  
T. Nordlander ◽  
L. Casagrande ◽  
M. Ireland ◽  
...  
Keyword(s):  
Fundamental Stellar Parameters ◽  
Subgiant Stars ◽  
Giant And Subgiant Stars

Chromospheric activity as a function of age in main-sequence stars

1966 ◽  
Vol 24 ◽  
pp. 40-43
Author(s):  
O. C. Wilson ◽  
A. Skumanich
Keyword(s):  
Main Sequence ◽  
The Sun ◽  
Main Sequence Stars ◽  
Tentative Conclusion ◽  
Chromospheric Activity ◽  
General Field ◽  
Large Clusters

Evidence previously presented by one of the authors (1) suggests strongly that chromospheric activity decreases with age in main sequence stars. This tentative conclusion rests principally upon a comparison of the members of large clusters (Hyades, Praesepe, Pleiades) with non-cluster objects in the general field, including the Sun. It is at least conceivable, however, that cluster and non-cluster stars might differ in some fundamental fashion which could influence the degree of chromospheric activity, and that the observed differences in chromospheric activity would then be attributable to the circumstances of stellar origin rather than to age.

Chromospheric activity in several single late-type stars

2015 ◽  
Vol 15 (2) ◽  
pp. 252-274 ◽  
Author(s):  
Li-Yun Zhang ◽  
Qing-Feng Pi ◽  
Zhong-Zhong Zhu
Keyword(s):  
Late Type ◽  
Chromospheric Activity

scholarly journals The large scale magnetic field of the G0 dwarf HD 206860 (HN Peg)

2013 ◽  
Vol 9 (S302) ◽  
pp. 146-147
Author(s):  
Sudeshna Boro Saikia ◽  
Sandra V. Jeffers ◽  
Pascal Petit ◽  
Stephen Marsden ◽  
Julien Morin ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Spectral Type ◽  
Large Scale ◽  
Longitudinal Magnetic Field ◽  
Chromospheric Activity ◽  
Large Scale Magnetic Field ◽  
Debris Disk ◽  
Infrared Triplet

AbstractHD 206860 is a young planet (HN Peg b) hosting star of spectral type G0V and it has a potential debris disk around it. In this work we measure the longitudinal magnetic field of HD 206860 using spectropolarimetric data and we measure the chromospheric activity using Ca II H&K, H-alpha and Ca II infrared triplet lines.

scholarly journals The AMBRE project: The thick thin disk and thin thick disk of the Milky Way

2017 ◽  
Vol 608 ◽  
pp. L1 ◽  
Author(s):  
M. R. Hayden ◽  
A. Recio-Blanco ◽  
P. de Laverny ◽  
S. Mikolaitis ◽  
C. C. Worley
Keyword(s):  
Vertical Velocity ◽  
Velocity Dispersion ◽  
Stellar Populations ◽  
Thin Disk ◽  
Thick Disk ◽  
Solar Neighborhood ◽  
Chemical Enrichment ◽  
History Of ◽  
External Galaxies ◽  
Subgiant Stars

We analyze 494 main sequence turnoff and subgiant stars from the AMBRE:HARPS survey. These stars have accurate astrometric information from Gaia DR1, providing reliable age estimates with relative uncertainties of ±1 or 2 Gyr and allowing precise orbital determinations. The sample is split based on chemistry into a low-[Mg/Fe] sequence, which are often identified as thin disk stellar populations, and high-[Mg/Fe] sequence, which are often associated with thick disk stellar populations. We find that the high-[Mg/Fe] chemical sequence has extended star formation for several Gyr and is coeval with the oldest stars of the low-[Mg/Fe] chemical sequence: both the low- and high-[Mg/Fe] sequences were forming stars at the same time. We find that the high-[Mg/Fe] stellar populations are only vertically extended for the oldest, most-metal poor and highest [Mg/Fe] stars. When comparing vertical velocity dispersion for the low- and high-[Mg/Fe] sequences, the high-[Mg/Fe] sequence has lower vertical velocity dispersion than the low-[Mg/Fe] sequence for stars of similar age. This means that identifying either group as thin or thick disk based on chemistry is misleading. The stars belonging to the high-[Mg/Fe] sequence have perigalacticons that originate in the inner disk, while the perigalacticons of stars on the low-[Mg/Fe] sequence are generally around the solar neighborhood. From the orbital properties of the stars, the high-[Mg/Fe] and low-[Mg/Fe] sequences are most likely a reflection of the chemical enrichment history of the inner and outer disk populations, respectively; radial mixing causes both populations to be observed in situ at the solar position. Based on these results, we emphasize that it is important to be clear in defining what populations are being referenced when using the terms thin and thick disk, and that ideally the term thick disk should be reserved for purely geometric definitions to avoid confusion and be consistent with definitions in external galaxies.

scholarly journals An investigation of chromospheric activity spanning the Vaughan-Preston gap: impact on stellar ages

2009 ◽  
Vol 499 (1) ◽  
pp. L9-L12 ◽  
Author(s):  
G. Pace ◽  
J. Melendez ◽  
L. Pasquini ◽  
G. Carraro ◽  
J. Danziger ◽  
...  
Keyword(s):  
Chromospheric Activity ◽  
Stellar Ages

scholarly journals Elemental abundances in the Galactic bulge from microlensed dwarf stars

2009 ◽  
Vol 5 (S265) ◽  
pp. 346-347
Author(s):  
T. Bensby ◽  
S. Feltzing ◽  
J. A. Johnson ◽  
A. Gould ◽  
H. Sana ◽  
...  
Keyword(s):  
Full Range ◽  
Galactic Bulge ◽  
Dwarf Stars ◽  
Elemental Abundances ◽  
Thick Disc ◽  
Abundance Trends ◽  
Subgiant Stars

AbstractWe present elemental abundances of 13 microlensed dwarf and subgiant stars in the Galactic bulge, which constitute the largest sample to date. We show that these stars span the full range of metallicity from Fe/H= −0.8 to +0.4, and that they follow well-defined abundance trends, coincident with those of the Galactic thick disc.

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