Chromospheric activity and ages of solar-type stars

Barry, D. C.; Cromwell, R. H.; Hege, E. K.

doi:10.1086/165131

Cited by 36 publications

(42 citation statements)

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“…I added data of NGC 752 and NGC 188 from Barry et al (1987), and from Pace et al (2009) The S-index measurements of Barry et al were made on spectra at a lower resolution (∼2 Å FWHM) than the classical Mount-Wilson data, but they were converted to match the Mount-Wilson system. However, when I transformed them into R HK using Noyes et al (1984), I obtained results completely inconsistent with the values published in Barry et al, with typical differences of 0.1 in logarithmic scale, and even larger when taking into account the correction suggested by Soderblom et al (1991).…”

Section: Open Cluster Datamentioning

confidence: 99%

“…The sample of Pace & Pasquini (2004) and Pace et al (2009) include, in addition to M 67 members, only seven stars older than 1 Gyr, two dwarfs in NGC 3680 and five in IC 4651, and they are all hotter than the Sun. Mamajek & Hillenbrand (2008) reported only two more open clusters older than 1 Gyr with CA measurements: NGC 752 (15 stars observed) and NGC 188 (3 stars observed) originally observed by Barry et al (1987) and Barry et al (1984). However, these data were considered suspicious (Soderblom et al 1991) and Mamajek & Hillenbrand (2008) did not use them either in their Table 5 or in their Fig.…”

Section: Introductionmentioning

confidence: 96%

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Chromospheric activity as age indicator

Pace

2013

A&A

147

106

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Context. Chromospheric activity has been calibrated and widely used as an age indicator. However, it has been suggested that the viability of this age indicator is, in the best case, limited to stars younger than about 1.5 Gyr. Aims. I aim to define the age range for which chromospheric activity is a robust astrophysical clock. Methods. I collected literature measurements of the S-index in field stars, which is a measure of the strength of the H and K lines of the Ca II and a proxy for chromospheric activity, and exploited the homogeneous database of temperature and age determinations for field stars provided by the Geneva-Copenhagen survey of the solar neighbourhood. Results. Field data, inclusive data previously used to calibrate chromospheric ages, confirm the result found using open cluster data, i.e. there is no decay of chromospheric activity after about 2 Gyr. Conclusions. The only existing indication supporting the viability of chromospheric ages older than 2 Gyr is the similarity of chromospheric activity levels in the components of 35 dwarf binaries. However, even in the most optimistic scenario, uncertainty in age determination for field stars and lack of sufficient data in open clusters make any attempt of calibrating an age activity relationship for old stars premature. The hypothesis that chromospheric activity follows the Skumanich law, i.e. that it is proportional to t −1/2 , should be relaxed.

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Section: Open Cluster Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Chromospheric activity as age indicator

Pace

2013

A&A

147

106

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“…The Barry et al (1987) data were reduced anew using a revised value of the basal flux given by Rutten (1987) 2. The empirical relation r c (B -V) determined by St §pieri (1989a) was used to calculate the stellar Rossby numbers 3.…”

Section: The Initial Period Of Rotation Of the Sunmentioning

confidence: 99%

“…Two different measures of the activity-related calcium emission flux have been suggested in the literature (see again St §pien 1989a for discussion). It is not yet clear which one is more correct and should be used with the Barry et al (1987) observations to calibrate the P ro t(t) relation 3. Even when one uses the excess calcium emission flux AFcaii (which is a better, in the opinion of the present author, measure of the chromospheric activity) one has to allow for uncertainty in the basal flux subtracted from the total measured flux to get Acaii-Its value was recently revised (Rutten, 1987) but is still known with insufficient accuracy.…”

Section: A Number Of T C (B -V) Relations Have Been Published (See Stmentioning

confidence: 99%

“…After integrating the resulting equation one gets the relation P ro t(t)-The constants appearing in this relation (including the value of the exponent describing geometry of the coronal magnetic field) were determined by Stepieri (1988b) from the observations of activity in open clusters of different age, obtained by Barry et al (1987). Since that, however, several new data have appeared and it became useful to revise the calibration of P ro t(t)-…”

Section: Introductionmentioning

confidence: 99%

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The History of Activity of the Sun and its Rotational Period on the ZAMS

Stępień¹

1991

International Astronomical Union Colloquium

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The rotation period of the Sun after it reached ZAMS is estimated from the present rotation rate, average X-ray emission flux and average calcium emission flux. Taking into account all existing uncertainties it is concluded that this initial period was within the range 1-9 days, with the most probable value 2-3 days. Possible influence of the solar activity on evolution of life on the Earth is briefly discussed.

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Heating of stellar chromospheres and coronae observational constraints and evidence for saturation

Vilhu

Lecture Notes in Physics

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Chromospheric-coronal emission of cool stars has a clear observed (spectral type dependent) upper limit (saturation). This boundary is seen in the surface flux vs. color (and flux vs. period) diagrams for different types of cool stars, excluding T Tauri-stars. The limit is occupied by rapid rotators (zJP_>3), either very young stars or components in close binaries with tidally forced rotation. Saturated stars seem to be almost totally filled with equipartition magnetic fields. This is one of the reason for the saturation: super-active regions with B= 1-2 kG fill the stellar surface, and no more magnetic flux can get out. This is due to the feed-backs between magnetic fields, convection and differential rotation.For saturated stars the observed average fluxes (over the disc) could also represent the local surface fluxes, if the many filling factors involved are really close to unity. Then a comparison with local heating is possible. The mechanical flux of subphotospheric convective motions is not very much larger than estimated total radiative losses from the chromospheric coronal plasma of saturated stars.Hence, the power of this mechanical driver of coronal heating sets another natural constraint to the extent of this hot plasma. We conclude that there is an ubiquitous need for hydrodynamic simulations of convection with magnetic fields and for future high resolution X-EUV-UV spectroscopic missions.

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Chromospheric activity and ages of solar-type stars

Cited by 36 publications

References 0 publications

Chromospheric activity as age indicator

Chromospheric activity as age indicator

The History of Activity of the Sun and its Rotational Period on the ZAMS

Heating of stellar chromospheres and coronae observational constraints and evidence for saturation

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