The chromospheric emission-age relation for stars of the lower main sequence and its implications for the star formation rate

Soderblom, David R.; Duncan, D. K.; Johnson, D. R. H.

doi:10.1086/170238

Cited by 234 publications

(300 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). I believe that Barry et al's S-index measurements are trustworthy, since their conversion into R HK gives reasonable results, while both Barry et al's values of R HK × 10 5 and their correction following Soderblom et al (1991) are suspicious.…”

Section: Open Cluster Datacontrasting

confidence: 56%

“…The data include the following sources: Arriagada (2011), Jenkins et al (2011), Baliunas et al (1995, Knutson et al (2010), López-Santiago et al (2010), Gray et al (2003), Schröder et al (2009), Cincunegui et al (2007, Lockwood et al (2007), Duncan et al (1991), Gray et al (2006), Tinney et al (2002), Hall et al (2007), White et al (2007), Henry et al (1996), and Wright et al (2004). Strassmeier et al (2000) measured absolute H and K emission-line fluxes of more than 1000 late-type stars, but they did not report S-index measurements.…”

Section: Field Datamentioning

confidence: 99%

“…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. 4, where other cluster data are reported.…”

Section: Introductionmentioning

confidence: 96%

“…Soderblom et al 1991;Donahue 1993;Lachaume et al 1999;Mamajek & Hillenbrand 2008) based on field stars, binary systems, or open-cluster members, and these calibrations are claimed to be valid at all ages.…”

Section: Introductionmentioning

confidence: 99%

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Chromospheric activity as age indicator

Pace

2013

A&A

146

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 Datacontrasting

confidence: 56%

Section: Field Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Chromospheric activity as age indicator

Pace

2013

A&A

146

106

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“…These analyses are complicated to some extent by likely variations in the activity of individual stars, such as the Maunder minimum phenomenon in solar-type dwarfs. However, Soderblom, Duncan, & Johnson (1991) have demonstrated that the available data for G dwarfs and M dwarfs are consistent with a uniform star formation rate over the past 9 Gyr. Henry, Soderblom, & Donahue (1996) have extended the observational sample to include some 800 G-type southern stars and to conÐrm the distribution of activity deduced from the northern samples.…”

Section: T He Stellar Birthrate and ((M)mentioning

confidence: 91%

L Dwarfs and the Substellar Mass Function

Reid

Kirkpatrick

Liebert

et al. 1999

ApJ

233

229

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Analysis of initial observations sky surveys has shown that the resulting photometric catalogs, combined with far-red optical data, provide an extremely e †ective method of Ðnding isolated, very lowtemperature objects in the general Ðeld. Follow-up observations have already identiÐed more than 25 sources with temperatures cooler than the latest M dwarfs. A comparison with detailed model predictions (Burrows & Sharp 1999) indicates that these L dwarfs have e †ective temperatures between B2000^100 K and 1500^100 K, while the available trigonometric parallax data place their luminosities at between 10~3.5 and 10. Those properties, together with the detection of lithium in one-third of the objects, are consistent with the majority having substellar masses. The mass function cannot be derived directly, since only near-infrared photometry and spectral types are available for most sources, but we can incorporate VLM/brown dwarf models in simulations of the solar neighborhood population and constrain ((M) by comparing the predicted L dwarf surface densities and temperature distributions against observations from the Deep Near-Infrared Survey (DENIS) and 2 Micron All-Sky Survey (2MASS) surveys. The data, although sparse, can be represented by a power-law mass function, ((M) P M~a, with 1 \ a \ 2. Current results favor a value nearer the lower limit. If a \ 1.3, then the local space density of brown dwarfs is 0.10 systems pc~3. In that case, brown 0.075 [ M/M _ [ 0.01 dwarfs are twice as common as main-sequence stars but contribute no more than D15% of the total mass of the disk.

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Measuring the ages of low‐mass stars and brown dwarfs

et al. 2013

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Age is among the most elusive, yet important, fundamental properties of low-mass stars and brown dwarfs. M dwarfs have main-sequence lifetimes that are estimated to be trillions of years, with little change in luminosity. In contrast, brown dwarfs cool and dim with time, resulting in a significant degeneracy between mass, age, and luminosity. Despite these inherent challenges, there have been recent efforts on both observational and theoretical fronts that may yield precise ages for low-mass stars and brown dwarfs. We feature some current observational efforts focused on estimating ages of these objects as presented in our Cool Stars 17 splinter session.

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The chromospheric emission-age relation for stars of the lower main sequence and its implications for the star formation rate

Cited by 234 publications

References 0 publications

Chromospheric activity as age indicator

Chromospheric activity as age indicator

L Dwarfs and the Substellar Mass Function

Measuring the ages of low‐mass stars and brown dwarfs

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