The Age, Stellar Content, and Star Formation Timescale of the B59 Dense Core

Covey, Kevin R.; Lada, Charles J.; Román-Zúñiga, C.; Muench, August; Forbrich, Jan; Ascenso, Joana

doi:10.1088/0004-637x/722/2/971

Cited by 88 publications

(102 citation statements)

References 92 publications

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“…They are not a result of variable accretion histories. However, we note that this does suggest that accreting isochrones may resolve the problem of systematically larger inferred ages for high-mass cluster members (e.g., Hillenbrand 2009;Covey et al 2010).…”

Section: Summary and Discussionmentioning

confidence: 82%

On the Reliability of Stellar Ages and Age Spreads Inferred From Pre-Main-Sequence Evolutionary Models

Hosokawa

Offner

Krumholz

2011

ApJ

140

157

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We revisit the problem of low-mass pre-main-sequence stellar evolution and its observational consequences for where stars fall on the Hertzsprung-Russell diagram (HRD). In contrast to most previous work, our models follow stars as they grow from small masses via accretion, and we perform a systematic study of how the stars' HRD evolution is influenced by their initial radius, by the radiative properties of the accretion flow, and by the accretion history, using both simple idealized accretion histories and histories taken from numerical simulations of star cluster formation. We compare our numerical results to both non-accreting isochrones and to the positions of observed stars in the HRD, with a goal of determining whether both the absolute ages and the age dispersions inferred from non-accreting isochrones are reliable. We show that non-accreting isochrones can sometimes overestimate stellar ages for more massive stars (those with effective temperatures above ∼3500 K), thereby explaining why non-accreting isochrones often suggest a systematic age difference between more and less massive stars in the same cluster. However, we also find the only way to produce a similar overestimate for the ages of cooler stars is if these stars grow from ∼0.01 M seed protostars that are an order of magnitude smaller than predicted by current theoretical models, and if the size of the seed protostar correlates systematically with the final stellar mass at the end of accretion. We therefore conclude that, unless both of these conditions are met, inferred ages and age spreads for cool stars are reliable, at least to the extent that the observed bolometric luminosities and temperatures are accurate. Finally, we note that the time dependence of the mass accretion rate has remarkably little effect on low-mass stars' evolution on the HRD, and that such time dependence may be neglected for all stars except those with effective temperatures above ∼4000 K.

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Section: Summary and Discussionmentioning

confidence: 82%

On the Reliability of Stellar Ages and Age Spreads Inferred From Pre-Main-Sequence Evolutionary Models

Hosokawa

Offner

Krumholz

2011

ApJ

140

157

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“…An index is a measure of the curvature of the spectrum in a particular region. This definition is identical to that given in Covey et al (2010) although they define bands to measure the level of H 2 O absorption in NIR spectra of M dwarfs, while we are interested in an empirical method to measure T eff with no preference for any particular absorption band.…”

Section: Temperature Sensitive Indicesmentioning

confidence: 99%

Spectro-Thermometry of M Dwarfs and Their Candidate Planets: Too Hot, Too Cool, or Just Right?

Mann

Gaidos

Ansdell

2013

ApJ

206

385

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We use moderate-resolution spectra of nearby late K and M dwarf stars with parallaxes and interferometrically determined radii to refine their effective temperatures, luminosities, and metallicities. We use these revised values to calibrate spectroscopic techniques to infer the fundamental parameters of more distant late-type dwarf stars. We demonstrate that, after masking out poorly modeled regions, the newest version of the PHOENIX atmosphere models accurately reproduce temperatures derived bolometrically. We apply methods to late-type hosts of transiting planet candidates in the Kepler field, and calculate effective temperature, radius, mass, and luminosity with typical errors of 57 K, 7%, 11%, and 13%, respectively. We find systematic offsets between our values and those from previous analyses of the same stars, which we attribute to differences in atmospheric models utilized for each study. We investigate which of the planets in this sample are likely to orbit in the circumstellar habitable zone. We determine that four candidate planets (KOI 854.01, 1298(KOI 854.01, .02, 1686.01, and 2992.01) are inside of or within 1σ of a conservative definition of the habitable zone, but that several planets identified by previous analyses are not (e.g., KOI 1422.02 and KOI 2626.01). Only one of the four habitable-zone planets is Earth sized, suggesting a downward revision in the occurrence of such planets around M dwarfs. These findings highlight the importance of measuring accurate stellar parameters when deriving parameters of their orbiting planets.

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“…The average timescale for a low-mass YSO population is τ ∼ 2 Myr (see for example Evans et al 2009;Covey et al 2010;Lada et al 2010). By using again the star count method, we can then calculate the amount of missing SFR as SFR M<M(lim) …”

Section: Catalog Completenessmentioning

confidence: 99%

An analysis of star formation withHerschelin the Hi-GAL survey

Veneziani

Elia

Noriega-Crespo

et al. 2013

A&A

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Aims. The Herschel survey of the Galactic plane (Hi-GAL) provides a unique opportunity to study star formation over large areas of the sky and different environments in the Milky Way. We use the best-studied Hi-GAL fields to date, two 2 • · 2 • tiles centered on ( , b) = (30 • , 0 • ) and ( , b) = (59 • , 0 • ), to study the star formation activity in these regions of the sky using a large sample of well-selected young stellar objects (YSOs). Methods. We used the science demonstration phase Hi-GAL fields, where a tremendous effort has been made to identify the newly formed stars and to derive their properties as accurately as possible, e.g. distance, bolometric luminosity, envelope mass, and stage of evolution. We estimated the star formation rate (SFR) for these fields using the number of candidate YSOs and their average time scale to reach the zero age main sequence, and compared it with the rate estimated using their integrated luminosity at 70 μm, combined with an extragalactic star formation indicator. Results. We measure an SFR of (9.5 ± 4.3) × 10 −4 M /yr and (1.6 ± 0.7) × 10 −4 M /yr with the source counting method, in = 30 • and = 59 • , respectively. Results with the 70 μm estimator are (2.4 ± 0.4) × 10 −4 M /yr and (2.6 ± 1.1) × 10 −6 M /yr. Since the 70 μm indicator is derived from averaging extragalactic star forming complexes, we extrapolated of these values to the whole Milky Way and obtain SFR MW = (0.71 ± 0.13) M /yr from l = 30 • and SFR MW = (0.10 ± 0.04) M /yr from = 59 • . The estimates in = 30 • agree with the most recent results for Galactic star formation activity. Conclusions. The source-counting method gives results that are only valid for the particular region under consideration. In contrast, the construction of the IR indicator leads to results that can be extrapolated to the whole Galaxy. In particular, when it is applied to the = 30 • field, it provides an SFR that is consistent with previous estimates, indicating that the characteristics of this field are very likely close to those of the star formation-dominated galaxies used for its derivation. Since the sky coverage is limited, this analysis will improve when the full Hi-GAL survey is available. It will cover the whole Galactic plane, sampling almost the totality of Galactic star forming complexes. By means of the candidate YSO-counting method, it will then be possible to calibrate an SFR Galactic indicator and to test the validity of the extragalactic estimators.

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The Age, Stellar Content, and Star Formation Timescale of the B59 Dense Core

Cited by 88 publications

References 92 publications

On the Reliability of Stellar Ages and Age Spreads Inferred From Pre-Main-Sequence Evolutionary Models

On the Reliability of Stellar Ages and Age Spreads Inferred From Pre-Main-Sequence Evolutionary Models

Spectro-Thermometry of M Dwarfs and Their Candidate Planets: Too Hot, Too Cool, or Just Right?

An analysis of star formation withHerschelin the Hi-GAL survey

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