A Multi-Color Optical Survey of the Orion Nebula Cluster. Ii. The H-R Diagram

Rio, Nicola Da; Robberto, M.; Soderblom, David R.; Panagia, N.; Hillenbrand, Lynne A.; Palla, F.; Stassun, Keivan G.

doi:10.1088/0004-637x/722/2/1092

Cited by 154 publications

(186 citation statements)

References 67 publications

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“…Neither possibility can be definitively ruled out, but neither is supported by any current observations or theory either. If we exclude very small initial radii on these grounds, we find that all the remaining models indicate that ages and age spreads inferred from non-accreting isochrones are reliable for cool stars, at least to the extent that the observationally determined luminosities and temperatures are reliable (e.g., Da Rio et al 2010a;2010b).…”

Section: Summary and Discussionmentioning

confidence: 90%

“…In some cases, it can be demonstrated that observational uncertainties alone are sufficient to induce an age spread of >10 Myr and mask a coeval stellar population (Slesnick et al 2008). However, Da Rio et al (2010a;2010b) carefully model these uncertainties and conclude that these effects alone cannot reproduce the entire spread. Other age indicators such as stellar rotation rate (Littlefair et al 2010), surface gravity (Slesnick et al 2008), and lithium abundances (Sestito et al 2008) also support the idea that the inferred age spreads are real, but are each subject to significant challenges.…”

Section: Introductionmentioning

confidence: 99%

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

Hosokawa

Offner

Krumholz

2011

ApJ

143

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: 90%

Section: Introductionmentioning

confidence: 99%

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

Hosokawa

Offner

Krumholz

2011

ApJ

143

157

View full text Add to dashboard Cite

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“…and modifying the photometric colors (e.g. Da Rio et al 2010). Moreover, the derivation of L line , from which L acc is determined, is affected by another stellar property, namely the chromospheric activity of the YSOs (Houdebine et al 1996;Franchini et al 1998).…”

Section: Introductionmentioning

confidence: 99%

X-shooter spectroscopy of young stellar objects

Manara

Testi

Rigliaco

et al. 2013

A&A

154

265

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Context. The lack of knowledge of photospheric parameters and the level of chromospheric activity in young low-mass pre-main sequence stars introduces uncertainties when measuring mass accretion rates in accreting (Class II) young stellar objects. A detailed investigation of the effect of chromospheric emission on the estimates of mass accretion rate in young low-mass stars is still missing. This can be undertaken using samples of young diskless (Class III) K and M-type stars. Aims. Our goal is to measure the chromospheric activity of Class III pre main sequence stars to determine its effect on the estimates of the accretion luminosity (L acc ) and mass accretion rate (Ṁ acc ) in young stellar objects with disks. Methods. Using VLT/X-shooter spectra, we analyzed a sample of 24 nonaccreting young stellar objects of spectral type between K5 and M9.5. We identified the main emission lines normally used as tracers of accretion in Class II objects, and we determined their fluxes in order to estimate the contribution of the chromospheric activity to the line luminosity. Results. We have used the relationships between line luminosity and accretion luminosity derived in the literature for Class II objects to evaluate the impact of chromospheric activity on the accretion rate measurements. We find that the typical chromospheric activity would bias the derived accretion luminosity by L acc,noise < 10 −3 L , with a strong dependence on the T eff of the objects. The noise oṅ M acc depends on stellar mass and age, and the typical values of log(Ṁ acc,noise ) range between ∼−9.2 to −11.6 M /yr. Conclusions. Values of L acc 10 −3 L obtained in accreting low-mass pre main sequence stars through line luminosity should be treated with caution because the line emission may be dominated by the contribution of chromospheric activity.

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“…To fully exploit this exceptional data set, an accurate estimate of the effective temperature (T eff ) is needed to derive A V from the observed colors and therefore the stellar luminosities. In our previous works (Da Rio et al 2009bRio et al , 2010, hereafter Paper I and Paper II, respectively), we have collected spectral types from the literature and complemented them with new optical spectroscopy. Moreover, we have presented a new observational technique, based on optical medium-band photometry at 6200 Å-a wavelength where the spectra of cool stars show a deep, T eff -dependent TiO absorption feature-to derive the spectral types of M-type sources.…”

Section: Introductionmentioning

confidence: 99%

The Initial Mass Function of the Orion Nebula Cluster Across the H-Burning Limit

Rio

Robberto

Hillenbrand

et al. 2012

ApJ

Self Cite

155

139

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We present a new census of the Orion Nebula Cluster over a large field of view ( 30 × 30 ), significantly increasing the known population of stellar and substellar cluster members with precisely determined properties. We develop and exploit a technique to determine stellar effective temperatures from optical colors, nearly doubling the previously available number of objects with effective temperature determinations in this benchmark cluster. Our technique utilizes colors from deep photometry in the I band and in two medium-band filters at λ ∼ 753 and 770 nm, which accurately measure the depth of a molecular feature present in the spectra of cool stars. From these colors we can derive effective temperatures with a precision corresponding to better than one-half spectral subtype, and importantly this precision is independent of the extinction to the individual stars. Also, because this technique utilizes only photometry redward of 750 nm, the results are only mildly sensitive to optical veiling produced by accretion. Completing our census with previously available data, we place some 1750 sources in the Hertzsprung-Russell diagram and assign masses and ages down to 0.02 solar masses. At faint luminosities, we detect a large population of background sources which is easily separated in our photometry from the bona fide cluster members. The resulting initial mass function of the cluster has good completeness well into the substellar mass range, and we find that it declines steeply with decreasing mass. This suggests a deficiency of newly formed brown dwarfs in the cluster compared to the Galactic disk population.

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A Multi-Color Optical Survey of the Orion Nebula Cluster. Ii. The H-R Diagram

Cited by 154 publications

References 67 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

X-shooter spectroscopy of young stellar objects

The Initial Mass Function of the Orion Nebula Cluster Across the H-Burning Limit

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