Elemental abundances of low-mass stars in the young clusters 25 Orionis and<i>λ</i> Orionis

Biazzo, K.; Randich, S.; Palla, F.

doi:10.1051/0004-6361/201116621

Cited by 38 publications

(26 citation statements)

References 46 publications

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“…This also agrees with existing studies of metallicity in other nearby star-formation regions (Padgett 1996;Santos et al 2008;D'Orazi et al 2009a;Biazzo et al 2011). Many stars in the stellar sample considered here are however not cluster members, and are therefore of unknown metallicity.…”

Section: Introductionsupporting

confidence: 91%

Gaia-ESO Survey: Empirical classification of VLT/Giraffe stellar spectra in the wavelength range 6440–6810 Å in theγVelorum cluster, and calibration of spectral indices

Damiani

Prisinzano

Micela

et al. 2014

A&A

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We present a study of spectral diagnostics available from optical spectra with R = 17 000 obtained with the VLT/Giraffe HR15n setup, using observations from the Gaia-ESO Survey, on the γ Vel young cluster, with the purpose of classifying these stars and finding their fundamental parameters. We define several spectroscopic indices, sampling the amplitude of TiO bands, the Hα line core and wings, and temperature-and gravity-sensitive sets of lines, each useful as a T eff or log g indicator over a limited range of stellar spectral types. Hα line indices are also useful as chromospheric activity or accretion indicators. Furthermore, we use all indices to define additional global T eff -and log g-sensitive indices τ and γ, valid for the entire range of types in the observed sample. We find a clear difference between gravity indices of main-sequence and premain-sequence stars, as well as a much larger difference between these and giant stars. The potentially great usefulness of the (γ, τ) diagram as a distance-independent age measurement tool for young clusters is discussed. We discuss the effect on the defined indices of classical T Tauri star veiling, which is however detected in only a few stars in the present sample. Then, we present tests and calibrations of these indices, on the basis of both photometry and literature reference spectra, from the UVES Paranal Observatory Project and the ELODIE 3.1 Library. The known properties of these stars, spanning a wide range of stellar parameters, enable us to obtain a good understanding of the performances of our new spectral indices. For non-peculiar stars with known temperature, gravity, and metallicity, we are able to calibrate quantitatively our indices, and derive stellar parameters for a wide range of stellar types. To this aim, a new composite index is defined, providing a good metallicity indicator. The ability of our indices to select peculiar, or otherwise rare classes of stars is also established. For pre-main-sequence stars outside the parameter range of the ELODIE dataset, index calibration relies on model isochrones. We check our calibrations against current Gaia-ESO UVES results, plus a number of Survey benchmark stars, and also against Gaia-ESO observations of young clusters, which contribute to establishing the good performance of our method across a wide range of stellar parameters. Our gravity determination for late-type PMS stars is found to be accurate enough to let us obtain gravity-based age estimates for PMS clusters. Finally, our gravity determinations support the existence of an older premain-sequence population in the γ Vel sky region, in agreement with evidence obtained from the lithium depletion pattern of the same stars.

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Section: Introductionsupporting

confidence: 91%

Gaia-ESO Survey: Empirical classification of VLT/Giraffe stellar spectra in the wavelength range 6440–6810 Å in theγVelorum cluster, and calibration of spectral indices

Damiani

Prisinzano

Micela

et al. 2014

A&A

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“…Among the 434 TTS in SIMBAD, 226 were published by us in B05, B07b, Biazzo et al (2011), another 77 in Downes et al (2014) and 53 by Suárez et al (2017). The other 78 are from various other studies (see 3.4.3).…”

Section: Crossmatch With Simbadmentioning

confidence: 99%

The CIDA Variability Survey of Orion OB1. II. Demographics of the Young, Low-mass Stellar Populations^*

et al. 2019

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We present results of our large scale, optical, multi-epoch photometric survey of ∼ 180 square degrees across the Orion OB1 association, complemented with extensive follow up spectroscopy. Our focus is mapping and characterizing in an uniform way the off-cloud, low-mass, pre-main sequence populations. We report 2064, mostly K and M-type, confirmed T Tauri members. Most (59%) are located in the OB1a subassociation, 27% are projected onto the OB1b subassociation, and the remaining 14% are located within the confines of the A and B molecular clouds. There is significant structure in the spatial distribution of the young stars. We characterize two new clusterings of T Tauri stars, the HD 35762 and HR 1833 groups, both located in the OB1a subassociation, not far form the 25 Ori cluster. We also confirm two stellar overdensities in OB1b, I and II, containing a total of 231 T Tauri stars. A ∼ 2 deg wide halo of young stars surrounds the Orion Nebula Cluster; the north and south parts corresponding to the low-mass populations of NGC 1977 and NGC 1980, respectively. There is indication of two populations of young stars in the OB1b region, located at two different distances, which may be due to the OB1a subassociation overlapping on front of OB1b. The various groups and regions can be ordered in an age sequence that agrees with the long standing picture of star formation starting in Orion OB1a some 10-15 Myr ago.We use the strength of the Hα line in emission, combined with characteristics of IR excesses and optical variability, to define a new type of T Tauri star, the C/W class, stars we propose may be nearing the end of their accretion phase, in an evolutionary state between that of Classical T Tauri and Weak-lined T Tauri stars. The evolution of the ensemble-wide equivalent width of the Li Iλ6707 line shows the depletion of Li with a timescale of 8.5 Myr. The decline of the accretion fraction, from ∼ 2 − 10 Myr, implies an accretion e-folding timescale of 2.1 Myr, consistent with previous studies. Finally, we use the median amplitude of the V -band variability in each type of star, to show the decline of stellar activity, from the accreting Classical T Tauri stars to the population of least active field dwarfs.

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“…25 Ori is a 7-10 Myr population located at 356±47 pc and presents a low visual extinction of 0.29±0.26 mag (see Appendix C), which facilitates the detection of members down to planetary-masses (Downes et al 2015). Several previous studies have focused on characterizing the 25 Ori population; Kharchenko et al (2005Kharchenko et al ( , 2013 for intermediate/high-mass stars, Briceño et al (2005); McGehee (2006); Briceño et al (2007); Hernández et al (2007); Biazzo et al (2011); Downes et al (2014); Suárez et al (2017); Briceño et al (2019) for LMSs and Downes et al (2015) for BDs.…”

Section: Introductionmentioning

confidence: 99%

System initial mass function of the 25 Ori group from planetary-mass objects to intermediate/high-mass stars

Suárez

Downes

Román-Zúñiga

et al. 2019

Monthly Notices of the Royal Astronomical Society

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The stellar initial mass function (IMF) is an essential input for many astrophysical studies but only in a few cases it has been determined over the whole cluster mass range, limiting the conclusions about its nature. The 25 Orionis group (25 Ori) is an excellent laboratory to investigate the IMF across the entire mass range of the population, from planetary-mass objects to intermediate/high-mass stars. We combine new deep optical photometry with optical and near-infrared data from the literature to select 1687 member candidates covering a 1.1 • radius area in 25 Ori. With this sample we derived the 25 Ori system IMF from 0.012 to 13.1 M . This system IMF is well described by a two-segment power-law with Γ = −0.74 ± 0.04 for m < 0.4 M and Γ = 1.50 ± 0.11 for m ≥ 0.4 M . It is also well described over the whole mass range by a tapered power-law function with Γ = 1.10 ± 0.09, m p = 0.31 ± 0.03 and β = 2.11 ± 0.09. The best lognormal representation of the system IMF has m c = 0.31 ± 0.04 and σ = 0.46 ± 0.05 for m < 1 M . This system IMF does not present significant variations with the radii. We compared the resultant system IMF as well as the BD/star ratio of 0.16±0.03 we estimated for 25 Ori with that of other stellar regions with diverse conditions and found no significant discrepancies. These results support the idea that general star formation mechanisms are probably not strongly dependent to environmental conditions. We found that the substellar and stellar objects in 25 Ori have similar spatial distributions and confirmed that 25 Ori is a gravitationally unbound stellar association.

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Elemental abundances of low-mass stars in the young clusters 25 Orionis andλ Orionis

Cited by 38 publications

References 46 publications

Gaia-ESO Survey: Empirical classification of VLT/Giraffe stellar spectra in the wavelength range 6440–6810 Å in theγVelorum cluster, and calibration of spectral indices

Gaia-ESO Survey: Empirical classification of VLT/Giraffe stellar spectra in the wavelength range 6440–6810 Å in theγVelorum cluster, and calibration of spectral indices

The CIDA Variability Survey of Orion OB1. II. Demographics of the Young, Low-mass Stellar Populations^*

System initial mass function of the 25 Ori group from planetary-mass objects to intermediate/high-mass stars

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Elemental abundances of low-mass stars in the young clusters 25 Orionis andλ Orionis

Cited by 38 publications

References 46 publications

Gaia-ESO Survey: Empirical classification of VLT/Giraffe stellar spectra in the wavelength range 6440–6810 Å in theγVelorum cluster, and calibration of spectral indices

Gaia-ESO Survey: Empirical classification of VLT/Giraffe stellar spectra in the wavelength range 6440–6810 Å in theγVelorum cluster, and calibration of spectral indices

The CIDA Variability Survey of Orion OB1. II. Demographics of the Young, Low-mass Stellar Populations*

System initial mass function of the 25 Ori group from planetary-mass objects to intermediate/high-mass stars

Contact Info

Product

Resources

About

The CIDA Variability Survey of Orion OB1. II. Demographics of the Young, Low-mass Stellar Populations^*