Disk Evolution in Cep OB2: Results from the<i>Spitzer Space Telescope</i>

Sicilia‐Aguilar, A.; Hartmann, L.; Calvet, Nuria; Megeath, S. Thomas; Muzerolle, James; Allen, Lori; D’Alessio, Paola; Merın, Bruno; Stauffer, J. R.; Young, Erick T.; Lada, Charles J.

doi:10.1086/498085

Cited by 246 publications

(327 citation statements)

References 46 publications

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“…We also find some stars with Hα higher than 200 km s −1 but with a low pEW (S23 and S47 is the most relevant case), and stars in the opposite situation (S93 and S94 are the most relevant cases). The former result is mainly due to the presence of intense absorption features overlapping the emission ones as already pointed out by Sicilia-Aguilar et al (2006) for some CTTSs belonging to the Tr37 cluster, while the latter result is due to the presence of accretion flows only in the direction perpendicular to the line of sight.…”

Section: Accretion Propertiesmentioning

confidence: 55%

“…Moreover, Hernández et al (2007) and Barrado y Navascués et al (2007) found a larger fraction of evolved thin disks in the older young clusters. Since a significant fraction of these evolved disks might have stopped the accretion onto the stars (Sicilia-Aguilar et al 2006, and references therein), it is likely that in young clusters the fraction of non-accreting disks grows with age. Following these considerations, the suggestion that the λ Ori population is more evolved than the σ Ori one could well explain the differences between the two clusters.…”

Section: The Age Hypothesismentioning

confidence: 99%

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FLAMES spectroscopy of low-mass stars in the young clusters σ Ori and λ Ori

Sacco

Franciosini²,

Randich

et al. 2008

A&A

181

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Aims. We performed a detailed membership selection and studied the accretion properties of low-mass stars in the two apparently very similar young (1-10 Myr) clusters σ Ori and λ Ori. Methods. We observed 98 and 49 low-mass (0.2-1.0 M ) stars in σ Ori and λ Ori respectively, using the multi-object optical spectrograph FLAMES at the VLT, with the high-resolution (R ∼ 17 000) HR15N grating (6470-6790 Å). We used radial velocities, Li and Hα to establish cluster membership and Hα and other optical emission lines to analyze the accretion properties of members. Results. We identified 65 and 45 members of the σ Ori and λ Ori clusters, respectively, and discovered 16 new candidate binary systems. We also measured rotational broadening for 20 stars and estimated the mass accretion rates in 25 stars of the σ Ori cluster, finding values between 10 −11 and 10 −7.7 M yr −1 and in 4 stars of the λ Ori cluster, finding values between 10 −11 and 10 −10.1 M yr −1 . Comparing our results with the infrared photometry obtained by the Spitzer satellite, we find that the fraction of stars with disks and the fraction of active disks is larger in the σ Ori cluster (52 ± 9% and 78 ± 16%) than in λ Ori (28 ± 8% and 40 ± 20%). Conclusions. The different disk and accretion properties of the two clusters could be due either to the effect of the high-mass stars and the supernova explosion in the λ Ori cluster or to different ages of the cluster populations. Further observations are required to draw a definitive conclusion.

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Section: Accretion Propertiesmentioning

confidence: 55%

Section: The Age Hypothesismentioning

confidence: 99%

FLAMES spectroscopy of low-mass stars in the young clusters σ Ori and λ Ori

Sacco

Franciosini²,

Randich

et al. 2008

A&A

181

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“…According to Bouvier (2007), at 10 Myr the fraction of stars that still have disk is around 10−25%. Sicilia-Aguilar et al (2006) reported that at an age of 5 Myr, about 90% of disks have already dispersed, and within 10 Myr, almost all pMS stars are diskless. More recently, Fedele et al (2010) determined an accretion timescale of 2.3 Myr and a near-to-mid infrared excess timescale of 3 Myr, indicating that mass accretion in pMS stars seems to drop below the detectable level earlier than near-to-mid infrared excess.…”

Section: As Inmentioning

confidence: 99%

Stellar models simulating the disk-locking mechanism and the evolutionary history of the Orion Nebula cluster and NGC 2264

Landin

Mendes

Vaz

et al. 2016

A&A

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Context. Rotational evolution in young stars is described by pre-main sequence evolutionary tracks including non-gray boundary conditions, rotation, conservation of angular momentum, and simulations of disk-locking. Aims. By assuming that disk-locking is the regulation mechanism for the stellar angular velocity during the early stages of pre-main sequence evolution, we use our rotating models and observational data to constrain disk lifetimes (T disk ) of a representative sample of low-mass stars in two young clusters, the Orion Nebula cluster (ONC) and NGC 2264, and to better understand their rotational evolution. Methods. The period distributions of the ONC and NGC 2264 are known to be bimodal and to depend on the stellar mass. To follow the rotational evolution of these two clusters' stars, we generated sets of evolutionary tracks from a fully convective configuration with low central temperatures (before D-and Li-burning). We assumed that the evolution of fast rotators can be represented by models considering conservation of angular momentum during all stages and of moderate rotators by models considering conservation of angular velocity during the first stages of evolution. With these models we estimate a mass and an age for all stars. Results. The resulting mass distribution for the bulk of the cluster population is in the ranges of 0.2−0.4 M and 0.1−0.6 M for the ONC and NGC 2264, respectively. For the ONC, we assume that the secondary peak in the period distribution is due to high-mass objects still locked in their disks, with a locking period (P lock ) of ∼8 days. For NGC 2264 we make two hypotheses: (1) the stars in the secondary peak are still locked with P lock = 5 days, and (2) NGC 2264 is in a later stage in the rotational evolution. Hypothesis 2 implies in a disk-locking scenario with P lock = 8 days, a disk lifetime of 1 Myr and, after that, constant angular momentum evolution. We then simulated the period distribution of NGC 2264 when the mean age of the cluster was 1 Myr. Dichotomy and bimodality appear in the simulated distribution, presenting one peak at 2 days and another one at 5−7 days, indicating that the assumption of P lock = 8 days is plausible. Our hypotheses are compared with observational disk diagnoses available in the literature for the ONC and NGC 2264, such as near-infrared excess, Hα emission, and spectral energy distribution slope in the mid-infrared. Conclusions. Disk-locking models with P lock = 8 days and 0.2 Myr ≤ T disk ≤ 3 Myr are consistent with observed periods of moderate rotators of the ONC. For NGC 2264, the more promising explanation for the observed period distribution is an evolution with disk-locking (with P lock near 8 days) during the first 1 Myr, approximately, but after this, the evolution continued with constant angular momentum.

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“…Haisch et al 2001;Bouwman et al 2006;Jayawardhana et al 2006;Sicilia-Aguilar et al 2006;Fedele et al 2010). At this age, stars lose their inner dusty disk and accretion stops.…”

Section: Stellar Spotsmentioning

confidence: 99%

HD 135344B: a young star has reached its rotational limit

Müller

Ancker

Launhardt

et al. 2011

A&A

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Aims. We search for periodic variations in the radial velocity of the young Herbig star HD 135344B to determine a rotation period. Methods. We analyze 44 high-resolution optical spectra taken over a time period of 151 days. The spectra were acquired with FEROS at the 2.2 m MPG/ESO telescope in La Silla. The stellar parameters of HD 135344B are determined by fitting synthetic spectra to the stellar spectrum. To obtain radial velocity measurements, the stellar spectra are cross-correlated with a theoretical template computed from determined stellar parameters. Results. We report the first direct measurement of the rotation period of a Herbig star from radial velocity measurements. The rotation period is found to be 0.16 d (3.9 h), which makes HD 135344B a rapid rotator at or close to its break-up velocity. The rapid rotation could explain some of the properties of the circumstellar environment of HD 135344B such as an inner disk with properties (composition, inclination) that differ significantly from the outer disk.

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Disk Evolution in Cep OB2: Results from theSpitzer Space Telescope

Cited by 246 publications

References 46 publications

FLAMES spectroscopy of low-mass stars in the young clusters σ Ori and λ Ori

FLAMES spectroscopy of low-mass stars in the young clusters σ Ori and λ Ori

Stellar models simulating the disk-locking mechanism and the evolutionary history of the Orion Nebula cluster and NGC 2264

HD 135344B: a young star has reached its rotational limit

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