Cepheus OB2

Disk evolution and accretion at 3-10 Myr

Aurora Sicilia-Aguilar (Lead / Corresponding author), Lee W. Hartmann (Lead / Corresponding author), Jesus Hernandez (Lead / Corresponding author), Cesar Briceno (Lead / Corresponding author), Nuria Calvet (Lead / Corresponding author)

Research output: Contribution to journalArticle

122 Citations (Scopus)

Abstract

We present the results of MMT observations of young stars for our study of protoplanetary disks at ages 1 - 10 Myr in two young clusters located in the Cepheus OB2 region: Trumpler 37 ( embedded in the H II region IC 1396) and NGC 7160. Using low-resolution optical spectra from the Hectospec multifiber spectrograph, we have tripled the number of known low-mass cluster members, identifying similar to 130 new members in Tr 37 and similar to 30 in NGC 7160. We use indicators of youth (Li absorption at 6707 angstrom) and accretion / chromospheric activity (H alpha emission) to identify and classify the low-mass cluster members. We derive spectral types for all the low-mass candidates and calculate the individual extinctions and the average over the clusters. With the extended member samples, we estimate the disk fraction in the clusters, finding that similar to 40% of the low-mass stars in Tr 37 are actively accreting, whereas only 1 of the similar to 55 low-mass stars in NGC 7160 shows indications of accretion. Optical photometry and theoretical isochrones are used to determine the age of the cluster members, confirming the estimates of similar to 4 Myr for Tr 37 and similar to 10 Myr for NGC 7160. Accretion rates in Tr 37 (similar to 10(-8) M-. yr(-1) on average) are derived from U-band photometry. We find that only similar to 50% of the accreting stars have near-IR excesses ( from 2MASS), which could be due to the geometry of their disks or be an indication dust of settling / grain growth. Finally, we study the high- and intermediate-mass members of the clusters. With the extended member list, we revise the spatial distribution of stars with disks. Our results are crucial for interpreting Spitzer Space Telescope studies of accretion disks at the ages of planet formation ( 3 - 10 Myr).
Original languageEnglish
Pages (from-to)188-209
Number of pages22
JournalAstronomical Journal
Volume130
Issue number1
DOIs
Publication statusPublished - Jul 2005

Fingerprint

accretion
stars
photometry
indication
Space Infrared Telescope Facility
protoplanetary disks
H II regions
settling
estimates
accretion disks
lists
planet
spectrographs
extinction
optical spectrum
planets
spatial distribution
dust
geometry
young

Keywords

  • accretion, accretion disks planetary systems : protoplanetary disks stars : pre -main-sequence T-TAURI STARS ORION NEBULA CLUSTER MAIN-SEQUENCE STARS EMISSION-LINE DIAGNOSTICS INTERMEDIATE-MASS STARS HERBIG AE/BE STARS MAGNETOSPHERIC ACCRETION CIRCUMSTELLAR DISKS STELLAR POPULATION UBVRI PHOTOMETRY

Cite this

Sicilia-Aguilar, A., Hartmann, L. W., Hernandez, J., Briceno, C., & Calvet, N. (2005). Cepheus OB2: Disk evolution and accretion at 3-10 Myr. Astronomical Journal, 130(1), 188-209. https://doi.org/10.1086/430748
Sicilia-Aguilar, Aurora ; Hartmann, Lee W. ; Hernandez, Jesus ; Briceno, Cesar ; Calvet, Nuria. / Cepheus OB2 : Disk evolution and accretion at 3-10 Myr. In: Astronomical Journal. 2005 ; Vol. 130, No. 1. pp. 188-209.
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abstract = "We present the results of MMT observations of young stars for our study of protoplanetary disks at ages 1 - 10 Myr in two young clusters located in the Cepheus OB2 region: Trumpler 37 ( embedded in the H II region IC 1396) and NGC 7160. Using low-resolution optical spectra from the Hectospec multifiber spectrograph, we have tripled the number of known low-mass cluster members, identifying similar to 130 new members in Tr 37 and similar to 30 in NGC 7160. We use indicators of youth (Li absorption at 6707 angstrom) and accretion / chromospheric activity (H alpha emission) to identify and classify the low-mass cluster members. We derive spectral types for all the low-mass candidates and calculate the individual extinctions and the average over the clusters. With the extended member samples, we estimate the disk fraction in the clusters, finding that similar to 40{\%} of the low-mass stars in Tr 37 are actively accreting, whereas only 1 of the similar to 55 low-mass stars in NGC 7160 shows indications of accretion. Optical photometry and theoretical isochrones are used to determine the age of the cluster members, confirming the estimates of similar to 4 Myr for Tr 37 and similar to 10 Myr for NGC 7160. Accretion rates in Tr 37 (similar to 10(-8) M-. yr(-1) on average) are derived from U-band photometry. We find that only similar to 50{\%} of the accreting stars have near-IR excesses ( from 2MASS), which could be due to the geometry of their disks or be an indication dust of settling / grain growth. Finally, we study the high- and intermediate-mass members of the clusters. With the extended member list, we revise the spatial distribution of stars with disks. Our results are crucial for interpreting Spitzer Space Telescope studies of accretion disks at the ages of planet formation ( 3 - 10 Myr).",
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Sicilia-Aguilar, A, Hartmann, LW, Hernandez, J, Briceno, C & Calvet, N 2005, 'Cepheus OB2: Disk evolution and accretion at 3-10 Myr', Astronomical Journal, vol. 130, no. 1, pp. 188-209. https://doi.org/10.1086/430748

Cepheus OB2 : Disk evolution and accretion at 3-10 Myr. / Sicilia-Aguilar, Aurora (Lead / Corresponding author); Hartmann, Lee W. (Lead / Corresponding author); Hernandez, Jesus (Lead / Corresponding author); Briceno, Cesar (Lead / Corresponding author); Calvet, Nuria (Lead / Corresponding author).

In: Astronomical Journal, Vol. 130, No. 1, 07.2005, p. 188-209.

Research output: Contribution to journalArticle

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T2 - Disk evolution and accretion at 3-10 Myr

AU - Sicilia-Aguilar, Aurora

AU - Hartmann, Lee W.

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AU - Briceno, Cesar

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AB - We present the results of MMT observations of young stars for our study of protoplanetary disks at ages 1 - 10 Myr in two young clusters located in the Cepheus OB2 region: Trumpler 37 ( embedded in the H II region IC 1396) and NGC 7160. Using low-resolution optical spectra from the Hectospec multifiber spectrograph, we have tripled the number of known low-mass cluster members, identifying similar to 130 new members in Tr 37 and similar to 30 in NGC 7160. We use indicators of youth (Li absorption at 6707 angstrom) and accretion / chromospheric activity (H alpha emission) to identify and classify the low-mass cluster members. We derive spectral types for all the low-mass candidates and calculate the individual extinctions and the average over the clusters. With the extended member samples, we estimate the disk fraction in the clusters, finding that similar to 40% of the low-mass stars in Tr 37 are actively accreting, whereas only 1 of the similar to 55 low-mass stars in NGC 7160 shows indications of accretion. Optical photometry and theoretical isochrones are used to determine the age of the cluster members, confirming the estimates of similar to 4 Myr for Tr 37 and similar to 10 Myr for NGC 7160. Accretion rates in Tr 37 (similar to 10(-8) M-. yr(-1) on average) are derived from U-band photometry. We find that only similar to 50% of the accreting stars have near-IR excesses ( from 2MASS), which could be due to the geometry of their disks or be an indication dust of settling / grain growth. Finally, we study the high- and intermediate-mass members of the clusters. With the extended member list, we revise the spatial distribution of stars with disks. Our results are crucial for interpreting Spitzer Space Telescope studies of accretion disks at the ages of planet formation ( 3 - 10 Myr).

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DO - 10.1086/430748

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