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J/AJ/129/363    Spectroscopy in Orion Nebula Cluster    (Sicilia-Aguilar+, 2005)

Accretion, kinematics, and rotation in the Orion Nebula Cluster: initial results from Hectochelle. Sicilia-Aguilar A., Hartmann L.W., Szentgyorgyi A.H., Fabricant D.G., Furesz G., Roll J., Conroy M.A., Calvet N., Tokarz S., Hernandez J. <Astron. J., 129, 363-381 (2005)> =2005AJ....129..363S
ADC_Keywords: Accretion ; Stars, pre-main sequence ; Clusters, open ; Equivalent widths ; Radial velocities Keywords: accretion, accretion disks - line: profiles - stars: pre-main-sequence - stars: rotation Abstract: We present results from high-resolution spectra of 237 stars in the Orion Nebula cluster (ONC) obtained during two engineering runs with the Hectochelle multifiber echelle spectrograph on the 6.5m MMT. The ONC is the nearest populous young (age ∼1Myr) cluster and is therefore an important object for studies of the evolution of protoplanetary disks. Using the high spectral resolution of Hectochelle, we are able to distinguish stellar accretion and wind emission-line profiles from nebular emission lines and identify accreting members of the cluster from Hα profiles with greater accuracy than previously possible. We find 15 new members on the basis of Li λ6707 absorption and Hα emission. Line profiles of Hα of some objects that are not too contaminated by nebular emission show features characteristic of mass inflow and ejection. We also present rotational velocities as part of an initial investigation into angular momentum evolution of very young stars, confirming a difference between classical T Tauri stars and weak-line T Tauri stars that had been found from period analysis. Finally, we present an initial study of the radial velocity dispersion of the brighter stars in the central cluster. The very small dispersion derived, 1.8km/s, is in good agreement with estimates from proper motions. Description: Hectochelle is a fiber-fed multiobject echelle spectrograph fed by a robotic fiber positioner and mounted at the Cassegrain focus of the MMT (Multiple Mirror Telescope) on Mount Hopkins, Arizona. The first set of observations was taken on the night of 2003 December 8. The second set of observations consisted of three 15 minute exposures in the Hα order on 2004 March 10. Objects: -------------------------------------------------------------- RA (2000) DE Designation(s) -------------------------------------------------------------- 05 35 12.0 -05 24 06 Orion Nebula Cluster = GAL 208.9-19.4 -------------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 75 185 Results from 2003 December table2.dat 92 153 Results from March 2004
See also: J/AJ/113/1733 : Orion Nebula Cluster population (Hillenbrand 1997) J/AJ/116/1816 : JHKLMNOPQ photometry in Orion cluster (Hillenbrand+, 1998) J/A+A/396/513 : Stellar Rotation in the Orion Nebula Cluster (Herbst+, 2002) II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 4 I4 --- [H97b] ? Identification number (G1) 5- 6 A2 --- m_[H97b] Multiple components 8- 23 A16 --- 2MASS The 2MASS identification (HHMMSSss+DDMMSSs) 25- 38 A14 --- SpType Hillenbrand et al. (1998, Cat. J/AJ/116/1816) spectral type 40- 41 A2 --- Type [CW: ] Type T Tauri star classification (G2) 43- 46 F4.2 0.1nm EW(Li) ? Equivalent width of Li (6707 Angstroms) in Angstroms 47 A1 --- u_EW(Li) Uncertainty flag in EW(Li) 49- 52 I4 0.1nm EW(Ha) ? Equivalent width of Hα in Angstroms 54- 75 A22 --- Com Additional comments (1)
Note (1): Proplyds named using their HST ID number as given in Hillenbrand et al. 1998, Cat. J/AJ/116/1816) , Bally et al. (1998AJ....116..293B). Winds (denoted PC, or P-Cygni profiles) and infall (denoted IPC, or inverse P-Cygni profiles) detected by asymmetries in Hα profile. Broad or very broad He (written as bHe or very bHe) refers to the detection of the broad component of the He emission line at 5876Å. Low signal to noise spectra are marked with the label lS/N. Colons have been added to uncertain values. Stars with near-IR excess in 2MASS are labeled as nIR. An additional comment has been included to distinguish stars with systematically broad lines as possible fast rotators. The label "(2004)" indicate stars that were observed again in March 2004, which have the additional information corresponding to the 2004 run in Table2.
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 4 I4 --- [H97b] Identification number (G1) 5- 6 A2 --- m_[H97b] Multiple components 8- 23 A16 --- 2MASS The 2MASS identification (HHMMSSss+DDMMSSs) 25- 29 F5.1 km/s cz Heliocentric radial velocity 31- 34 F4.1 km/s e_cz Uncertainty in cz 36- 39 F4.1 --- S/N ? Signal-to-noise value of cross-correlation peak (see text) 41- 45 F5.1 km/s vsini ? Rotational velocity 47- 50 F4.1 km/s e_vsini ? Uncertainty in vsini 52- 56 A5 --- Type T Tauri star classification (G2) 58- 63 F6.1 0.1nm EW(Ha) ? Equivalent width of Hα in Angstroms 64 A1 --- u_EW(Ha) Uncertainty flag in EW(Ha) 66- 77 A12 --- SpType Spectral type (1) 79- 92 A14 --- Com Additional comments (2)
Note (1): From Hillenbrand (1997, Cat. J/AJ/113/1733) and subsequent updates to electronically-available table except where noted: P = Prosser & Stauffer, unpublished; Sam = A.E. Samuel, 1993 unpublished PhD thesis; D = Duncan (1993ApJ...406..172D); Strand (1958AJ.....63..152S); Her = Herbig, quoted in Walker (1969ApJ...155..447W); LR = Luhman et al. 2000, Cat. J/ApJ/540/1016; e = Ca II infrared triplet emission; : = uncertain values. Note (2): Additional comments, defined as follows: PC = P Cygni profile; IPC = inverse P Cygni profile (see text); SB2s = new double-lined binary; nIR = star with near-IR excess in 2MASS; NM = non-member from proper motions.
Global Notes: Note (G1): From Jones & Walker (1988AJ.....95.1755J) number if < 2000, otherwise from Hillenbrand (1997, Cat. J/AJ/113/1733) and subsequent updates to electronically-available table. The objects are identified by [H97b] NNNNa in Simbad. Note (G2): Type T Tauri star classification, defined as follows: C = classical T Tauri star; W = weak T Tauri star.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Marianne Brouty [CDS] 04-Jul-2005
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