J/ApJ/831/116 Photometry & spectroscopy of PMS stars in NGC 2264 (Lim+, 2016)
A Constraint on the Formation Timescale of the Young Open Cluster NGC 2264:
Lithium Abundance of Pre-main Sequence Stars.
Lim B., Sung H., Kim J.S., Bessell M.S., Hwang N., Park B.-G.
<Astrophys. J., 831, 116 (2016)>
=2016ApJ...831..116L 2016ApJ...831..116L
ADC_Keywords: Clusters, open - Abundances - Stars, pre-main sequence
Keywords: open clusters and associations: individual (NGC 2264) ;
stars: abundances ; stars: activity ; stars: formation ;
stars: pre-main sequence
Abstract:
The timescale of cluster formation is an essential parameter in order
to understand the formation process of star clusters. Pre-main
sequence (PMS) stars in nearby young open clusters reveal a large
spread in brightness. If the spread were considered to be a result of
a real spread in age, the corresponding cluster formation timescale
would be about 5-20Myr. Hence it could be interpreted that star
formation in an open cluster is prolonged for up to a few tens of Myr.
However, difficulties in reddening correction, observational errors,
and systematic uncertainties introduced by imperfect evolutionary
models for PMS stars can result in an artificial age spread.
Alternatively, we can utilize Li abundance as a relative age indicator
of PMS star to determine the cluster formation timescale. The optical
spectra of 134 PMS stars in NGC 2264 have been obtained with
MMT/Hectochelle. The equivalent widths have been measured for 86 PMS
stars with a detectable Li line (3500<{T}eff[K]≤6500).
Description:
Queue scheduled observations were carried out on 2015 April 1 and
November 24 with the multi-object high resolution echelle spectrograph
Hectochelle attached to the 6.5m telescope of the MMT observatory. The
resolving power of the spectrograph (R∼34,000) is high enough to
detect the LiI λ6708 resonance doublet with little blending
from adjacent metallic lines. The multi-object capability allowed us
to simultaneously obtain 240 target and sky spectra in a single
observation. The OB 26 filter transmits the wavelength range
6530-6715Å, and therefore the useful spectral features Hα
λ6563 and HeI λ6678 could also be observed along with
the LiI λ6708 line. The spectra of a total of 134 PMS stars
were taken in two sets of exposure times -8 minutes x3 for bright
stars (V<13.6mag) and 30 minutes x3 for fainter stars. Offset sky
spectra were also obtained to correct for the contributions of locally
variable nebula emission lines to the spectra of the faint stars.
Calibration frames, such as dome flat and comparison spectra, were
also acquired, just before and after the target exposure.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . this file
table2.dat 82 86 Photometric and spectroscopic data of 86 pre-main
sequence stars
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See also:
III/274 : Galactic O-Star Spectroscopic Survey (Sota+, 2014)
J/AJ/106/1059 : Lithium in the Pleiades (Soderblom+, 1993)
J/AJ/105/2299 : Li abundance of solar-type stars. II. (Soderblom+, 1993)
J/AJ/114/2644 : UBVRIHa photometry of NGC2264 (Sung+, 1997)
J/A+A/333/231 : O-M stars model atmospheres (Bessell+ 1998)
J/A+A/345/521 : BVRI photometry of NGC 2264 (Flaccomio+, 1999)
J/ApJ/581/1194 : Taurus-Auriga PMS stars ages and Teff (Palla+, 2002)
J/AJ/126/1916 : JHK photometry of young clusters near the Sun
(Porras+, 2003)
J/AJ/128/1684 : NGC 2264: VRIHα photometry (Sung+, 2004)
J/AJ/129/829 : Hα emission stars in NGC 2264 (Dahm+, 2005)
J/ApJ/648/1090 : Radial velocities of NGC 2264 stars (Furesz+, 2006)
J/AJ/134/999 : X-ray observations of NGC 2264 (Dahm+, 2007)
J/AJ/135/441 : VRIHα photometry in NGC 2264 (Sung+, 2008)
J/AJ/138/1116 : A Spitzer view of NGC 2264 (Sung+, 2009)
J/AJ/145/46 : UBVIc photometry in Westerlund 1 (Lim+, 2013)
J/AJ/145/37 : UBVI and Hα CCD photometry of NGC 6231 (Sung+, 2013)
J/MNRAS/438/1451 : UBVIHα photometry of IC 1848 (Lim+, 2014)
J/MNRAS/443/454 : UBVIHα photometry in NGC 1893 (Lim+, 2014)
J/ApJ/813/42 : O and B type stars in W3: first results (Kiminki+, 2015)
J/AJ/149/127 : The SOS project. IV. NGC 1624 and NGC 1931 (Lim+, 2015)
J/A+A/575/A57 : LQ Hya activity and Li variations (Flores Soriano+, 2015)
J/AJ/149/119 : Radial velocities of stars in NGC 2264 (Tobin+, 2015)
J/A+A/590/A78 : NGC2264 weak-line T Tauri lithium abundances
(Bouvier+, 2016)
J/A+A/586/A52 : NGC 2264, NGC 2547 and NGC 2516 stellar radii
(Jackson+, 2016)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- ID ? Source ID
8- 9 I2 h RAh [6] Hour of Right Ascension (J2000)
11-12 I2 min RAm [39/42] Minute of Right Ascension (J2000)
14-18 F5.2 s RAs [0.25/59.74] Second of Right Ascension (J2000)
20 A1 --- DE- [+] Sign of the Declination (J2000)
21-22 I2 deg DEd [9/10] Degree of Declination (J2000)
24-25 I2 arcmin DEm [0/58] Arcminute of Declination (J2000)
27-30 F4.1 arcsec DEs [2.8/59.3] Arcsecond of Declination (J2000)
32-37 F6.3 mag Vc [11.25/17.49] Cousins V band magnitude (1)
39-43 F5.3 mag Vc-Ic [0.626/2.261] Cousins V-I color index (1)
45-49 F5.3 0.1nm EW(Li) [0.102/0.792] Equivalent width of the LiI
λ6708 doublet blended with adjacent
neutral iron lines, in Angstroms (Å)
51-55 F5.3 0.1nm EW(Li)c [0.094/0.765] Deblended equivalent width of the
LiI λ6708 doublet, in Angstroms (Å)
57-61 F5.2 --- A(Li) [-0.78/3.93] Lithium abundance
63-69 F7.3 0.1nm EW(Ha) [-63.831/5.4]? Equivalent width of Hα
λ, in Angstroms (Å)
71-75 F5.1 km/s Ha10 [53.5/575.1]? Full width at 10% of peak Hα
flux
77-82 F6.3 0.1nm EW(HeI) [-1.595/0.243]? Equivalent width of HeI
λ6678, in Angstroms (Å)
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Note (1): Photometric data from Sung et al. (2008, Cat. J/AJ/135/441).
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Nomenclature Notes:
Table 2: Sources are <Cl* NGC 2264 CID CNNNNN>, <Cl* NGC 2264 WID WNNNN>,
and <Cl* NGC 2264 SID SNNNN> in SIMBAD.
History:
From electronic version of the journal
(End) Marianne Brouty [CDS] 19-Apr-2018