J/ApJ/745/119 Close companions to young stars. I. ChaI & Tau (Nguyen+, 2012)
Close companions to young stars.
I. A large spectroscopic survey in Chamaeleon I and Taurus-Auriga.
Nguyen D.C., Brandeker A., van Kerkwijk M.H., Jayawardhana R.
<Astrophys. J., 745, 119 (2012)>
=2012ApJ...745..119N 2012ApJ...745..119N
ADC_Keywords: Binaries, spectroscopic ; YSOs ; Radial velocities ;
Rotational velocities ; Spectral types ; Spectroscopy
Keywords: binaries: close - binaries: spectroscopic - brown dwarfs -
line: profiles - methods: data analysis - planetary systems -
stars: formation - stars: low-mass - stars: pre-main sequence -
stars: statistics
Abstract:
We present the results of a multiplicity survey of 212 T Tauri stars
in the Chamaeleon I and Taurus-Auriga star-forming regions, based on
high-resolution spectra from the Magellan Clay 6.5m telescope. From
these data, we achieved a typical radial velocity (RV) precision of
∼80m/s with slower rotators yielding better precision, in general. For
174 of these stars, we obtained multi-epoch data with sufficient time
baselines to identify binaries based on RV variations. We identified
eight close binaries and four close triples, of which three and two,
respectively, are new discoveries. The spectroscopic multiplicity
fractions we find for Chamaeleon I (7%) and Taurus-Auriga (6%) are
similar to each other, and to the results of field star surveys in the
same mass and period regime. However, unlike the results from imaging
surveys, the frequency of systems with close companions in our sample
is not seen to depend on primary mass. Additionally, we do not find a
strong correlation between accretion and close multiplicity. This
implies that close companions are not likely the main source of the
accretion shut down observed in weak-lined T Tauri stars. Our results
also suggest that sufficient RV precision can be achieved for at least
a subset of slowly rotating young stars to search for hot Jupiter
planets.
Description:
Our data were taken using the Magellan Inamori Kyocera Echelle (MIKE)
spectrograph on the Magellan Clay 6.5m telescope at the Las Campanas
Observatory, Chile. For this study, we used only the red region
spanning 4800-9400Å with R∼60000.
We obtained 813 high-resolution optical spectra of 212 members of the
Cha I and Tau-Aur star-forming regions. The data were collected on 15
nights during four observing runs between 2006 February and 2006
December.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 116 184 Measurements of stars without close companions
in Cha I and Tau-Aur
table3.dat 101 53 Measurements of stars with close companions
in Cha I and Tau-Aur (28 binaries)
figs/* . 213 Individual figures for each member and "all_fig"
file containing all the figures
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See also:
J/ApJ/703/1511 : Wide binaries in Taurus and Upper Sco (Kraus+, 2009)
J/ApJ/703/1964 : Spectra of three nearby star-forming regions (Furlan+, 2009)
J/PASJ/60/209 : Faint companions around YSOs in TMC (Itoh+, 2008)
J/ApJ/684/654 : Low-mass members of Chamaeleon I (Luhman+, 2008)
J/ApJ/662/413 : Wide multiplicity in 3 associations with 2MASS (Kraus+, 2007)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Reg Region name (ChaI or Tau-Aur)
9- 26 A18 --- Name Object name
28- 29 I2 h RAh Hour of right ascension (J2000)
30- 31 I2 min RAm Minute of right ascension (J2000)
32- 36 F5.2 s RAs Second of right ascension (J2000)
38 A1 --- DE- Sign of declination (J2000)
39- 40 I2 deg DEd Degree of declination (J2000)
41- 42 I2 arcmin DEm Arcminute of declination (J2000)
43- 46 F4.1 arcsec DEs Arcsecond of declination (J2000)
48- 52 A5 --- SpT MK spectral type
54 A1 --- TTS [?cw] T Tauri classification (c=classical TTauri
star, w=weak-lined, ?=unknown)
56- 58 I3 km/s Ha [53/647]? Hα 10% width (G1)
60- 61 I2 km/s e_Ha [3/98]? Hα width scatter (G2)
63 A1 --- f_Ha [a] a=absorp.
65- 70 F6.2 km/s vsini [0.8/127] Rotational velocity (G1)
72- 76 F5.2 km/s e_vsini [0.11/10] vsini uncertainty (G3)
78- 83 F6.3 km/s RV [3.6/32.1] Radial velocity
85- 89 F5.3 km/s e_RV [0.006/3] RV uncertainty
91 A1 --- f_RV [d] Possible non-member (1)
93 A1 --- l_SigRV Limit flag on SigRV
94- 99 F6.3 km/s SigRV [0.01/12]? Weighted standard deviation of RV (2)
101 A1 --- l_SigN Limit flag on SigN
102-107 F6.3 km/s SigN [0.01/13]? Systematic noise of RV (2)
109 I1 --- Nobs [1/7] Number of observations
111-116 A6 --- Fig Corresponding figure number
(column added by CDS) (G4)
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Note (1):
d = the overall radial velocity deviates from that of the associated
star-forming region.
Note (2): Weighted standard deviation and systematic noise of the radial
velocity as described in Section 4.2; equations 5 and 6.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- SBT Spectroscopic Binary type (SB1, SB2, SB3, ?)
5 A1 --- n_SBT [d] d = long period
7- 9 A3 --- Reg Region name (Cha or Tau)
11- 27 A17 --- Name Object name
29- 30 I2 h RAh Hour of right ascension (J2000)
31- 32 I2 min RAm Minute of right ascension (J2000)
33- 37 F5.2 s RAs Second of right ascension (J2000)
39 A1 --- DE- Sign of declination (J2000)
40- 41 I2 deg DEd Degree of declination (J2000)
42- 43 I2 arcmin DEm Arcminute of declination (J2000)
44- 47 F4.1 arcsec DEs Arcsecond of declination (J2000)
49- 53 A5 --- SpT MK spectral type
55 A1 --- TTS T Tauri classification (c=classical,
w=weak-lined, ?=unknown)
57- 59 I3 km/s Ha [101/600]? Hα 10% width (G1)
61- 63 I3 km/s e_Ha [8/126]? Hα width scatter (G2)
65 A1 --- f_Ha [a] a=Absorp.
67 I1 --- Nobs [1/7]? Number of observations
69- 71 A3 --- m_Name [ABCab12 ] Component
73- 77 F5.2 km/s vsini [7.4/94.1] Rotational velocity (G1)(3)
79- 83 F5.2 km/s e_vsini [0.12/15] vsini uncertainty (G3)
85- 89 F5.3 --- FR [0.07/1]? Flux ratio between the companion
and the primary star (see section 3.2)
91- 95 F5.3 --- e_FR [0.005/0.4]? FR uncertainty
97-101 A5 --- Fig Corresponding figure number
(column added by CDS) (G4)
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Note (3): The vsini were adopted from Nguyen et al. (2009ApJ...695.1648N 2009ApJ...695.1648N) where
available, or measured using the same method for SB1s and the
broadening function method described in Section 3.2 for SB2s and SB3s,
otherwise.
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Global notes:
Note (G1): The Hα 10% widths and vsini were adopted from Nguyen et al.
(2009ApJ...695.1648N 2009ApJ...695.1648N) where available, or measured using the same
method otherwise.
Note (G2): The Hα 10% width uncertainty does not correspond to the
measurement uncertainty, but to the scatter in our multi-epoch data.
Note (G3): The vsini uncertainty represents the combined measurement scatter
between results using different template spectra, and over different
epochs.
Note (G4): See also the erratum in 2012, ApJ, 749, 94 where new Tables 4-6 are
given for the modified Julian dates (MJDs) were incorrectly listed
in the published article: they were too large by 0.5 days. This
offset propagated to the figures of individual sources, but not to
any of the analysis (in particular, barycentric corrections were
calculated using the correct times).
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 31-Jul-2013