2006A&A...448..655J


Query : 2006A&A...448..655J

2006A&A...448..655J - Astronomy and Astrophysics, volume 448, 655-663 (2006/3-3)

Improved kinematics for brown dwarfs and very low-mass stars in Chamaeleon I and a discussion of brown dwarf formation.

JOERGENS V.

Abstract (from CDS):

We present a precise kinematic study of very young brown dwarfs in the Cha I cloud based on radial velocities (RVs) measured with UVES at the VLT. The kinematics of the brown dwarfs in ChaI are compared to the kinematics of T Tauri stars in the same field, based on both UVES measurements for very low-mass ones and on RVs from the literature. More UVES spectra were taken compared with a former paper (Joergens & Guenther, 2001A&A...379L...9J), and the reduction of the spectra was improved, while studying the literature for RVs of T Tauri stars in ChaI led to a cleaned and enlarged sample of T Tauri stars. The result is an improved empirical RV distribution of brown dwarfs, as well as of T Tauri stars in ChaI. We found that the RVs of the nine brown dwarfs and very low-mass stars (M6-M8) in ChaI that were studied have a mean value of 15.7km/s and a dispersion measured in terms of a standard deviation of 0.9km/s, and they cover a total range of 2.6km/s. The standard deviation is consistent with the dispersion measured earlier in terms of fwhm of 2.1km/s. The studied sample of 25 T Tauri stars (G2-M5) has a mean RV of 14.7km/s, a dispersion in terms of standard deviation of 1.3km/s and in terms of fwhm of 3.0km/s, and a total range of 4.5km/s. The RV dispersion of the brown dwarfs is consistent within the errors with that of T Tauri stars, which is in line with the finding of no mass dependence in some theoretical models of the ejection-scenario for the formation of brown dwarfs. In contrast to current N-body simulations, we did not find a high-velocity tail for the brown dwarfs RVs. We found hints suggesting different kinematics for binaries compared to predominantly single objects in ChaI, as suggested by some models. The global RV dispersion for ChaI members (1.24km/s) is significantly lower than for Taurus members (2.0km/s), despite higher stellar density in ChaI showing that a fundamental increase in velocity dispersion with stellar density of the star-forming region is not established observationally. The RVs of brown dwarfs observed in ChaI are less dispersed than predicted by existing models for the ejection-scenario.

Abstract Copyright:

Journal keyword(s): stars: low-mass, brown dwarfs - techniques: radial velocities - stars: pre-main sequence - stars: formation

Simbad objects: 38

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Number of rows : 38
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 NAME Tau-Aur Complex SFR 04 30 +25.0           ~ 1301 0
2 NAME Taurus Complex SFR 04 41.0 +25 52           ~ 4015 0
3 NAME Orion Nebula Cluster OpC 05 35.0 -05 29           ~ 2174 1
4 V* SX Cha Or* 10 55 59.802000 -77 24 40.12524   16.01 14.57 14.23 12.35 M1.5+M3 84 0
5 V* SY Cha Or* 10 56 30.3883129248 -77 11 39.401977596         11.29 K5Ve 118 0
6 Sz 4 TT* 10 57 42.0977196408 -76 59 35.641299948   14.1 14.80   12.17 M4Ve 42 0
7 V* TW Cha Or* 10 59 01.0607352312 -77 22 40.947126636     13.40   11.68 K8Ve 122 0
8 Hen 3-545 Or* 10 59 06.9715593000 -77 01 40.309233240   12.91 11.136   9.596 K4Ve 200 0
9 V* CS Cha Or* 11 02 24.8763629208 -77 33 35.667131796   12.88 11.69   10.123 K2Ve 211 0
10 V* CT Cha Or* 11 04 09.0989256840 -76 27 19.329779664   13.44 13.00   10.89 K7Ve 118 0
11 Ass Cha T 2-21 TT* 11 06 15.3471261840 -77 21 56.720362608   12.58 11.01   9.35 G5Ve 130 0
12 [NC98] Cha HA 12 Em* 11 06 37.9647720216 -77 43 09.113892564     20.6   15.91 M6.5e 37 0
13 NAME Cha 1 MoC 11 06 48 -77 18.0           ~ 1076 1
14 CHXR 74 TT* 11 06 57.3114166800 -77 42 10.639632780         13.66 M3Ve 42 0
15 [NC98] Cha HA 1 Y*O 11 07 16.6710048312 -77 35 53.212777692   22.8 21.0   16.38 M7.5/8e 83 0
16 V* DI Cha Or* 11 07 20.7276076008 -77 38 07.308086352   12.02 10.74 10.72   G2Ve 159 0
17 V* VV Cha Or* 11 07 28.241088 -76 52 11.92620   16.00 14.72 14.48 12.19 M1.5+M3 62 0
18 CHXR 76 Or* 11 07 35.1774430800 -77 34 49.286652024   20.04 18.15   14.39 M4e 42 0
19 CHSM 10496 Em* 11 07 37.7410696536 -77 35 30.793352928   23.7 22.2   17.03 ~ 38 0
20 V* HK Cha Or* 11 07 42.3364909752 -77 33 59.394350844   21.9 19.8   15.26 ~ 76 0
21 [NC98] Cha HA 8 SB* 11 07 46.0912894776 -77 40 08.918309388   22.2 20.1   15.61 ~ 42 1
22 V* HL Cha Or* 11 07 52.2574621728 -77 36 57.037742172   21.5 19.51   15.07 ~ 45 0
23 RX J1108.2-7728 Y*O 11 07 55.775088 -77 27 25.52724   15.26 13.40 13.07 11.04 K3Ve 53 0
24 Sz 23 Or* 11 07 58.0951794888 -77 42 41.352365124   15.8 18.04   14.63 M4Ve 59 0
25 V* VW Cha Or* 11 08 01.3974165580 -77 42 28.579297348 13.91 14.04 12.80   10.69 K7+M0 172 0
26 CHSM 12180 Em* 11 08 18.9694304592 -77 39 17.131209948   20.5 18.52   14.50 ~ 39 0
27 ISO-ChaI 144 Em* 11 08 24.1193575992 -77 41 47.438803392   21.3 19.18   14.85 ~ 46 0
28 V* HQ Cha Or* 11 08 39.5017287912 -77 34 16.733892756   21.7 19.75   15.06 ~ 61 0
29 [CCE98] 1-74 TT* 11 09 17.6942588064 -76 27 57.926988648   15.48 13.92   11.72 K4Ve 40 0
30 V* VZ Cha Or* 11 09 23.7739008528 -76 23 20.857480836   13.82 12.94   12.14 K7e 131 0
31 V* WY Cha Or* 11 10 07.0339153464 -76 29 37.674167388   15.29 13.87   11.62 K8Ve 80 1
32 Glass Q Y*O 11 10 37.8987149352 -77 32 39.881630256   16.89 14.97   11.90 K5.5+K7 67 0
33 CHX 18N TT* 11 11 46.3370290776 -76 20 08.948823324   13.27 11.96   10.37 K5IVe 66 1
34 Sz 41 TT* 11 12 24.3973943352 -76 37 06.181395384   11.2 11.60   10.22 K7+M2.5 92 1
35 V* CV Cha Or* 11 12 27.7055693328 -76 44 22.302807396   12.02 10.98 10.51 9.76 G9Ve 183 1
36 HJM E 4-3 Y*O 11 12 42.1036824000 -76 58 40.108452312   14.74 13.29 12.98   K5Ve 28 0
37 Ass Cha T 2-54 TT* 11 12 42.6709132056 -77 22 22.943489160     11.103   9.653 G8+K7 81 2
38 HJM E 1-8 TT* 11 12 42.9828272280 -76 37 04.868196276         10.95 K3Ve 30 0

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2022.10.02-01:58:39

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