The TW Hydrae Association is a cluster chain of Sco-Cen

Open Access

Table 1

Properties of the TWA chain.

Cluster	#members		Age	\|X_{σ Cen}\|	\|V_{σ Cen}\|	X	Y	Z	U	V	W
	All	HQ	(Myr)	(pc)	(km/s)	(pc)	(pc)	(pc)	(km/s)	(km/s)	(km/s)
Sco-Cen_>15Myr	7511	−	15–20	−	−	106 ± 38	−70 ± 27	27 ± 15	−6.9 ± 5.8	−19.9 ± 2.7	−5.6 ± 1.9
σ Cen	1805	−	$15_{- 1}^{+ 1}$ $\[15_{-1}^{+1}\]$	−	−	60 ± 12	−96 ± 14	17 ± 10	−8.6 ± 1.7	−20.7 ± 2.5	−6.2 ± 1.2
TWA-a	45	15	$9_{- 1}^{+ 2}$ $\[9_{-1}^{+2}\]$	51 ± 10	4.2 ± 1.1	25 ± 12	−61 ± 12	26 ± 8	−12.1 ± 1.1	−19.0 ± 1.4	−6.2 ± 0.7
TWA-b	21	14	$6_{- 1}^{+ 2}$ $\[6_{-1}^{+2}\]$	78 ± 4	6.2 ± 1.0	6 ± 4	−40 ± 6	23 ± 7	−13.6 ± 0.9	−17.0 ± 1.24	−7.2 ± 1.7

Notes. Columns indicate (1) cluster (or sample) name, (2–3) the number of members (total and in the 6D high-quality sample), (4) age, (5) 3D distance (|X_{σ Cen}|) and (6) relative speed (|V_{σ Cen}|) to the σ Cen cluster, (7–9) 3D heliocentric positions (XYZ) and (10–12) velocities (UVW). For columns 5–12, we provide the median and standard deviation of the cluster members, the standard deviations are dominated by the intrinsic scatter rather than the errors on the medians. The velocities of the TWA-a and TWA-b samples are computed with the TWA-6D-HQ sample.

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