TY - JOUR
T1 - The η chamaeleontis cluster
T2 - Origin in the sco-cen ob association
AU - Mamajek, Eric E.
AU - Lawson, Warrick A.
AU - Feigelson, Eric D.
N1 - Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2000/11/20
Y1 - 2000/11/20
N2 - A young, nearby compact aggregate of X-ray-emitting pre-main-sequence stars was recently discovered in the vicinity of η Chamaeleontis. In this paper, we further investigate this cluster: its membership, its environs, and its origins. ROSAT High Resolution Imager X-ray data for the cluster's T Tauri stars show high levels of magnetic activity and variability. The cluster has an anomalous X-ray luminosity function compared to other young clusters, deficient in stars with low but detectable X-ray luminosities. This suggests that many low-mass members have escaped the surveyed core region. Photographic photometry from the USNO-A2.0 catalog indicates that additional, X-ray-quiet members exist in the cluster core region. The components of the eclipsing binary RS Cha, previously modeled in the literature as post-main sequence (MS) with discordant ages, are shown to be consistent with being coeval pre-MS stars. We compute the Galactic motion of the cluster from Hipparcos data and compare it to other young stars and associations in the fourth Galactic quadrant. The kinematic study shows that the η Cha cluster, as well as members of the TW Hya association and a new group near ∈ Cha, probably originated near the giant molecular cloud complex that formed the two oldest subgroups of the Sco-Cen OB association roughly 10-15 Myr ago. Their dispersal is consistent with the velocity dispersions seen in giant molecular clouds. A large H I filament and dust lane located near η Cha has been identified as part of a superbubble formed by Sco-Cen OB winds and supernova remnants. The passage of the superbubble may have terminated star formation in the η Cha cluster and dispersed its natal molecular gas.
AB - A young, nearby compact aggregate of X-ray-emitting pre-main-sequence stars was recently discovered in the vicinity of η Chamaeleontis. In this paper, we further investigate this cluster: its membership, its environs, and its origins. ROSAT High Resolution Imager X-ray data for the cluster's T Tauri stars show high levels of magnetic activity and variability. The cluster has an anomalous X-ray luminosity function compared to other young clusters, deficient in stars with low but detectable X-ray luminosities. This suggests that many low-mass members have escaped the surveyed core region. Photographic photometry from the USNO-A2.0 catalog indicates that additional, X-ray-quiet members exist in the cluster core region. The components of the eclipsing binary RS Cha, previously modeled in the literature as post-main sequence (MS) with discordant ages, are shown to be consistent with being coeval pre-MS stars. We compute the Galactic motion of the cluster from Hipparcos data and compare it to other young stars and associations in the fourth Galactic quadrant. The kinematic study shows that the η Cha cluster, as well as members of the TW Hya association and a new group near ∈ Cha, probably originated near the giant molecular cloud complex that formed the two oldest subgroups of the Sco-Cen OB association roughly 10-15 Myr ago. Their dispersal is consistent with the velocity dispersions seen in giant molecular clouds. A large H I filament and dust lane located near η Cha has been identified as part of a superbubble formed by Sco-Cen OB winds and supernova remnants. The passage of the superbubble may have terminated star formation in the η Cha cluster and dispersed its natal molecular gas.
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U2 - 10.1086/317181
DO - 10.1086/317181
M3 - Article
AN - SCOPUS:0034693539
VL - 544
SP - 356
EP - 374
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 1 PART 1
ER -