TY - JOUR
T1 - The η Chamaeleontis cluster
T2 - A remarkable new nearby young open cluster
AU - Mamajek, Eric E.
AU - Lawson, Warrick A.
AU - Feigelson, Eric D.
N1 - Funding Information:
E. E. M. thanks the J. William Fulbright program and the Australian-American Education Foundation (AAEF) for support. E. D. F.’s research is supported in part by NASA contract NAS8-38252. We thank the director of Mount Stromlo and Siding Springs Observatories, J. Mould, for the allocation of telescope time. This research made use of the SIMBAD database operated by the CDS in Strasbourg, France, the SkyView service provided by NASA-GSFC, the ESA Hip-parcos and Tycho databases, the USNO-A2.0 catalog, and DENIS data obtained at the European Southern Observatory.
PY - 1999/5/10
Y1 - 1999/5/10
N2 - A cluster of young, X-ray-emitting stars is found in the vicinity of η Chamaeleontis from a deep ROSAT high-resolution imager observation. The 12 X-ray sources have prominent (R = 5-14) stellar counterparts, including two early-type stars (η Cha and RS Cha) and 10 Li-rich, Hα emission-line, late-type stars (K3-M5). Hipparcos astrometry reveals that η Cha, RS Cha, and nearby HD 75505 are comoving at d ≃ 97 pc. The late-type stars have all the properties of pre-main-sequence weak-lined T Tauri stars: high magnetic activity, high Li abundance, and (assuming d = 97 pc) bolometric luminosities 1-2 mag above the main sequence, with ages ranging from 2 to 18 Myr. As with the TW Hya association, the η Cha cluster is far from any significant molecular cloud and thus has mysterious origins. The cluster appears to share proper motions with other young stars in the Chamaeleon region and may be a compact extension of the Sco-Cen OB association.
AB - A cluster of young, X-ray-emitting stars is found in the vicinity of η Chamaeleontis from a deep ROSAT high-resolution imager observation. The 12 X-ray sources have prominent (R = 5-14) stellar counterparts, including two early-type stars (η Cha and RS Cha) and 10 Li-rich, Hα emission-line, late-type stars (K3-M5). Hipparcos astrometry reveals that η Cha, RS Cha, and nearby HD 75505 are comoving at d ≃ 97 pc. The late-type stars have all the properties of pre-main-sequence weak-lined T Tauri stars: high magnetic activity, high Li abundance, and (assuming d = 97 pc) bolometric luminosities 1-2 mag above the main sequence, with ages ranging from 2 to 18 Myr. As with the TW Hya association, the η Cha cluster is far from any significant molecular cloud and thus has mysterious origins. The cluster appears to share proper motions with other young stars in the Chamaeleon region and may be a compact extension of the Sco-Cen OB association.
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U2 - 10.1086/312005
DO - 10.1086/312005
M3 - Article
AN - SCOPUS:0033541747
SN - 0004-637X
VL - 516
SP - L77-L80
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2 PART 2
ER -