Physics
Scientific paper
Aug 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006iaujd...8e..59l&link_type=abstract
Solar and Stellar Activity Cycles, 26th meeting of the IAU, Joint Discussion 8, 17-18 August 2006, Prague, Czech Republic, JD08,
Physics
Scientific paper
We approached the physical properties of the members of the ɛ Chamaeleontis pre-main sequence (PMS) star cluster by using the flux-calibrated low-resolution spectra (λλ 3500-10200 Å). Using synthetic broadband colours and narrow-band continuum-, temperature- and gravity-sensitive indices derived from the spectra, we confirmed a B-band excess (Figure1) and lower surface gravity (Figure2) for late-M stars of this cluster than those of the standard dwarfs, like ≈ 9 Myr-old η Chamaeleontis cluster. In Na I index (λ 8183, 8195 Å), it shows a tendency that the surface gravity of the ɛ Cha cluster stars are lower than that of the η Cha cluster. Figure1. (a) Synthetic (B-V)/(R-I), (b) (V-R)/(R-I) and (c) (V-I)/(R-I) colour-colour diagrams for ɛ Cha cluster stars (filled circles) and main-sequence dwarfs (open circles). The filled triangle in each graph is the HD104237D which shows blue excess due to the contamination of the nearby HAeBe star, HD104237A. The bold lines are the locus of main-sequence stars from spectral type B0 - K6 (Kenyon & Hartmann 1995) and K7 - M6 (Bessell 1991). Figure 2. Comparison of gravity-sensitive indices measuring the strength of (a) the λ 8183, 8195 Na I doublet, and (b) the λ 9896 FeH band for the ɛ Cha cluster (filled circles), old disk dwarfs (open circles), giants (open triangles)and the η Cha cluster (crosses; from Lyo et al., 2004). We also plotted standard main-sequence data (open circles) from Lyo et al. (2004) due to the lack of the late M-type dwarfs in this observation run. The connected three pairs of stars in both graphs are GL 514.1, GL 473 and GL 406 which are observed in both observation runs in 2002 (Lyo et al. 2004) and this time. Their scatters of different epochs of observations give us a good indication for uncertainties of these two indices. For both indices the distribution for ɛ Cha cluster stars occupies the region between that of the dwarfs and the giants. In Na I index, the values of the ɛ Cha cluster stars are smaller than those of the ≈ 9Myr-old η Cha cluster.
Bessell Michael S.
Lawson Warrick A.
Lyo A.-Ran
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