All Figures

$\begin{figure} \par\mbox{\includegraphics[width=5.9cm]{8600f1a.ps} ~~ \includegr... ...=5.9cm]{8600f1b.ps} ~~ \includegraphics[width=5.9cm]{8600f1c.ps} }\end{figure}$ Figure 1: Color-color diagrams of S Ori 70 (solid circle) and field T-dwarfs (open circles). For clarity, only the error bars of S Ori 70 are plotted. In the left and middle panels, the sequence defined by the field brown dwarfs is displayed with a solid line. Spectral types are indicated. The right panel shows the solar-metallicity models by Tsuji et al. (2004) superimposed onto the data. Gravities of log g = 3.0, 3.5, 4.0, 4.5, and 5.5 cm s^-2 are depicted with solid lines. The triangles along each model curve are in $T_{\rm eff}$ invervals of 100 K, ranging from 700 ( bottom) to 1500 K (log g = 3.0), 1400 K (log g = 3.5), 1600 K (log g = 4.0 and 4.5), and 1700 K (log g = 5.5). The log g = 5.0 track is not plotted for clarity. The dotted line connects the $T_{\rm eff}$ = 1100 K points in each model.
Open with DEXTER

In the text

$\begin{figure} \par\mbox{\includegraphics[width=8.8cm,clip]{8600f2a.ps} ~~~ \includegraphics[width=8.8cm,clip]{8600f2b.ps} }\end{figure}$ Figure 2: Color-magnitude diagram of $\sigma$ Orionis low mass members. S Ori 70 is labeled. The 3-Myr isochrone by Chabrier & Baraffe (2000) is overplotted onto the data as a solid line in the left panel (see text for $T_{\rm eff}$ , log $L/L_\odot$ conversion into observables). The right panel shows the sequence of M5.5-T8 field dwarfs at the distance of the cluster (solid line, spectral types are indicated). The dotted line stands for the field sequence shifted by -1.8 mag in the J-band to match the photometric trend delineated by $\sigma$ Orionis members. Objects with J - [3.6] colors significantly redder than the cluster sequence show infrared flux excesses likely due to circum(sub)stellar disks (Caballero et al. 2007).
Open with DEXTER

In the text

$\begin{figure} \par\mbox{\includegraphics[width=5.9cm]{8600f3a.ps} ~~ \includegr... ...=5.9cm]{8600f3b.ps} ~~ \includegraphics[width=5.9cm]{8600f3c.ps} }\end{figure}$ Figure A.1: Passbands of the J ( left), H ( middle), and K ( right) filters used in this work convolved with the observatories atmospheric transmission curves. Labels correspond to the NIRSPEC (Keck) and Omega-2000 (CAHA 3.5 m) instruments, and 2MASS filters. Data have been taken from the observatories' web pages. The Omega-2000 filter passbands were convolved with the 2MASS atmospheric transmission curve because this information is not available on the CAHA web site.

In the text