Abstract
We present recent spectroscopic (resolution ≥ 1750 at λ = 6708 Å) and photometric (ubvy- β ) observations of the singular weak-line Tstar HBC 498 (= DL Ori/G1) still associated with its parental dust cloud and of at least four other bright neighboring stars associated with reflection nebulosities that together form a tight trapezium in L1641 in Orion. Most of them have the youth signature of Li 0 in their spectra. We find that two of the objects are "classic" Tand another two are "weak-line" Tstars. From the data and their comparison with models of pre-main sequence stellar evolution we find that they are coeval, and that they have masses of the order of 1 M⊙ and ages of the order of their gravitational contraction times or less (≈ 1 - 5×105 yr). Finally, we briefly discuss their evolutionary state and its repercussions.
