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Revista mexicana de astronomía y astrofísica
versión impresa ISSN 0185-1101
Rev. mex. astron. astrofis vol.41 no.1 Ciudad de México abr. 2005
On the PMS Star HBC 498 and its associated nebolous stars1 (Research note)
C. Chavarría-K2, M. A. Moreno-Corral2, L. Terranegra3 and E. de Lara2
2 Instituto de Astronomía, UNAM/Campus Ensenada, P.O. Box 439027, San Diego, CA 92143-9027, USA (chavarri@astrosen.unam.mx, mam@astrosen.unam.mx).
3 Osservatorio Astronomico di Capodimonte, Via Moiariello 16, I-80131 Napoli, Italia.
Received, 2004 August 19
Accepted 2005 January 7
RESUMEN
Presentamos observaciones espectroscópicas (resolución ≥ 1750 en λ = 6708 Å) y fotométricas (ubvy-β) recientes de la singular estrella T Tauri con líneas en emisión débiles HBC 498 (= DL Ori/G1), aún asociada a su nube de polvo progenitora, y de otras cuatro estrellas vecinas y brillantes, todas ellas con nebulosidades de reflexión asociadas, las cuales conforman un trapecio estrecho en L1641 en la constelación de Orión. Dos estrellas resultan ser del tipo T Tauri "clásicas" y dos del tipo T Tauri "con líneas en emisión débiles". La mayoría presentan la huella de juventud del Li I en su espectro. De los datos y su comparación con modelos evolutivos de estrellas pre-secuencia principal, encontramos que son coetáneas, con masas alrededor de 1 M๏ y edades del orden del tiempo de contracción gravitacional o menor (≈ 1 5 x 105 años). Finalmente, discutimos brevemente el estado evolutivo de estos objetos y sus repercusiones.
ABSTRACT
We present recent spectroscopic (resolution ≥ 1750 at λ = 6708 Å) and photometric (ubvy-β) observations of the singular weak-line T Tauri star 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 I in their spectra. We find that two of the objects are "classic" T Tauri and another two are "weak-line" T Tauri stars. 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 x 105 yr). Finally, we briefly discuss their evolutionary state and its repercussions.
Key Words: Stars: Abundances Stars: Emission line Stars: Individual (HBC 498) Stars: Pre-main sequence.
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ACKNOWLEDGMENTS
This work was partially supported by Consejo Nacional de Ciencia y Tecnología, México (projects 400340-4-2243-PE and 400354-5-27757 E) and by CNR-GNA98 and COFIN98-MURST of Italy.
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1 Based on observations collected at the Observatorio Astronómico Nacional in San Pedro Mártir, B. C., México, operated by the Instituto de Astronomía of the Universidad Nacional Autónoma de México.