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Search and characterization of T-type planetary mass candidates in the σ Orionis cluster

Published online by Cambridge University Press:  10 November 2011

Karla Peña Ramírez
Affiliation:
Instituto de Astrofísica de Canarias. E-38205 La Laguna, Tenerife.Spain email: karla@iac.es
Maria R. Zapatero Osorio
Affiliation:
Centro de Astrobiología (CSIC-INTA). E-28850 Torrejón de Ardoz, Madrid. Spain
Victor J.S. Béjar
Affiliation:
Instituto de Astrofísica de Canarias. E-38205 La Laguna, Tenerife.Spain email: karla@iac.es
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Abstract

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We present new photometric and astrometric data available for S Ori 70 and 73, the two T-type planetary-mass member candidates in the σ Orionis cluster (~3 ± 2 Myr, d~360 pc). S Ori 70 (J ~ 19.9 mag) has a spectral type of T5.5 ± 1.0 measured from published near-infrared spectra, while no spectroscopic data are available for S Ori 73 (J ~ 21 mag). We estimate the spectral type of S Ori 73 by using J, H, and CH4offc=1.575 μm, Δλ=0.112 μm) photometry and comparing the H-CH4off index of S Ori 73 with the colors of field stars and brown dwarfs of spectral types in the range F to late T. The locations of S Ori 70 and 73 in the J-H vs H-CH4off color-color diagram are consistent with spectral types T8 ± 1 and T4 ± 1, respectively. Proper motion measurements of the two sources are larger than the motion of the central σ Ori star, making their cluster membership somehow uncertain.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2011

References

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