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

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 spectrosco...

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Bibliographic Details
Published in:Proceedings of the International Astronomical Union 2010-10, Vol.6 (S276), p.489-490
Main Authors: Ramírez, Karla Peña, Zapatero Osorio, Maria R., Béjar, Victor J.S.
Format: Article
Language:English
Subjects:
Clusters
Contributed Papers
Estimates
Photometry
Planetary mass
Searching
Spectra
Spectroscopy
Stars
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Summary: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 CH4off (λc=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.
ISSN:1743-9213
1743-9221
DOI:10.1017/S1743921311020928