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Optical spectroscopy of isolated planetary mass objects in the sigma Orionis cluster
D. Barrado-y-Navascués, M. R. Zapatero-Osorio, V. J. S. Béjar +5
We have obtained low resolution optical spectra of 15 isolated planetary mass objects (IPMOs) in the sigma Orionis cluster, and derived spectral types by comparison with nearby M a…
Keck NIRC Observations of Planetary-mass Candidate Members in the sigma Orionis Open Cluster
E. L. Martin, M. R. Zapatero Osorio, D. Barrado y Navascues +2
We present K-band photometry and low-resolution near-infrared spectroscopy from 1.44 to 2.45 micron of isolated planetary-mass candidate members in the sigma Orionis cluster found…
The orbit of the brown dwarf binary Gl 569B
B. F. Lane, M. R. Zapatero Osorio, M. C. Britton +2
We present photometric, astrometric and spectroscopic observations of the nearby (9.8 pc) low-mass binary Gl 569Bab (in turn being a companion to the early-M star Gl 569A), made wi…
Photometric Variability in the Ultracool Dwarf BRI 0021-0214: Possible Evidence for Dust Clouds
E. L. Martin, M. R. Zapatero Osorio, H. J. Lehto
We report CCD photometric monitoring of the nonemission ultracool dwarf BRI 0021-0214 (M9.5) obtained during 10 nights in 1995 November and 4 nights in 1996 August, with CCD camera…
The Substellar Mass Function in sigma Orionis
V. J. S. Bejar, E. L. Martin, M. R. Zapatero Osorio +7
We combine results from imaging searches for substellar objects in the sigma Orionis cluster and follow-up photometric and spectroscopic observations to derive a census of the brow…
CCD-based observations of PG 0856+121 and a theoretical analysis of its oscillation modes
A. Ulla, M. R. Zapatero Osorio, F. Perez Hernandez +1
BVRI CCD-based and near-IR (J) imaging, together with unfiltered photometry of the hot subdwarf B star PG 0856+121 are reported. Two close, faint, red, point-like sources are resol…