M R Zapatero Osorio

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The number of substellar companions (m 2 sini < 0:075 M) now discovered already permits a rst determination of the mass function below the hydrogen-burning limit. The shape of the mass function is probably the most signiicant observable to determine the upper mass limit for giant planets. The distributions of orbital elements of secondaries of solar-type(More)
We present the discovery by optical and near-infrared imaging of an extremely red, low-luminosity population of isolated objects in the young, nearby stellar cluster around the multiple, massive star final sigma Orionis. The proximity (352 parsecs), youth (1 million to 5 million years), and low internal extinction make this cluster an ideal site to explore(More)
We have obtained new images and high-resolution (R ∼ 22400) near-infrared (1.2400–1.2575 µm) spectra of each component of the brown dwarf binary GJ 569 Bab – 2 – using the Adaptive Optics facility of the Keck II telescope and the NIRSPEC spectrometer. These data have allowed us to improve the determination of the astrometric orbit and to measure radial(More)
We report on the linear polarimetric observations in the Johnson I-band filter of 44 ultracool dwarfs with spectral types between M6 and L7.5, corresponding to effective temperatures in the range 2800–1400 K, and one M4.5-type star. Based on our measurements of polarization (P) and their associated error bars (σ P), eleven (10 L and 1 M) dwarfs appear to(More)
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