Search

We present the status of an ongoing study to built a a high resolution near infrared Echelle spectrograph (NAHUAL) for the 10.4-m-Gran Telescopio Canarias (GTC) which will be especially optimised for planet searches by means of high precision radial velocity measurements. We show that infrared radial velocity programs are particularly suitable to search for planets very low mass stars and brown dwarfs, as well as active stars. The goal of NAHUAL is to reach an accuracy of the radial velocity measurement of a few m/s, which would allow the detection of planets with a few earth-masses orbiting low-mass stars and brown dwarfs. It is planed that NAHUAL covers simultaneously the full wavelength range in the J, H, and K-band, and will also serve as a general purpose high resolution near infrared spectrograph of the GTC. The planed instrument will have a resolution of R=50,000 with a 0.175 arcsec slit, and an AO-system. An absorption cell will serve as a simultaneous wavelength reference., 8 pages, 3 figures, conference

We present a photometric and spectroscopic study of the young open cluster M35, including very deep and accurate photometry of the stellar (including white dwarfs) and substellar population of the cluster, a complete mass function, rotational and radial velocities, and lithium abundances., Proceedings of the IV Scientific Meeting of the Spanish Astronomical Society, held in Santiago de Compostela, Spain, September 11-14, 2000

We review our the status of the photometric searches of brown dwarfs and vely low mass stars in several young open clusters and present some results on the spectroscopic follow-up, including new cluster ages based on the position of the lithium depletion boundary., 4 pages. "Proceedings of the III Scientific Meeting of the Spanish Astronomical Society", 1999, Astrophysics and Space Sciences, in press

We estimate here the age of one of the prototypes of the Beta Pic-like stars, Fomalhaut, based on the properties of its common proper motion companion Gl879. By combining constraints derived from the lithium abundance, rotational velocity, HR diagram position, and coronal activity we conclude that the age for Gl879, and hence the age for Fomalhaut, is 200$\pm$100 Myr. This age estimate agrees quite well with the completely independent age estimate derived directly from isochrone--fitting to Fomalhaut's position in an HR diagram, and thus confirms that circumstellar dust disks can persist in A stars for several hundred Myr., Comment: 27 pages, Postscript file

We estimate here the age of one of the prototypes of the Beta Pic-like stars, Fomalhaut, based on the properties of its common proper motion companion Gl879. By combining constraints derived from the lithium abundance, rotational velocity, HR diagram position, and coronal activity we conclude that the age for Gl879, and hence the age for Fomalhaut, is 200$\pm$100 Myr. This age estimate agrees quite well with the completely independent age estimate derived directly from isochrone--fitting to Fomalhaut's position in an HR diagram, and thus confirms that circumstellar dust disks can persist in A stars for several hundred Myr., 27 pages, Postscript file

The observation of the Ca II H and K lines in red giants in NGC 6940 allows the strength of chromospheres and their behavior to be evaluated in a population whose evolution is well understood. Spectra in the Ca II lines have been obtained for giant stars in this cluster. Emission reversals are present in some objects. The absolute flux in the chromospheric emission is determined as a function of effective temperature for stars on the red giant branch. The stellar surface flux in the Ca II lines decreases smoothly with increasing $(B-V)$ in contradiction to model predictions., Comment: 4 pages, LATEX file. Mem.S.A.It style macro (included). Contribution to "Cool Stars in Clusters and Associations: Magnetic Activity and Age Indicators", Palermo, May 1997