Subvenciones relacionadas:
General
Se investigan los procesos que conducen a la formación de estrellas de baja masa, enanas marrones y exoplanetas y caracterizar las propiedades físicas de estos astros en varias etapas evolutivas. Las estrellas de muy baja masa y las enanas marrones son probablemente los objetos más numerosos de nuestra Galaxia, pero no por ello están suficientemente bien establecidas sus propiedades. En particular, los objetos subestelares constituyen uno de los grupos más difíciles de estudiar desde el punto de vista observacional dada su baja luminosidad intrínseca. Se pretende establecer la frecuencia, multiplicidad y distribución espacial de estrellas ultrafrías y objetos subestelares en la vecindad del Sol y en regiones de formación estelar y cúmulos cercanos con el fin de proporcionar información sobre los mecanismos que los originan, caracterizar sus propiedades ópticas e infrarrojas, y establecer relaciones entre sus propiedades espectrales, masas y luminosidades. Se hace especial énfasis en empujar la frontera de detección hacia los objetos de menor masa, bien sea como objetos ligados por atracción gravitatoria a otros, o flotando libremente en el espacio interestelar. Los objetos menos masivos también suelen ser los de menor luminosidad intrínseca y temperaturas superficiales más frías por lo que entrañan notable dificultad de detección por medio de imagen directa. Sin embargo, la detección directa permite una caracterización fotométrica y espectroscópica mucho más completa y una mejor determinación de sus propiedades físicas y químicas. También se pretende investigar la presencia de exoplanetas en estrellas de baja masa empleando técnicas de medida de velocidad radial con muy alta precisión y técnicas de muy alta resolución espacial. Se trabaja en el desarrollo de espectrógrafos ultraestables para grandes telescopios y de sistemas de imagen ultrarrápida. Con los primeros es posible lograr la detección de planetas con masas similares a la de la Tierra en estrellas de tipos G, K y M un objetivo que se persigue es establecer la frecuencia de estos planetas en las estrellas de la vecindad solar y caracterizar las propiedades de los sistemas planetarios a los que pertenecen.
Miembros
Resultados
- La secuencia visible y infrarroja de las enanas de tipo L de 10 Myr de edad en la asociación OB mas cercana al Sol, Upper Scorpius
- El limite estelar/subestelar del cumulo más cercano al Sol, las Hiades
Actividad científica
Publicaciones relacionadas
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Two new young, wide, magnetic + non-magnetic double-degenerate binary systems
We report the discovery of two, new, rare, wide, double-degenerate binaries that each contain a magnetic and a non-magnetic star. The components of SDSS J092646.88+132134.5 + J092647.00+132138.4 and of SDSS J150746.48+521002.1 + J150746.80+520958.0 have angular separations of only 4.6 arcsec (a˜ 650 au) and 5.1 arcsec (a˜ 750 au), respectively
Dobbie, P. D. et al.Fecha de publicación:
32012 -
Further investigation of white dwarfs in the open clusters NGC 2287 and NGC 3532
We report the results of a CCD imaging survey, complemented by astrometric and spectroscopic follow-up studies, that aims to probe the fate of heavy-weight intermediate-mass stars by unearthing new, faint, white dwarf members of the rich, nearby, intermediate-age open clusters NGC 3532 and NGC 2287. We identify a total of four white dwarfs with
Dobbie, P. D. et al.Fecha de publicación:
72012 -
Discovery of the benchmark metal-poor T8 dwarf BD +01° 2920B
We have searched the Wide-field Infrared Survey Explorer first data release for widely separated (≤10 000 au) late T dwarf companions to Hipparcos and Gliese stars. We have discovered a new binary system containing a K-band suppressed T8p dwarf WISEP J142320.86+011638.1 and the mildly metal poor ([Fe/H] =-0.38 ± 0.06) primary BD +01° 2920 (HIP
Pinfield, D. J. et al.Fecha de publicación:
52012 -
Disc frequencies for brown dwarfs in the Upper Scorpius OB association: implications for brown dwarf formation theories
We have investigated the brown dwarf (BD) and stellar disc fractions in the Upper Scorpius (USco) OB association and compared them with several other young regions. We have compiled the most complete sample of all spectroscopically confirmed BDs in USco and have made use of the Wide-field Infrared Survey Explorer (WISE) catalogue to identify the
Riaz, B. et al.Fecha de publicación:
32012 -
Astrometric and photometric initial mass functions from the UKIDSS Galactic Clusters Survey - I. The Pleiades
We present the results of a deep wide-field near-infrared survey of the entire Pleiades cluster recently released as part of the UKIRT Infrared Deep Sky Survey (UKIDSS) Galactic Clusters Survey (GCS) Data Release 9 (DR9). We have identified a sample of ˜1000 Pleiades cluster member candidates combining photometry in five near-infrared passbands and
Lodieu, N. et al.Fecha de publicación:
52012 -
A census of very-low-mass stars and brown dwarfs in the σ Orionis cluster
Context: The knowledge of the initial mass function (IMF) in open clusters constitutes one way of constraining the formation of low-mass stars and brown dwarfs, along with the frequency of multiple systems and the properties of disks. Aims: The aim of the project is to determine the shape of the mass function in the low-mass and substellar regimes
Lodieu, N. et al.Fecha de publicación:
102009 -
Enhanced lithium depletion in Sun-like stars with orbiting planets
The surface abundance of lithium on the Sun is 140 times less than the protosolar value, yet the temperature at the base of the surface convective zone is not hot enough to burn-and hence deplete-Li (refs 2, 3). A large range of Li abundances is observed in solar-type stars of the same age, mass and metallicity as the Sun, but such a range is
Israelian, Garik et al.Fecha de publicación:
112009 -
On the HU Aquarii planetary system hypothesis
In this paper, we investigate the eclipse timing of the polar binary HU Aquarii that has been observed for almost two decades. Recently, Qian et al. attributed large (O-C) deviations between the eclipse ephemeris and observations to a compact system of two massive Jovian companions. We improve the Keplerian, kinematic model of the light travel time
Goździewski, Krzysztof et al.Fecha de publicación:
92012 -
New ultracool subdwarfs identified in large-scale surveys using Virtual Observatory tools. I. UKIDSS LAS DR5 vs. SDSS DR7
Aims: The aim of the project is to improve our knowledge of the low-mass and low-metallicity population to investigate the influence of metallicity on the stellar (and substellar) mass function. Methods: We present the results of a photometric and proper motion search aimed at discovering ultracool subdwarfs in large-scale surveys. We employed and
Lodieu, N. et al.Fecha de publicación:
62012 -
The Substellar Population of σ Orionis: A Deep Wide Survey
We present a deep I, Z photometric survey covering a total area of 1.12 deg2 of the σ Orionis cluster and reaching completeness magnitudes of I = 22 and Z = 21.5 mag. From I, I - Z color-magnitude diagrams we have selected 153 candidates that fit the previously known sequence of the cluster. They have magnitudes in the range I = 16-23 mag, which
Béjar, V. J. S. et al.Fecha de publicación:
122011 -
Search and characterization of T-type planetary mass candidates in the σ Orionis cluster
Context. The proper characterization of the least massive population of the young σ Orionis star cluster is required to understand the form of the cluster mass function and its impact on our comprehension of the substellar formation processes. S Ori 70 (T5.5 ± 1) and 73, two T-type cluster member candidates, are likely to have masses between 3 and
Peña-Ramírez, K. et al.Fecha de publicación:
82011 -
Polarisation of very-low-mass stars and brown dwarfs. I. VLT/FORS1 optical observations of field ultra-cool dwarfs
Context: Ultra-cool dwarfs of the L spectral type (T_eff = 1400-2200 K) are known to have dusty atmospheres. Asymmetries of the dwarf surface may arise from rotationally-induced flattening and dust-cloud coverage, and may result in non-zero linear polarisation through dust scattering. Aims: We aim to study the heterogeneity of ultra-cool dwarfs'
Goldman, B. et al.Fecha de publicación:
82009 -
New Isolated Planetary-mass Objects and the Stellar and Substellar Mass Function of the σ Orionis Cluster
We report on our analysis of the VISTA Orion ZY JHKs photometric data (completeness magnitudes of Z = 22.6 and J = 21.0 mag) focusing on a circular area of 2798.4 arcmin2 around the young σ Orionis star cluster (~3 Myr, ~352 pc, and solar metallicity). The combination of the VISTA photometry with optical, WISE and Spitzer data allows us to identify
Peña-Ramírez, K. et al.Fecha de publicación:
72012 -
New constraints on the membership of the T dwarf S Ori 70 in the σ Orionis cluster
Aims:The nature of S Ori 70 (S Ori J053810.1-023626), a faint mid-T type object found towards the direction of the young σ Orionis cluster, is still under debate. We intend to find out whether it is a field brown dwarf or a 3-Myr old planetary-mass member of the cluster. Methods: We report on near-infrared {JHK}s and mid-infrared [3.6] and [4.5]
Zapatero Osorio, M. R. et al.Fecha de publicación:
12008 -
Near-infrared low-resolution spectroscopy of Pleiades L-type brown dwarfs
Context. The fundamental properties of brown dwarfs evolve with age. Models describing the evolution of luminosities and effective temperatures, among other physical parameters, can be empirically constrained using brown dwarfs of various masses in star clusters of well-determined age and metallicity. Aims: We aim to carry out a spectroscopic and
Bihain, G. et al.Fecha de publicación:
92010 -
Lucky Imaging Adaptive Optics of the brown dwarf binary GJ569Bab
The potential of combining Adaptive Optics (AO) and Lucky Imaging (LI) to achieve high-precision astrometry and differential photometry in the optical is investigated by conducting observations of the close 0.1 arcsec brown dwarf binary GJ569Bab. We took 50 000 I-band images with our LI instrument FastCam attached to NAOMI, the 4.2-m William
Femenía, B. et al.Fecha de publicación:
52011 -
Infrared and Kinematic Properties of the Substellar Object G 196-3 B
We report unusual near- and mid-infrared photometric properties of G 196-3 B, the young substellar companion at 16'' from the active M2.5-type star G 196-3 A, using data taken with the IRAC and MIPS instruments onboard Spitzer. G 196-3 B shows markedly redder colors at all wavelengths from 1.6 up to 24 μm than expected for its spectral type, which
Zapatero Osorio, M. R. et al.Fecha de publicación:
62010 -
High-contrast optical imaging of companions: the case of the brown dwarf binary HD 130948 BC
Context. High-contrast imaging at optical wavelengths is limited by the modest correction of conventional near-IR optimized AO systems. We take advantage of new fast and low-readout-noise detectors to explore the potential of fast imaging coupled to post-processing techniques to detect faint companions of stars at small angular separations. Aims
Labadie, L. et al.Fecha de publicación:
22011 -
Discovery of a Wide Companion near the Deuterium-burning Mass Limit in the Upper Scorpius Association
We present the discovery of a companion near the deuterium-burning mass limit located at a very wide distance, at an angular separation of 4.6''+/-0.1'' (projected distance of ~ 670 AU) from UScoCTIO 108, a brown dwarf of the very young Upper Scorpius association. Optical and near-infrared photometry and spectroscopy confirm the cool nature of both
Béjar, V. J. S. et al.Fecha de publicación:
22008 -
CLOUDS search for variability in brown dwarf atmospheres. Infrared spectroscopic time series of L/T transition brown dwarfs
Context: L-type ultra-cool dwarfs and brown dwarfs have cloudy atmospheres that could host weather-like phenomena. The detection of photometric or spectral variability would provide insight into unresolved atmospheric heterogeneities, such as holes in a global cloud deck. Indeed, a number of ultra-cool dwarfs have been reported to vary. Additional
Goldman, B. et al.Fecha de publicación:
82008
