arXiv subjects

R. Angel

Publications and source records attributed to R. Angel.

3 recordsLinked to original sources

arXiv2018

ARGOS at the LBT. Binocular laser guided ground layer adaptive optics

Having completed its commissioning phase, the Advanced Rayleigh guided Ground-layer adaptive Optics System (ARGOS) facility is coming online for scientific observations at the Large Binocular Telescope (LBT). With six Rayleigh laser guide stars in two constellations and the corresponding wavefront sensing, ARGOS corrects the ground-layer distortions for both LBT 8.4m eyes with their adaptive secondary mirrors. Under regular observing conditions, this set-up delivers a point spread function (PSF) size reduction by a factor of ~2--3 compared to a seeing-limited operation. With the two LUCI infrared imaging and multi-object spectroscopy instruments receiving the corrected images, observations in the near-infrared can be performed at high spatial and spectral resolution. We discuss the final ARGOS technical set-up and the adaptive optics performance. We show that imaging cases with ground-layer adaptive optics (GLAO) are enhancing several scientific programmes, from cluster colour magnitude diagrams and Milky Way embedded star formation, to nuclei of nearby galaxies or extragalactic lensing fields. In the unique combination of ARGOS with the multi-object near-infrared spectroscopy available in LUCI over a 4x4 arcmin field of view, the first scientific observations have been performed on local and high-z objects. Those high spatial and spectral resolution observations demonstrate the capabilities now at hand with ARGOS at the LBT.

astro-ph.IM↗

arXiv2009

Terrestrial Planet Finder Coronagraph (TPF-C) Flight Baseline Concept

The Terrestrial Planet Finder Coronagraph (TPF-C) mission presented here is an existence proof for a flagship-class internal coronagraph space mission capable of detecting and characterizing Earth-like planets and planetary systems at visible wavelengths around nearby stars, using an existing launch vehicle. TPF-C will use spectroscopy to measure key properties of exoplanets including the presence of atmospheric water or oxygen, powerful signatures in the search for habitable worlds.

astro-ph.IM↗

arXiv2001

Gliese 569B: A young multiple brown dwarf system?

The nearby late M star Gliese 569B was recently found by adaptive optics imaging to be a double with separation ~1 AU. To explore the orbital motion and masses, we have undertaken a high resolution (~0.05 arcsec) astrometric study. Images were obtained over 1.5 years with bispectrum speckle interferometry at the 6.5m MMT and 6m SAO telescopes. Our data show motion corresponding to more than half the orbital period, and constrain the total mass to be > 0.115 M_solar, with a most probable value of 0.145 M_solar. Higher masses cannot be excluded without more extended observations, but from statistical analysis we find an 80% probability that the total mass is less than 0.21 M_solar. An infrared spectrum of the blended B double obtained with the MMT has been modeled as a blend of two different spectral types, chosen to be consistent with the measured J and K band brightness difference of a factor ~2. The blended fit is not nearly as good as that to a pure M8.5+ template. Therefore we hypothesize that the brighter component likely has two unresolved components with near equal masses, each the same as the fainter component. If Gl 569B is a triple our dynamical limits suggest each component has a mass of 50 (+23/-4) M_jupiter. We infer an age for the system of 300 Myr, from its kinematic motion which places its as a member of the Ursa Major moving group. All the above parameters are consistent with the latest DUSTY evolutiuon models for brown dwarfs.

astro-ph↗