6 research outputs found
Probing micro-arcsec astrometry with NACO
Relative astrometric measurements with a precision far better than 1 mas
(milli-arcsec) are commonly regarded as the domain of interferometry.
Pioneering work by Pravdo & Shaklan (1996), made in the optical, reached a
precision of 150 micro-arcsec in direct imaging but is ultimately limited by
atmospheric turbulence and differential chromatic refraction (DCR) effects.
Neuhaeuser et al. (2006, 2007) demonstrated that AO assisted observations with
NACO in a near-infrared narrow band filter allow measurements with a precision
of ~50 muas (micro-arsec) on a 0.6 arcsec binary within one hour and are
unaffected by DCR effects. This opens new possibilities for astrometric
detections of extrasolar planets and the determination of their true masses. We
discuss here how to improve the measurements and address the necessary
calibrations.Comment: To be published in the proceedings of the 2007 ESO Instrument
Calibration Worksho
The Physics of turbulent and dynamically unstable Herbig-Haro jets
The overall properties of the Herbig-Haro objects such as centerline
velocity, transversal profile of velocity, flow of mass and energy are
explained adopting two models for the turbulent jet. The complex shapes of the
Herbig-Haro objects, such as the arc in HH34 can be explained introducing the
combination of different kinematic effects such as velocity behavior along the
main direction of the jet and the velocity of the star in the interstellar
medium. The behavior of the intensity or brightness of the line of emission is
explored in three different cases : transversal 1D cut, longitudinal 1D cut and
2D map. An analytical explanation for the enhancement in intensity or
brightness such as usually modeled by the bow shock is given by a careful
analysis of the geometrical properties of the torus.Comment: 17 pages, 10 figures. Accepted for publication in Astrophysics &
Spac