16. We thank the entire Voyager team at NASA Headquarters and the Jet Propulsion Laboratory (JPL) for their support. We are especially grateful to R. Poynter for his invaluable assistance and support. We also thank E. Miner and J. Diner for their efforts to arrange the wideband coverage; J. Anderson, P. Jepsen, and G. Garneau for their assistance with the wideband data processing; C. Stembridge for his help in solving numerous problems; H. Bridge, J. Belcher, J. Scudder, and N. Ness for providing data in advance of publication and for their helpful discussions; and R. Anderson, R. West, L. Granroth, and R. Brechwald for carrying out the data reduction. The research at the University of Iowa was supported by NASA through contract 954013 with JPL, through grants NGL-16-001-002 and NGL-16-001-043 from NASA Headquarters, and by the Office of Naval Research. The research at TRW was supported by NASA through contract 954012 with JPL.
Context. In April 2004, the first image was obtained of a planetary mass companion (now known as 2M1207 b) in orbit around a self-luminous object different from our own Sun (the young brown dwarf 2MASSW J1207334-393254, hereafter 2M1207 A). That 2M1207 b probably formed via fragmentation and gravitational collapse offered proof that such a mechanism can form bodies in the planetary mass regime. However, the predicted mass, luminosity, and radius of 2M1207 b depend on its age, distance, and other observables, such as effective temperature. Aims. To refine our knowledge of the physical properties of 2M1207 b and its nature, we accurately determined the distance to the 2M1207 A and b system by measuring of its trigonometric parallax at the milliarcsec level. Methods. With the ESO NTT/SUSI2 telescope, we began a campaign of photometric and astrometric observations in 2006 to measure the trigonometric parallax of 2M1207 A.Results. An accurate distance (52.4 ± 1.1 pc) to 2M1207A was measured. From distance and proper motions we derived spatial velocities that are fully compatible with TWA membership. Conclusions. With this new distance estimate, we discuss three scenarios regarding the nature of 2M1207 b: (1) a cool (1150 ± 150 K) companion of mass 4 ± 1 M Jup , (2) a warmer (1600 ± 100 K) and heavier (8 ± 2 M Jup ) companion occulted by an edge-on circumsecondary disk, or (3) a hot protoplanet collision afterglow.
We present SCIDAR measurements made at the Pic du Midi Observatory with PISCO. A series of vertical profiles of the refractive-index structure constant C 2 N (h) was obtained with the observations of the binary stars γ Del and γ Ari, with 30 second time sampling. In the free atmosphere, the turbulence was dominated by the contribution of a few well-separated atmospheric layers at altitudes in the range 8-20 km, with significant changes within a few minutes. We describe a new method based on the CLEAN algorithm applied on the 2-D covariance function of the irradiance fluctuations in the pupil plane and compare it with the widely-used Maximum Entropy Method applied on a slice of this 2-D function. Our method is much less sensitive to the noise. Vertical profiles of the wind velocity and direction were obtained with an automatic procedure working on the mean cross-correlation function of consecutive frames. Furthermore, we validate a model for the SCIDAR detectivity threshold in terms of distance to the turbulent layers.
Abstract. A first CCD 512 × 512 camera working in scan mode (declination field 14 ) was mounted in 1994 on the Bordeaux CCD meridian circle. After a testing period, this camera was installed on the Valinhos CCD meridian circle (near São Paulo, Brazil), as part of a collaboration between Bordeaux Observatory and the Instituto Astronomico e Geofisico of São Paulo. A second improved CCD 1024 × 1024 camera, with a declination field of 28 , was installed on the Bordeaux instrument in June 1996. The mean internal precision of a single observation is about 0.04 in both coordinates for 9 ≤ V ≤ 14. In the same magnitude range, magnitudes can also be obtained with an internal precision of about 0.05 mag. Both instruments can participate efficiently in extending the HipparcosTycho frame, during the next decade. Among other duties, the Bordeaux CCD meridian circle is being used since January 1997 for completing the Méridien 2000 project. The characteristics of both instruments and some results obtained with them are presented in this paper.
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