Chemical segregation in the young protostars Barnard 1b-N and S Evidence of pseudo-disk rotation in Barnard 1b-S.

The extremely young Class 0 object B1b-S and the first hydrostatic core (FSHC) candidate, B1b-N, provide a unique opportunity to study the chemical changes produced in the elusive transition from the prestellar core to the protostellar phase. We present 40"×70" images of Barnard 1b in the CO 1→0, CO 1→0, NHD 1→1, and SO 3→2 lines obtained with the NOEMA interferometer. The observed chemical segregation allows us to unveil the physical structure of this young protostellar system down to scales of ∼500 au.

Nascent bipolar outflows associated with the first hydrostatic core candidates Barnard 1b-N and 1b-S.

In the theory of star formation, the first hydrostatic core (FHSC) phase is a critical step in which a condensed object emerges from a prestellar core. This step lasts about one thousand years, a very short time compared with the lifetime of prestellar cores, and therefore is hard to detect unambiguously. We present IRAM Plateau de Bure observations of the Barnard 1b dense molecular core, combining detections of HCO and CHOH spectral lines and dust continuum at 2.

Inverse problem approach in particle digital holography: out-of-field particle detection made possible.

We propose a microparticle detection scheme in digital holography. In our inverse problem approach, we estimate the optimal particles set that best models the observed hologram image. Such a method can deal with data that have missing pixels.

Analysis of stellar interferometers as wave-front sensors.

The basic principle and theoretical relationships of an original method are presented that allow the wave-front errors of a ground or spaceborne telescope to be retrieved when its main pupil is combined with a second, decentered reference optical arm. The measurement accuracy of such a telescope-interferometer is then estimated by means of various numerical simulations, and good performance is demonstrated, except in limited areas near the telescope pupil's rim. In particular, it permits direct phase evaluation (thus avoiding the use of first- or second-order derivatives), which will be of special interest for the cophasing of segmented mirrors in future giant-telescope projects.

Extraterrestrial meteors: a martian meteor and its parent comet.

Regular meteor showers occur when a planet approaches the orbit of a periodic comet--for example, the Leonid shower is evident around 17 November every year as Earth skims past the dusty trail of comet Tempel-Tuttle. Such showers are expected to occur on Mars as well, and on 7 March last year, the panoramic camera of Spirit, the Mars Exploration Rover, revealed a curious streak across the martian sky. Here we show that the timing and orientation of this streak, and the shape of its light curve, are consistent with the existence of a regular meteor shower associated with the comet Wiseman-Skiff, which could be characterized as martian Cepheids.

Photometric observations of a polychromatic laser guide star.

We report the photometric observation of a polychromatic laser guide star (PLGS) using the AVLIS laser at the Lawrence Livermore National Laboratory (LLNL). The process aims at providing a measurement of the tilt of the incoming wave front at a telescope induced by atmospheric turbulence. It relies on the two-photon coherent excitation of the 4D5/2 energy level of sodium atoms in the mesosphere.

Method for a quantitative investigation of the frozen flow hypothesis.

We present a technique to test the frozen flow hypothesis quantitatively, using data from wave-front sensors such as those found in adaptive optics systems. Detailed treatments of the theoretical background of the method and of the error analysis are presented. Analyzing data from the 1.