Young suns and infant planets: probing the origins of solar systems

Even though more than 4000 extra-solar planets are known today, only a small fraction of these has been captured in an image. To better understand the planet formation mechanisms in solar-like environments we started the Young Suns Exoplanet Survey (YSES). YSES targets a homogeneous sample of seventy young (~15Myr), Sun-like stars of the Scorpius-Centaurus association to search for sub-stellar companions. High-contrast imaging observations that were collected with the SPHERE instrument at the Very Large Telescope revealed (i) a shadowed transition disk around Wray 15-788 that shows significant signs of ongoing planet formation and (ii) one of the lowest-mass companions imaged to date: YSES 2b has a mass of 6.5 Jupiter masses and is orbiting its solar-mass primary at a separation of 110 au. Most intriguing, though, was (iii) the discovery of the first directly imaged multi-planet system around a Sun-like star. The detection of two gas-giant companions of 14±3 and 6±1 Jupiter masses that are orbiting YSES 1 at separations of 160 au and 320 au, respectively, provides important implications for the outer architecture of planetary systems and the underlying formation mechanisms.Sterrewacht - OU

The Young Suns Exoplanet Survey: imaging infant planets around young, solar analogs

Instrumentatio

Photoassociation spectroscopy of cold calcium atoms

Photoassociation spectroscopy experiments on 40Ca atoms close to the dissociation limit 4s4s 1S0 - 4s4p 1P1 are presented. The vibronic spectrum was measured for detunings of the photoassociation laser ranging from 0.6 GHz to 68 GHz with respect to the atomic resonance. In contrast to previous measurements the rotational splitting of the vibrational lines was fully resolved. Full quantum mechanical numerical simulations of the photoassociation spectrum were performed which allowed us to put constraints on the possible range of the calcium scattering length to between 50 a_0 and 300 a_0

Quantum Corrections to Dilute Bose Liquids

It was recently shown (A. Bulgac. Phys. Rev. Lett. {\bf 89}, 050402 (2002)) that an entirely new class of quantum liquids with widely tunable properties could be manufactured from bosons (boselets), fermions (fermilets) and their mixtures (ferbolets) by controlling their interaction properties by the means of a Feshbach resonance. We extend the previous mean--field analysis of these quantum liquids by computing the lowest order quantum corrections to the ground state energy and the depletion of the Bose--Einstein condensate and by estimating higher order corrections as well. We show that the quantum corrections are relatively small and controlled by the diluteness parameter $\sqrt{n|a|^3} \ll 1$, even though strictly speaking in this case there is no low density expansion.Comment: final published version, typos corrected, updated references and added one referenc

Superfluid pairing in a polarized dipolar Fermi gas

We calculate the critical temperature of a superfluid phase transition in a polarized Fermi gas of dipolar particles. In this case the order parameter is anisotropic and has a nontrivial energy dependence. Cooper pairs do not have a definite value of the angular momentum and are coherent superpositions of all odd angular momenta. Our results describe prospects for achieving the superfluid transition in single-component gases of fermionic polar molecules.Comment: 12 pages, 2 figure

High-precision calculations of van der Waals coefficients for heteronuclear alkali-metal dimers

Van der Waals coefficients for the heteronuclear alkali-metal dimers of Li, Na, K, Rb, Cs, and Fr are calculated using relativistic ab initio methods augmented by high-precision experimental data. We argue that the uncertainties in the coefficients are unlikely to exceed about 1%.Comment: 11 pages, 2 figs, graphicx.st