Catalog of Wide Binary, Trinary and Quaternary Candidates from the Gaia Data Release 2 (Region ∣b∣ > 25°)

The occurrence of multiple stars, dominantly binaries, is studied using the Gaia-ESA DR2 catalog. We apply the optimized statistical method that we previously developed for the analysis of 2D patterns. The field of stars is divided into a mosaic of small pieces that represent a statistical set for analysis. Specifically, data input is represented by a grid of circles (events) with radius 0.°02 covering the sky in the field of galactic latitude ∣b∣ > 25°. The criteria for selecting candidates for multiple stars are based on two parameters: angular separation and collinearity of proper motion. Radial separation, due to limited accuracy, is used only as a weaker supplementary constraint. Due attention is paid to the accurate calculation of the background, which is a necessary input for evaluating the quality of the candidates. Our selection algorithm generates the catalog of candidates: 900,842 binaries, 5282 trinaries, and 30 quaternaries.

Illuminating a tadpole’s metamorphosis III: quantifying past and present environmental impact

ABSTRACT We combine Multi-Unit Spectroscopic Explorer and Atacama Large Millimeter/sub-millimeter Array observations with theoretical models to evaluate how a tadpole-shaped globule located in the Carina Nebula has been influenced by its environment. This globule is now relatively small (radius ∼2500 au), hosts a protostellar jet+outflow (HH 900), and, with a blueshifted velocity of ∼10 km s−1, is travelling faster than it should be if its kinematics were set by the turbulent velocity dispersion of the precursor cloud. Its outer layers are currently still subject to heating, but comparing the internal and external pressures implies that the globule is in a post-collapse phase. Intriguingly the outflow is bent, implying that the Young Stellar Object (YSO) responsible for launching it is comoving with the globule, which requires that the star formed after the globule was up to speed since otherwise it would have been left behind. We conclude that the most likely scenario is one in which the cloud was much larger before being subject to radiatively driven implosion, which accelerated the globule to the high observed speeds under the photoevaporative rocket effect and triggered the formation of the star responsible for the outflow. The globule may now be in a quasi-steady state following collapse. Finally, the HH 900 YSO is likely ≳1 M⊙ and may be the only star forming in the globule. It may be that this process of triggered star formation has prevented the globule from fragmenting to form multiple stars (e.g. due to heating) and has produced a single higher mass star.