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About 20% of stars in the solar vicinity are in the Hercules stream, a bundle of stars that move together with a velocity distinct from the Sun. Its origin is still uncertain. Here, we explore the possibility that Hercules is made of trojans, stars captured at L4, one the Lagrangian points of the stellar bar. Using GALAKOS--a high-resolution N-body simulation of the Galactic disk--we follow the motions of stars in the co-rotating frame of the bar and confirm previous studies on Hercules being formed by stars in co-rotation resonance with the bar. Unlike previous work, we demonstrate that the retrograde nature of trojan orbits causes the asymmetry in the radial velocity distribution, typical of Hercules in the solar vicinity. We show that trojans remain at capture for only a finite amount of time, before escaping L4 without being captured again. We anticipate that in the kinematic plane the Hercules stream will de-populate along the bar major axis and be visible at azimuthal angles behind the solar vicinity with a peak towards L4. This test can exclude the OLR origin of the Hercules stream and be validated by Gaia DR3 and DR4.
The radio source J1819+3845 underwent a period of extreme interstellar scintillation between circa 1999 and 2007. The plasma structure responsible for this scintillation was determined to be just $1$-$3,$pc from the solar system and to posses a densi
In the light of the new observational data related to fluorine abundances in the solar neighborhood stars, we present here chemical evolution models testing different fluorine nucleosynthesis prescriptions with the aim to best fit those new data rela
For the past 150 years, the prevailing view of the local Interstellar Medium (ISM) was based on a peculiarity known as the Goulds Belt, an expanding ring of young stars, gas, and dust, tilted about 20$^circ$ to the Galactic plane. Still, the physical
The surface density and vertical distribution of stars, stellar remnants, and gas in the solar vicinity form important ingredients for understanding the star formation history of the Galaxy as well as for inferring the local density of dark matter by
We report the discovery of 30 stars with extreme space velocities ($>$ 480 km/s) in the Gaia-DR2 archive. These stars are a subset of 1743 stars with high-precision parallax, large tangential velocity ($v_{tan}>$ 300 km/s), and measured line-of-sight