2020/12/17 by Yang Huang, Qingzheng Li, Huawei Zhang +5 · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Dwarf galaxy #Dwarf spheroidal galaxy #Galactic Center #Galaxies: Formation, Evolution, Phenomena #Galaxy #Globular cluster #Hypervelocity #Milky Way #Sagittarius #Stellar, planetary, and galactic studies #astro-ph.GA
paper · pdf · doi:10.3847/2041-8213/abd413
6 pages, 4 figures, 2 tables, accepted for publication in ApJL
arxiv created 2020/12/17 · openalex created_date 2020/12/21 · openalex publication_date 2021/02/01 · arxiv updated 2021/02/10 · openalex updated_date 2026/08/05
Abstract In this Letter, we report the discovery of an intriguing hypervelocity star (HVS; J1443+1453) candidate that is probably from the Sagittarius Dwarf Spheroidal galaxy (Sgr dSph). The star is an old and very metal-poor low-mass main-sequence turn-off star (age ∼14.0 Gyr and [Fe/H] = −2.23 dex) and has a total velocity of km s −1 in the Galactic rest frame and a heliocentric distance of kpc. The velocity of J1443+1453 is larger than the escape speed at its position, suggesting that it is a promising HVS candidate. By reconstructing its trajectory in the Galactic potential, we find that the orbit of J1443+1453 intersects closely with that of Sgr dSph Myr ago, when the latter has its latest pericentric passage through the Milky Way. The encounter occurs at a distance kpc from the center of Sgr dSph, a distance that is smaller than the size of the Sgr dSph. The chemical properties of this star are also consistent with those of an Sgr dSph-associated globular cluster, or of the Sgr stream member stars. Our finding suggests that J1443+1453 is an HVS that is either tidally stripped from the Sgr dSph or ejected from the Sgr dSph by the gravitational slingshot effect, requiring a (central) massive/intermediate-mass black hole or a (central) massive primordial black hole in the Sgr dSph.