ESTRELAS COM ALTA VELOCIDADE NOS LEVANTAMENTOS SDSS/APOGEE, J-PLUS E S-PLUS

Abstract

Stars with high velocities in the Galaxy are linked to extreme astrophysical events. The number of stars and the chemical and kinematic information of this population is essential to infer their places of origin, the possible mechanisms of generation of the high velocities, and the occurrence frequency of these phenomena. In this work, using astrometric, photometric and spectroscopic information, we performed the kinematic and chemical characterization of 84 stars, with galactocentric velocities greater than 400-450 km/s. From this sample, 23 stars were selected from the data crossmatch between the APOGEE DR17 catalog and the Gaia eDR3, 28 stars from the crossmatch between the J-PLUS DR2 catalog and the Gaia DR3, and 33 stars from the crossmatch between the S-PLUS catalog and the Gaia DR3. According to the position in the Hertzsprung-Russell diagram, 90% of the sample is located in the red giant branch and the rest in the turn-off region. Kinematic analysis, using astrometric information from Gaia and supplemented with radial velocities from APOGEE, shows that all 23 stars in APOGEE have a kinematic behavior of the halo population. For the J-PLUS and S-PLUS stars, using only the astrometric information from Gaia, the kinematic analysis shows that all have a behavior of halo stars too. Moreover, the chemical analysis of the stars in APOGEE, using information on the abundances of O, Mg, Al, Si, Mn, Ni, and the stellar parameters, shows that most of them have chemical properties typical of halo stars, in agreement with the kinematics. However, some of them display peculiar chemical patterns. For the J-PLUS and S-PLUS stars, using only information on the metallicity and the stellar parameters derived from photometry, the chemical analysis shows that most of the stars have metallicities typical of halo stars, but some could have an origin in the disc or in the bulge. The kinematic and dynamical studies, complemented with the chemical study, show that the stars are dynamically bounded to the Galaxy and a large fraction could be accreted stars from dwarf galaxies that merged with the Milky Way in the past.