A recent re-acceleration of the Local Bubble revealed by kinematics of young star associations

ABSTRACT The low-density region of the interstellar medium (ISM) where the Sun is located is known as the Local Bubble, a cavity filled with high-temperature and low-density plasma that may be created by a series of supernova explosions (SNe) over the past 14 Myr. However, the effects of these SNe on the formation and evolution of the Local Bubble, as well as on nearby star formation, remain not fully understood. To study the expansion history of the Local Bubble, we use the kinematic data of the young stars obtained by cross-matching the pre-main-sequence (PMS) star catalog of Zari et al. (2018) with the high-precision astrometric and photometric data from the Gaia DR3 database. We perform a three-dimensional spatial clustering analysis on these young stars to identify star associations. We discover three unique star associations that exhibit a wiggle-like velocity pattern. The distances of these18 star associations are 108.5308, 141.5284, and 176.0318 pc, respectively. Their radial velocities in the Local Standard of Rest (LSR) are 10.0622, 5.4982, and 9.0581 km/s, showing a pattern of decreasing and then increasing. This velocity pattern, as predicted by Krause & Diehl (2014), is caused by a recent re-acceleration affected by the SNe, reinforcing the picture of the Local Bubble as an evolving entity.