Seminario: Victor Almendros (INAF)

Speaker: Victor Almendros (INAF)

Title: Evolution of the mass accretion rate and its relationship with the stellar and disk mass from brown dwarfs to stars

Abstract:
The time evolution of the dependence of the mass accretion rate with the stellar mass and the disk mass represents a fundamental way to understand the evolution of protoplanetary disks and the formation of planets. Recent studies suggest the existence of a bimodal accretion behavior at 2-3 Myr in the relationship of the stellar mass and the mass accretion rate, which may indicate that low-mass stars evolve faster (than higher-mass stars) into lower accretion rates. We recently measured the mass accretion rate of 26 new brown dwarfs and low-mass stars in the Ophiuchus, Cha-I and Upper Scorpius star-forming regions using X-Shooter/VLT. Combining these new observations with data from the literature, we compared the relations between accretion rate and stellar/disk properties of four different star-forming regions with different ages: Ophiuchus (1 Mar), Lupus (2 Myr), Cha-I (3 Myr) and Upper Scorpius (5-12 Myr). Overall, we observe hints of a faster evolution into low accretion rates of low-mass stars and brown dwarfs. At the same time, we also found that brown dwarfs present larger Mdisk/Macc ratios than stars in Ophiuchus, Lupus and Cha-I. This apparently contradictory result may imply that the evolution of protoplanetary disks around brown dwarfs may be different than in the stellar regime.