Fr.: taux d'accrétion
The amount of mass → accreted during unit time. The accretion rate for the → collapse of a singular → isothermal sphere is expressed by: dM/dt = 0.975 cs3/G, where cs is the isothermal → sound speed (Shu 1977, ApJ 214, 488). This relation can be written as: dM/dt = 4.36 x 10-6 (T / 20 K)3/2 in units of solar masses per year, where T is the temperature. Observed temperatures of 10-20 K in regions of → low-mass star formation imply accretion rates of about 10-6 to 10-5 solar masses per year. Accretion rates for → massive stars amount to values of 10-4 to 10-3 solar masses per year.