Low-mass pre-main-sequence stars in the Large Magellanic Cloud.: III.: Accretion rates from Hubble Space Telescope WFPC2 observations

We have measured the present accretion rate of roughly 800 low-mass (similar to1 - 1.4 M-.) pre-main-sequence stars in the field of supernova 1987A in the Large Magellanic Cloud ( Z similar or equal to 0.3 Z(.)). It is the first time that this fundamental parameter for star formation has been determined for low-mass stars outside our Galaxy. The Balmer continuum emission used to derive the accretion rate positively correlates with the Halpha excess. Both these phenomena are believed to originate from accretion from a circumstellar disk, so their simultaneous detection provides an important confirmation of the pre-main-sequence nature of the Halpha and UV excess objects, which are likely to be the LMC equivalent of Galactic classical T Tauri stars. The stars with statistically significant excesses are measured to have accretion rates larger than similar to1.5 x 10(-8) M-. yr(-1) at an age of 12 - 16 Myr. For comparison, the timescale for disk dissipation observed in the Galaxy is of the order of 6 Myr. Moreover, the oldest classical T Tauri star known in the Milky Way (TW Hydrae, with 10 Myr of age) has a measured accretion rate of only 5 x 10(-10) M-. yr(-1), i.e., 30 times less than what we measure for stars at a comparable age in the LMC. Our findings indicate that metallicity plays a major role in regulating the formation of low-mass stars.