Photometric determination of the mass accretion rates of pre-main-sequence stars VII. The low-density cluster NGC 376 in the Small Magellanic Cloud

Aims. We study the properties of low-mass stars recently formed in the field of the NGC376 cluster in the Small Magellanic Cloud (SMC). Methods. Using photometric observations acquired with the Hubble Space Telescope (HST) in the V, I, and H alpha bands, we identify 244 candidate pre-main-sequence (PMS) stars showing H alpha excess emission at the 5 sigma level and with H alpha equivalent width of 20 angstrom or more. We derive physical parameters for all PMS stars, including masses, ages, and mass accretion rates. We compare the effective mass accretion rate of stars in NGC376 to that of objects in the NGC346 cluster, with NGC346 featuring similar metallicity but higher total mass and gas density. Results. We find a median age of 28 Myr for this population (with 25th and 75th percentiles at about 20 and 40 Myr, respectively), in excellent agreement with previous studies of massive stars in the same field. The PMS stars are rather uniformly distributed across the field, whereas massive stars are more clustered. The spatial distribution of PMS objects is compatible with them having formed in the centre of the cluster and then migrating outwards. We find that in NGC376 the mass accretion rate is systematically lower than in NGC346 for stars of the same mass and age. This indicates that, in addition to metallicity, there are other environmental factors a ffecting the rate of mass accretion onto PMS stars. Our observations suggest that the gas density in the star-forming region might play a role.

Automated summary

In this study, we investigate the properties of low-mass stars in the NGC376 cluster of the Small Magellanic Cloud using photometric observations from the Hubble Space Telescope. We identify 244 candidate pre-main-sequence stars showing H alpha excess emission and calculate their physical parameters including masses, ages, and mass accretion rates. Comparing with the NGC346 cluster, we find that the mass accretion rate is lower in NGC376, suggesting the influence of other environmental factors on this process.