REM near-IR and optical photometric monitoring of pre-mainsequence stars in Orion Rotation periods and starspot parameters

摘要

We aim at determining the rotational periods and the starspot properties in very young low-mass stars belonging to the OriOB lc star forming region, contributing to the study of the angular momentum and magnetic activity evolution in these objects.Methods. We performed an intensive photometric monitoring of the PMS stars falling in a field of about 10' x 10' in the vicinity of theOrion nebula cluster (ONC), also containing the BD eclipsing system 2MASS J05352184-0546085. Photometric data were collectedbetween November 2006 and January 2007 with the REM telescope in the VRIJHK' bands. The largest number of observations is inthe I band (about 2700 images) and in J and H bands (about 500 images in each filter). From the observed rotational modulation,induced by the presence of surface inhomogeneities, we derived the rotation periods. The long time-baseline (nearly three months)allowed us to detect rotation periods, also for the slowest rotators, with sufficient accuracy (API P < 2). The analysis of the spectralenergy distributions and, for some stars, of high-resolution spectra provided us with the main stellar parameters (luminosity, effectivetemperature, mass, age, and v sin i) which are essential for the discussion of our results. Moreover, the simultaneous observationsin six bands, spanning from optical to near-infrared wavelengths, enabled us to derive the starspot properties for these very younglow-mass stars.