VLBA DETERMINATION of the DISTANCE to NEARBY STAR-FORMING REGIONS. VII. MONOCEROS R2

We present a series of 16 Very Long Baseline Array high angular resolution observations of a cluster of suspected low-mass young stars in the Monoceros R2 region. Four compact and highly variable radio sources are detected; three of them in only one epoch, the fourth one a total of seven times. This latter source is seen in the direction of the previously known UC H ii region VLA 1, and has radio properties that resemble those of magnetically active stars; we shall call it VLA 1sstarf. We model its displacement on the celestial sphere as a combination of proper motion and trigonometric parallax. The fit obtained using a uniform proper motion yields a parallax piv = 1.10 ± 0.18 mas, but with a fairly high post-fit dispersion. If acceleration terms (probably due to an undetected companion) are included, the quality of the fit improves dramatically, and the best estimate of the parallax becomes piv = 1.12 ± 0.05 mas. The magnitude of the fitted acceleration suggests an orbital period of the order of a decade. The measured parallax corresponds to a distance d = ${893}_{-40}^{+44},mathrm{pc}$ , in very good agreement with previous, indirect determinations.