We aim to refine the dynamical masses of the individual component of the low-mass pre-main sequence binary Haro 1-14 C. We combine the data of the preliminary orbit presented previously with new interferometric observations obtained with the four 8m
telescopes of the Very Large Telescope Interferometer. The derived masses are $M_a=0.905pm0.043,Msun$ and $M_b=0.308pm0.011,Msun$ for the primary and secondary components, respectively. This is about five times better than the uncertainties of the preliminary orbit. Moreover, the possibility of larger masses is now securely discarded. The new dynamical distance, $d=96pm,9,$pc, is smaller than the distance to the Ophiuchus core with a significance of $2.6,sigma$. Fitting the spectral energy distribution yields apparent diameters of $phi_a=0.13pm0.01mas$ and $phi_b=0.10pm0.01mas$ (corresponding to $Ra=1.50,Rsun$ and $Rb=1.13,Rsun$) and a visual extinction of $A_vapprox1.75$. Although the revised orbit has a nearly edge-on geometry, the system is unlikely to be a long-period eclipsing binary. The secondary in Haro~1-14C is one of the few low-mass, pre-main sequence stars with an accurately determined dynamical mass and distance.
We aim at measuring the stellar parameters of the two Chemically Peculiar components of the B9.5Vp HgMn + A2 Vm double-lined spectroscopic binary HD141556, whose period is 15.25 days. We combined historical radial velocity measurements with new spati
ally resolved astrometric observations from PIONIER/VLTI to reconstruct the three-dimensional orbit of the binary, and thus obtained the individual masses. We fit the available photometric points together with the flux ratios provided by interferometry to constrain the individual sizes, which we compared to predictions from evolutionary models.The individual masses of the components are $Ma = 2.84 pm 0.12 Msun$ and $Mb = 1.94 pm 0.09 Msun$. The dynamical distance is compatible with the Hipparcos parallax. We find linear stellar radii of $Ra=2.85 pm 0.15 Rsun$ and $Rb=1.75 pm 0.18 Rsun$. This result validates a posteriori the flux ratio used in previous detailed abundance studies. We determine a sub-solar initial metallicity $Z=0.012pm0.003$ and an age of $(2.8pm0.3)times10^8 $years. Our results imply that the primary rotates more slowly than its synchronous velocity, while the secondary is probably synchronous. We show that strong tidal coupling during the pre-main sequence evolution followed by a full decoupling at zero-age main sequence provides a plausible explanation for these very low rotation rates.
The visitor instrument PIONIER provides VLTI with improved imaging capabilities and sensitivity. The instrument started routinely delivering scientific data in November 2010, that is less than 12 months after being approved by the ESO Science and Tec
hnical Committee. We recall the challenges that had to be tackled to design, built and commission PIONIER. We summarize the typical performances and some astrophysical results obtained so far. We conclude this paper by summarizing lessons learned.
PIONIER stands for Precision Integrated-Optics Near-infrared Imaging ExpeRiment. It combines four 1.8m Auxilliary Telescopes or four 8m Unit Telescopes of the Very Large Telescope Interferometer (ESO, Chile) using an integrated optics combiner. The i
nstrument has been integrated at IPAG starting in December 2009 and commissioned at the Paranal Observatory in October 2010. It provides scientific observations since November 2010. In this paper, we detail the instrumental concept, we describe the standard operational modes and the data reduction strategy. We present the typical performance and discuss how to improve them. This paper is based on laboratory data obtained during the integrations at IPAG, as well as on-sky data gathered during the commissioning at VLTI. We illustrate the imaging capability of PIONIER on the binaries deltaSco and HIP11231. PIONIER provides 6 visibilities and 3 independent closure phases in the H band, either in a broadband mode or with a low spectral dispersion (R=40), using natural light (i.e. unpolarized). The limiting magnitude is Hmag=7 in dispersed mode under median atmospheric conditions (seeing<1, tau0>3ms) with the 1.8m Auxiliary Telescopes. We demonstrate a precision of 0.5deg on the closure phases. The precision on the calibrated visibilities ranges from 3 to 15% depending on the atmospheric conditions. PIONIER has been installed and successfully tested as a visitor instrument for the VLTI. It permits high angular resolution imaging studies at an unprecedented level of sensitivity. The successful combination of the four 8m Unit Telescopes in March 2011 demonstrates that VLTI is ready for 4-telescope operation.
