Discovery of new companions to high proper motion stars from the VVV Survey

Abstract

Context. The severe crowding in the direction of the inner Milky Way suggests that the census of stars within a few tens of parsecs in that direction may not be complete. Aims. We searched for new nearby object companions of known high proper motion (HPM) stars located towards the densest regions of the southern Milky Way where the background contamination presented a major problem to previous observations. Methods. The common proper motion (PM) method was used. We inspected the area around 167 known HPM (≥200 mas yr −1 ) stars: 67 in the disk and 100 in the bulge. Multi-epoch images were provided by the Two Micron All Sky Survey (2MASS) and the VISTA Variables in Via Lactea (VVV). The VVV is a new on-going ZY JHK S plus multi-epoch K S survey of ∼562 deg 2 of the Milky Way bulge and inner southern disk. Results. Seven new co-moving companions were discovered around known HPM stars (L 149-77, LHS 2881, L 200-41, LHS 3188, LP 487-4, LHS 5333, and LP 922-16 , and OGLE BUL−SC32 388121); last but not least, spectral types ranging from G8V to M5V were derived from new infrared spectroscopy for seventeen stars, members of the co-moving pairs. Conclusions. The seven newly discovered stars constitute ∼4% of the nearby HPM star list, but this is not a firm limit on the HPM star incompleteness because our starting point -the HPM list assembled from the literature -is incomplete itself, missing many nearby HPM M-and L-type objects, and it is contaminated with non-HPM stars. We have demonstrated that the superior sub-arcsec spatial resolution, with respect to previous surveys, allows the VVV to examine in greater detail the binary nature nature of known HPM stars. The ≥5 yr span of VVV will provide a sufficient baseline for finding new HPM stars from VVV data alone.

Speckle Interferometry at Soar in 2014

“…This is the high-PM star LTT 6467 with a low metallicity [Fe/H] = −0.78. Ivanov et al (2013) found no CPM companions.…”

Spectrophotometric characterization of high proper motion sources fromWISE

“…The VVV is a variability survey primarily designed to trace the 3-D structure of the Milky Way, observing 562 •2 towards the Galactic Bulge and southern inner disk (Gonzalez et al 2011;Dékány et al 2013;Minniti et al 2014). This survey matches the requirements for good estimations of the proper motions (PMs) and parallaxes, as demonstrated previously by Beamín et al (2013); Ivanov et al (2013). The data were reduced at the Cambridge Astronomy Survey Unit (CASU) with pipeline v1.3.…”

Overlooked wide companions of nearby F stars

“…The CPM method continues to be useful, in particular for new deep surveys (e.g. Ivanov et al 2013;Deacon et al 2014). Focusing on a sample of nearby F stars, we demonstrate how much we can still improve the CPM statistics and find previously overlooked wide companions, even of wellknown bright stars, in existing public surveys.…”