English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

We present the analysis of MOA-2007-BLG-197Lb, the first brown dwarfcompanion to a Sun-like star detected through gravitational microlensing. Theevent was alerted and followed-up photometrically by a network of telescopesfrom the PLANET, MOA, and uFUN collaborations, and observed at high angularresolution using the NaCo instrument at the VLT. From the modelling of themicrolensing light curve, we derived the binary lens separation in Einsteinradius units (s~1.13) and a mass ratio of (4.732+/-0.020)x10^{-2}. Annualparallax, lens orbital motion and finite source effects were included in themodels. To recover the lens system's physical parameters, we combined theresulting light curve best-fit parameters with (J,H,Ks) magnitudes obtainedwith VLT NaCo and calibrated using IRSF and 2MASS data. We derived a lens totalmass of 0.86+/-0.04 Msun and a lens distance of 4.2+/-0.3 kpc. We find that thecompanion of MOA-2007-BLG-197L is a brown dwarf of 41+/-2 Mjup observed at aprojected separation of 4.3+/-0.1 AU, and orbits a 0.82+/-0.04 Msun G-K dwarfstar. We study the statistical properties of this population of brown dwarfsdetected by microlensing, transit, radial velocity, and direct imaging (most ofthese objects orbit solar-type stars), and we performed a two-dimensional,non-parametric probability density distribution fit to the data, which draws astructured brown dwarf landscape. We confirm the existence of a region that isstrongly depleted in objects at short periods and intermediate masses (P<30 d,M~30-60 Mjup), but also find an accumulation of objects around P~500 d and M~20Mjup, as well as another depletion region at long orbital periods (P>500 d) andhigh masses (M>50 Mjup). While these data provide important clues on mechanismsof brown dwarfs formation, more data are needed to establish their relativeimportance, in particular as a function of host star mass.

MOA-2007-BLG-197: Exploring the brown dwarf desert