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 Plus annual

Presents the access of premium content as premium feature

Premium Content

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 annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

According to current plans, the SIM/NASA mission will be launched just afterthe end of operations for the Gaia/ESA mission. This is a new situation whichenables long term astrometric projects that could not be achieved by eithermission alone. Using the well-known perspective acceleration effect onastrometric measurements, the true heliocentric radial velocity of a nearbystar can be measured with great precision if the time baseline of theastrometric measurements is long enough. Since white dwarfs are compactobjects, the gravitational redshift can be quite large (40-80 km/s), and is thepredominant source of any shift in wavelength. The mismatch of the true radialvelocity with the spectroscopic shift thus leads to a direct measure of theMass--Radius relation for such objects. Using available catalog informationabout the known nearby white dwarfs, we estimate how many masses/gravitationalredshift measurements can be obtained with an accuracy better than 2%. Nearbywhite dwarfs are relatively faint objects (10 < V < 15), which can be easilyobserved by both missions. We also briefly discuss how the presence of a longperiod planet can mask the astrometric signal of perspective acceleration.

Perspective acceleration and gravitational redshift. Measuring masses of individual white dwarfs using Gaia + SIM astrometry