Discovery of an equal-mass "twin" binary population reaching 1000+ AU separations

Understand

We use a homogeneous catalog of 42,000 main-sequence wide binaries identified by Gaia to measure the mass ratio distribution, p(q), of binaries with primary masses $0.1<M_1/M_{\odot}<2.5$, mass ratios $0.1 \lesssim q<1$, and separations $50<s/{\rm AU}<50,000$.

• A well-understood selection function allows us to constrain p(q) in 35 independent bins of primary mass and separation, with hundreds to thousands of binaries in each bin.
• Our investigation reveals a sharp excess of equal-mass &#34;twin&#34; binaries that is statistically significant out to separations of 1,000 to 10,000 AU, depending on primary mass.
• The excess is narrow: a steep increase in p(q) at $0.95 \lesssim q<1$, with no significant excess at $q\lesssim 0.95$.