NASAのハッブル宇宙望遠鏡、老化した褐色矮星が孤独に成長することを発見(NASA’s Hubble Finds that Aging Brown Dwarfs Grow Lonely)


2024-03-21 NASA



T8~Y1褐色矮星33個のHSTサーベイ: 褐色矮星で最も冷たい天体の近赤外測光と多重度 An HST survey of 33 T8 to Y1 brown dwarfs: NIR photometry and multiplicity of the coldest isolated objects

Clémence Fontanive, Luigi R Bedin, Matthew De Furio, Beth Biller, Jay Anderson, Mariangela Bonavita, Katelyn Allers, Blake Pantoja
Monthly Notices of the Royal Astronomical Society  Published:22 September 2023

Magnitudes distributions in F127M (left) and F139M (right) of all injected stars with consistent detections in ≥3/4 images and measured fluxes above the local sky value (dotted lines), compared to those left after applying the selection criteria described in the text (solid line). The blue and red histograms represent artificial stars that were well and poorly measured by the algorithms, respectively, showing that our adopted selections successfully exclude the vast majority of poorly measured sources. This example is shown for the analyses made on the data for WISE 1639−6847.


We present results from a Hubble Space Telescope imaging search for low-mass binary and planetary companions to 33 nearby brown dwarfs with spectral types of T8–Y1. Our survey provides new photometric information for these faint systems, from which we obtained model-derived luminosities, masses, and temperatures. Despite achieving a deep sensitivity to faint companions beyond 0.2–0.5 arcsec, down to mass ratios of 0.4–0.7 outside ∼5 au, we find no companions to our substellar primaries. From our derived survey completeness, we place an upper limit of ƒ<4.9 per cent at the 1σ level (<13.0 per cent at the 2σ level) on the binary frequency of these objects over the separation range 1–1000 au and for mass ratios above q = 0.4. Our results confirm that companions are extremely rare around the lowest mass and coldest isolated brown dwarfs, continuing the marginal trend of decreasing binary fraction with primary mass observed throughout the stellar and substellar regimes. These findings support the idea that if a significant population of binaries exist around such low-mass objects, it should lie primarily below 2–3 au separations, with a true peak possibly located at even tighter orbital separations for Y dwarfs.