Abstract
Mass is the most fundamental parameter of a star, yet it is also one of the most difficult to measure directly. In general, astronomers estimate stellar masses by determining the luminosity and using the ‘mass–luminosity’ relationship1,2, but this relationship has never been accurately calibrated for young, low-mass stars and brown dwarfs3. Masses for these low-mass objects are therefore constrained only by theoretical models1,2. A new high-contrast adaptive optics camera4,5,6 enabled the discovery of a young (50 million years) companion only 0.156 arcseconds (2.3 au) from the more luminous (> 120 times brighter) star AB Doradus A. Here we report a dynamical determination of the mass of the newly resolved low-mass companion AB Dor C, whose mass is 0.090 ± 0.005 solar masses. Given its measured 1–2-micrometre luminosity, we have found that the standard mass–luminosity relations1,2 overestimate the near-infrared luminosity of such objects by about a factor of ∼2.5 at young ages. The young, cool objects hitherto thought to be substellar in mass are therefore about twice as massive, which means that the frequency of brown dwarfs and planetary mass objects in young stellar clusters has been overestimated.
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Acknowledgements
We thank A. Kaufer, M. Kasper, J. Spyromilio, P. Gandhi and R. Gilmozzi for assistance with SDI commissioning. We thank O. Marco for support during the spectral observations. We thank D. McCarthy and M. Rademacher for help with the initial design of the NACO SDI optics. L.M.C. and B.B. acknowledge support from a NASA Origins grant. J.C.G. acknowledges support from a Spanish DGICYT grant. E.E.M. is supported by a Clay Fellowship from the Smithsonian Astrophysical Observatory. L.M.C. acknowledges support from an NSF Career award and SEC and EMC.
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Close, L., Lenzen, R., Guirado, J. et al. A dynamical calibration of the mass–luminosity relation at very low stellar masses and young ages. Nature 433, 286–289 (2005). https://doi.org/10.1038/nature03225
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DOI: https://doi.org/10.1038/nature03225
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