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Context. Brown dwarfs are transition objects between stars and planets that are still poorly understood, for which several competing mechanisms have been proposed to describe their formation. Mass measurements are generally difficult to carry out for isolated objects as well as for brown dwarfs orbiting low-mass stars, which are often too faint for a spectroscopic follow-up. Aims. Microlensing provides an alternative tool for the discovery and investigation of such faint systems. Here, we present an analysis of the microlensing event OGLE-2019-BLG-0033/MOA-2019-BLG-035, which is caused by a binary system composed of a brown dwarf orbiting a red dwarf. Methods. Thanks to extensive ground observations and the availability of space observations from Spitzer, it has been possible to obtain accurate estimates of all microlensing parameters, including the parallax, source radius, and orbital motion of the binary lens. Results. Following an accurate modeling process, we found that the lens is composed of a red dwarf with a mass of M 1 = 0.149 ± 0.010 M ⊙ and a brown dwarf with a mass of M 2 = 0.0463 ± 0.0031 M ⊙ at a projected separation of a ⊥ = 0.585 au. The system has a peculiar velocity that is typical of old metal-poor populations in the thick disk. A percent-level precision in the mass measurement of brown dwarfs has been achieved only in a few microlensing events up to now, but will likely become more common in the future thanks to the Roman space telescope. 

Characteristics of the life history of the coral reef‐dwelling cardinalfishSiphamia tubifer, from Okinawa, Japan, were defined. A paternal mouthbrooder,S. tubifer, is unusual in forming a bioluminescent symbiosis withPhotobacterium mandapamensis. The examinedS. tubifer(n = 1273) ranged in size from 9·5 to 43·5 mm standard length (L_S), and the minimum size at sexual maturity was 22 mmL_S. The number ofS. tubiferassociated during the day among the spines of host urchins was 22·9 ± 16·1 (mean ± s.d.;Diadema setosum) and 3·6 ± 3·2 (Echinothrix calamaris). Diet consisted primarily of crustacean zooplankton. Batch fecundity (number of eggs;F_B) was related toL_Sby the equations: males (fertilized eggs)F_B = 27·5L_S − 189·46; females (eggs)F_B = 31·3L_S − 392·63. Individual mass (M; g) as a function ofL_Swas described by the equation:. Growth, determined from otolith microstructure analysis, was described with the von Bertalanffy growth function with the following coefficients:L_∞ = 40·8 mmL_S,K = 0·026 day⁻¹andt₀ = 23·25 days. Planktonic larval duration was estimated to be 30 days. The age of the oldest examined individual was 240 days. The light organ ofS. tubifer, which harbours the symbiotic population ofP. mandapamensis, increased linearly in diameter asS. tubifer L_Sincreased, and the bacterial population increased logarithmically withS. tubifer L_S. These characteristics indicate that once settled,S. tubifergrows quickly, reproduces early and typically survives much less than 1 year in Okinawa. These characteristics are generally similar to other small reef fishes but they indicate thatS. tubiferexperiences higher mortality.