11:15 〜 11:30
[PCG19-09] Characterizing the nearest brown dwarfs with ExoJAX
キーワード：大気リトリーバル、高分散分光、褐色矮星、ExoJAX
Brown dwarfs have relatively low surface temperatures and low brightness at visible so it has been difficult to find. Recently, technological advances have made it possible to observe objects in the near-infrared, making it possible to detect brown dwarfs. Since the first detection of a brown dwarf in 1995(Nakajima et al., 1995), approximately 2000 brown dwarfs have been discovered. Furthermore, large telescopes(e.g. Subaru) and near-infrared high-dispersion spectrometers(e.g. REACH/Subaru) have made it possible to obtain a high-dispersion spectrum of brown dwarfs, and their properties are becoming clearer(McLean et al., 2007).
The high-dispersion spectrum of brown dwarfs contains precise information on an abundance of molecules in the brown dwarf atmosphere and a variety of physical parameters of brown dwarfs, including temperature, surface gravity, and so on. Therefore, we can understand brown dwarfs well by analyzing the high-dispersion spectrum of brown dwarfs. Furthermore, analyzing the high-dispersion spectrum of brown dwarfs is becoming increasingly important as a prototype for the understanding of exoplanets in the future, because brown dwarfs have similar properties to young and warm exoplanets. As brown dwarfs are brighter and able to be precisely measured more than exoplanets, they can be also a test bed for establishing a method for characterizing exoplanets. However, studies analyzing the high-dispersion spectrum of brown dwarfs are still few and underdeveloped.
Here, we present the results and progress of the analysis of both near-infrared high-dispersion spectrum of Luhman16A and B(2.288-2.345 um, R~100,000), obtained by CRIRES on the Very Large Telescope, to characterize both brown dwarfs. Luhman16AB(WISE J104915.57−531906.1) is a close brown dwarf binary and both components are the nearest known brown dwarfs to the Sun(~2 pc from the Sun). Because both Luhman16A and B have been measured in a variety of ways(e.g. astrometry, Lazorenko et al., 2018), dynamics and physical parameters(e.g. mass) have been obtained precisely by a method that does not analyze the high-dispersion spectrum. Therefore, Luhman16A and B are important samples for establishing a method for analyzing the high-dispersion spectrum of brown dwarfs because we can compare the results of analyzing the high-dispersion spectrum of them with known values such as mass and so on. Both also have been known for their age so we can compare the results with the isochrone evolution of the brown dwarf(Gagne et al., 2023). We use the auto-differentiable spectral modeling tool, ExoJAX(Kawahara et al., 2022) for high dispersion characterization of Luhman16A and B.
The high-dispersion spectrum of brown dwarfs contains precise information on an abundance of molecules in the brown dwarf atmosphere and a variety of physical parameters of brown dwarfs, including temperature, surface gravity, and so on. Therefore, we can understand brown dwarfs well by analyzing the high-dispersion spectrum of brown dwarfs. Furthermore, analyzing the high-dispersion spectrum of brown dwarfs is becoming increasingly important as a prototype for the understanding of exoplanets in the future, because brown dwarfs have similar properties to young and warm exoplanets. As brown dwarfs are brighter and able to be precisely measured more than exoplanets, they can be also a test bed for establishing a method for characterizing exoplanets. However, studies analyzing the high-dispersion spectrum of brown dwarfs are still few and underdeveloped.
Here, we present the results and progress of the analysis of both near-infrared high-dispersion spectrum of Luhman16A and B(2.288-2.345 um, R~100,000), obtained by CRIRES on the Very Large Telescope, to characterize both brown dwarfs. Luhman16AB(WISE J104915.57−531906.1) is a close brown dwarf binary and both components are the nearest known brown dwarfs to the Sun(~2 pc from the Sun). Because both Luhman16A and B have been measured in a variety of ways(e.g. astrometry, Lazorenko et al., 2018), dynamics and physical parameters(e.g. mass) have been obtained precisely by a method that does not analyze the high-dispersion spectrum. Therefore, Luhman16A and B are important samples for establishing a method for analyzing the high-dispersion spectrum of brown dwarfs because we can compare the results of analyzing the high-dispersion spectrum of them with known values such as mass and so on. Both also have been known for their age so we can compare the results with the isochrone evolution of the brown dwarf(Gagne et al., 2023). We use the auto-differentiable spectral modeling tool, ExoJAX(Kawahara et al., 2022) for high dispersion characterization of Luhman16A and B.