Quanz and coworkers have reported the discovery of the coolest known member of the Taurus star-forming complex (L2+/-0.5) and Barrado and coworkers have identified a possible protostellar binary brown dwarf in the same region. We have performed infrared spectroscopy on the former and the brighter component of the latter to verify their substellar nature. The resulting spectra do not exhibit the strong steam absorption bands that are expected for cool objects, demonstrating that they are not young brown dwarfs. The optical magnitudes and colors for these sources are also indicative of background stars rather than members of Taurus. Although the fainter component of the candidate protostellar binary lacks spectroscopy, we conclude that it is a galaxy rather than a substellar member of Taurus based on its colors and the constraints on its proper motion.
We report our study of two proto-brown dwarf candidates in Taurus, [GKH94]~41 and IRAS~04191+1523B. Based on continuum maps at 102~GHz (or 2.9~mm), spectral types and the spectral energy distribution of both targets, we confirmed the class I evolutionary stage of [GKH94]~41 and IRAS~04191+1523B, and estimated the upper limit to the final masses to be 49$^{+56}_{-27}$~$M_{\rm J}$ and 75$^{+40}_{-26}$~$M_{\rm J}$ for [GKH94]~41 and IRAS~04191+1523B, respectively. This indicates that they will likely end up as brown dwarfs or very low-mass stars. The existence of these class I very low-mass objec…
Whether BDs form as stars through gravitational collapse ("star-like") or BDs and some very low-mass stars constitute a separate population which form alongside stars comparable to the population of planets, e.g. through circumstellar disk ("peripheral") fragmentation, is one of the key questions of the star-formation problem. For young stars in Taurus-Auriga the binary fraction is large with little dependence on primary mass above ~0.2Msun, while for BDs it is <10%. We investigate a case in which BDs in Taurus formed dominantly through peripheral fragmentation. The decline of the binary frequ…
We are conducting a proper-motion survey for young brown dwarfs in the Taurus-Auriga molecular cloud based on the Pan-STARRS1 3$π$ Survey. Our search uses multi-band photometry and astrometry to select candidates, and is wider (370 deg$^{2}$) and deeper (down to $\approx$3 M$_{\rm Jup}$) than previous searches. We present here our search methods and spectroscopic follow-up of our high-priority candidates. Since extinction complicates spectral classification, we have developed a new approach using low-resolution ($R \approx 100$) near-infrared spectra to quantify reddening-free spectral types, …
Discovery of a Wide Binary Brown Dwarf Born in Isolation
在使用斯皮策太空望远镜对金牛座恒星形成区中具有圆盘的恒星进行调查期间，我们在巴纳德215暗云中发现了一对年轻的棕矮星FU Tau A和B。它们的投影角距为5.7”，相当于金牛座距离的800 AU。为了评估这两个对象的性质，我们已经获得了它们的光谱，并构建了它们的光谱能量分布。这两个来源都是年轻的（~ 100万年），根据他们的阿尔法发射，重力敏感的光谱特征，和中红外过量发射。FU Tau A的自行提供了它属于金牛座的额外证据。根据Chabrier和Baraffe的演化模型，我们分别测量了FU Tau A和B的M7.25和M9.25的光谱类型，其对应于~0.05和~0.015 M \cdot的质量。相对于通过FU Tau B的等时线，以及相对于金牛座光谱类型附近的其他成员，FU Tau A显着过亮，这可能表明它是一个无法解析的双星。基于金牛座产生两颗不相关的棕矮星的概率很低（~ 3x 10 ^-4），预测的距离为a </- 6”，FU Tau A和B很可能是一个双星系统的组成部分。巴纳德215只包含另一颗年轻恒星，位于金牛座的偏远地区，使FU Tau A和B成为第一颗被光谱证实的褐矮星，它们是孤立形成的，而不是在星团或聚集体中形成的。由于它们是孤立诞生的，并且是一个弱束缚的双星，与恒星的动力学相互作用在它们的形成中不可能发挥作用，因此对褐矮星的诞生来说不是必不可少的。勘误：表1中FU …
We present the initial results from a survey for planetary-mass brown dwarfs in the Taurus star-forming region. We have identified brown dwarf candidates in Taurus using proper motions and photometry from several ground- and space-based facilities. Through spectroscopy of some of the more promising candidates, we have found 18 new members of Taurus. They have spectral types ranging from mid M to early L and they include the four faintest known members in extinction-corrected K_s, which should have masses as low as ~4-5 M_Jup according to evolutionary models. Two of the coolest new members (M9.…
The formation scenario of brown dwarfs is still unclear because observational studies to investigate its initial condition are quite limited. Our systematic survey of nearby low-mass star-forming regions using the Atacama Compact Array (aka Morita array) and the IRAM 30 m telescope in 1.2 mm continuum has identified a centrally concentrated starless condensation with a central H$_2$ volume density of $\sim$10$^6$ cm$^{-3}$, MC5-N, connected to a narrow (width $\sim$0.03 pc) filamentary cloud in the Taurus L1495 region. The mass of the core is $\sim$0.2-0.4 $M_{\odot}$, which is an order of mag…
Wide-field near-infrared (NIR) polarimetry was used to examine disk systems around two brown dwarfs (BD) and two young stellar objects (YSO) embedded in the Heiles Cloud 2 (HCl2) dark molecular cloud in Taurus as well as numerous stars located behind HCl2. Inclined disks exhibit intrinsic NIR polarization due to scattering of photospheric light which is detectable even for unresolved systems. After removing polarization contributions from magnetically aligned dust in HCl2 determined from the background star information, significant intrinsic polarization was detected from the disk systems of o…
OGLE-2016-BLG-0523: A Low-mass Brown Dwarf or super-Jupiter in a $>100$ au Orbit
Westlake University（西湖大学）；Korea Astronomy and Space Science Institute（韩国天文学与空间科学研究所）；Astronomical Observatory, University of Warsaw（华沙大学天文台）；University of Canterbury（坎特伯雷大学）；Max-Planck-Institute for Astronomy（马克斯·普朗克天体物理学研究所）；Department of Astronomy, Ohio State University（俄亥俄州立大学天文学系）；Department of Physics, Chungbuk National University（忠北国立大学物理系）；National University of Science and Technology (UST)（韩国科学技术院）
