论文标题
绝对幅度$ m_j $，二进制分数和M7与M9.5矮人的二进制质量比
The absolute magnitudes $M_J$, the binary fraction, and the binary mass ratios of M7 to M9.5 dwarfs
论文作者
论文摘要
我们使用与$ \ textit {gaia} $ dr2相匹配的大型M矮人，M7至M9.5的大型同质样品，以测量绝对幅度和光谱类型之间的关系，并推断人口的多样性分数，以及在二进制系统中的质量比例分布。二进制文件在光度法上被鉴定为过度浮力的来源。为了定义相对于多重性公正的样本，我们使用距离$ g-j $颜色函数的距离限制来定义2706个系统的体积完整样本。 $ G-J $颜色非常精确，随机错误均小于0.02。我们测量的绝对幅度$ m_j $平均为0.5 mag。比以前的确定更明亮。我们发现证据表明差异是由于不同样品中光谱类型的差异引起的。测得的二进制分数为$ 16.5 \ pm0.8 \％$，其中$ 98 \％$尚未解决：这两个值都与以前的研究结果一致。与单打相比，二进制文件中多余通量的分布用于推断质量比分布$ f（q）\ propto q^γ$，其中$ q = m_s/m_p $。我们在此光谱范围内推断出非常陡峭的分布，其中$γ> 10 $（$ 99 \％$概率）。这说明未解决的超级矮化二进制文件几乎完全存在于相等的质量系统中，这意味着未解决的二进制文件的光谱类型与0.5个光谱亚型匹配。以固定的$ g-j $颜色为0.21 mag，以绝对幅度的$ m_j $中的固有散布$ m_j $。
We use the large homogeneous sample of late M dwarfs, M7 to M9.5, of Ahmed & Warren (2019) matched to $\textit{Gaia}$ DR2, to measure the relation between absolute magnitude and spectral type, and to infer the multiplicity fraction of the population, and the distribution of mass ratios in the binary systems. Binaries are identified photometrically as overluminous sources. In order to define a sample that is unbiased with respect to multiplicity we use distance limits that are a function of $G-J$ colour to define a volume-complete sample of 2706 systems. The $G-J$ colours are very precise, with random errors all less than 0.02. We measure absolute magnitudes $M_J$ that are on average 0.5 mag. brighter than previous determinations. We find evidence that the discrepancies arise from differences in spectral types in different samples. The measured binary fraction is $16.5\pm0.8\%$, of which $98\%$ are unresolved: both values are consistent with results of previous studies. The distribution of excess flux in the binaries, compared to the singles, is used to infer the mass ratio distribution $f(q)\propto q^γ$, where $q=M_s/M_p$. We infer a very steep distribution over this spectral range, with $γ>10$ ($99\%$ probability). This says that unresolved ultracool M dwarf binaries reside almost exclusively in equal mass systems, and implies that the spectral types of the unresolved binaries match to with 0.5 spectral subtypes. The intrinsic scatter in absolute magnitude $M_J$ for ultracool M dwarfs at fixed $G-J$ colour is measured to be 0.21 mag.
