MBM 12 and MBM 16 distances

Дата и время публикации : 2012-02-16T14:21:32Z

Авторы публикации и институты :
J. Knude
H. E. P. Lindstrøm

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Первичная категория: astro-ph.GA

Все категории : astro-ph.GA

Краткий обзор статьи: Among the multitude of intrinsic SDSS index vs. index diagrams the $(g-r) vs. (r-i)$ diagram is characterized by showing only minor $(g-r)$ variation for the M dwarfs. The $(g-r) vs. (r-i)$ reddening vector has a slope almost identical to the slope of the main sequence earlier than $approx$M2, meaning that dwarfs later than $sim$M2 are not contaminated by reddened dwarfs of earlier type. Chemical composition, stellar activity and evolution have only minor effects on the location of the M2$-$M7 dwarfs in the $(g-r) vs. (r-i)$ diagram implying that reddening may be isolated in a rather unique way. From $r$, $M_{r,(r-i)_0}$ and $E_{g-r}$ we may construct distance vs. $A_r$ diagrams. This purely photometric method is applied on SDSS DR8 data in the MBM 12 region. We derive individual stellar distances with a precision $approx20-26$%. For extinctions in the $r-band$ the estimate is better than 0.2 mag for $approx 67%$ and between 0.3 and 0.4 for the remaining $approx 33%$. The extinction discontinuities noticed in the distance vs. $A_r$ diagrams suggest that MBM 12 is at $approx$160 pc and MBM 16 at a somewhat smaller distance $approx$100 pc. The distance for which $Delta (A_r)/sigma (Delta(A_r))$ = 3, where $Delta (A_r)$ refers to $bar{A_{r, on}}-bar{A_{r, off}}$, may possibly be used as an indicator for the cloud distance as well: For MBM 12 and 16 these distance estimates equal 160 and 100 pc, respectively

Category: Physics