INNOCENT BYSTANDERS: CARBON STARS FROM THE SLOAN DIGITAL SKY SURVEY
INNOCENT BYSTANDERS: CARBON STARS FROM THE SLOAN DIGITAL SKY SURVEY
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DOI：
10.1088/0004-637x/765/1/12
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发表时间：
2013-01
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影响因子：
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通讯作者：
P. Green
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作者：
P. Green
在显示碳分子带的恒星（C星）中，主序矮星（可能存在于质量转移后的双星中）在银河系中在数量上占主导地位。通过斯隆数字巡天的光谱选择，我们检索到了 1220 颗高银河纬度 C 星，比之前已知的多约 5 倍，其中包括比颜色或棱镜选择等过去技术所捕获的种类更广泛的恒星，此外还获得了 167 颗 DQ 白矮星。在进行自行测量的 C 星中，我们清楚地识别出 69% 为矮星 (dC)，而 ∼7% 为巨星。 dC 的绝对星等 Mi 的范围可能从 ∼6.5 到 10.5。具有弱 CN 和相对蓝色的“G 型”dC 星可能是质量最大的 dC，但仍然足够冷以显示 C2 带。我们报告了 22 个 dC 的巴尔默发射，其中没有一个是 G 型的。我们在复合光谱双星中发现了 8 颗新的 DA/dC 恒星，使这些 AGB 双星质量传递的“铁证”样本总数增加了四倍。 11 颗具有强烈红色 CN 带的非常红的 C 星似乎是距离银心距离较远的“N”型 AGB 星，其中一颗可能是 dIrr 星系 Leo A 中的新发现。两颗彼此相距 30 英尺以内的此类恒星可能追踪先前未识别的矮星系或~40 kpc 的潮汐流。我们探索了样本的多波长特性，并报告了对 dC 星的首次 X 射线探测，该星显示出强烈的巴尔默发射。我们自己的光谱调查还提供了受星等、颜色和自行限制的完整矮星样本的直流表面密度。
Among stars showing carbon molecular bands (C stars), the main-sequence dwarfs, likely in post-mass transfer binaries, are numerically dominant in the Galaxy. Via spectroscopic selection from the Sloan Digital Sky Survey, we retrieve 1220 high galactic latitude C stars, ∼5 times more than previously known, including a wider variety than past techniques such as color or grism selection have netted, and additionally yielding 167 DQ white dwarfs. Of the C stars with proper motion measurements, we identify 69% clearly as dwarfs (dCs), while ∼7% are giants. The dCs likely span absolute magnitudes Mi from ∼6.5 to 10.5. “G-type” dC stars with weak CN and relatively blue colors are probably the most massive dCs still cool enough to show C2 bands. We report Balmer emission in 22 dCs, none of which are G-types. We find 8 new DA/dC stars in composite spectrum binaries, quadrupling the total sample of these “smoking guns” for AGB binary mass transfer. Eleven very red C stars with strong red CN bands appear to be “N”-type AGB stars at large Galactocentric distances, one likely a new discovery in the dIrr galaxy Leo A. Two such stars within 30′ of each other may trace a previously unidentified dwarf galaxy or tidal stream at ∼40 kpc. We explore the multiwavelength properties of the sample and report the first X-ray detection of a dC star, which shows strong Balmer emission. Our own spectroscopic survey additionally provides the dC surface density from a complete sample of dwarfs limited by magnitude, color, and proper motion.