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A Far Ultraviolet Spectroscopic Explorer Survey of Late-Type Dwarf Stars

机译:远紫外光谱探测器对晚型矮星的观测

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摘要

We describe the 910-1180 ? spectra of seven late-type dwarf stars obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. The stars include Altair (A7 IV), Procyon (F5 IV-V), α Cen A (G2 V), AB Dor (K1 V), α Cen B (K2 V), Eri (K2 V), and AU Mic (M0 V). We present line identifications, fluxes, Doppler shifts, and widths. Doppler shifts are measured with respect to heliocentric wavelength scales determined from interstellar absorption lines, and are compared with transition region line shifts seen in Hubble Space Telescope (HST) ultraviolet spectra. For the warmer stars the O VI lines extend the trend of increasing redshift with line formation temperature, but for the cooler stars the O VI line redshifts are essentially zero. The C III and O VI lines of most stars in the sample are best fit with two Gaussians, and we confirm the correlation of increasing importance of the broad component with increasing stellar activity. The nonthermal velocities of the narrow component are subsonic and exhibit a trend toward larger velocities with decreasing surface gravity, while the nonthermal velocities of the broad components show no obvious trend with stellar gravity. The C III and O VI lines of Altair show unique broad horned profiles. Two flares were observed on AU Mic. One shows increasing continuum flux to shorter wavelengths, which we interpret as free-free emission from hot plasma, and relatively narrow, redshifted C III and O VI emission. The other shows very broad line profiles.
机译:我们描述910-1180吗?远紫外光谱浏览器(FUSE)卫星获得的七颗晚型矮星的光谱。星星包括Altair(A7 IV),Procyon(F5 IV-V),αCen A(G2 V),AB Dor(K1 V),αCen B(K2 V),Eri(K2 V)和AU Mic( M0 V)。我们介绍了线识别,通量,多普勒频移和宽度。针对从星际吸收线确定的日心波长尺度测量多普勒频移,并将其与在哈勃太空望远镜(HST)紫外光谱中看到的过渡区域线频移进行比较。对于较暖的恒星,O VI线会随着线形成温度而增加红移趋势,但对于较冷的恒星,O VI线的红移基本上为零。样品中大多数恒星的C III和O VI线最适合两个高斯,并且我们确认了广泛成分的重要性与恒星活动增加之间的相关性。窄分量的非热速度是亚音速的,并且随着表面重力的减小呈现出更大的速度趋势,而宽分量的非热速度随着恒星的重力没有明显的趋势。 Altair的C III和O VI线显示出独特的宽角轮廓。在AU Mic上观察到两个耀斑。一个显示出连续光通量增加到较短的波长,我们将其解释为热等离子体的自由自由发射,以及相对较窄的红移C III和O VI发射。另一个显示非常宽的线轮廓。

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