论文标题
A型恒星中的冠状和色球发射
Coronal and chromospheric emission in A-type stars
论文作者
论文摘要
主序列上的酷星会产生由对流发电机提供动力的冠状活动的X射线。随着温度的升高，对流包膜变小，X射线发射器淡淡。我们介绍了四个具有早期频谱类型的单颗恒星的Chandra/HRC-I观察结果。只有此样品中最酷的恒星，$τ^3 $ eri（$ t_ \ mathrm {eff} \ log（l_x/l_ \ mathrm {bolm {bol}）= -7.6 $，而三个热星（$ t_ \ mathrm k） $δ$ leo，$β$ leo和$ b cen尚未发现上限$ \ log（l_x/l_ \ mathrm {bol}）<-8.4 $。因此，X射线发射的下降发生在$ \ sim 8100 $ k左右的狭窄有效温度范围内，并与C III和O VI过渡区域线中的活性下降相匹配。
Cool stars on the main sequence generate X-rays from coronal activity, powered by a convective dynamo. With increasing temperature, the convective envelope becomes smaller and X-ray emission fainter. We present Chandra/HRC-I observations of four single stars with early A spectral types. Only the coolest star of this sample, $τ^3$ Eri ($T_\mathrm{eff}\approx8\,,000$ K), is detected with $\log(L_X/L_\mathrm{bol})=-7.6$ while the three hotter stars ($T_\mathrm{eff}\geq8\,,000$ K), namely $δ$ Leo, $β$ Leo, and $ι$ Cen, remain undetected with upper limits $\log(L_X/L_\mathrm{bol})<-8.4$. The drop in X-ray emission thus occurs in a narrow range of effective temperatures around $\sim 8100$ K and matches the drop of activity in the C III and O VI transition region lines.
