Chandra spectral measurements of the O supergiant $ζ$ Puppis indicate a surprising increase in the wind mass-loss rate over 18 years
David H. Cohen, Jiaming Wang, Véronique Petit, Maurice A. Leutenegger, Lamiaa Dakir, Chloe Mayhue, Alexandre David-Uraz
备注：
Accepted by MNRAS. No longer a letter, but rather a nine page paper with several multi-panel figures showing all the line profiles. We have now included an analysis of the entire cycle 19 data set and present two model-independent confirmations of the line profile changes
New long Chandra grating observations of the O supergiant $ζ$ Pup show not only a brightening of the x-ray emission line flux of 13 per cent in the 18 years since Chandra's first observing cycle, but also clear evidence - at more than four sigma significance - of increased wind absorption signatures in its Doppler-broadened x-ray emission line profiles. We demonstrate this with non-parametric analysis of the profiles as well as Gaussian fitting and then use the line-profile model fitting to derive a mass-loss rate of $2.47 \pm 0.09 \times 10^{-6}$ Msun/yr, which is a 40 per cent increase over the value obtained from the cycle 1 data. The increase in the individual emission line fluxes is greater for short-wavelength lines than long-wavelength lines, as would be expected if a uniform increase in line emission is accompanied by an increase in the wavelength-dependent absorption by the cold wind in which the shock-heated plasma is embedded.
BRITE-Constellation high-precision time-dependent photometry of the early-O-type supergiant $ζ$ Puppis unveils the photospheric drivers of its small- and large-scale wind structures
从$5.5$月的双波段光学光度监测在$1$ mmag水平，BRITE星座揭示了两个同时类型的变化在O 4 I（n）fp星$ζ$船尾座：一个单一的周期性非正弦分量叠加在一个随机分量。单周期分量是先前由Coriolis/SMEI检测到的$1.78$ d信号，但这次与突出的第一谐波一起。这种信号的形状随着时间的推移而变化，这种行为与恒星振荡不相容，但与不断发展的明亮表面不均匀性所产生的旋转调制一致。通过约束非线性光变曲线反演算法，我们映射的亮表面斑点的位置，并跟踪其演变。我们同时对该恒星进行的地面多站点光谱监测揭示了其He II $\lambda4686$风发射线与$1.78$日旋转周期的周期性调制，显示了共转相互作用区（CIR）的特征，这些特征被证明是由BRITE观察到的明亮光球斑驱动的。在He II $\lambda4686$线中也观察到风团的痕迹，并与BRITE在光球探测的光变化的随机分量的振幅相关，这表明BRITE观测还揭示了$ζ$ Pup中风团的光球驱动因素，并且聚集现象始于风的最底部。明亮的表面不均匀性和随机光变化的起源仍然未知，但地下对流区可能在这两种类型的光球变化的产生中发挥重要作用。
Hidden massive eclipsing binaries in red supergiant systems: The hierarchical triple system KQ Puppis and other candidates
Masaryk University（马萨里克大学）；European Southern Observatory (ESO)（欧洲南方天文台）；Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences（孔科利天文台，匈牙利研究与创新科学院地球科学与天文学研究中心）；Eötvös Loránd University（罗兰大学）；Argelander-Institut für Astronomie（阿尔根德天体物理研究所）；Yunnan Observatories, Chinese Academy of Sciences (CAS)（中国科学院云南天文台）
A constant upper luminosity limit of cool supergiant stars down to the extremely low metallicity of I Zw 18
Argelander-Institut für Astronomie, Universität Bonn（波恩大学阿根兰德天文学研究所）；Institute of Science and Technology Austria (ISTA)（奥地利科学和技术研究所）；Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）；Department of Astronomy, The Oskar Klein Centre, Stockholm University（斯德哥尔摩大学奥斯卡·克莱因中心天文学系）；Department of Physics & Engineering Physics, Morgan State University（摩根州立大学物理与工程物理系）；Centro de Astrobiología (CSIC-INTA)（天体生物学中心（西班牙国家科学技术研究委员会-国家航空航天技术研究所））
