从热彗星的大气逃逸
Atmospheric Escape from Hot Jupiters
摘要：
来自入射到热彗星大气层上的紫外线辐射的光电离加热可能会导致行星质量损失。我们构建了一个逃逸模型，其中包括现实的加热和冷却，电离平衡，潮汐引力和压力约束的主机星风。我们表明，质量损失的形式，流体动力学（“帕克”）风，从行星的向阳面在恒星风的间歇期间发出。当昼侧风被恒星风的限制作用抑制时，如果有足够的热量水平输送，夜侧风可能会增加。一颗热木星在主序星前阶段的最大质量损失率约为2 x 10^12 g/s，在主序星寿命期间约为2 x 10^10 g/s，总的最大损失率分别约为行星质量的0.06%和0.6%。当紫外线通量F_UV < 10^4 erg/cm^2/s时，质量损失率近似为能量极限，与F_UV ^0.9成正比。对于更大的紫外线通量，例如金牛座T星的典型特征，辐射损失和等离子体复合迫使质量损失率以F_UV ^[0.6]的速度缓慢增加。在金牛座T星的相位期间，昼侧风被熄灭，因为受到压倒性的恒星风压的限制。我们的结论是，虽然紫外线辐射确实可以驱动风从炎热的彗星，这样的风不能显着改变行星的质量在任何进化阶段。然而，它们可以产生可观察的签名。解释HD 209458的莱曼α光子在多普勒频移速度为+/- 100 km/s时被吸收的候选者包括行星风和恒星风之间的激波中的电荷交换。
英文摘要：
Photoionization heating from UV radiation incident on the atmospheres of hot Jupiters may drive planetary mass loss. We construct a model of escape that includes realistic heating and cooling, ionization balance, tidal gravity, and pressure confinement by the host star wind. We show that mass loss takes the form of a hydrodynamic ("Parker") wind, emitted from the planet's dayside during lulls in the stellar wind. When dayside winds are suppressed by the confining action of the stellar wind, nightside winds might pick up if there is sufficient horizontal transport of heat. A hot Jupiter loses mass at maximum rates of ~2 x 10^12 g/s during its host star's pre-main-sequence phase and ~2 x10^10 g/s during the star's main sequence lifetime, for total maximum losses of ~0.06% and ~0.6% of the planet's mass, respectively. For UV fluxes F_UV < 10^4 erg/cm^2/s, the mass loss rate is approximately energy-limited and is proportional to F_UV^0.9. For larger UV fluxes, such as those typical of T Tauri stars, radiative losses and plasma recombination force the mass loss rate to increase more slowly as F_UV^0.6. Dayside winds are quenched during the T Tauri phase because of confinement by overwhelming stellar wind pressure. We conclude that while UV radiation can indeed drive winds from hot Jupiters, such winds cannot significantly alter planetary masses during any evolutionary stage. They can, however, produce observable signatures. Candidates for explaining why the Lyman-alpha photons of HD 209458 are absorbed at Doppler-shifted velocities of +/- 100 km/s include charge-exchange in the shock between the planetary and stellar winds.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
