arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2006.13835astro-ph.HEastro-ph.GA
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活动星系核吸积盘中的暖日冕

Sustaining a Warm Corona in Active Galactic Nuclei Accretion Discs

D. R. Ballantyne, X. Xiang

摘要:

活动星系核(AGN)吸积盘表面存在温度为$\sim 1$ keV的厚($τ_{\mathrm{T}}\approx 10$ - $20$,其中$τ_{\mathrm{T}}$为汤姆逊深度)康普顿化区。通过与反射光谱相结合,暖日冕可能是产生活动星系核X射线光谱中所见的平滑软过剩的原因。本文研究如何温暖的日冕必须调整,以维持软过剩通过大的变化,活动星系核通量。光谱从一维恒定密度和流体静力学温暖的日冕模型计算假设照明硬X射线幂律,气体密度,汤姆逊深度和日冕加热强度变化的吸积率的变化。我们确定的模型,产生温暖的日冕与温度之间的$0.3$和$1.1$千电子伏,并测量光子指数和发射通量的$0.5$ - $2$千电子伏和$2$ - $10$千电子伏波段。这些量之间的相关性和反相关性取决于暖日冕的演化和结构。通过这些相关性追踪活动星系核所遵循的路径,将限制温暖的日冕被加热和连接到吸积盘的程度。暖日冕的密度结构和日冕加热强度的变化将导致活动星系核中各种各样的软过剩强度和形状。平均而言,较大的吸积率将导致温暖的日冕,产生更强的软过剩,与当地塞弗特星系的观测一致。

英文摘要:

Warm coronae, thick ($τ_{\mathrm{T}}\approx 10$-$20$, where $τ_{\mathrm{T}}$ is the Thomson depth) Comptonizing regions with temperatures of $\sim 1$ keV, are proposed to exist at the surfaces of accretion discs in active galactic nuclei (AGNs). By combining with the reflection spectrum, warm coronae may be responsible for producing the smooth soft excess seen in AGN X-ray spectra. This paper studies how a warm corona must adjust in order to sustain the soft excess through large changes in the AGN flux. Spectra from one-dimensional constant density and hydrostatic warm coronae models are calculated assuming the illuminating hard X-ray power-law, gas density, Thomson depth and coronal heating strength vary in response to changes in the accretion rate. We identify models that produce warm coronae with temperatures between $0.3$ and $1.1$ keV, and measure the photon indices and emitted fluxes in the $0.5$-$2$ keV and $2$-$10$ keV bands. Correlations and anti-correlations between these quantities depend on the evolution and structure of the warm corona. Tracing the path that an AGN follows through these correlations will constrain how warm coronae are heated and connected to the accretion disc. Variations in the density structure and coronal heating strength of warm coronae will lead to a variety of soft excess strengths and shapes in AGNs. A larger accretion rate will, on average, lead to a warm corona that produces a stronger soft excess, consistent with observations of local Seyfert galaxies.

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