High-resolution X-ray spectroscopy of the stellar wind in Vela X-1 during a flare
High-resolution X-ray spectroscopy of the stellar wind in Vela X-1 during a flare
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DOI：
10.1051/0004-6361/202037807
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发表时间：
2020-07
影响因子：
6.5
通讯作者：
M. Lomaeva;V. Grinberg;M. Guainazzi;Natalie Hell;S. Bianchi;M. Kühnel;F. Fürst;P. Kretschmar;M. Martínez-Chicharro;S. Martínez-Núñez;J. Torrejón
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文献类型：
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作者：
M. Lomaeva;V. Grinberg;M. Guainazzi;Natalie Hell;S. Bianchi;M. Kühnel;F. Fürst;P. Kretschmar;M. Martínez-Chicharro;S. Martínez-Núñez;J. Torrejón
上下文。我们对XMM-Newton在0.12和0.28之间的轨道相位上收集的典型的风吸积高质量x射线双星Vela X-1进行了~130 k的观测。在观测期间发生了一次强烈的耀斑，使我们能够研究团块恒星风对增加的x射线辐射的反应。目标。为了研究风对耀斑的反应，我们对RGS光谱进行了时间平均和时间分辨分析，并研究了潜在的光谱变化。方法。我们重点研究了XMM-Newton RGS的高分辨率光谱，并将观测分为耀斑前、耀斑后和耀斑后三个阶段。我们用现象学成分和在耀斑前阶段通过CLOUDY和XSTAR计算的自一致光电离模型对时间平均和时间分辨光谱进行了建模，在耀斑前阶段，由于高电离离子的共振跃迁，可以看到强发射线。结果。在光谱中，我们发现了与氧、氖、镁和硅等高电荷离子的k壳跃迁相对应的发射谱线，以及氧的辐射复合连续体（RRC）。此外，我们观察到镁在低电离阶段的潜在吸收谱线和铁L谱线的特征。CLOUDY和XSTAR光电离模型提供了相互矛盾的结果，要么指向理论上的不确定性，要么可能指向更复杂的多相等离子体，或者两者兼而有之。结论。我们能够证明大量可变窄特征的存在，包括对氧谱线和RRC的坚定检测，RGS首次能够在这个源中观察到。我们表明，Vela X-1是未来高分辨率任务的理想来源，如XRISM和雅典娜。
Context. We present a ~130 ks observation of the prototypical wind-accreting, high-mass X-ray binary Vela X-1 collected with XMM-Newton at orbital phases between 0.12 and 0.28. A strong flare took place during the observation that allows us to investigate the reaction of the clumpy stellar wind to the increased X-ray irradiation. Aims. To examine the wind’s reaction to the flare, we performed both time-averaged and time-resolved analyses of the RGS spectrum and examined potential spectral changes. Methods. We focused on the high-resolution XMM-Newton RGS spectra and divided the observation into pre-flare, flare, and post-flare phases. We modeled the time-averaged and time-resolved spectra with phenomenological components and with the self-consistent photoionization models calculated via CLOUDY and XSTAR in the pre-flare phase, where strong emission lines due to resonant transitions of highly ionized ions are seen. Results. In the spectra, we find emission lines corresponding to K-shell transitions in highly charged ions of oxygen, neon, magnesium, and silicon as well as radiative recombination continua (RRC) of oxygen. Additionally, we observe potential absorption lines of magnesium at a lower ionization stage and features identified as iron L lines. The CLOUDY and XSTAR photoionization models provide contradictory results, either pointing towards uncertainties in theory or possibly a more complex multi-phase plasma, or both. Conclusions. We are able to demonstrate the existence of a plethora of variable narrow features, including the firm detection of oxygen lines and RRC that RGS enables to observe in this source for the first time. We show that Vela X-1 is an ideal source for future high-resolution missions, such as XRISM and Athena.