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High-resolution X-ray spectroscopy of the stellar wind in Vela X-1 during a flare

Lomaeva M, Grinberg V, Guainazzi M, Hell N, Bianchi S, Bissinger M, Fürst F, Kretschmar P, Martínez-Chicharro M, Martínez-Núñez S, Torrejón JM (2020)

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Publication Type: Journal article

Publication year: 2020

Journal

Book Volume: 641

Article Number: A144

DOI: 10.1051/0004-6361/202037807

Abstract

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.

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APA:

Lomaeva, M., Grinberg, V., Guainazzi, M., Hell, N., Bianchi, S., Bissinger, M.,... Torrejón, J.M. (2020). High-resolution X-ray spectroscopy of the stellar wind in Vela X-1 during a flare. Astronomy & Astrophysics, 641. https://doi.org/10.1051/0004-6361/202037807

MLA:

Lomaeva, M., et al. "High-resolution X-ray spectroscopy of the stellar wind in Vela X-1 during a flare." Astronomy & Astrophysics 641 (2020).

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