High-resolution X-ray spectroscopy of the stellar wind in Vela X-1 during a flare
Journal Article
·
· Astronomy and Astrophysics
- Univ. College London (United Kingdom); ESA European Space Research and Technology Centre (ESTEC), Noordwijk (Netherlands)
- Eberhard Karls Univ. Tuebingen (Germany)
- ESA European Space Research and Technology Centre (ESTEC), Noordwijk (Netherlands)
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Univ. degli Studi Roma Tre, Rome (Italy)
- Univ. Erlangen-Nurnberg, Bamberg (Germany)
- European Space Astronomy Centre (ESAC), Madrid (Spain)
- Univ. de Alicante (Spain)
- Univ. de Cantabria, Santander (Spain). Inst. de Fisica de Cantabria
In this work, 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. 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. 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. 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. 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.
- Research Organization:
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- FEDER; Italian Space Agency; MCIU; USDOE National Nuclear Security Administration (NNSA)
- Grant/Contract Number:
- AC52-07NA27344
- OSTI ID:
- 1756722
- Report Number(s):
- LLNL-JRNL--805671; 1010838
- Journal Information:
- Astronomy and Astrophysics, Journal Name: Astronomy and Astrophysics Vol. 641; ISSN 0004-6361
- Publisher:
- EDP SciencesCopyright Statement
- Country of Publication:
- United States
- Language:
- English
X-ray observations from cosmic objects 4: stars
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