References of "Knapen, J. H"
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See detailSpectroscopic variability of two Oe stars
Rauw, Grégor ULg; Morel, Thierry ULg; Nazé, Yaël ULg et al

in Astronomy and Astrophysics (2015), 575

Context. The two Oe stars HD 45 314 and HD 60 848 have recently been found to exhibit very different X-ray properties: whilst HD 60 848 has an X-ray spectrum and the emission level typical of most OB ... [more ▼]

Context. The two Oe stars HD 45 314 and HD 60 848 have recently been found to exhibit very different X-ray properties: whilst HD 60 848 has an X-ray spectrum and the emission level typical of most OB stars, HD 45 314 features a much harder and brighter X-ray emission, making it a so-called γ Cas analogue. Aims: Monitoring the optical spectra could provide hints towards the origin of these very different behaviours. Methods: We analyse a large set of spectroscopic observations of HD 45 314 and HD 60 848, extending over 20 years. We further attempt to fit the Hα line profiles of both stars with a simple model of emission line formation in a Keplerian disk. Results: Strong variations in the strengths of the Hα, Hβ, and He i λ 5876 emission lines are observed for both stars. In the case of HD 60 848, we find a time lag between the variations in the equivalent widths of these lines, which is currently not understood. The emission lines are double peaked with nearly identical strengths of the violet and red peaks. The Hα profile of this star can be successfully reproduced by our model of a disk seen under an inclination of 30°. In the case of HD 45 314, the emission lines are highly asymmetric and display strong line profile variations. We find a major change in behaviour between the 2002 outburst and the one observed in 2013. This concerns both the relationship between the equivalent widths of the various lines and their morphologies at maximum strength (double-peaked in 2002 versus single-peaked in 2013). Our simple disk model fails to reproduce the observed Hα line profiles of HD 45 314. Conclusions: Our results further support the interpretation that Oe stars do have decretion disks similar to those of Be stars. Whilst the emission lines of HD 60 848 are explained well by a disk with a Keplerian velocity field, the disk of HD 45 314 seems to have a significantly more complex velocity field that could be another signature of the phenomenon that produces its peculiar X-ray emission. [less ▲]

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See detail2009: A Colliding-Wind Odyssey
Fahed, R.; Moffat, A. F. J.; Zorec, J. et al

in Astronomical Society of the Pacific Conference Series (2013, January 01)

We present the results from two optical spectroscopic campaigns on colliding-wind binaries (CWB) which both occurred in 2009. The first one was on WR 140 (WC7pd + O5.5fc), the archetype of CWB, which ... [more ▼]

We present the results from two optical spectroscopic campaigns on colliding-wind binaries (CWB) which both occurred in 2009. The first one was on WR 140 (WC7pd + O5.5fc), the archetype of CWB, which experienced periastron passage of its highly elliptical 8-year orbit in January. The WR 140 campaign consisted of a unique and constructive collaboration between amateur and professional astronomers and took place at half a dozen locations, including Teide Observatory, Observatoire de Haute Provence, Dominion Astrophysical Observatory, Observatoire du Mont-Mégantic and at several small private observatories. The second campaign was on a selection of 5 short-period WR + O binaries not yet studied for colliding-wind effects: WR 12 (WN8h), WR 21 (WN5o + O7 V), WR 30 (WC6 + O7.5 V), WR 31 (WN4o + O8), and WR 47 (WN6o + O5). The campaign took place at Leoncito Observatory, Argentina, during 1 month. We provide updated values of most of these systems for the orbital parameters, new estimates for the WR and O star masses and new constraints on the mass-loss rates and colliding wind geometry. [less ▲]

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See detailSpectroscopy of the archetype colliding-wind binary WR 140 during the 2009 January periastron passage
Fahed, R.; Moffat, A. F. J.; Zorec, J. et al

in Monthly Notices of the Royal Astronomical Society (2011), 418

We present the results from the spectroscopic monitoring of WR 140 (WC7pd + O5.5fc) during its latest periastron passage in 2009 January. The observational campaign consisted of a constructive ... [more ▼]

We present the results from the spectroscopic monitoring of WR 140 (WC7pd + O5.5fc) during its latest periastron passage in 2009 January. The observational campaign consisted of a constructive collaboration between amateur and professional astronomers. It took place at six locations, including Teide Observatory, Observatoire de Haute Provence, Dominion Astrophysical Observatory and Observatoire du Mont Mégantic. WR 140 is known as the archetype of colliding-wind binaries and it has a relatively long period (?8 yr) and high eccentricity (?0.9). We provide updated values for the orbital parameters, new estimates for the WR and O star masses and new constraints on the mass-loss rates and colliding-wind geometry. [less ▲]

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See detailThe WR 140 periastron passage 2009: first results from MONS and other optical sources
Fahed, R.; Moffat, A. F. J.; Zorec, J. et al

in Eversberg, Thomas; Knapen, Johan (Eds.) Stellar Winds in Interaction (2011, January 01)

We present the results from the spectroscopic follow-up of WR140 (WC7 + O4-5) during its last periastron passage in January 2009. This object is known as the archetype of colliding wind binaries and has a ... [more ▼]

We present the results from the spectroscopic follow-up of WR140 (WC7 + O4-5) during its last periastron passage in January 2009. This object is known as the archetype of colliding wind binaries and has a relatively large period (~ 8 years) and eccentricity (~ 0.89). We provide updated values for the orbital parameters, new estimates for the WR and O star masses and new constraints on the mass-loss rates. [less ▲]

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See detailThe Mons campaign on OB stars
Morel, Thierry ULg; Rauw, Grégor ULg; Eversberg, T. et al

in Bulletin de la Société Royale des Sciences de Liège (2011), 80

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