References of "Pollock, A. M. T"
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See detailSimultaneous X-ray and Optical Variability Study of the O-star Binary delta Orionis with Chandra and MOST
Nichols, Joy; Moffat, Anthony F. J.; Ignace, Richard et al

in Massive Stars: From alpha to Omega (2013, June 01)

We report preliminary results from variability analysis of delta Ori in Chandra high-resolution X-ray spectroscopy and concurrent MOST high-precision optical photometry. With nearly complete phase ... [more ▼]

We report preliminary results from variability analysis of delta Ori in Chandra high-resolution X-ray spectroscopy and concurrent MOST high-precision optical photometry. With nearly complete phase coverage of the 5-day eclipsing binary orbit, it is possible to measure directly radial velocity and flux variations as a function of phase, leading to a mapping of the stellar wind distribution for the massive primary star. The phase dependence of the X-ray overall intensity and the comparative behavior of the emission lines are also presented. [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 detailXMM-Newton observation of the enigmatic object WR 46
Gosset, Eric ULg; De Becker, Michaël ULg; Nazé, Yaël ULg et al

in Astronomy and Astrophysics (2011), 527

Aims: To further investigate the nature of the enigmatic object WR 46 and better understand the X-ray emission in massive stars and in their evolved descendants, we observed this variable object for more ... [more ▼]

Aims: To further investigate the nature of the enigmatic object WR 46 and better understand the X-ray emission in massive stars and in their evolved descendants, we observed this variable object for more than two of its supposed cycles. The X-ray emission characteristics are appropriate indicators of the difference between a genuine Wolf-Rayet star and a specimen of a super soft source as sometimes suggested in the literature. The X-ray emission analysis might contribute to understanding the origin of the emitting plasma (intrinsically shocked wind, magnetically confined wind, colliding winds, and accretion onto a white dwarf or a more compact object) and to substantiating the decision about the exact nature of the star. <BR /> Methods: The X-ray observations of WR 46 were performed with the XMM-Newton facility over an effective exposure time of about 70 ks. <BR /> Results: Both the X-ray luminosity of WR 46, typical of a Wolf-Rayet star, and the existence of a relatively hard component (including the Fe-K line) rule out the possibility that WR 46 could be classified as a super soft source, and instead favour the Wolf-Rayet hypothesis. The X-ray emission of the star turns out to be variable below 0.5 keV but constant at higher energies. The soft variability is associated to the Wolf-Rayet wind, but revealing its deep origin necessitates additional investigations. It is the first time that such a variability is reported for a Wolf-Rayet star. Indeed, the X-ray emission exhibits a single-wave variation with a typical timescale of 7.9 h which could be related to the period observed in the visible domain both in radial velocities (single-wave) and in photometry (double-wave). The global X-ray emission seems to be dominated by lines and is closely reproduced by a three-temperature, optically thin, thermal plasma model. The derived values are 0.1-0.2 keV, 0.6 keV, and ~4 keV, which indicates that a wide range of temperatures is actually present. The soft emission part could be related to a shocked-wind phenomenon. The hard tail of the spectrum cannot presently be explained by such an intrinsic phenomenon as a shocked wind and instead suggests there is a wind-wind collision zone, as does the relatively high L[SUB]X[/SUB]/L[SUB]bol[/SUB] ratio. We argue that this scenario implies the existence of an object farther away from the WN3 object than any possible companion in an orbit related to the short periodicity. Based on observations with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA). [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 detailSpectroscopic follow-up of the colliding-wind binary WR140 during the 2009 January periastron passage
Fahed, R.; Moffat, A. F. J.; Zorec, J. et al

in Bulletin de la Societe Royale des Sciences de Liege (2011), 80

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 (≃0.9). 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. [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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See detailNew insights into the nature of the SMC WR/LBV binary HD 5980
Foellmi, C.; Koenigsberger, G.; Georgiev, L. et al

in Revista Mexicana de Astronomía y Astrofísica (2008), 44(1), 3-27

We present the results of optical wavelength observations of the unusual SMC eclipsing binary system HD 5980 obtained in 1999 and 2004-2005. Radial velocity curves for the erupting LBV/WR object (star A ... [more ▼]

We present the results of optical wavelength observations of the unusual SMC eclipsing binary system HD 5980 obtained in 1999 and 2004-2005. Radial velocity curves for the erupting LBV/WR object (star A) and its close WR-like companion (star B) are obtained by deblending the variable emission-line profiles of NIV and NV lines. The derived masses M-A = 58 - 79 M-circle dot and M-B = 51 - 67 M-circle dot, are more consistent with the the stars' location near the top of the HRD than previous estimates. The presence of a wind-wind interaction region is inferred from the orbital phase-dependent behavior of He I P Cygni absorption components. The emission-line intensities continued with the declining trend previously seen in UV spectra. The behavior of the photospheric absorption lines is consistent with the results of Schweickhardt (2000) who concludes that the third object in the combined spectrum, star C, is also a binary system with P-starC similar to 96.5 days, e=0.83. [less ▲]

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See detailHD 148937: A multiwavelength study of the third galactic member of the Of?p class
Nazé, Yaël ULg; Walborn, Nolan R.; Rauw, Grégor ULg et al

in Astronomical Journal (The) (2008), 135(5), 1946-1957

Three Galactic O-type stars belong to the rare class of Of? p objects: HD 108, HD 191612, and HD 148937. The first two stars show a wealth of phenomena, including strong X-ray emission, light variability ... [more ▼]

Three Galactic O-type stars belong to the rare class of Of? p objects: HD 108, HD 191612, and HD 148937. The first two stars show a wealth of phenomena, including strong X-ray emission, light variability, and dramatic periodic spectral variability. We present here the first detailed optical and X-ray study of the third Galactic Of? p star, HD 148937. Spectroscopic monitoring has revealed low-level variability in the Balmer and He II lambda 4686 lines, but constancy at He I and C III lambda 4650. The H alpha line exhibits profile variations at a possible periodicity of similar to 7 days. Model atmosphere fits yield T-eff = 41000 +/- 2000 K, log(g) = 4.0 +/- 0.1, M-sph less than or similar to 10(-7) M-circle dot yr(-1), and an overabundance of nitrogen by a factor of 4. At X-ray wavelengths, HD 148937 resembles HD 108 and HD 191612 in having a thermal spectrum dominated by a relatively cool component (kT = 0.2 keV), broad lines (>= 1700 km s(-1)), and an order-of-magnitude overluminosity compared to normal O stars (log[L-X(unabs) / L-BOL]similar to -6). [less ▲]

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