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See detailHD 150136: towards one of the most massive systems?
Mahy, Laurent ULg; Gosset, Eric ULg; Sana, Hugues et al

in Neiner, Coralie; Wade, G.; Meynet, G. (Eds.) et al Active OB stars: structure, evolution, mass loss and critical limits (2011, July 01)

We present the preliminary results of an intensive monitoring devoted to HD 150136. Already quoted as an O3+O6 binary, we detected a third O-type component physically linked to the system, making it one ... [more ▼]

We present the preliminary results of an intensive monitoring devoted to HD 150136. Already quoted as an O3+O6 binary, we detected a third O-type component physically linked to the system, making it one of the nearest (1.3 kpc) most massive systems known until now (~134M[SUB]solar[/SUB]). To determine the physical parameters of this system, we applied a disentangling program to study individually the three components. It allows us to constrain their spectral types and to derive a new orbital solution for the short-period system. [less ▲]

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See detailHD 150136: towards one of the most massive systems?
Mahy, Laurent ULg; Gosset, Eric ULg; Rauw, Grégor ULg et al

Poster (2010)

The improvement of the astronomical instrumentation allowed scientists to develop new analysis techniques to investigate binary and multiple stars. In this context, we present the preliminary results of ... [more ▼]

The improvement of the astronomical instrumentation allowed scientists to develop new analysis techniques to investigate binary and multiple stars. In this context, we present the preliminary results of an intense monitoring devoted to the triple system, HD 150136. Supposed to be the nearest O3 star (1.3 kpc), this object is also composed of two other early O-type stars, making it one of the most massive systems known until now (~ 134Mʘ). This multiple star is a non-thermal radio emitter and presents a colliding wind interaction zone. To determine the physical parameters of this system, we applied a disentangling program to study individually the three components. It allows us to revise their spectral classification and to derive a new orbital solution for the short-period system but also the first one for the entire system. [less ▲]

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See detailHD 151932 variability revisited
Vreux, Jean-Marie ULg; Manfroid, Jean ULg; Scuflaire, Richard ULg et al

in Astronomy and Astrophysics (1987), 180

The observation of variations in the blue absorption component of the He I lines as well as in the Si IV 4089 emission line of HD 151932 is reported. Possible explanations for these variations are ... [more ▼]

The observation of variations in the blue absorption component of the He I lines as well as in the Si IV 4089 emission line of HD 151932 is reported. Possible explanations for these variations are addressed, and it is concluded that none is satisfactory. The possibility of a periodicity in the variations is briefly considered. [less ▲]

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See detailHD 152248: Evidence for a colliding wind interaction
Sana, H.; Rauw, Grégor ULg; Gosset, Eric ULg

in Astronomy and Astrophysics (2001), 370

We present the results of a four year spectroscopic campaign on the early-type binary system HD 152248. Our analysis yields a new classification as O7.5III(f) + O7III(f), in contradiction with previous ... [more ▼]

We present the results of a four year spectroscopic campaign on the early-type binary system HD 152248. Our analysis yields a new classification as O7.5III(f) + O7III(f), in contradiction with previous classifications of the components as supergiants. We derive improved orbital elements and the corresponding masses (M_1=29.6 M[SUB]sun[/SUB] and M_2=29.9 M[SUB]sun[/SUB]) are somewhat larger than previously reported in the literature, although they are still significantly lower than the ones expected from evolutionary tracks. Both components of the system are close to filling their Roche lobe at periastron passage. We also investigate the equivalent width variations of the lines of the two components and we discuss their relation to the Struve-Sahade effect. Finally, we show that the line profile variability of the He Iil4686 and Halpha lines is consistent with a strong wind interaction between the two stars, quite as predicted by current colliding wind models. Based on data collected at the European Southern Observatory (La Silla, Chile) and at the Cerro Tololo Inter-American Observatory (Cerro Tololo, Chile). [less ▲]

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See detailHD 166181 = V815 Herculis, a Single-lined Spectroscopic Multiple System
Fekel, Francis C.; Barlow, D. J.; Scarfe, C. D. et al

in Astronomical Journal (The) (2005), 129

We have obtained extensive spectroscopic and velocity spectrometer observations of HD 166181, a previously known single-lined spectroscopic binary. Our improved orbit for the G6 V primary has a period of ... [more ▼]

We have obtained extensive spectroscopic and velocity spectrometer observations of HD 166181, a previously known single-lined spectroscopic binary. Our improved orbit for the G6 V primary has a period of 1.8098343 days and is circular. Although the lines of additional components have not been detected, radial velocity measurements confirm that the system has additional velocity variations with a period of 2092 days, or 5.73 yr. This long-period orbit has an eccentricity of 0.76. An analysis of the Hipparcos observations produces a well-determined astrometric orbit for the long-period system that has an inclination of 78°. Mass estimates of the components in this zero-age main-sequence multiple system indicate that the unseen secondary in the 5.73 yr orbit may also be a binary. Thus, HD 166181 is at least a triple system and possibly quadruple. [less ▲]

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See detailHD 167362, an object similar to Campbell's Hydrogen Envelope Star
Swings, Polydore ULg; Struve, Otto

in Proceedings of the National Academy of Sciences of the United States of America (1940), 26

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See detailHD 172256 Revisited
Heck, A.; Manfroid, Jean ULg; Percy, J. R.

in Information Bulletin on Variable Stars (1984), 2501

Not Available

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See detailHD 174884: a strongly eccentric, short-period early-type binary system discovered by CoRoT
Maceroni, C.; Montalban Iglesias, Josefa ULg; Michel, E. et al

in Astronomy and Astrophysics (2009), 508

Accurate photometric CoRoT space observations of a secondary seismological target, HD 174884, led to the discovery that this star is an astrophysically important double-lined eclipsing spectroscopic ... [more ▼]

Accurate photometric CoRoT space observations of a secondary seismological target, HD 174884, led to the discovery that this star is an astrophysically important double-lined eclipsing spectroscopic binary in an eccentric orbit (eË 0.3), unusual for its short 3.65705° orbital period. The high eccentricity, coupled with the orientation of the binary orbit in space, explains the very unusual observed light curve with strongly unequal primary and secondary eclipses having the depth ratio of 1-to-100 in the CoRoT â seismoâ passband. Without the high accuracy of the CoRoT photometry, the secondary eclipse, 1.5 mmag deep, would have gone unnoticed. A spectroscopic follow-up program provided 45 high dispersion spectra. The analysis of the CoRoT light curve was performed with an adapted version of PHOEBE that supports CoRoT passbands. The final solution was obtained by a simultaneous fitting of the light and the radial velocity curves. Individual star spectra were obtained by spectrum disentangling. The uncertainties of the fit were achieved by bootstrap resampling and the solution uniqueness was tested by heuristic scanning. The results provide a consistent picture of the system composed of two late B stars. The Fourier analysis of the light curve fit residuals yields two components, with orbital frequency multiples and an amplitude of ~0.1 mmag, which are tentatively interpreted as tidally induced pulsations. An extensive comparison with theoretical models is carried out by means of the Levenberg-Marquardt minimization technique, and the discrepancy between the models and the derived parameters is discussed. The best fitting models yield a young system age of 125 million years which is consistent with the eccentric orbit and synchronous component rotation at periastron. Based on photometry collected by the CoRoT space mission and spectroscopy obtained with the CORALIE spectrograph attached to the 1.2 m Euler telescope at ESO, La Silla, Chile. The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programs, Austria, Belgium, Brazil, Germany and Spain. Postdoctoral fellow of the Fund for Scientific Research of Flanders (FWO). [less ▲]

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See detailHD 192163 variability revisited - A very short period WR binary or a pulsating star?
Vreux, Jean-Marie ULg; Andrillat, Y.; Gosset, Eric ULg

in Astronomy and Astrophysics (1985), 149

The present reexamination of emission line variations in HD 192163 on the basis of 23 spectra takes into account stratification effects in the atmosphere of the WR stars, as well as the necessity for a ... [more ▼]

The present reexamination of emission line variations in HD 192163 on the basis of 23 spectra takes into account stratification effects in the atmosphere of the WR stars, as well as the necessity for a high N/R ratio. Because of the peculiar shape of the profiles, the wavelength shifts are measured by comparing the position of every observation to a nearly noise-free profile that is taken as reference. The most probable period supported by the present data is either 0.45 or 0.31 days; these two periods are one-day aliases of each other. [less ▲]

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See detailHD 203608, a quiet asteroseismic target in the old galactic disk
Mosser, B.; Deheuvels, S.; Michel, Eric et al

in Astronomy and Astrophysics (2008), 488

Context: We conducted a 5-night observing run with the spectrometer harps at the ESO 3.6-m telescope in August 2006, to continue exploring the asteroseismic properties of F-type stars. In fact, Doppler ... [more ▼]

Context: We conducted a 5-night observing run with the spectrometer harps at the ESO 3.6-m telescope in August 2006, to continue exploring the asteroseismic properties of F-type stars. In fact, Doppler observations of F-type on the main sequence are demanding and remain currently limited to a single case (HD 49933). Comparison with photometric results obtained with the CoRoT space mission (Convection, Rotation and planetary Transits) on similar stars will be possible with an enhanced set of observations. Aims: We selected the 4th magnitude F8V star HD 203608 to investigate the oscillating properties of a low-metallicity star of the old galactic disk. Methods: We reduced the spectra with the on-line data reduction software provided by the instrument. We developed a new statistical approach for extracting the significant peaks in the Fourier domain. Results: The oscillation spectrum shows a significant excess power in the frequency range [1.5, 3.0 mHz]. It exhibits a large spacing of about 120.4 muHz at 2.5 mHz. Variations of the large spacing with frequency are clearly identified, which require an adapted asymptotic development. The modes identification is based on the unambiguous signature of 15 modes with l = 0 and 1. Conclusions: These observations show the potential diagnostic of asteroseismic constraints. Including them in the stellar modeling significantly enhances the precision on the physical parameters of HD 203608, resulting in a much more precise position in the HR diagram. The age of the star is now determined in the range 7.25±0.07 Gyr. Based on observations obtained with the harps échelle spectrometer mounted on the 3.6-m telescope at ESO-La Silla Observatory (Chile), programme 077.D-0720. Data corresponding to Figs. [see full textsee full textsee full text], [see full textsee full textsee full text], and Table [see full textsee full textsee full text] are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/488/635 [less ▲]

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See detailHD 259440: The Proposed Optical Counterpart of the γ-ray Binary HESS J0632+057
Aragona, C.; McSwain, M. V.; De Becker, Michaël ULg

in Astrophysical Journal (2010), 724

HD 259440 is a B0pe star that was proposed as the optical counterpart to the γ-ray source HESS J0632+057. Here, we present optical spectra of HD 259440 acquired to investigate the stellar parameters, the ... [more ▼]

HD 259440 is a B0pe star that was proposed as the optical counterpart to the γ-ray source HESS J0632+057. Here, we present optical spectra of HD 259440 acquired to investigate the stellar parameters, the properties of the Be star disk, and evidence of binarity in this system. Emission from the Hα line shows evidence of a spiral density wave in the nearly edge-on disk. We find a best-fit stellar effective temperature of 27,500-30,000 K and a log surface gravity of 3.75-4.0, although our fits are somewhat ambiguous due to scattered light from the circumstellar disk. We derive a mass of 13.2-19.0 M sun and a radius of 6.0-9.6 R sun. By fitting the spectral energy distribution, we find a distance between 1.1 and 1.7 kpc. We do not detect any significant radial velocity shifts in our data, ruling out orbital periods shorter than one month. If HD 259440 is a binary, it is likely a long-period (>100 d) system. [less ▲]

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See detailHD 35155: the First Eclipsing Binary S Star (P=642 Days)
Jorissen, A.; Mayor, M.; Manfroid, Jean ULg et al

in Information Bulletin on Variable Stars (1992), 3730

Not Available

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See detailHD 45314: a new γ Cassiopeiae analog among Oe stars
Rauw, Grégor ULg; Nazé, Yaël ULg; Spano, M. et al

in Astronomy and Astrophysics (2013), 555

Context. Oe stars possibly form an extension to higher temperatures of the Be phenomenon, but it is still unclear whether these stars have disks. <BR /> Aims: X-ray spectra could provide hints for ... [more ▼]

Context. Oe stars possibly form an extension to higher temperatures of the Be phenomenon, but it is still unclear whether these stars have disks. <BR /> Aims: X-ray spectra could provide hints for interactions of the star with a putative surrounding disk. <BR /> Methods: We obtained XMM-Newton observations of two Oe stars, HD 45314 and HD 60848. Spectra and light curves were extracted and analysed. Optical spectra were also obtained to support the X-ray observations. <BR /> Results: We find that both stars display very different X-ray properties. Whilst HD 60848 has an X-ray spectrum and emission level typical for its spectral type, HD 45314 displays a very hard X-ray emission, dominated by a thermal plasma with kT ~ 21 keV. Furthermore, HD 45314 displays count rate variations by a factor 2 on timescales of ~ 10[SUP]3[/SUP] s and a high log (L[SUB]X[/SUB]/L[SUB]bol[/SUB]) = -6.10 ± 0.03. <BR /> Conclusions: The X-ray properties of HD 45314 indicate that this star is a new member of the class of γ Cas analogs, the first one among the original category of Oe stars. Based on observations collected with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA), and observations collected at the European Southern Observatory (La Silla, Chile) and the Observatoire de Haute Provence (France). [less ▲]

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See detailHD 45677 est-elle une étoile variable ?
Swings, Jean-Pierre ULg; Swings, Polydore ULg

in Astronomy and Astrophysics (1972), 17(1), 142-145

Whereas HD 45677 has faded by approximately one magnitude since 1969, the amplitude of variation in photographic magnitude between 1899 and 1969 has always been smaller than 0.3 mag.

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See detailHD 65949: Rosetta Stone or Red Herring
Cowley, C. R.; Hubrig, S.; Palmeri, P. et al

in Monthly Notices of the Royal Astronomical Society (2010), 405

HD 65949 is a late B star with exceptionally strong Hg II λ3984, but it is not a typical HgMn star. The Re II spectrum is of extraordinary strength. Abundances or upper limits are derived here for 58 ... [more ▼]

HD 65949 is a late B star with exceptionally strong Hg II λ3984, but it is not a typical HgMn star. The Re II spectrum is of extraordinary strength. Abundances or upper limits are derived here for 58 elements based on a model with Teff = 13 100K and log(g) = 4.0. Even-Z elements through nickel show minor deviations from solar abundances. Anomalies among the odd-Z elements through copper are mostly small. Beyond the iron peak, a huge scatter is found. Enormous enhancements are found for the elements rhenium through mercury (Z = 75–80). We note the presence of Th III in the spectrum. The abundance pattern of the heaviest elements resembles the N = 126 r-process peak of solar material, though not in detail. An odd-Z anomaly appears at the triplet (Zr Nb Mo), and there is a large abundance jump between Xe (Z = 54) and Ba (Z = 56). These are signatures of chemical fractionation. We find a significant correlation of the abundance excesses with second ionization potentials for elements withZ > 30. If this is not a red herring (false lead), it indicates the relevance of photospheric or near-photospheric processes. Large excesses (4–6 dex) require diffusion from deeper layers with the elements passing through a number of ionization stages. That would make the correlation with second ionization potential puzzling. We explore a model with mass accretion of exotic material followed by the more commonly accepted differentiation by diffusion. That model leads to a number of predictions which challenge future work. New observations confirm the orbital elements of Gieseking and Karimie, apart from the systemic velocity, which has increased. Likely primary and secondary masses are near 3.3 and 1.6 M , with a separation of ca. 0.25 au. New atomic structure calculations are presented in two appendices. These include partition functions for the first through third spectra of Ru, Re and Os, as well as oscillator strengths in the Re II spectrum. [less ▲]

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See detailHD 85037 nouvelle variable à éclipses probable
Renson, Pierre ULg; Heck, A.

in Information Bulletin on Variable Stars (1983), 2298

Not Available

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See detailHD 97658 and its super-Earth: Spitzer transit analysis and seismic modeling of the host star
Van Grootel, Valérie ULg; Gillon, Michaël ULg; Valencia, Diana et al

Conference (2013, December)

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See detailHD160529 - a New Galactic Luminous Blue Variable
Sterken, C.; Gosset, Eric ULg; Juttner, A. et al

in Astronomy and Astrophysics (1991), 247

The galactic early-type A hypergiant HD 160529 has been photometrically monitored in the Strömgren system during the past 18 years. HD 160529 has become fainter in the optical range by 0.5 mag during the ... [more ▼]

The galactic early-type A hypergiant HD 160529 has been photometrically monitored in the Strömgren system during the past 18 years. HD 160529 has become fainter in the optical range by 0.5 mag during the past eight years. In addition, pulsation-like variations with a quasi-period of 57 days and with a peak-to-peak amplitude of about 0.1 mag in b and y were found. The fading was not completely monotonous a fall of at least 0.2 mag in b and y within about 40 days around JD2446500 is particularly remarkable. This jump is accompanied by a change in the temperature-sensitive c[SUB]1[/SUB] index of about -0.14 mag. HD 160529 has become visually fainter and hotter during the past eight years, thus becoming a new case of a galactic Luminous Blue Variable (LBV). Model calculations on the basis of the photometry and previously published as well as new spectroscopic observations have shown HD 160529 to be a close counterpart of R 110, a recently discovered LBV in the LMC. From this comparison an absolute magnitude of M[SUB]V[/SUB] = -8.9 and a distance of 2.5 kpc is derived. The stellar parameters characterising the maximum state are estimated to be T[SUB]eff[/SUB] ≍ 8000 K, log g ≍ 0.55, R ≍ 330 R[SUB]sun[/SUB], from which the mass is estimated to be only M ≍ 13 M[SUB]sun[/SUB]. From the Hα profile a lower limit of the mass-loss rate of HD 160529 was calculated, which is about 10 times higher than that of R 110; this could be a consequence of the higher metallicity of the galactic LBV. The low mass of HD 160529 makes this luminous blue star a good candidate for a post-RSG (red supergiant phase) object, providing some evidence that (as sometimes argued) low metallicity is not a necessary prerequisite for evolution of massive stars backward to higher temperatures. [less ▲]

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See detailHD160529: a new galactic Luminous Blue Variable
Stahl, O.; Sterken, C.; Gosset, Eric ULg et al

(1992)

Not Available

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See detailHD46407 - the First Eclipsing Binary Barium Star
Jorissen, A.; Manfroid, Jean ULg; Sterken, C.

in Evolutionary Processes in Interacting Binary Stars (1992)

Not Available

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