References of "Hutsemekers, Damien"
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See detailDeformation of P Cygni line profiles by gravitational microlensing effects
Hutsemekers, Damien ULg; Surdej, Jean ULg; Vandrom, E.

in Kayser, R.; Schramm, T.; Nieser, L. (Eds.) Gravitational Lenses, Lecture Notes in Physics, volume 406 (1992)

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See detailUnusual solar halos over La Silla
Hutsemekers, Damien ULg

in The Messenger (1991), 66

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See detailThe nature of the nebula associated with the luminous blue variable star WRA 751
Hutsemekers, Damien ULg; van Drom, E.

in Astronomy and Astrophysics (1991), 251

Narrow-band filter imagery as well as medium to high resolution spectroscopy of the nebula surrounding the luminous blue variable (LBV) star WRA 751 are presented. The nebula appears as a slowly expanding ... [more ▼]

Narrow-band filter imagery as well as medium to high resolution spectroscopy of the nebula surrounding the luminous blue variable (LBV) star WRA 751 are presented. The nebula appears as a slowly expanding H II region of low excitation characterized by a significant N/O overabundance which may be due to the presence in the nebula of nuclear processed material ejected by the star. With the recent discovery of a nebula around HR Car, all but one known galactic LBVs are now shown to be associated with a nebula. These nebula have rather similar physical characteristics, one of the most important being that all of them apparently contain processed material. [less ▲]

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See detailHR Carinae - A luminous blue variable surrounded by an arc-shaped nebula
Hutsemekers, Damien ULg; van Drom, E.

in Astronomy and Astrophysics (1991), 248

New high and medium dispersion spectroscopic observations of the luminous blue variable (LBV) star HR Car are presented, showing that this star has a multiple shell expanding atmosphere and undergoes ... [more ▼]

New high and medium dispersion spectroscopic observations of the luminous blue variable (LBV) star HR Car are presented, showing that this star has a multiple shell expanding atmosphere and undergoes spectral variations apparently correlated with the light variations similarly to the other LBVs. Most striking are the very broad emission wings (FWZI of about 3000 km/s) of the Balmer lines, reminiscent from the broad lines observed in the spectra of Of and WR stars. A kinematic distance of 5.4 kpc and a bolometric magnitude of -9.4 put HR Car among the most luminous stars of the Galaxy. The narrow band filter imagery also reveals an arc-shaped jet like nebula associated with HR Car. Spectroscopic observations of this nebula reveal an emission nature with very low excitation. Like the star itself, the nebula is characterized by a significant N/O overabundance, probably due to the presence of nuclear processed material ejected by the star. [less ▲]

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See detailA Model to Explain the Activity of Comet Levy (1990c)
Samarasinha, N. H.; A'Hearn, M. F.; Weaver, H. A. et al

in Bulletin of the American Astronomical Society (1991, June 01)

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See detailThe very massive star HDE269676 and its components
Heydari-Malayeri, M.; Hutsemekers, Damien ULg

in Astronomy and Astrophysics (1991), 244

It is shown that one of the most luminous stars of the LMC, HDE269676, is in fact a massive star cluster. On the basis of observations with the ESO New Technology Telescope (NTT) the main components of ... [more ▼]

It is shown that one of the most luminous stars of the LMC, HDE269676, is in fact a massive star cluster. On the basis of observations with the ESO New Technology Telescope (NTT) the main components of the cluster are classified and it is shown that there are several O type stars in HDE269676 instead of the one or two previously known. This is interesting for the initial mass function in the LMC and implies that the number of O type stars in the LMC is generally underestimated. The most massive star of the system being about a factor three less luminous than previously estimated is a super-giant O5f with a zero age main sequence mass of about 80 solar. [less ▲]

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See detailThe most massive star of the largest H II region in the Small Magellanic Cloud
Heydari-Malayeri, M.; Hutsemekers, Damien ULg

in Astronomy and Astrophysics (1991), 243

It is shown that the brightest star in the most important H II region of the Small Magellanic Cloud (SMC) is a multiple system. The zero-age main sequence mass of this star drops significantly from the ... [more ▼]

It is shown that the brightest star in the most important H II region of the Small Magellanic Cloud (SMC) is a multiple system. The zero-age main sequence mass of this star drops significantly from the previously estimated value of 130 or 110 solar masses to less than 85 solar masses, while its present mass falls from 113 to 58 solar masses, both due to multiplicity and extinction correction. This is another piece of evidence against the existence of stars more massive than about 100 solar masses in the SMC. It is also shown that the present mass of one of the two known O3 stars in the SMC is significantly smaller than presently believed. [less ▲]

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See detailFormation of P Cygni line profiles in relativistically expanding atmospheres
Hutsemekers, Damien ULg; Surdej, Jean ULg

in Astrophysical Journal (1990), 361

The probabilistic approach of Surdej (1979) is followed to generalize the Sobolev (1958) formalism to the case of special relativity, in order to interpret accurately the P Cygni line profiles observed in ... [more ▼]

The probabilistic approach of Surdej (1979) is followed to generalize the Sobolev (1958) formalism to the case of special relativity, in order to interpret accurately the P Cygni line profiles observed in the spectrum of broad absorption-line quasars and supernovae. The expressions of the source function and of the line profile are derived, and it is shown that the relativistic P Cygni line profiles are significantly different from those computed in the framework of the classical theory. Thus, for increasing values of the terminal wind velocity, the red emission wing becomes definitely narrower than the blue one, while the line center emission increases. This is no longer symmetrical in accordance with the relativistic expression of the Doppler effect. [less ▲]

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See detailThe nth order moment W(n)D of a resonance doublet P Cygni line profile
Surdej, Jean ULg; Hutsemekers, Damien ULg

in Astronomy and Astrophysics (1990), 233

The theory of the nth order moment W(n)D of a P Cygni line profile due to a resonance doublet line transition is developed here in the framework of the Sobolev approximation. It is shown that, in the ... [more ▼]

The theory of the nth order moment W(n)D of a P Cygni line profile due to a resonance doublet line transition is developed here in the framework of the Sobolev approximation. It is shown that, in the optically thick approximation, the asymptotic value W(n)D,t is entirely dependent on both the doublet separation and the type of the velocity field characterizing the expanding atmosphere. The most useful P Cygni profiles seem to be those which are unsaturated. [less ▲]

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See detailFurther observations of the light echoes from SN 1987 A
Detal, Alain ULg; Surdej, Jean ULg; Hutsemekers, Damien ULg et al

in Astronomy and Astrophysics (1990), 229

Further direct observations of the light echoes from SN 1987 A were obtained on November 12 1988 with the 3.6-m telescope and EFOSC at ESO. In agreement with predictions made from earlier observations ... [more ▼]

Further direct observations of the light echoes from SN 1987 A were obtained on November 12 1988 with the 3.6-m telescope and EFOSC at ESO. In agreement with predictions made from earlier observations, the radii of the two light rings are measured to be 43.3 and 72.5 arcsec. However, a noticeable diaplacement of the center of the outer ring by 2.6 arcsec to the NE from the SN position is also reported. Application of the model of planar-like sheets of material located between the SN and the observer leads to improved results. [less ▲]

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See detailThe supergiant Bep star CD - 42 11721 deg and its surrounding nebula
Hutsemekers, Damien ULg; van Drom, E.

in Astronomy and Astrophysics (1990), 238

New spectroscopic and direct imagery observations of the supergiant Bep star CD - 42 11721 deg and its surrounding nebula are reported. The spectrum of the star essentially consists of Balmer and Fe II ... [more ▼]

New spectroscopic and direct imagery observations of the supergiant Bep star CD - 42 11721 deg and its surrounding nebula are reported. The spectrum of the star essentially consists of Balmer and Fe II emission lines, He I emission lines are also observed, confirming the presence of spectral variations on long timescales. The clumpy arc-shaped structure of the nebula as well as the presence of motions relative to the central star highly suggest that it has been influenced by a variable mass-loss. The nebula shows both the reflection and emission characteristics. Its spectrum displays the red forbidden N II and S II lines while no oxygen forbidden lines can be detected. Its tempting to interpret this situation by a N/O overabundance which may indicate the presence of processed material in the nebula and thus confirm the evolved nature of the star. [less ▲]

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See detailA search for gravitational lensing among highly luminous quasars - Observational strategy and survey
Swings, Jean-Pierre ULg; Magain, Pierre ULg; Remy, M. et al

in Soucail, G.; Mellier, Y.; Fort, B. (Eds.) Gravitational Lensing (1990)

The observational techniques employed to search for gravitational lensing effects in highly luminous quasars (HLQs) are given, along with results of the observations. The program, begun in 1986, considers ... [more ▼]

The observational techniques employed to search for gravitational lensing effects in highly luminous quasars (HLQs) are given, along with results of the observations. The program, begun in 1986, considers the visible and dark matter distributions at different scales in the universe to determine which extragalactic objects are gravitationally lensed. The Hubble parameter and galaxy masses are determined from the observations, and observations of microlensing effects provide data on HLQ size and structures. The redshifts are found to be between 1 and 3.6, with apparent visual magnitudes 16-18.5 and absolute visual magnitudes between -29 and -30.6. About one quarter of the images exhibit either multiple components, elongated structures, jetlike features, or faint nearby galaxies. The double quasar UM 673 and its 'overlying' lens galaxy is given as a prime example of an HLQ that is gravitationally lensed. It is theorized many more HLQs are gravitationally lensed, and specific future observations are recommended. [less ▲]

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See detailRevisited mass-loss rates for a sample of central stars of planetary nebulae
Hutsemekers, Damien ULg; Surdej, Jean ULg

in Astronomy and Astrophysics (1989), 219

Using improved relations for the first order moment of a P Cygni line profile, mass-loss rates have been rederived for a sample of seventeen central stars of planetary nebulae observed with IUE in the low ... [more ▼]

Using improved relations for the first order moment of a P Cygni line profile, mass-loss rates have been rederived for a sample of seventeen central stars of planetary nebulae observed with IUE in the low resolution mode. The average value of the mass-loss rates lies between 10 to the -7th and 10 to the -8th solar masses/yr. It is confirmed that the mass-loss rates of central stars of planetary nebulae cannot be simply extrapolated from the 'mass-loss rate-luminosity' relation existing for Population I OB stars. [less ▲]

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See detailA new and improved camera for the 1.5m B&C spectrograph
Jarvis, B.; Hutsemekers, Damien ULg

in The Messenger (1989), 56

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See detailProfiles of a Key Programme: Gravitational Lensing
Surdej, Jean ULg; Arnaud, J.; Borgeest, U. et al

in The Messenger (1989), 55

Prior to Professor van der Laan's enquiry, in the March 1988 issue of the Messenger, on the general interest among astronomers from the European community to possibly participate in Key Programmes (KPs ... [more ▼]

Prior to Professor van der Laan's enquiry, in the March 1988 issue of the Messenger, on the general interest among astronomers from the European community to possibly participate in Key Programmes (KPs) at the European 80uthern Observatory, at least three distinct groups (including more than half of the above authors) were already involved in the study of "gravitational lensing" effects (see box on pages 10-11). Observations were being performed with the help of various telescopes on La 8illa as weil as at other observatories (VLA, CFHT, Palomar, Kitt Peak, etc.). [less ▲]

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See detailRevisited Mass-Loss Rates of Planetary Nebula Nuclei Observed with IUE
Hutsemekers, Damien ULg; Surdej, Jean ULg

in Torres-Peimbert, Silvia (Ed.) Planetary Nebulae, 131st. Symposium of the International Astronomical Union (1989)

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See detailStudy of AG Carinae. I - The 1977 spectrum of the star
Hutsemekers, Damien ULg; Kohoutek, L.

in Astronomy and Astrophysics. Supplement Series (1988), 73

Spectroscopic observations of the variable P Cygni-like star AG Car have been obtained in February 1977. At this epoch, the star was in a relative minimum phase (V = 7.6) observed during a long and ... [more ▼]

Spectroscopic observations of the variable P Cygni-like star AG Car have been obtained in February 1977. At this epoch, the star was in a relative minimum phase (V = 7.6) observed during a long and comparatively quiet period of intermediate brightness. The spectrum displays prominent P Cygni lines of He I, Si III, N II and Fe III. The corresponding equivalent spectral type is B2-3 Ib. The presence of an outward accelerated envelope with a multiple shell structure is confirmed. The observation of broad [Fe II] emission lines, in contrast with the absence of permitted ones, implies the presence of a low density shell expanding at about 200 km/s. [less ▲]

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See detailNew arguments supporting the intrinsic origin of BAL QSOs - Formation of the complex Ly-alpha+NV line profile
Hutsemekers, Damien ULg; Surdej, Jean ULg

in Bianchi, L.; Gilmozzi, R. (Eds.) Proceedings of the Second Torino Workshop "Mass Outflows from Stars and Galactic Nuclei" (1988)

A study is presented to further elucidate the question of whether or not all quasars are affected by the BAL phenomenon. The possibility that observed BAL profiles are formed in spherically symmetric ... [more ▼]

A study is presented to further elucidate the question of whether or not all quasars are affected by the BAL phenomenon. The possibility that observed BAL profiles are formed in spherically symmetric expanding atmospheres is investigated. [less ▲]

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See detailImproved first order moment method for determination of mass-loss rates
Hutsemekers, Damien ULg; Surdej, Jean ULg

in Bianchi, L.; Gilmozzi, R. (Eds.) Mass outflows from stars and galactic nuclei; Proceedings of the Second Torino Workshop (1988)

The first order moment of P Cygni line profiles has been computed for the case of doublets and subordinate line transitions. This improved method can be used for deriving more accurate mass-loss rates of ... [more ▼]

The first order moment of P Cygni line profiles has been computed for the case of doublets and subordinate line transitions. This improved method can be used for deriving more accurate mass-loss rates of planetary nebula nuclei, broad absorption line quasars, etc. [less ▲]

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