References of "Surdej, Jean"
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See detailAsteroid rotation - Hunting for a record: 1689 Floris-Jan
Schober, H. J.; Surdej, Jean ULg

in The Messenger (1982), 29

Last year, in June 1981 - ESO Messenger No. 24, p. 22-23 - H. J. Schober published areport on "Spinning Asteroids and Photometry". There he mainly gave a general introduction about what can be done using ... [more ▼]

Last year, in June 1981 - ESO Messenger No. 24, p. 22-23 - H. J. Schober published areport on "Spinning Asteroids and Photometry". There he mainly gave a general introduction about what can be done using UBV photometry in order to derive physical properties of asteroids such as geometrie forms, diameters, reflectance on the surface, bimodality of asteroids with respect to typology. A special effort was made to report about the activities to deal with asteroids as "variable objects" like variable stars - showing Iightcurves with defined rotation rates to be derived. Among asteroids it was stated that the longest rotation periods found before 1975 were not larger than 20 hours - followed by 654 Zelinda 31 ~9 (1975). 393 Lampetia 38h7, 128 Nemesis 39h0 (1979), 709 Fringilla 52h4 (1979) and 182 Eisa 80~00 (1980), the latter corresponding to 3d33. [less ▲]

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See detailQuasars in a control field far from bright galaxies
Arp, H.; Surdej, Jean ULg

in Astronomy and Astrophysics (1982), 109

The density of quasars in a control field of the sky selected to be free of bright galaxies is investigated in order to derive a value for the average background density of quasars and to analyze quasar ... [more ▼]

The density of quasars in a control field of the sky selected to be free of bright galaxies is investigated in order to derive a value for the average background density of quasars and to analyze quasar distribution within the field. Schmidt plates were obtained in the ultraviolet and blue for a control field surrounding SAO 45758 at R.A. 15 h 49 min, declination plus 48 deg 38 arcmin. Examination of the spectra of 25 of the 137 objects found to exhibit an ultraviolet excess reveals 12 of them to be quasars, indicating a quasar density of 6.7 plus or minus 0.9/sq deg down to a limiting magnitiude of 20 over the 19 sq deg area of the field. This value is noted to be in agreement with previous values of quasar background density deduced for other regions of the sky. Large fluctuations of quasar density are found, however, within the field which may be correlated with groups of intermediate brightness galaxies. [less ▲]

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See detailSpectroscopic observations of thirteen optically-selected QSOs in a large field centred around NGC 5334
Surdej, Jean ULg; Swings, Jean-Pierre ULg; Arp, H. C. et al

in Astronomy and Astrophysics (1982), 114

A large field (approximately 25 sq deg) around NGC 5334 was searched for QSO candidates with ultraviolet-excess, in order to investigate the space density, distribution, and luminosity of quasars near as ... [more ▼]

A large field (approximately 25 sq deg) around NGC 5334 was searched for QSO candidates with ultraviolet-excess, in order to investigate the space density, distribution, and luminosity of quasars near as well as far from bright galaxies. Spectroscopic data obtained with the European Southern Observatory 3.6 m telescope are presented for 13 quasars identified within a sample of 23 observed candidates. As expected, the redshift of these optically selected quasars was found to fall in the range 0.23-2.08, with only one exception. Two, and possibly three, of the quasars of the largest redshift show absorption lines, while the remaining 10 faint blue objects display zero-redshift stellar spectra. [less ▲]

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See detailThe six-day rotation period of 1689 Floris-Jan - A new record among slowly rotating asteroids
Schober, H. J.; Surdej, Jean ULg; Harris, A. W. et al

in Astronomy and Astrophysics (1982), 115

Abstract image available at: http://esoads.eso.org/abs/1982A&A...115..257S

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See detailSpectral variations and evidence for edge and/or line locking mechanism/s/ in the low-excitation planetary nebula HD 138403
Surdej, Anna ULg; Surdej, Jean ULg; Swings, Jean-Pierre ULg

in Astronomy and Astrophysics (1982), 105

Spectral variations detected within the last three decades for He II 4686 A, forbidden lines O III and other high excitation lines in the low-excitation planetary nebula HD 138403, are shown to suggest ... [more ▼]

Spectral variations detected within the last three decades for He II 4686 A, forbidden lines O III and other high excitation lines in the low-excitation planetary nebula HD 138403, are shown to suggest appreciable activity in the deep atmospheric layers of the nucleus, and an increase of the excitation of the nebula. The spectrum of the nebula is found to be unusual due to the presence of red and blue emission satellites around the central Balmer (H-beta - H9) lines and forbidden lines O II 3726, 3729 A, with a velocity separation equal to plus 122 and minus 126 km/s, respectively. These features are interpreted as evidence for mass outflow from the central object via the selective radiation process of edge and/or line locking mechanisms. [less ▲]

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See detailFurther spectroscopic observations of 25 quasi-stellar objects
Surdej, Jean ULg; Swings, Jean-Pierre ULg

in Astronomy and Astrophysics. Supplement Series (1981), 46

Spectroscopic observations are reported for 25 quasars suspected of having line profiles which are indicative of mass outflow from the central quasar. The quasars were selected on the basis of optical ... [more ▼]

Spectroscopic observations are reported for 25 quasars suspected of having line profiles which are indicative of mass outflow from the central quasar. The quasars were selected on the basis of optical variability and/or the presence of P Cygni spectral profiles, and large emission redshift, and observed on widened spectrograms obtained at the Cassegrain focus of the ESO 3.6-m telescope at La Silla during December 1977 and July 1978. Observations confirm the previously detected emission and absorption redshifts for most of the quasars, and reveal previously undetected lines and absorption redshifts in a few cases. [less ▲]

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See detailFormation of P Cygni profiles with limb darkening of the stellar core
Surdej, Jean ULg

in Astrophysics & Space Science (1981), 79

In the framework of the Sobolev approximation, the effects of limb darkening of the stellar core on the formation of line profiles in rapidly expanding envelopes are investigated. For the case of outward ... [more ▼]

In the framework of the Sobolev approximation, the effects of limb darkening of the stellar core on the formation of line profiles in rapidly expanding envelopes are investigated. For the case of outward-accelerating envelopes, it is shown that the P Cygni profiles, calculated with and without limb darkening, do appear almost identical as long as the size of the envelope remains large with respect to the radius of the star. As the extent of the envelope decreases, the resulting profiles are found to differ appreciably close to the line center. When considering outward-decelerating (or equivalently inward-accelerating) envelopes, calculations with the limb darkening effects reveal that the P Cygni profiles are more strongly affected than in the previous case. These effects are specially important in the blue wing and near the center of the resulting line profiles, irrespective of the size of the envelope. [less ▲]

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See detailDecelerated flows of matter around the quasars PHL 5200 and RS 23
Surdej, Jean ULg; Swings, Jean-Pierre ULg

in Astronomy and Astrophysics (1981), 96

Line profile calculations are performed within the framework of the Sobolev approximation in order to simulate the P Cygni-like profiles observed for the resonance doublets of C IV and Si IV in the ... [more ▼]

Line profile calculations are performed within the framework of the Sobolev approximation in order to simulate the P Cygni-like profiles observed for the resonance doublets of C IV and Si IV in the spectrum of the quasar PHL 5200 and of C IV in that of RS 23. Taking into account the structure of the resonance doublets and the nonlocal transfer of line photons in an outward-decelerating envelope, it is shown that good agreement between the theory and the observations is achieved for symmetrically spherical outward-flows decelerated in the gravitational field of the central quasars. [less ▲]

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See detailThe Reflection Nebula Surrounding HD87643
Surdej, Anna ULg; Surdej, Jean ULg; Swings, Jean-Pierre ULg et al

in Astronomy and Astrophysics (1981), 93

Direct plates in narrow bands (H , [0 NI], [S Ii]) and in the broad (B)-band show that the nebula surrounding the nova- like object HD 87643 is of reflective origin. Furthermore, a spectrogram of the ... [more ▼]

Direct plates in narrow bands (H , [0 NI], [S Ii]) and in the broad (B)-band show that the nebula surrounding the nova- like object HD 87643 is of reflective origin. Furthermore, a spectrogram of the filamentary condensation lying east-west at 17" north of HD 87643 reveals strong Balmer emission lines, with a P Cygni structure at H fl H e, as well as many diffuse emission lines of Fe II: such features essentially form a replica of the spectrum of the central object. These results and other arguments strongly support the idea that the reflection nebula surrounding HD 87643 is associated with the mass-outflow observed from the central hot star. Key words: reflection nebula - HD 87643 - mass-loss [less ▲]

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See detailSpectroscopic and photometric observations of galaxies from the ESO/Uppsala list - Third catalogue
West, R. M.; Surdej, Jean ULg; Schuster, H.-E. et al

in Astronomy and Astrophysics. Supplement Series (1981), 46

Abstract image available at: http://esoads.eso.org/abs/1981A&AS...46...57W

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See detail(201) Penelope
Surdej, Jean ULg; Cramer, N.

Report (1980)

IAUC 3527 available at Central Bureau for Astronomical Telegrams.

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See detailRotation period and photoelectric lightcurves of asteroids 68 Leto and 563 Suleika
Surdej, Jean ULg; Schober, H. J.

in Astronomy and Astrophysics. Supplement Series (1980), 41

Abstract image available at: http://esoads.eso.org/abs/1980A&AS...41..335S

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See detailCorrelations between line profile and photometric variations in the B2 IV[e] star HD 45677.
Swings, Jean-Pierre ULg; Barbier, R.; Klutz, M. et al

in Be Star Newsletter (1980), 1

Not Available

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See detailCorrelations between line-profile and photometric variations in the B 2 IV /e/ star HD 45677
Swings, Jean-Pierre ULg; Klutz, M.; Surdej, Anna ULg et al

in Astronomy and Astrophysics (1980), 90

Abstract image available at: http://esoads.eso.org/abs/1980A&A....90..116S

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See detailOn the structure of the nebula M 2-9
Kohoutek, L.; Surdej, Jean ULg

in Astronomy and Astrophysics (1980), 85

The structure of planetary nebula M 2-9 has been investigated on direct plates taken with the ESO 3.6 m-telescope in 1977-78. Compared with the photographs from 1952, 1971, and 1973 the main condensations ... [more ▼]

The structure of planetary nebula M 2-9 has been investigated on direct plates taken with the ESO 3.6 m-telescope in 1977-78. Compared with the photographs from 1952, 1971, and 1973 the main condensations in the wings show a remarkable shift approximately in the W-E direction which can be explained as a rotating motion about the nebular axis of symmetry (N-S axis). The angular velocity seems to increase with the distance from the core. Two faint loops extending to about 1 arcmin on each side of the core and lying on the nebular axis were discovered. The very elongated shape of the nebula indicates the presence of an anisotropic velocity field in it. [less ▲]

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See detailFormation of resonance doublet profiles in rapidly expanding envelopes
Surdej, Jean ULg

in Astrophysics & Space Science (1980), 73

Sobolev's escape probability method is used to investigate the transfer of spectral line radiation for a resonance doublet in a rapidly expanding envelope. A three-level atom model is used to derive ... [more ▼]

Sobolev's escape probability method is used to investigate the transfer of spectral line radiation for a resonance doublet in a rapidly expanding envelope. A three-level atom model is used to derive expressions for the spectral radiation fields J12 and J13, the resulting radiative force exerted per atom, and the resonance doublet profile for the cases of outward-accelerating (or equivalently inward-decelerating) and outward-decelerating (or equivalently inward-accelerating) envelopes. Criteria are deduced under which resonance doublet profiles formed in outward-accelerating and/or outward-decelerating envelopes would appear to be resolved into double P Cygni profiles. [less ▲]

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See detailUBV photometry of the asteroids 9 Metis, 87 Sylvia and 247 Eukrate during their oppositions in 1978 with respect to lightcurves
Schober, H. J.; Surdej, Jean ULg

in Astronomy and Astrophysics. Supplement Series (1979), 38

Abstract image available at: http://esoads.eso.org/abs/1979A&AS...38..269S

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See detailPhotoelectric observations of two unusual asteroids - 1978 CA and 1978 DA
Schuster, H. E.; Surdej, Anna ULg; Surdej, Jean ULg

in Astronomy and Astrophysics. Supplement Series (1979), 37

The two fast-moving asteroids 1978 CA and 1978 DA, discovered in February 1978 with the ESO Schmidt telescope at La Silla (Chile), were observed with a photoelectric photometer attached to the 1-m ESO ... [more ▼]

The two fast-moving asteroids 1978 CA and 1978 DA, discovered in February 1978 with the ESO Schmidt telescope at La Silla (Chile), were observed with a photoelectric photometer attached to the 1-m ESO telescope. The light curve of 1978 CA displays two fairly symmetric maxima and minima with a total amplitude of 0.8 mag in V. The synodic period of rotation found is 3 h 45 m and places 1978 CA as the third fastest rotator among all known solar objects. Concerning the minor planet 1978 DA, light variations covering one full cycle of rotation could not be monitored. Nevertheless, the rotation period exceeds 5 h, and the total amplitude is greater than 0.35 mag. [less ▲]

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See detailPhotoelectric lightcurves and rotation period of the minor planet 148 Gallia
Surdej, Anna ULg; Surdej, Jean ULg

in Astronomy and Astrophysics. Supplement Series (1979), 37

Abstract image available at: http://esoads.eso.org/abs/1979A&AS...37..471S

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