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See detailLongterm Photometry of Variables at ESO - Part Two - the Second Data Catalogue 1986-1990
Sterken, C.; Manfroid, Jean ULg; Anton, K. et al

in Astronomy and Astrophysics. Supplement Series (1993), 102

In this paper we present the second catalogue of photometric data in the Strömgren system obtained during the period October 1986- September 1990 in the framework of the Long-Term Photometry of Variables ... [more ▼]

In this paper we present the second catalogue of photometric data in the Strömgren system obtained during the period October 1986- September 1990 in the framework of the Long-Term Photometry of Variables (LTPV) program at the European Southern Observatory. The catalogue is available in computer readable form at the Centre de Données de Strasbourg. [less ▲]

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See detailLong-Term Photometry of Variables at ESO. II. The Second Data Catalogue (1986-1990).
Sterken, C.; Manfroid, Jean ULg; Anton, K. et al

in European Southern Observatory Scientific Report (1993), 12

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See detailA few considerations on photometric databases.
Heck, A.; Manfroid, Jean ULg

in European Southern Observatory Astrophysics Symposia (1988)

Problems related to the homogenization of photometric data are commented, in the perspective of existing and potential photometric data banks. The need for keeping individual photometric measurements of ... [more ▼]

Problems related to the homogenization of photometric data are commented, in the perspective of existing and potential photometric data banks. The need for keeping individual photometric measurements of programme and standard objects accessible is stressed. A complete description of each instrumental system should also be archived. [less ▲]

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See detailCDS Special Publication no 10. IDAAS 1988
Heck, A.; Manfroid, Jean ULg

in Bulletin d'Information du Centre de Données Stellaires (1987), 33

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See detailHot carbon stars - More about V348 SGR
Houziaux, Léo ULg; Bouchet, P.; Heck, A. et al

in Quarterly Journal of the Royal Astronomical Society (1987), 28

New observational techniques (sensitive receivers, access to ultraviolet and infrared spectroscopy), as well as recent theoretical investigations on advanced stages of stellar evolution focus attention ... [more ▼]

New observational techniques (sensitive receivers, access to ultraviolet and infrared spectroscopy), as well as recent theoretical investigations on advanced stages of stellar evolution focus attention again on hydrogen-poor and helium-rich objects known as "carbon stars". The case of the hot peculiar variable V348 Sgr is discussed. New visible and infrared observations are presented, but the exact nature of the star remains much of an enigma. [less ▲]

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See detailPhotometric variability of some CP stars
Heck, A.; Mathys, G.; Manfroid, Jean ULg

in Astronomy and Astrophysics. Supplement Series (1987), 70

The photometric data relative to twenty-three southern CP stars have been re-analysed. New or improved parameters of the lightcurves are presented for eleven of them.

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See detailEvolution of the periodicity of the W UMa system Epsilon CrA
Manfroid, Jean ULg; Heck, A.; Lunel, M. et al

in Astronomy and Astrophysics (1987), 176

Photometric uvby observations of Epsilon CrA obtained with the 1-m telescope at ESO during 1985 are compiled in tables along with published photometry from the period 1960-1984 and analyzed ... [more ▼]

Photometric uvby observations of Epsilon CrA obtained with the 1-m telescope at ESO during 1985 are compiled in tables along with published photometry from the period 1960-1984 and analyzed comprehensively. The results are presented in O-C diagrams and discussed, and a relative increase of 0.00001 in the period of the object is detected. It is pointed out that this change may have been gradual (over a 5-10-yr period) or abrupt (at about HJD 2,440,000), but that the period appears to have become stable again in the most recent observations. [less ▲]

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See detailInternational Directory of Astronomical Associations and Societies. I.D.A.A.S. 1988.
Heck, A.; Manfroid, Jean ULg

in International Directory of Astronomical Associations and Societies. I.D.A.A.S 1988 (1987)

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See detailLitterae Uraniae: Dates de fondation des sociétés astronomiques
Heck, A.; Manfroid, Jean ULg

Article for general public (1987)

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See detailInternational Directory of Astronomical Associations and Societies - I.D.A.A.S. 1986
Heck, A.; Manfroid, Jean ULg

Article for general public (1986)

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See detailCDS Special Publication n° 9: International Directory of Professional Astronomical Institutions 1987
Heck, A.; Manfroid, Jean ULg

in Bulletin d'Information du Centre de Données Stellaires (1986), 31

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See detailInternational Directory of Professional Astronomical Institutions
Heck, A.; Manfroid, Jean ULg

in Bulletin d'Information du Centre de Données Stellaires (1986), 30

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See detailTitres des périodiques astronomiques
Heck, A.; Manfroid, Jean ULg

Article for general public (1986)

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See detailA propos de la couleur de Sirius
Manfroid, Jean ULg; Heck, A.

Article for general public (1986)

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See detailPhotometric variations of the irregular variable V348 SGR
Heck, A.; Houziaux, Léo ULg; Manfroid, Jean ULg et al

in Astronomy and Astrophysics. Supplement Series (1985), 61

The authors report visual estimates and photometric observations in various wavelength ranges of the irregular variable V348 Sgr. They cover dramatic drops of brightness (from V â 12.5 to â 18) which ... [more ▼]

The authors report visual estimates and photometric observations in various wavelength ranges of the irregular variable V348 Sgr. They cover dramatic drops of brightness (from V â 12.5 to â 18) which occurred in 1972, 1973 and 1981 with a time scale much shorter than the characteristic time mentioned by previous observers. These deep minima are, to our knowledge, the best followed up to now. The maximum brightness of the object seems also to correspond to V â 12 and not 10.5 as reported earlier. The minima reach V â 18, but this might represent the nebular contribution while the star itself might even go fainter. The main conclusions of this compilation are probably that the characteristic times given by Herbig (1958) from appearances on Harvard plates are most likely incorrect and that it is impossible to give one at all. The field of V348 Sgr has also been observed in the uvby system and a sequence is provided in this paper. [less ▲]

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See detailCatch the Minima: A Real Challenge on V348 Sgr
Heck, A.; Manfroid, Jean ULg

in International Amateur-Professional Photoelectric Photometry Communications (1985), 20

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See detailIs HD 23878 A Mild CP Star?
Mathys, G.; Manfroid, Jean ULg; Heck, A.

in Information Bulletin on Variable Stars (1985), 2738

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See detailPhotometric variations of HD 25267
Manfroid, Jean ULg; Mathys, G.; Heck, A.

in Astronomy and Astrophysics (1985), 144

Two periodicities are found in the photometric variations of HD 25267. One of the periods (1.2 d) seems to be the same as the magnetic period and is thus attributed to a CP component. The origin of the ... [more ▼]

Two periodicities are found in the photometric variations of HD 25267. One of the periods (1.2 d) seems to be the same as the magnetic period and is thus attributed to a CP component. The origin of the variations with the second period (3.8 d) remains uncertain. [less ▲]

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See detailVariations in the variability of RR Tel
Heck, A.; Manfroid, Jean ULg

in Astronomy and Astrophysics (1985), 142

The visible-light periodicity of the very slow nova RR Tel is inferred to vary in cycles of 350- to 410-day periods, based on the uvby photometric data, IUE FES measurements, and AAVSO visual estimates ... [more ▼]

The visible-light periodicity of the very slow nova RR Tel is inferred to vary in cycles of 350- to 410-day periods, based on the uvby photometric data, IUE FES measurements, and AAVSO visual estimates. Besides a general increase in magnitude, the visible lightcurve is also marked by two events corresponding to sudden decreases of brightness in 1949 and 1962/1963. A comparison with infrared data does not rule out the possibility of a phase shift of 10 days at most between both sets of data for a common time coverage. It is noted that additional spectroscopic and photometric observations are necessary to link the Mira components to the variations in the visible range. [less ▲]

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See detailOn period determination methods
Heck, A.; Manfroid, Jean ULg; Mersch, G.

in Astronomy and Astrophysics. Supplement Series (1985), 59

It is noted that the two large families of period determination techniques based on the Fourier transform and on the nonparametric algorithms derived from the theta-criterion by Lafler and Kinman (1965 ... [more ▼]

It is noted that the two large families of period determination techniques based on the Fourier transform and on the nonparametric algorithms derived from the theta-criterion by Lafler and Kinman (1965) are not equivalent to each other under general conditions. Instead, at best, all criteria may be expressed as the ratio of two quadratic forms. Numerical simulations have been conducted in order to compare the performance of Deeming's (1975) Fourier method, Burki et al.'s (1978) autocorrelation method, Lafler and Kinman's (1965) method, and the Renson (1978) and Stellingwerf (1978) methods. When applied to single-periodic phenomena, the tests indicate that none of the methods is clearly superior. [less ▲]

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