Longterm Photometry of Variables at ESO - Part Two - the Second Data Catalogue 1986-1990

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 ▲]

The evolution of atmospheric extinction at La Silla derived from measurements in the Stromgren photometric system

in Astronomy and Astrophysics (1992), 266

We describe atmospheric extinction data obtained at the La Silla Observatory in the Stromgren photometric system. Our measurements, covering a time interval of almost fifteen years, show three episodes of ... [more ▼]

We describe atmospheric extinction data obtained at the La Silla Observatory in the Stromgren photometric system. Our measurements, covering a time interval of almost fifteen years, show three episodes of increased extinction due to airborne aerosols of volcanic origin. A small-amplitude seasonal variation and a short-timescale pseudo-periodic oscillation are also revealed. Implications on the observing procedures and photometric reduction schemes are discussed. [less ▲]

Photometric accuracy - The impact of extrapolation in differing color-transformation schemes

in Astronomy and Astrophysics (1992), 264

We discuss photometric errors that arise from the use of differing color-transformation schemes when extrapolating outside the range of the standard values that define the system. An example based on data ... [more ▼]

We discuss photometric errors that arise from the use of differing color-transformation schemes when extrapolating outside the range of the standard values that define the system. An example based on data from the Long-Term Photometry of Variables project (LTPV) at ESO is analyzed. Practically, the extrapolation errors are most evident as systematic brightness jumps of some program stars, seen when monitored over several observing runs. Conclusions are drawn about the choice of standard stars in the Stromgren system. [less ▲]

HD 35155: the First Eclipsing Binary S Star (P=642 Days)

in Information Bulletin on Variable Stars (1992), 3730

Not Available

HD160529: a new galactic Luminous Blue Variable

(1992)

Not Available

On the Homogeneity of Visual Photometry

in Variable Star Research (1992)

Not Available

Discovery of the first eclipsing binary barium star

in The Messenger (1991), 66

Photometric monitoring of barium stars is discussed with particular attention given to the first eclipsing binary barium star, HD 46407. The spectroscopic ephemeris of HD 46407 was used to predict the ... [more ▼]

Photometric monitoring of barium stars is discussed with particular attention given to the first eclipsing binary barium star, HD 46407. The spectroscopic ephemeris of HD 46407 was used to predict the times of a possible eclipse of the companion by the barium star. It is concluded that the light curve of HD 46407 derived from the photometric observations in the D50 system displays a sharp 'primary' eclipse (companion behind the barium star) and a possible shallow 'secondary' eclipse. The primary eclipse occurred in November 1988 and had a depth of about 0.02 mag. [less ▲]

HD160529 - a New Galactic Luminous Blue Variable

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 ▲]

Long-term photometry of variables at ESO. I - The first data catalogue (1982-1986)

in Astronomy and Astrophysics. Supplement Series (1991), 87

This paper presents the catalog of photometric data in the Stromgren system obtained during the first four years (October 1982 - September 1986) of the Long-Term Photometry of Variables (LTPV) program at ... [more ▼]

This paper presents the catalog of photometric data in the Stromgren system obtained during the first four years (October 1982 - September 1986) of the Long-Term Photometry of Variables (LTPV) program at ESO. The data are available in computer-readable form. [less ▲]

Automatic Photometric Telescopes and Photometric Accuracy

in Precision Photometry: Astrophysics of the Galaxy (1991)

Not Available