Photometric variations in Ap stars observable at La Silla in November and December

in Astronomy and Astrophysics. Supplement Series (1981), 44

Photometric observations of 13 Ap stars made at the European Southern Observatory at La Silla during November 1977 and December 1978 are reported. Observations were made in the uvby with the four-channel ... [more ▼]

Photometric observations of 13 Ap stars made at the European Southern Observatory at La Silla during November 1977 and December 1978 are reported. Observations were made in the uvby with the four-channel photometer at the 40-cm telescope in November, and with the one-channel photometer at the 50-cm telescope in December. Light variations with periods from 0.724 to 4.64 days are obtained for 11 of the stars, including the Hg-Mn star HR 2202, which was believed not to vary. Extremely small variations are observed in Upsilon 4 Eri, with a possible period of 0.51 days, although the two Mn components are likely to vary independently. HR 1800 was not observed to vary over two-week observation period. The stars 20 Eri, HR 1194, Alpha Dor, 11 Ori and HD 36916 are also noted to exhibit relatively large variations for Ap stars. [less ▲]

Photometric variations of Ap stars

in Astronomy and Astrophysics (1994), 281

The photometric variations of seven Ap stars have been analyzed from observations mainly obtained in the framework of the Long-Term Photometry of Variables project at European Southern Observatory (ESO ... [more ▼]

The photometric variations of seven Ap stars have been analyzed from observations mainly obtained in the framework of the Long-Term Photometry of Variables project at European Southern Observatory (ESO). New values for the periods and detailed light curves in the uvby system are provided. Alpha Scl is shown to display anomalous variations that set it apart from the other stars. [less ▲]

Photometric variations of some Ap stars.

in Astronomy and Astrophysics. Supplement Series (1976), 23

Abstract image available at: http://cdsads.u-strasbg.fr/abs/1976A&AS...23..413R

The photometric variations of the Ap star HD34631

in Astronomy and Astrophysics. Supplement Series (1991), 90

The photometric behavior in the uvby system of the Ap star HD34631 has been reanalyzed on the basis of data collected over a time span of 16 years. A more accurate value of the period is deduced: P = 2 ... [more ▼]

The photometric behavior in the uvby system of the Ap star HD34631 has been reanalyzed on the basis of data collected over a time span of 16 years. A more accurate value of the period is deduced: P = 2.20269 +/-0.00004d. The lightcurves show a double-wave shape. The variations are smallest in the v band. [less ▲]

Photometric variations of the irregular variable V348 SGR

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 ▲]

Photometry of comet Austin.

in The Messenger (1990), 59

Strömgren photometry of Gomet Austin (1989 c 1) has been obtained at La Silla with the ESO-SAT 50-cm telescope, between February 12 and February 25, 1990. Two diaphragms were selected, 35 arcsec and 240 ... [more ▼]

Strömgren photometry of Gomet Austin (1989 c 1) has been obtained at La Silla with the ESO-SAT 50-cm telescope, between February 12 and February 25, 1990. Two diaphragms were selected, 35 arcsec and 240 arcsec, in an attempt to distinguish between the nucleus and the coma. [less ▲]

Photometry of HR 3413.

in IAU Archives of unpublished observations of variable stars file number :, 55, 1 (1977) (1977), 55

Not Available

Photometry of southern stars in the uvby system.

in Bulletin de la Société Royale des Sciences de Liège (1980), 49

Not Available

Photometry of the Wolf-Rayet Star HD 191765

in Information Bulletin on Variable Stars (1985), 2821

Not Available

Photometry with FORS at the ESO VLT

in Sterken, C. (Ed.) The Future of Photometric, Spectrophotometric and Polarimetric Standardization (2007, April 01)

ESO's two FOcal Reducer and low dispersion Spectrographs (FORS) are the primary imaging cameras for the VLT. Since they are not direct-imaging cameras, the accuracy of photometry which can routinely be ... [more ▼]

ESO's two FOcal Reducer and low dispersion Spectrographs (FORS) are the primary imaging cameras for the VLT. Since they are not direct-imaging cameras, the accuracy of photometry which can routinely be obtained is limited by significant sky concentration and other effects. Photometric standard observations are routinely obtained by ESO, and nightly zero points are computed mainly for the purpose of monitoring the instrument performance. The accuracy of these zero points is about 10%. Recently, we have started a program to investigate, if and how percent-level absolute photometric accuracy with FORS can be achieved. The main results of this project are presented in this paper. We first discuss the quality of the flatfields and how it can be improved. We then use data with improved flatfielding to investigate the usefulness of {Stetson standard fields} for FORS calibration and the accuracy which can be achieved. The main findings of the FORS Absolute Photometry Project program are as follows. There are significant differences between the sky flats and the true photometric response of the instrument which partially depend on the rotator angle. A second order correction to the sky flat significantly improves the relative photometry within the field. Percent level photometric accuracy can be achieved with FORS1. To achieve this accuracy, observers need to invest some of the assigned science time for imaging of photometric standard fields in addition to the routine nightly photometric calibration. [less ▲]