Astron. Astrophys. 321, 145-150 (1997)

Astron. Astrophys. 321, 145-150 (1997)

2. Observations

The observations have been carried out at the Pico del Veleta Observatory (Granada, Spain) in 1987, during 5 nights, with a 62 cm telescope, a "Geneva" type photometer and two filters (UV #4 and blue #5 in Sareyan et al., 1976); and in 1992 in San Pedro Martir Observatory (Baja California, Mexico) both for 5 nights with a 84 cm telescope (photometer "Cuentapulsos", Johnson's V with a neutral filter, and Stromgren's b), and for 6 nights with a 150 cm telescope and the "Danish" spectrophotometer, i.e. in simultaneous Stromgren's u v b y , b and v channels beeing attenuated by a factor [FORMULA] 2 neutral filter, located inside the spectrophotometer (Table 1).

[TABLE]

Table 1. The observations.

The comparison stars were HR 8766 (2 And, A3Vn) and HR 8708 (A3m+F6V); HR 8733 (B2IV-V) was also added in the observing cycles at San Pedro Martir Observatory. These stars have been checked for constancy within a few millimagnitudes (Sareyan et al., 1994). The Figs. 1 and 2 give examples of observations. All the present data will be sent to the IAU Archives of unpublished observations of variables stars.

Fig. 1. Example of a blue filter light curve for a single night in 1987 (16Lac - HR8766). Vertical ticks are 5 mmag apart, horizontal scale is HJD - 2400000. Light increases upwards (magnitudes downwards) in the Figs. 1, 2, 3 of this paper.

Fig. 2. As Fig. 1 in 1992

The filter #5 mentionned above is close to Stromgrens' b, so that the observations made in these narrow bandpass blue filters can be compared, and the derived amplitudes directly fit together, as already mentionned in Garrido et al.(1983). In order to do so, we applied corrections to the 84 cm telescope b data and to the 150 cm telescope b data (-0.41581 and -0.40427 magnitude, respectively), so that the mean magnitude on the comparison star HR8766 is zero for both instrumental systems. We used here the GBFOM programs described in Sareyan et al. (1992).

Online publication: June 30, 1998
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