2. Observations

We mainly selected bright stars, i.e. not fainter than about 7.5 mag, whose period was known from visible light variability.

The observations have been carried out in the near IR bands J, H, and K at the 1 m photometric telescope at ESO, La Silla, Chile, using an InSb detector cooled with liquid nitrogen. Central wavelengths and bandwidths (in m) of the used filters are:

J 1.24 0.32

H 1.63 0.28

K 2.19 0.39.

A detailed description of the ESO infrared photometers can be found in Bouchet (1989). The integration times, the number of cycles, and the desired rms accuracy in the mean level were optimized to get a 2% maximum error in the observations: the resulting accuracy in the final reduced data is typically 0.006 mag. ESO standard software was used for all reduction steps.

All program stars were measured relative to closeby comparisons, which were chosen to have as similar color and brightness as possible. Magnitudes in the standard IR system (Bouchet et al. 1991) have also been obtained by observing suitable standard stars from the ESO list. The program stars and their comparisons are listed in Table 1 (click here).

The data have been collected during several observing runs from July 1986 through January 1993. The list of the observing runs is given in Table 2 (click here) together with the symbols used in the figures to identify the observations made in each run.

For many stars we could get phase covering observations which we shall present here in more detail.

 

Program Stars Comparison Stars

HD  HR Sp. type m_V <J> <H> <K> HD   HR Sp. type m_V <J> <H> <K>

3980 183 A7 SrCrEu 5.71 5.606 5.621 5.598 4150 191 A0 IV 4.36 4.354 4.345 4.317

24712 1217 A9 Sr 5.99 5.454 5.325 5.285 25165 1235 gK5 5.90 3.109 2.340 2.159

49976 2534 A1 SrCrEu 6.29 6.301 6.333 6.321 49481 -- B8 6.7 7.035 7.083 7.093

72968 3398 A2 SrCr 5.72 5.717 5.754 5.752 73997 3285 A8 IV 6.15 6.640 6.666 6.657

83368 3831 A7 SrCrEu 6.17 5.750 5.647 5.614 82578 -- A9 IV/V 6.54 6.060 5.950 5.915

96616 4327 A3 Sr 5.15 5.066 5.060 5.049 95370 4293 A3 IV 4.39 4.155 4.104 4.075

98088 4369 A9 SrCrEu 6.14 5.842 5.806 5.774 96620 4315 F0 Vn 6.09 5.531 5.393 5.347

101065 -- F0 HoDy 8.02 7.166 7.001 6.955 101388 -- A5 7.8 7.396 7.311 7.272

111133 4854 A1 SrCrEu 6.34 6.341 6.376 6.368 109860 4805 A1 V 6.33 6.288 6.301 6.282

118022 5105 A2 CrEuSr 4.94 4.915 4.940 4.926 121607 5244 A8 V 5.91 5.507 5.402 5.359

125248 5355 A1 EuCr 5.87 5.902 5.922 5.917 124683 5332 A1 V 5.43 5.582 5.606 5.599

126515 -- A2 CrSr 7.1 7.132 7.164 7.162 121607 5244 A8 V 5.91 5.515 5.399 5.367

137949 -- F0 SrEuCr 6.7 6.352 6.319 6.293 138268 5756 A8 V 6.22 5.938 5.857 5.824

148898 6153 A7 Sr 4.45 4.261 4.233 4.210 150453 6202 F4 IV 5.57 4.718 4.478 4.425

153882 6326 A1 CrEu 6.31 6.227 6.205 6.178 153809 -- A0 7.0 7.089 6.997 6.954

164258 6709 A3 SrCrEu 6.37 6.069 6.019 5.982 164259 6710 F2 IV 4.62 3.955 3.772 3.725

203006 8151 A2 CrEuSr 4.82 4.744 4.725 4.700 202135 8117 K2 III 6.21 5.885 5.924 5.915

206088 8278 F0 p 3.68 3.202 3.093 3.045 206677 8302 F0 V 5.99 5.565 5.460 5.418

220825 8911 A1 CrSr 4.95 4.957 4.979 4.968 221675 8944 A2m 5.87 4.609 4.065 3.948

221760 8949 A2 SrCrEu 4.70 4.547 4.525 4.498 220401 8896 K0 6.09 3.681 2.932 2.753

 

 

Run N. Dates symbol observer

1 1986 Oct. 13 - 23 RK

2 1987 Nov. 1 - 8 FAC

3 1989 Apr. 19 - 26 FAC

4 1991 Mar. 23 - 31 FAC

5 1991 Oct. 19 - 31 FAC

6 1993 Jan. 19 - 31 FAC

7 1993 Oct. 1 - 11 FAC

Table 2: The list of the runs and the symbols used to represent in the figures the observations collected in different runs