These stars are a subset of the UKIRT Faint Standards (Casali & Hawarden, 1992) which have subsequently been re-observed on numerous nights between late 1994 and early 1998, using the facility imager IRCAM3 (which has subsequently been rebuilt) during the extended UKIRT standard-star programme.

The stars retained from the earlier list have 10.0 > K > 15.0, so that most are readily observable by telescopes up to 10 m aperture, and are either single or, if double, of small enough separation to be easily reduced using standard aperture photometry. The results are in the natural system of the IRCAM3 imager, which used an InSb array behind a gold-coated dichroic (silver-dielectric coated after the beginning of 1997) and gold-coated fore-optics. Guarnieri et al. (1991) showed that the the system of the imager with an InSb array is close to that of the single-channel InSb photometer UKT9 with which the Casali & Hawarden's measurements were made. Transformations from that system to the CIT system of Elias et al. (1982) are given by Casali & Hawarden.

The Table lists the mean K magnitudes and J-H and H-K colours and their formal internal standard errors (``sem'', in parentheses), and the number of nights from which results were retained [``nights'', in square brackets]. Since these stars were being used as primary reference standards for a larger programme, the number of observations on each night was often 2 or more. The zero-points are derived from the Casali & Hawarden results for the same list of stars and are therefore self-referential. The number of other standards observed from the list on the nights from which data was retained ranged from 3 to 21 and averaged 11.

The internal mean errors are 0.^m0045 for the K magnitudes and 0.^m0034 and 0.^m0040 for the J-H and H-K colours, respectively. These are greatly improved relative to those of Casali & Hawarden, and for the most part correspond to stars of accuracy class a+ in Elias et al. 1982.

These results are being readied for formal publication (Hawarden, T.G., Letawsky, M.B., Ballantyne, D.R. & Casali, M.M., 2000, MNRAS, in preparation).

NB: An expanded list of stars has also been observed with results that are presented below.

Table 1.

Positions, JHK magnitudes and colours (with errors and number of nights observed) for the UKIRT Fundamental List.

NO         RA  (J2000)  Dec        K     sem      N      J-H   sem      N      H-K   sem      N

FS 1   00 33 54.48 -12 07 58.1   12.964 (0.004) [ 9]    0.387 (0.003) [10]    0.057 (0.004) [ 9]
FS 2   00 55 09.93 +00 43 13.1   10.472 (0.004) [12]    0.206 (0.003) [11]    0.035 (0.002) [12]
FS 3   01 04 21.63 +04 13 36.0   12.823 (0.003) [ 7]   -0.111 (0.003) [ 7]   -0.089 (0.005) [ 8]
FS 4   01 54 37.70 +00 43 00.5   10.284 (0.002) [11]    0.239 (0.004) [11]    0.032 (0.002) [11]
FS 5   01 54 34.65 -06 46 00.4   12.339 (0.005) [ 8]    0.004 (0.002) [ 7]   -0.005 (0.002) [ 8]
FS 6   02 30 16.64 +05 15 51.1   13.382 (0.005) [ 8]   -0.059 (0.005) [ 8]   -0.069 (0.005) [ 8]
FS 7   02 57 21.21 +00 18 38.2   10.945 (0.002) [14]    0.126 (0.002) [14]    0.032 (0.001) [14]
FS 10  03 48 50.20 -00 58 31.2   14.983 (0.011) [ 9]   -0.104 (0.006) [ 9]   -0.118 (0.010) [ 9]
FS 11  04 52 58.92 -00 14 41.6   11.254 (0.002) [18]    0.065 (0.001) [18]    0.022 (0.001) [18]
FS 12  05 52 27.66 +15 53 14.3   13.916 (0.006) [13]   -0.115 (0.003) [13]   -0.094 (0.005) [13]
FS 13  05 57 07.59 +00 01 11.4   10.140 (0.002) [12]    0.313 (0.002) [13]    0.048 (0.001) [12]
FS 14  07 24 14.40 -00 33 04.1   14.198 (0.008) [ 8]   -0.065 (0.007) [ 8]   -0.031 (0.010) [ 8]
FS 15  08 51 05.81 +11 43 46.9   12.348 (0.003) [13]    0.337 (0.003) [13]    0.054 (0.002) [13]
FS 16  08 51 15.01 +11 49 21.2   12.628 (0.004) [11]    0.290 (0.003) [11]    0.041 (0.002) [11] 
FS 17  08 51 19.31 +11 52 10.4   12.274 (0.002) [10]    0.327 (0.003) [10]    0.056 (0.002) [10] 
FS 18+ 08 53 35.51 -00 36 41.7   10.527 (0.002) [11]    0.252 (0.003) [11]    0.041 (0.002) [11] 
FS 19  10 33 42.75 -11 41 38.3   13.782 (0.006) [ 9]   -0.085 (0.005) [ 9]   -0.115 (0.007) [ 9] 
FS 20  11 07 59.93 -05 09 26.1   13.501 (0.010) [ 6]   -0.038 (0.006) [ 6]   -0.065 (0.008) [ 6]
FS 21  11 37 05.15 +29 47 58.4   13.147 (0.002) [ 9]   -0.069 (0.004) [ 9]   -0.090 (0.004) [ 9] 
FS 33  12 57 02.30 +22 01 52.8   14.254 (0.005) [ 6]   -0.112 (0.002) [ 5]   -0.103 (0.008) [ 5] 
FS 23  13 41 43.57 +28 29 49.5   12.375 (0.003) [11]    0.527 (0.003) [11]    0.066 (0.003) [11] 
FS 27  16 40 41.56 +36 21 12.4   13.128 (0.005) [10]    0.306 (0.005) [10]    0.048 (0.004) [10] 
FS 35  18 27 13.52 +04 03 09.4   11.748 (0.005) [14]    0.369 (0.003) [15]    0.084 (0.002) [15]
FS 34  20 42 34.73 -20 04 34.8   13.000 (0.004) [ 9]   -0.077 (0.003) [ 9]   -0.074 (0.005) [ 9] 
FS 29  21 52 25.36 +02 23 20.7   13.311 (0.003) [11]   -0.068 (0.002) [11]   -0.070 (0.003) [11] 
FS 30  22 41 44.72 +01 12 36.5   12.022 (0.003) [15]   -0.042 (0.002) [13]   -0.031 (0.002) [14]
FS 31  23 12 21.60 +10 47 04.1   14.037 (0.007) [10]   -0.130 (0.005) [10]   -0.099 (0.005) [10] 
FS 32  23 16 12.37 -01 50 34.6   13.676 (0.007) [ 8]   -0.107 (0.003) [ 8]   -0.086 (0.005) [ 8] 
 

NB: FS18 is a double; separation = 1."36, p.a. 96 degrees, Delta(K) = 2.2
(Y. Clenet 1999, personal communication)

Table 2.

Cross references, spectral types and optical photometry for the stars in Table 1.

FS   Other     Source Spec   Spec   V      B-V     U-B     V-R     R-I  Phot
                Ref   Type   Ref                                        Ref

 1  G158-100     2     DK-G   2   14.89   0.69     -       -       -     2
 2  SA92-342     1      F5    5   11.613  0.436  -0.042   0.266   0.270  9
 3  F11        1,2    sdB     6   12.065 -0.240  -0.978  -0.120  -0.142  9
 4  SA93-317     1      F5    5   11.546  0.488  -0.055   0.293   0.298  9
 5  F16        1,2      A0    6   12.406 -0.012   0.009  -0.003   0.002  9
 
 6  F22        1,2     DA3    8   12.799 -0.054  -0.806  -0.103  -0.105  9
 7  SA94-242     1      A2    5   11.728  0.301   0.107   0.178   0.184  9
10  GD50         2     DA2    8   13.99  -0.21   -1.22     -       -     8
11  SA96-83      1      A3    5   11.719  0.179   0.202   0.093   0.097  9
12  GD71         1     sdO    8   13.032 -0.249  -1.107  -0.137  -0.164  9
 
13  SA97-249     1      G4V   5   11.735  0.648   0.100   0.369   0.353  9
14  Rubin 149    2    O9-B2p  2   13.86  -0.14     -       -       -     2
15  M67-I-48     3    G5IV-V  *   14.05   0.70    0.17     -       -     3
16  M67-IV-8     3     G1V    *   14.18   0.61    0.09     -       -     3
17  M67-IV-27    3     G4V    *   13.95   0.61    0.05     -       -     3
 
18  SA100-280    1      F8    5   11.799  0.494  -0.002   0.295   0.291  9
19  G162-66    1,2     DA2    8   13.012 -0.165  -0.996  -0.126  -0.141  9
20  G163-50    1,2     DA3    8   13.059  0.035  -0.688  -0.085  -0.072  9
21  GD140        4     DA3    8   12.50  -0.06   -0.98     -       -     8
23  M3-VZ193     4    G8III   *   14.75   0.90      -      -       -    10

27  M13-A14      4     
29  G93-48     1,2     DA3    8   12.739 -0.008  -0.792  -0.097  -0.094  9
30  SA114-750    1      B9    5   11.916 -0.041  -0.354   0.027  -0.015  9
31  GD246      1,2     DA1    8   13.094 -0.318  -1.187  -0.148  -0.183  9
32  F108       1,2     DAs    7   12.958 -0.235  -1.052  -0.103  -0.135  9

33  GD153        4     DA1    8   13.42  -0.25   -1.18     -       -     8
34  EG141        4     DA3    8   12.34  -0.07   -0.83     -       -     8
35    -     See Note

*MK Spectral type estimated from J-K colours (Koorneef 1983) and
position in cluster CMD.

1. Landolt, 1983
2. Turnshek  et al., 1990
3. Eggen and Sandage,
4. B. Zuckerman, 1990, personal communication.
5. Drilling & Landolt, 1979
6. Klemola 1962 A.J., 67, 740
7. Greenstein, 1966
8. McCook & Sion, 1987
9. Landolt, 1992.
10. Sandage & Katem, 1982

(1) FS 35 is not the originally intended target, G21-15, but a nearby anonymous star. The coordinates for G21-15 in Turnshek et al (1990) are incorrect. (Those in Landolt 1983, 1992 are correct, however.) The star we have designated FS 35 has no optical photometry or spectroscopy known to us so the chance of variability is higher than for the other standards. However the 15 JHK observations on 8 nights show no significant signs of variability.

(2) Of the original Provisional List, several stars (FS 8, 9, 24, 25, 26 and 28) have not been retained. FS 8, FS 9 and FS 26 were too bright to observe with IRCAM on UKIRT in normal mode. FS 24 is SA 106-1024, a Delta Scuti variable (Landolt, 1990) which proves to have appreciable amplitude in the NIR. FS 25 and FS 28 are double. FS 28 in particular has a companion 3."6 N which is bright enough to affect our standardised photometry, which uses 8" apertures. (FS 18 is also double, but at 1."4 separation is only a threat to photometry in small apertures and was therefore well calibrated in this programme.)

References

Drilling,J.S. & Landolt, A.U., 1979. ApJ, 84, 783

Eggen, O.J. & Sandage, A.R., 1964 ApJ, 140, 130

Elias, J.H., Frogel, J.A., Matthews, K. & Neugebauer, G., 1982. AJ, 87, 1029

Greenstein,J.L., 1966. ApJ, 144, 496

Guarnieri, M.D., Dixon, R.I. & Longmore, A.J., 1991. PASP, 103, 675

Klemola, A.R., 1962. AJ, 67, 740

Koorneef, J., 1983. A&A, 128, 84

Landolt, A.U., 1983. AJ, 88, 439

Landolt, A.U., 1990. PASP, 102, 1382

Landolt, A.U., 1992. AJ, 104, 340

Sandage, A.R., & Katem, B., 1982. AJ, 87, 537

Turnshek, D.A., Bohlin, R.L., Williamson, R.L. II, Lupie, O.L., Koorneef, J, & Morgan, D.H., 1990. AJ, 99, 1243