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APPENDIX

Although the J and K filters used in this study are similar to those employed in the original infrared photometric system as described by H. L. Johnson and others, the need for a high degree of internal accuracy required the determination of a new set of standard magnitudes. Twenty-one stars, selected so that a reasonably large range of brightness and color could be spanned were set up as standards.

Individual standards were typically observed on 10-20 different nights with between one and three observations per night. The system was closed once around the sky, and no systematic closure errors were found. We estimate that the internal accuracy of the system is ± 0.01 mag at H, K, and in the CO index; and ± 0.03 mag at J. A combination of the transmission characteristics of the J filter, the atmosphere, and the field lens, and the rounded nature of the beam profile, causes the J measurements to have the largest uncertainty.

Table Al contains the J - H and H - K colors, K-magnitudes, and CO indices for our grid of standards. The zero-point of this system is set by defining the magnitudes and colors of alpha Lyr to be 0.00 at all wavelengths. If allowance is made for the fact that Johnson (1966b and references therein) takes K(alpha Lyr) = + 0.02, there is no systematic difference between the magnitude scales of Johnson and of Table Al based on a comparison of 16 stars. Thus, except for the zero-point shift, the V - K values in this paper are on the system of Johnson. Because the effective wavelength of our J-filter is different from that of Johnson, a small transformation exists between the two systems. To transform the J-magnitudes of this paper to the Johnson (1966b) system, the following equation is adequate

JJ = 1.09(J - H) + H (A1)

i. e., the J - K colors in this paper are systematically blue compared with Johnson's. We caution other observers using the photometric system defined by these stars to check carefully for the presence of a color equation, particularly at 1.2 µm.

Table A1. Standard Stars

Name Sp. Type V K J-H H-K CO

BS 117 MO III 5.71 1.87 0.74 0.16 0.155
BS 134 KO III 6.30 4.07 0.45 0.08 0.04
BS 718 B9 III 4.28 4.38 -0.05 -0.02 0.00
BS 923 KO III 5.99 3.74 0.49 0.08 0.05
BS 1552 B2 III 3.69 4.14 -0.04 -0.05 0.00
BS 1698 K3 III 4.46 1.84 0.53 0.10 0.095
BS 3304 KS III 5.63 2.37 0.66 0.13 0.15
BS 3403 K2 III 4.59 1.88 0.54 0.06 0.08
BS 3427 KO III 6.39 4.25 0.48 0.07 0.04
BS 4039 dF5 5.82 4.49 0.28 0.03 -0.005
BS 4550 G8 VI 6.45 4.42 0.44 0.06 0.005
BS 4608 G8 III 4.13 1.89 0.47 0.05 0.05
BS 4689 A2 V 3.88 3.77 -0.05 -0.01 -0.005
HD 107906 K - 7.04 0.39 0.05 0.035
HD 132950 K - 6.33 0.51 0.07 0.04
BS 5634 F5 V 4.92 3.88 0.22 0.02 0.00
BS 6092 B5 IV 3.89 4.30 -0.06 -0.05 0.01
BS 6136 K4 III 5.39 2.02 0.66 0.14 0.145
BS 6228 K5 III 5.16 1.44 0.72 0.15 0.165
BS 7001 AO V 0.00 0.00 0.00 0.00 0.00
BS 8498 K3 II-III 4.12 0.99 0.62 0.13 0.15
BS 8551 KO III-IV 4.80 2.29 0.53 0.09 0.07

Table A2 contains measurements of selected high luminosity late-type stars. These data were used to define mean relationships between colors, CO index, and spectral type, and can be employed to establish transformations from the present photometric system to any other system. The three supergiants in Cygnus, plus the stars identified with BD numbers, are heavily reddened (Lee 1970).

Table A2. Selected M Giants and Supergiants

Name Sp. Type K J-H H-K CO

BS 3027 M2 II-III 2.01 0.83 0.20 0.20
BS 3705 M0 III -0.61 0.84 0.16 0.17
BS 4008 MO III 2.10 0.80 0.17 0.20
BS 4069 MO III -0.84 0.79 0.15 0.18
BS 4336 M2 III 1.44 0.79 0.18 0.20
BS 4902 M3 III 0.14 0.82 0.20 0.20
BS 4910 M3 III -1.25 0.80 0.18 0.21
BS 5879 gMl 0.05 0.82 0.17 0.19
BS 7139 M4 II -1.17 0.85 0.21 0.26
BS 7157 M5 III -2.06 0.83 0.26 0.25
BK Vir M7 III -0.91 0.89 0.33 0.25
SW Vir M7 III -1.88 0.91 0.34 0.27
RT Vir M8 III -1.18 0.90 0.36 0.24
BC Cyg M4 Ia 0.25 1.17 0.54 0.33
AZ Cyg M2 Ia 1.31 0.97 0.38 0.34
KY Cyg M4 Ia 1.54 1.27 0.59 0.30
+9° 3920 M2 III 4.37 0.85 0.22 0.21
+29° 3730 M4 III 1.95 0.85 0.24 0.21
+35° 4138 M3 III 3.89 0.86 0.23 0.20
+59° 2541 M2.5 III 4.46 0.85 0.26 0.18
+64° 1842 M2 II 3.11 1.03 0.33 0.19
+42° 1065 MO III 5.66 0.83 0.20 0.14

Table A3 gives the adopted mean relationships based on the system of Tables Al and A2. The V - K and J - K colors as functions of spectral type for the giants are transformed from Johnson (1966b) for stars earlier than M0 and from Lee (1970) for MO-M6. The H - K colors and CO indices of the giants are from the data of Tables Al and A2 and from additional unpublished measurements. All of the mean values for the dwarf's are based on our own infrared measurements plus V-magnitudes from the literature. The agreement with most of the recently published infrared photometry of dwarfs (e.g., Mould and Hyland 1976) is generally better than ± 0.02 mag at all wavelengths. A complete discussion of our observations of late-type dwarfs will be presented elsewhere.

Table A3. Adopted Mean Colors

Giants

Dwarfs

Sp. Type V-K J-H H-K CO V-K J-H H-K CO

G5 2.08 0.47 0.05 0.03 1.25 0.26 0.04 0.01
G8 2.16 0.49 0.06 0.04 1.50 0.32 0.05 0.02
KO 2.35 0.51 0.08 0.07 1.75 0.37 0.06 0.02
K1 2.48 0.54 0.09 0.09 2.00 0.42 0.07 0.03
K2 2.59 0.56 0.10 0.11 2.25 0.47 0.08 0.04
K3 2.92 0.62 0.12 0.12 2.50 0.52 0.09 0.04
K4 3.24 0.68 0.13 0.14 2.75 0.56 0.10 0.04
K5 3.67 0.73 0.15 0.15 3.00 0.59 0.11 0.04
MO 3.74 0.74 0.16 0.17 3.25 0.63 0.13 0.04
M1 3.90 0.76 0.17 0.18 3.50 0.65 0.14 0.04
M2 4.16 0.77 0.18 0.19 3.75 0.65 0.16 0.03
M3 4.63 0.79 0.20 0.21 4.00 0.63 0.21 0.02
M4 5.34 0.81 0.23 0.22 4.25 0.60 0.22 0.00
M5 6.20 0.86 0.26 0.23 4.50 0.57 0.24 -0.02
M6 7.20 0.89 0.30 0.24 4.75 0.54 0.25 -0.03
M7 - 0.91: 0.33: 0.25: 5.00 0.53 0.26 -0.04
M8 - 0.89: 0.37: 0.26: 5.25 0.52 0.28 -0.05
          5.50 0.53 0.29 -0.05
          5.75 0.54 0.31 -0.04
          6.00 0.55 0.32 -0.04
          6.25 0.57 0.33 -0.03
          6.50 0.59 0.35 -0.03
          6.75 0.61 0.36 -0.02
          7.00 0.62 0.37 -0.02
          7.25 0.63 0.38 -0.01
          7.50 0.65 0.39 -0.01

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