NB: There is also a very good, up to date article on general photometric systems by Mike Bessell, 2005, Ann. Rev. 43, 293.
References:
References:
m(AB) = -2.5 log(f) - 48.60where the value of the constant is selected to define m(AB)=V for a flat-spectrum source. In this system, an object with constant flux per unit frequency interval has zero color.
References:
V = V(AB) + 0.044 (+/- 0.004) B = B(AB) + 0.163 (+/- 0.004) Bj = Bj(AB) + 0.139 (+/- INDEF) R = R(AB) +-0.055 (+/- INDEF) I = I(AB) +-0.309 (+/- INDEF) g = g(AB) + 0.013 (+/- 0.002) r = r(AB) + 0.226 (+/- 0.003) i = i(AB) + 0.296 (+/- 0.005) Rc = Rc(AB) +-0.117 (+/- 0.006) Ic = Ic(AB) +-0.342 (+/- 0.008)Source: Frei & Gunn 1995
Band | lambda_c | dlambda/lambda | Flux at m=0 | Reference |
---|---|---|---|---|
&mu | Jy | |||
U | 0.36 | 0.15 | 1810 | Bessel (1979) |
B | 0.44 | 0.22 | 4260 | Bessel (1979) |
V | 0.55 | 0.16 | 3640 | Bessel (1979) |
R | 0.64 | 0.23 | 3080 | Bessel (1979) |
I | 0.79 | 0.19 | 2550 | Bessel (1979) |
J | 1.26 | 0.16 | 1600 | Campins, Reike, & Lebovsky (1985) |
H | 1.60 | 0.23 | 1080 | Campins, Reike, & Lebovsky (1985) |
K | 2.22 | 0.23 | 670 | Campins, Reike, & Lebovsky (1985) |
g | 0.52 | 0.14 | 3730 | Schneider, Gunn, & Hoessel (1983) |
r | 0.67 | 0.14 | 4490 | Schneider, Gunn, & Hoessel (1983) |
i | 0.79 | 0.16 | 4760 | Schneider, Gunn, & Hoessel (1983) |
z | 0.91 | 0.13 | 4810 | Schneider, Gunn, & Hoessel (1983) |
Also useful are these identities:
1 Jy = 10^-23 erg sec^-1 cm^-2 Hz^-1 1 Jy = 1.51e7 photons sec^-1 m^-2 (dlambda/lambda)^-1Example: How many V-band photons are incident per second on an area of 1 m^2 at the top of the atmosphere from a V=23.90 star? From the table, the flux at V=0 is 3640 Jy; hence, at V=23.90 the flux is diminished by a factor 10^(-0.4*V)=2.75e-10, yielding a flux of 1.e-6 Jy. Since dlambda/lambda=0.16 in V, the flux per second on a 1 m^2 aperture is
f=1.e-6 Jy * 1.51e7 * 0.16 = 2.42 photons sec^-1
Bands | Equation | Reference |
---|---|---|
Gunn g to Johnson B: | B = g + 0.51 + 0.60*(g-r) | [1] |
Gunn g to Johnson V: | V = g - 0.03 - 0.42*(g-r) | [1] |
Gunn r to Mould R: | R = r - 0.51 - 0.15*(g-r) | [1] |
Gunn g to Photographic J: | J = g + 0.39 + 0.37*(g-r) | [1] |
Gunn r to Photographic F: | F = r - 0.25 + 0.17*(g-r) | [1] |
Gunn i to Mould I: | I = i - 0.75 (approx) | [1] |
Lunar Age | U | B | V | R | I |
---|---|---|---|---|---|
(days) | |||||
0 | 22.0 | 22.7 | 21.8 | 20.9 | 19.9 |
3 | 21.5 | 22.4 | 21.7 | 20.8 | 19.9 |
7 | 19.9 | 21.6 | 21.4 | 20.6 | 19.7 |
10 | 18.5 | 20.7 | 20.7 | 20.3 | 19.5 |
14 | 17.0 | 19.5 | 20.0 | 19.9 | 19.2 |
Source: NOAO Newsletter #10.