Unformatted text preview: Ideally, Flux would be the total energy emitted, but in practice we measure
dierent wavelength bands with dierent instruments or detectors. In such
cases we label it by a letter telling which band (e.g. V = visual) and it then
means \energy per area per time arriving in that band."
The most common bands are U = \ultraviolet," B = \blue," V = \visual,"
R = \red," I, J, K = \infrared."
Transparency (%) 100
3000 4000 5000 6000 A Wavelength Light Transmission Through UBV Filters. This graph shows the wavelength ranges over which the standardized U, B, and V lters are transparent to light. The U lter is
transparent to the near-ultraviolet. The B lter is transparent from about 380 to 550 nm,
and the V lter is transparent from about 500 to 650 nm.
3650 4400 5500 7000 9000 1.25 2.2
Eective width (dened 680 980 890 2200 2400 0.38 :48
(by area under curve)
log f (erg cm 2 s 1 1 ) -4.37 -4.18 -4.42 -4.76 -5.08 -5.48 -6.40
for m = 0 Note that 1000= 100 nm = 0.1. We write F , F , F , etc. for in-band
A uxes. When we need a word for \real, total energy" we say bolometric, so:
U B V L = total luminosity in all bands.
bol To interpret the last line in the above table, we need to know about the
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This note was uploaded on 12/29/2011 for the course AST 350 taught by Professor Dion during the Fall '09 term at SUNY Stony Brook.
- Fall '09