Star temperature from B-V color

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SUMMARY

The calculation of a star's temperature from its B-V color index involves specific equations that relate the B and V magnitudes to flux ratios. The formulas provided are B = -2.5log(F440)+C and V = -2.5log(F550)+C, leading to B-V = -2.5log(F440/F550). For practical temperature estimation, the equations B-V = -3.684 log(T) + 14.551 (for log(T) < 3.961) and B-V = 0.344 (log(T))^2 -3.402 log(T) +8.037 (for log(T) > 3.961) are utilized. These relationships are derived from experimental fits to the Hertzsprung-Russell diagram and can be connected to Planck's law and the Stefan-Boltzmann law.

PREREQUISITES
  • Understanding of B-V color index in astronomy
  • Familiarity with logarithmic equations
  • Knowledge of Planck's law
  • Basic principles of the Stefan-Boltzmann law
NEXT STEPS
  • Study the derivation of the B-V color index and its significance in stellar classification
  • Learn about Planck's law and its application in astrophysics
  • Explore the Hertzsprung-Russell diagram and its relevance to stellar temperatures
  • Investigate the Stefan-Boltzmann law and its implications for blackbody radiation
USEFUL FOR

Astronomy students, astrophysicists, and anyone interested in stellar temperature calculations and the relationships between color indices and flux ratios.

poiuy
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Homework Statement



I need to know how to calculate the temperature of a star from it's B-V color



Homework Equations




B = -2.5log(F440)+C
V = -2.5log(F550)+C
B-V = -2.5log(F440/F550)


The Attempt at a Solution



Really no idea, all my textbooks say that B-V color is used to measure temperature but none of them say how. I also can't find anything linking flux ratios to temperature.

Any help appreciated :)
 
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From my list of handy astronomy values
B-V = -3.684 log(T) + 14.551 (for log(T) < 3.961)
B-V = 0.344 (log(T))^2 -3.402 log(T) +8.037 (for log(T) >3.961)

Note that B-V is also called the color-index of a star.

These are experimental fits to the HR diagram for some cluster - you can probably derive it from Planck's law + stefan-boltzmann if you know the filter bandwidth.
 
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