How to calculate magnitude of a star in a triple star system?

  • I want to find a star's magnitude in a triple star. I already knew the the magnitude of the triple star and the other two star, but I don't quit know how to solve it. Is there a way to find it?

  • Warrick

    Warrick Correct answer

    7 years ago

    Basically you need to convert between luminosities (which you can add) and magnitudes using
    Let's call the total luminosity $L_0$ and magnitude $M_0$ and the individual luminosities and magnitudes $L_1$, $L_2$ and $L_3$ and $M_1$, $M_2$ and $M_3$.
    Then, you have the total luminosity of the system, directly
    and as the sum of the components
    Solving these equations for $M_3$ gives
    I'm assuming you have absolute magnitudes, but you can rewrite the formulae in terms of apparent magnitudes using
    but I think the result then also depends on the distance.

    Surely the absolute magnitude of the Sun needs to be subtracted from the LHS of eqn. 4?

    @RobJeffries: You're right! Fixed.

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Content dated before 7/24/2021 11:53 AM