# Stellar extinction

1. Aug 3, 2009

### Sux

Hi! In this problem I have to calculate the distance to a cefeide star, I know visual magnitude, $$m_{v}$$, his magnitude in B range, $$m_{b}$$ and its period, $$P$$.

Well, if I ignore extinction, I can calculate the distance with $$M_{V}$$:

$$m_{v}=M_{V}+5log(\frac{r}{10})+A_{v}$$

Where $$A{v}$$ is visual magnitude extinction.

As I know color index:

$$m_{b}-m_{v}=M_{B}-M_{V}+E_{B-V}$$

Where: $$E_{B-V}$$ is color excess.

And:

$$\frac{A_{V}}{E_{B-V}}\approx3$$

I just need to calculate absolute magnitude in B range, $$M_{B}$$, to calculate extinction and be able to calculate the distance.

Any ideas about how could I do it?

I apologize for my mistakes, I am still learning English.

Thanks.

2. Aug 3, 2009

### negitron

Your English is quite good, although I don't understand what you mean by "extinction" (it means something specific in English--it's what happened to the dinosaurs). If you define it clearly, I can probably give you the correct word.

3. Aug 3, 2009

### captn

Stellar extinction has to do with the loss of light due to gas/dust in the path to the observer --atmospheric extinction due to volcanic dust, extinction due to dust around a star, for example.

It must be corrected for to determine the intrinsic brightness of a star.

Neil

4. Aug 4, 2009

### Sux

Yes, stellar "extinction" is the loss of flux or brightness due to interstellar dust.

Here you have it: http://nedwww.ipac.caltech.edu/level5/Mathis/Mathis1.html" [Broken]