I Is this the correct representation for showing the direction of a star on CMD?

[hraghav]

Homework Statement: Effects of extinction in the Colour- Magnitude Diagram (CMD) of NGC 5139;
Since extinction affects the position of a star on both the x-axis and y-axis, then draw an arrow that shows the direction a star moves on the CMD for Av = 1.0
Relevant Equations: No equations are needed for this

Is the red arrow marking the star's direction correctly for Av = 1 magnitude? Im a little confused with this, also is there any other points we could keep in mind while doing such problems?
Thank you

 

[ergospherical]

= (reddening, dimming)
= ($\Delta(B-V)$, $\Delta m_V$)
= ($A_V/R_V$, $A_V$)
= ($1/R_V$, $1$)

If you want the slope you need the dust law $R_V$
You can use a local R_V ~ 3

 

[hraghav]

= (reddening, dimming)
= ($\Delta(B-V)$, $\Delta m_V$)
= ($A_V/R_V$, $A_V$)
= ($1/R_V$, $1$)

If you want the slope you need the dust law $R_V$
You can use a local R_V ~ 3

What would the coordinates be for the initial and final positions of B-V and mv?
I know that initial position of B-V is 0.333 but how would I find its final position since I do not know what (B-V)not is. Also as -1 is not on the scale of mv how would I choose the coordinates for mv?

 

[ergospherical]

The start coordinates whatever are the intrinsic color and magnitude of the star. When we see the star from Earth, we get reddening and dimming effects due to the dust. The position of the star on the CMD appears to shift by the vector ($\Delta$color, $\Delta$magnitude).

 

[hraghav]

The start coordinates whatever are the intrinsic color and magnitude of the star. When we see the star from Earth, we get reddening and dimming effects due to the dust. The position of the star on the CMD appears to shift by the vector ($\Delta$color, $\Delta$magnitude).

So my arrow marking location would be an appropriate representation of the direction since the star does travel upwards as it gets dimmer and towards the right as it gets redder?

 

[ergospherical]

An oddity of astronomy is that dimmer ==> larger m_V.
It's because m_V := C - 2.5 log (F),
(F being observed flux)

So you need to be careful to figure out which way the star goes. It doesn't help that astronomers like to write the scales upside down either