Vega Spectrum

[johnb]

Hi

So a few bits to sort but I think im on my way

Regards

John B

[ncjunk]

That looks good, whats the next step? How would you try to improve on it?

I know nothing about taking these kind of measurements

[the rev]

Great image , lots of good clear points showing. What's next - creating an instrument response and dividing it by the above spectrum to get a corrected version.

Kate

[Gasman]

Nice one John and nicely presented/labeled, The Qhy is giving you a lot more detail!

Steve

[johnb]

Thanks for the feedback, I will do an instrument response, can I determine the temperature of the star from the Spectrum ?

John B

[the rev]

I'm sure there was something on one of the yahoo forums about using spectra to sort a stars temperature, but I can't find it at the moment. Will keep looking.

[robin_astro]

Very nice John. You are indeed on your way. Congratulations!

Once you have corrected for the instrument respnse, there are a couple of ways you can tell the temperature from a low resolution spectrum like this.

1. Match the broad shape of the curve to a black body curve. Some programs, like Visual Spec for example have this feature bult in. Note though that this is very rough as stars are not really very good black bodies and the effects of our atmosphere and the interstellar medium affects the shape of the spectrum.

2. What lines appear in the spectrum and their intensity depends on the temperature (The basis of the MK system of spectral classification OBAGBKM) You can therefore compare the features in the spectrum with standard stars of differerent classes, for example using the Pickles standards built into programs such as RSpec, Vspec and ISIS (The temperature is known for each class) This is in theory a better technique as it is not affected by atmospheric or interstellar extinction but it can be difficult to do accurately at the Star Analyser resolution as the lines can become blended together and indistinct.

There are other ways, for example by modelling the exact shape of the line, which depends on factors such as temperature, pressure and how fast the star is rotating but this needs a high resolution spectrograph.

Cheers

Robin

[robin_astro]

the MK system of spectral classification OBAGBKM)

Oops that seems to have come out as somewhat dyslexic version . It should of course be OBAFGKM(S)

http://en.wikipedia.org/wiki/MK_spectral_classificatio

Robin

[robin_astro]

1. Match the broad shape of the curve to a black body curve. Some programs, like Visual Spec for example have this feature bult in.

Here is a step by step guide on how to do this using a Star Analyser and Visual Spec software from the Shelyak website

http://www.shelyak.com/dossier.php?id_dossier=18

Cheers

Robin