Week 7: Applying Corrections Using Standard Stars, Equations, and Fixing Big Errors

Hello, everyone! Welcome back to my blog! In last week’s post, I detailed how I finished using exposure times to correct my data. I also began using standard stars to fix my data, and explained why having these constant stars as a reference matters. 

This week, I’ll be (hopefully) finishing up my project’s standard star stint.

Standard Stars:

I had already chosen USNOA2 0450-17805518 (which is pretty much just a random boring star) for my standard star. I finally managed to successfully extract the counts (a value which can be converted into brightness) and stored my counts in an array. I used this equation to correct my values:

https://ibb.co/k9Dr15H

However, the graph I generated after was not very nice-looking. There were still some strange values which didn’t lie on the curve. This suggested that there was some problem with what I did. For reference, the graph at this point looked like this:

https://ibb.co/C9jjchY

It looks a lot nicer, but a correct version would not have any outliers (or at max, one or two), since supernovae grow dimmer at a steady rate. I spent a few days going over my process and seeing if I could identify any errors.

I decided to see if my data would magically fix itself if I used another standard star. So I repeated the process for another star, and the problem persisted.

Whoops:

So it turns out that the actual magnitudes of the standard stars — which I got from Sky Map — were wrong. All my data is in the g-band, which is a specific wavelength of light. Stars can have different magnitudes at different wavelengths, and I forgot to check which band Sky Map defaults to (hint: it’s not the g-band).

Sadly, I only recognized that mistake on the day that I’m posting this blog, which means that hopefully, by next week, we will have a nice-looking graph to look at.

Thank you for reading my blog, and see you all next time!