P03: Variable Stars

Observing Goals:

You will observe the light curve of a short period variable star over the course of a night Useful Background and References:

Observation Planning:

  • Observation Time

    • You will be observing a HALF night. You will share your data with another team observing the other half of the night.

      • One group (Variable Star 1 and 3) will use the B and V filter images

      • One group (Variable Star 2 and 4) will use the V and R filter images

  • Target Selection

    • Together with the other group, select a target that will reach its highest point in the sky at around 1:30am (half way between sunset and sunrise). A list of possible targets with finder charts is attached.

  • Observations

    • You will observe the variable star in the B,V and R filters over the duration of the night

    • If possible, take standard star fields at the start and end of your observations to allow for calibration to the magnitude scale.

  • Tools

    • Read the “Automatic filter changer” under “Tools for observing”.

Data Analysis:

  • Data Reduction Basic Steps

  • Further for this project

    • You need to align all of your images – but no not combine them

    • For each filter the you are assigned, you will do relative photometry (measuring brightness) over time to create a light curve

    • Identify other, non-variable, stars in the field to use as reference

  • Further Analysis for this project

    • Plot the corrected magnitude of the star as a function of time for each filter – note that you should get the observation time from the header of the image, and account for the length of the exposure!

    • (You can also investigate if the colour between bands changes over time)

Results:

Can you answer these questions with your work?

  • What is the shape of the variability? Is it sinusoidal or some other shape?

  • What is the period of the variability (the time between successive peaks or dips)?

  • What is the total amplitude of the variability? Does it change with band?

  • Does the star’s colour change with time?

  • What kind of star is this? Why do these sort of stars pulsate?

Presenting your results: