a) (6 marks) What three measurements (and from what data) do you need to produce
ID: 1624112 • Letter: A
Question
a) (6 marks) What three measurements (and from what data) do you need to produce a plot of absolute magnitude as a function of period for Cepheids?
b) (7 marks) Using the lower relation from Leavitt and Pickering (left panel) and the contem- porary Cepheid Period-Luminosity relation from Benedict et al. (right panel), determine the approximate distance to the Small Magellanic Cloud.
00 02 06 Q8 LO 12 IA 20 22 0.2 0.0 12 I4. I4 15 16 16 a -4.05 t 0.02 2.43 t 0.12 FIG. 2. 0.6 0.8 1.0 1.2 1.4 1.6 log P The original Small Magellanic Cloud Cepheid Period-Luminosity relation from Leavitt and Pickering (left panel) and a contemporary Cepheid Period-Luminosity relation from Benedict et al. (right panel). For both plots the x-axis is log period in days. The y-axis for the Leavitt and Pickering plot (left) is in apparent magnitude while the y-axis for the Benedict et al. (2007) plot is absolute magnitudeExplanation / Answer
a)
The (average) relative magnitude. Measure the maximum and minimum relative magnitude of the star for at least one full cycle, and then compute the average. `
The period over which the star’s brightness changes. If the period is short, an accurate result can be obtained by making measurements over more than one cycle, then dividing by the number of cycles
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