Nicole Engel & Tom Wachsmuth
In the context of an advanced lab exercise we observed the transit of the exoplanet TOI-4145A b orbiting the star TOI-4145A in the constellation Cepheus. A transit occurs, when a planet orbiting another star moves between said star and the observer on earth. By measuring the relative brightness of the star compared to stars of constant brightness a light curve can be created, that gives information about the transit and the planet.
The observation took place on November 7th 2023 between 00:20 h to 05:00 h UTC. This time frame was ideal, as there was little cloud coverage at the observation location during this time and the moon did not appear in the sky as well. We used a remote controlled reflector telescope (CDK17 by PlaneWave) located near Fregenal de la Sierra in Spain.
By using the methods called differential photometry and aperture photometry, the apparent brightness of the star we want to observe (var) and the stars with which we want to compare it (comp) is determined. This gives us the relative brightness SV/SC of the star over the observation duration, which is called a light curve. By fitting a trapezoidal curve to the light curve a transit depth of ∆m = 0.0188(6) mag and a transit duration of Ttransit = 0.079(5) d is determined. From this the ratio of the radius of the exoplanet RP to the radius of the star it orbits R* can be calculated to RP/R* = 0.0867(15).
