Speakers
Description
Through the investigation of radial-velocity measurements of standard stars, we study the stability of the ACE fiber-fed échelle spectrograph at Piszkéstető and how instrumental and environmental effects influence the measured radial velocities. Understanding these effects is important in stellar spectroscopy, since systematic shifts in the measured spectra can affect the velocities derived from observations and consequently the physical conclusions obtained from them. Our work consisted of identifying which factors can contribute to these inaccuracies. Using existing data, conducting our own observations, and a physical site visit to inspect the spectrograph, we were able to identify a considerable drift.
We benchmarked our measurements against the well-known radial velocities of standard stars and used piszkespipe, a spectral-reduction pipeline specifically developed for the spectrograph, to obtain the radial velocities, which we then compared with the reference values to calibrate the instrument and account for any drift. Furthermore, suspecting the existence of same-night systematic drift due to environmental factors, we studied the individual and combined effects of different environmental factors such as humidity, atmospheric pressure, and temperature, both indoors and outdoors. We found a global zero-point offset of approximately +0.50 km/s, which can be corrected consistently, while we also found evidence that environmental factors affect the measured radial velocities. However, we were not able to find a reliable correction that worked across all stars and nights. Following the identification of two anomalous observing nights, we also investigated atmospheric seeing as a potential contributor to the observed radial-velocity deviations.