Lichtcurves

Light curves, also known in German as Lichtkurven, are graphs that show the brightness of an astronomical object as a function of time. In practice brightness is measured as flux or apparent magnitude in one or more wavelength bands, and the curve tracks how the object brightens or dims over minutes, hours, days, or years. Light curves are produced by time-series photometry, typically using differential measurements against comparison stars to reduce atmospheric and instrumental effects. Time stamps are usually given in Julian Date or barycentric Julian Date to account for light-travel time.

Light curves are used to study variability and to infer physical properties. They reveal periodic phenomena such as pulsating stars, rotating spotted stars, and eclipsing binaries, as well as non-periodic events like stellar outbursts, novae, and supernovae. They are central to exoplanet detection via transits, which produce characteristic shallow, often box-shaped dips; microlensing events create symmetric magnifications; and tidal disruption events show rapid brightening.

Analysis often involves determining periods with Lomb-Scargle or Fourier methods, folding data to produce a phase curve, and fitting physical models or templates. The shape, amplitude, and time scale of a light curve constrain radii, temperatures, binary inclinations, and distances. Large surveys such as Kepler, TESS, OGLE, and LSST continually generate vast light curves for millions of objects, enabling population studies and time-domain astronomy. Data quality depends on cadence, photometric precision, and calibration, including flat-fielding, bias subtraction, and sky background estimation.