Lomb-Scargle periodogram for finding periodic signals in unevenly sampled time series data. Use when analyzing light curves, radial velocity data, or any astronomical time series to detect periodic variations. Works for stellar rotation, pulsation, eclipsing binaries, and general periodic phenomena. Based on lightkurve library.
The Lomb-Scargle periodogram is the standard tool for finding periods in unevenly sampled astronomical time series data. It's particularly useful for detecting periodic signals in light curves from space missions like Kepler, K2, and TESS.
The Lomb-Scargle periodogram extends the classical periodogram to handle unevenly sampled data, which is common in astronomy due to observing constraints, data gaps, and variable cadences.
import lightkurve as lk
import numpy as np
# Create a light curve object
lc = lk.LightCurve(time=time, flux=flux, flux_err=error)
# Create periodogram (specify maximum period to search)
pg = lc.to_periodogram(maximum_period=15) # Search up to 15 days
# Find strongest period
strongest_period = pg.period_at_max_power
max_power = pg.max_power
print(f"Strongest period: {strongest_period:.5f} days")
print(f"Power: {max_power:.5f}")
import matplotlib.pyplot as plt
pg.plot(view='period') # View vs period (not frequency)
plt.xlabel('Period [days]')
plt.ylabel('Power')
plt.show()
Important: Use view='period' to see periods directly, not frequencies. The default view='frequency' shows frequency (1/period).
Choose appropriate period ranges based on your science case:
# Search specific period range
pg = lc.to_periodogram(minimum_period=2.0, maximum_period=7.0)
Higher power indicates stronger periodic signal, but be cautious:
Once you find a period, you can fit a model:
# Get the frequency at maximum power
frequency = pg.frequency_at_max_power
# Create a model light curve
model = pg.model(time=lc.time, frequency=frequency)
# Plot data and model
import matplotlib.pyplot as plt
lc.plot(label='Data')
model.plot(label='Model')
plt.legend()
plt.show()
pip install lightkurve numpy matplotlib
For exoplanet detection, consider using TLS after Lomb-Scargle for initial period search.