Peranso supports the EEBLS (Edge Enhanced Box-fitting Least Squares) period analysis method. Box-fitting Least Squares (BLS) algorithms1 are particularly effective to analyze stellar photometric time series in search for periodic transits by exoplanets. It searches for signals characterized by a periodic alternation between two discrete levels, with much less time spent at the lower (transit) level. EEBLS is an extension to BLS, that takes into account edge effects during exoplanet transits, as suggested by Dr. Peter McCullough (STScI). We will see in Tutorial 8 that EEBLS is also very effective in finding orbital periods of eclipsing binaries.

Peranso allows calculating and visualizing the EEBLS frequency spectrum, folding of the time series over the most dominant EEBLS period, calculating the epoch of mid-transit events, the transit depth and duration, etc. In addition, Peranso graphically displays the fit obtained by the EEBLS method in the Phase Window.

In this tutorial we will use observations of exoplanet XO-1b obtained by NASA's TESS2 (Transiting Exoplanet Survey Satellite) in April and May 2020. Peranso can pull TESS light curve data directly from the TESS website. You can do this of course also manually, using for instance the MAST Portal. Time data in TESS are expressed in BJD (Barycentric Julian Date) and 'brightness' is expressed in so called PDC SAP flux3.

Exoplanet XO-1b was discovered in 2006 by the XO consortium, a collaboration of professional and amateur astronomers. The XO lead investigator, Dr. Peter McCullough, recruited four amateur astronomers in 2005 - including myself - to assist with the photometric follow-up of XO candidates, one of which was XO-1b. At the time of its discovery, only 4 other exoplanets were known to transit stars brighter than V=12, including famous HD209458b and TrES-1b. 


(1) Kovacs G., Zucker S., Mazeh T., A box-fitting algorithm in the search for periodic transits, A&A, 2002. 

(2) Data presented in this tutorial were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX13AC07G and by other grants and contracts. 

(3) SAP flux is Simple Aperture Photometry flux, and PDC stands for Pre-search Data Conditioning. In simple terms: PDC SAP flux is usually cleaner than simple SAP flux and will have fewer systematic trends.