UBVRI photometry of Betelgeuse over 23 years since 1999

TL;DR

This study presents 23 years of consistent UBVRI photometry of Betelgeuse, revealing multiple periodicities, long-term variations, and peculiar color index changes during the 2019-2020 Great Dimming event.

Contribution

It provides a unique, long-term, homogeneous photometric dataset of Betelgeuse, including U-band data, and identifies multiple periodicities and long-term variations.

Findings

Detected ~405- and ~2160-day periodicities.

Identified long-term variation over 20 years.

Analyzed U-B color index changes during the Great Dimming.

Abstract

We report the results of our continuous UBVRI-band photometry of Betelgeuse from 1999 to 2022 using the same photometric system. There are two advantages in our observation: (1) we used a photodiode as a detector to avoid saturation, and (2) our data set includes U-band light curve, which is not widely observed in recent CCD photometries. Using our light curves, we conducted the periodicity analysis, and found ~405- and ~2160-day periods. We also discuss the tentative detection of a long-period variation over 20 years or longer. Finally, we discuss the peculiar variation of the U-B color index during the "Great Dimming" event between late 2019 and early 2020.