SSRP Abstract

Board 11: Imaging Starspots on LO Pegasi via Lightcurve Inversion

Student Scientists: Kyleigh Beck ’24 and James Doerle ’23
Research Mentor: Bob Harmon (OWU Department of Physics & Astronomy)

Sunspots are cooler and darker regions on the surface of the Sun that are caused by magnetic fields. When sunspots occur on other stars, they are called starspots. We are studying how starspots on a Sun-like star named LO Pegasi change over time. This is done by using a telescope at Perkins Observatory to measure how LO Pegasi’s brightness changes as it rotates and its spots come into and out of view. We then use Light-curve Inversion (LI), a program developed by Dr. Harmon, to map the starspots of LO Pegasi based on the measurements of brightness we obtain.

LO Pegasi is a spectral-type K8, main-sequence, variable star located 81 lightyears from Earth in the constellation Pegasus. The variation in its brightness is due to the presence of large starspots on its surface (analogous to sunspots on the Sun). Starspots are cooler, darker regions on the surface of a star that are caused when strong magnetic fields prevent convection in the star’s outer layers. As LO Pegasi rotates and its spots come into view, it appears darker. As the rotation carries the spots out of view, the star appears brighter. LO Pegasi has a rotational period of 10.153 hours. In comparison, the Sun’s rotational period is approximately 27 days. LO Pegasi’s quick rotation rate causes it to be highly magnetically active. As a result, LO Pegasi’s surface features an ever-present polar spot in addition to mid-latitude starspots. In order to obtain data, a CCD camera was used to take digital images through standard B, V, R, and I photometric filters at Perkins Observatory over a series of nights in June and July. Aperture photometry was performed on the images to obtain LO Pegasi’s brightness relative to a set of comparison stars as it rotated. The resulting data was plotted to create light curves and fed into a program called Light-curve Inversion (LI) that created maps of LO Pegasi’s surface. We present these maps in comparison to previous data from 2014-2021.