AAVSO: American Association of Variable Star Observers

Spectral Classification of Algol C

Volume 50 number 1 (2022)

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Megan G. Frank
Department of Physics, Austin College, Sherman, TX; mfrank18@austincollege.edu
David G. Whelan
Department of Physics, Austin College, Sherman, TX; dwhelan@austincollege.edu
Jessica C. Junginger
Department of Physics, Austin College, Sherman, TX


The spectral classification of Algol C, the third star in the Algol triple system, has long been a matter of some uncertainty. There is good reason to suspect that it should be a metallic-line A-type star, and one study in particular showed that this was so, but further studies have cast doubt on that assessment. We utilized a simple spectral subtraction method between spectra taken in and out of primary eclipse to reveal the light of Algol C in the absence of the light from the brightest star. Our resultant spectrum is well-matched to an F1 V spectroscopic standard and shows no evidence of metallic-line spectral anomalies. We note that this classification matches recent abundance determinations for this source.