HD 37824 is a single-lined spectroscopic binary, meaning only the light from the luminous primary can be observed in the system's spectra.[3] The two stars orbit each other in a circular orbit (eccentricity 0.0) with a period of 53.57 days. The star features prominent starspots, which are known to display the flip-flop effect; other stars that show this effect include FK Comae Berenices and HD 181809.[2]
In 1973, astronomers William P. Bidelman and Darrell Jack MacConnell reported the detection of Ca II H & Kemission lines in the spectra of HD 37824. As such, Douglas S. Hall et al. suspected it to be a RS Canum Venaticorum variable. As expected, in 1983, the star was shown to vary in brightness by 0.11 mag, with photometric and orbital periods of 52.6 and 53.6 days, respectively.[7] It was given its variable star designation in 1985.[8]
The starspots on the surface of the primary star, which are thought to cause the variability, were analyzed using photometric data taken between late 1978 and early 1990. The results were published in 1991, identifying six starspots, which each made the star dim by about 0.1–0.3 mag and lasted for several years. The same study refined the orbital period to 53.58 ± 0.02 days.[9]
Observations in 1992 showed a large excess of Hα emission alongside strong Ca II H & K and Hεemission lines. A follow-up study in 1997 reported a lower but still strong Hα emission, as well as a clear emission line from singly ionizedhelium revealed by spectral subtraction.[10] Additional observations in 2000 discovered high variability in the profile of the Hα line.[3]
^Høg, E.; et al. (February 2000). "The Tycho-2 Catalogue of the 2.5 Million Brightest Stars". Astronomy and Astrophysics. 355 (1): L27–L30. Bibcode:2000A&A...355L..27H.
^Hall, Douglas S.; Fekel, Francis C.; Henry, Gregory W.; Barksdale, William S. (1991). "The 11 year history of starspots on V1149 ORI = HD 37824". The Astronomical Journal. 102: 1808. doi:10.1086/116004.
