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False Planets around Giant Stars: A Case Study of Sanders 364

Presentation #401.07 in the session Exoplanet Radial Velocities — iPoster Session.

Published onJun 29, 2022
False Planets around Giant Stars: A Case Study of Sanders 364

Surveying planet occurrence rates in star clusters and in the field can help us understand how the stellar environment influences planet formation. A paper by Brucalassi et al. reports the discovery of several planets in the M67 open cluster and claims that the occurrence rate of Jupiter-mass planets in the M67 cluster is comparable to or slightly higher than the occurrence rate in the field. However, this paper presents an independent set of 354 radial velocity (RV) observations to test one of Brucalassi et al.’s planet discoveries: a giant planet orbiting the K giant star Sanders 364. From our analysis of our radial velocities, we have found no evidence of the giant planet reported by Brucalassi et al. We speculate that since Brucalassi et al.’s observations were fewer and sparser than our observations, their analysis of periodic radial velocity variations may not have been able to resolve longer period peaks in the periodogram that were comparatively more significant than the peak they reported. In addition, large scale features and motions in the atmospheres of evolved stars may cause long-term quasi-periodic signals to appear, which are hard to disentangle from orbital motion. Thus, our findings suggest that radial velocity signals from evolved stars, and thereby surveys of star occurrence rates with evolved stars in the sample, should be treated with caution.

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