STELLAR ACTIVITY MIMICS A HABITABLE-ZONE PLANET AROUND KAPTEYN'S STAR

Paul Robertson, Arpita Roy, Suvrath Mahadevan

Research output: Contribution to journalArticle

36 Scopus citations

Abstract

Kapteyn's star is an old M subdwarf believed to be a member of the Galactic halo population of stars. A recent study has claimed the existence of two super-Earth planets around the star based on radial velocity (RV) observations. The innermost of these candidate planets - Kapteyn b (P = 48 days) - resides within the circumstellar habitable zone (HZ). Given recent progress in understanding the impact of stellar activity in detecting planetary signals, we have analyzed the observed HARPS data for signatures of stellar activity. We find that while Kapteyn's star is photometrically very stable, a suite of spectral activity indices reveal a large-amplitude rotation signal, and we determine the stellar rotation period to be 143 days. The spectral activity tracers are strongly correlated with the purported RV signal of "planet b," and the 48-day period is an integer fraction (1/3) of the stellar rotation period. We conclude that Kapteyn b is not a planet in the HZ, but an artifact of stellar activity.

Original languageEnglish (US)
Article numberL22
JournalAstrophysical Journal Letters
Volume805
Issue number2
DOIs
StatePublished - Jun 1 2015

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Fingerprint Dive into the research topics of 'STELLAR ACTIVITY MIMICS A HABITABLE-ZONE PLANET AROUND KAPTEYN'S STAR'. Together they form a unique fingerprint.

  • Cite this