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American Astronomical Society, Astrophysical Journal, 1(794), p. 51, 2014

DOI: 10.1088/0004-637x/794/1/51

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The NASA-UC-UH eta-earth program. IV. A low-mass planet orbiting an M dwarf 3.6 PC from earth

Journal article published in 2014 by Andrew W. Howard, Geoffrey W. Marcy, Debra A. Fischer, Howard Isaacson, Philip S. Muirhead ORCID, Gregory W. Henry, Tabetha S. Boyajian, Kaspar von Braun, Juliette C. Becker ORCID, Jason T. Wright ORCID, John Asher Johnson
This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

We report the discovery of a low-mass planet orbiting Gl 15 A based on radial velocities from the Eta-Earth Survey using HIRES at Keck Observatory. Gl 15 Ab is a planet with minimum mass M sin i = 5.35 ± 0.75 M_⊕, orbital period P = 11.4433 ± 0.0016 days, and an orbit that is consistent with circular. We characterize the host star using a variety of techniques. Photometric observations at Fairborn Observatory show no evidence for rotational modulation of spots at the orbital period to a limit of ~0.1 mmag, thus supporting the existence of the planet. We detect a second RV signal with a period of 44 days that we attribute to rotational modulation of stellar surface features, as confirmed by optical photometry and the Ca ii H & K activity indicator. Using infrared spectroscopy from Palomar-TripleSpec, we measure an M2 V spectral type and a sub-solar metallicity ([M/H] = −0.22, [Fe/H] = −0.32). We measure a stellar radius of 0.3863 ± 0.0021 R_☉ based on interferometry from CHARA.