Two Odd Exoplanets Around GJ 221

TWO PLANETARY COMPANIONS AROUND THE K7 DWARF GJ 221: A HOT SUPER-EARTH AND A CANDIDATE IN THE SUB-SATURN DESERT RANGE

Authors:

1. Pamela Arriagada (a,b)
2. Guillem Anglada-Escudé (b,c)
3. R. Paul Butler (b)
4. Jeffrey D. Crane (d)
5. Stephen A. Shectman (d)
6. Ian Thompson (d)
7. Sebastian Wende (c)
8. Dante Minniti (a,e,f)

Affiliations:

a. Department of Astronomy, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile

b. Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington, DC 20015-1305, USA

c. Institut für Astrophysik, Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany

d. The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101, USA

e. Vatican Observatory, V00120 Vatican City State, Italy

f. Departamento de Ciencia Físicas, Universidad Andrés Bello, Santiago, Chile

Abstract:

We report two low-mass companions orbiting the nearby K7 dwarf GJ 221 that have emerged from reanalyzing 4.4 yr of publicly available HARPS spectra complemented with 2 years of high-precision Doppler measurements with Magellan/PFS. The HARPS measurements alone contain the clear signal of a low-mass companion with a period of 125 days and a minimum mass of 53.2 M ⊕ (GJ 221b), falling in a mass range where very few planet candidates have been found (sub-Saturn desert). The addition of 17 PFS observations allows the confident detection of a second low-mass companion (6.5 M ⊕) in a hot orbit (3.87 day period, GJ 221c). Spectroscopic and photometric calibrations suggest that GJ 221 is slightly depleted ([Fe/H] ~ –0.1) compared to the Sun, so the presence of two low-mass companions in the system confirms the trend that slightly reduced stellar metallicity does not prevent the formation of planets in the super-Earth to sub-Saturn mass regime.