MagAO imaging of long-period objects (MILO). I. A benchmark M dwarf companion exciting a massive planet around the sun-like star HD 7449
- Department of Terrestrial Magnetism, Carnegie Institute of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015 (United States)
- School of Physics and Astronomy, Queen Mary, University of London, 327 Mile End Road London (United Kingdom)
- Homer L. Dodge Department of Physics and Astronomy, The University of Oklahoma, 440 W. Brooks Street Norman, OK 73019 (United States)
- The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)
- Steward Observatory, The University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States)
- Departamento de Ciencias Fisicas, Universidad Andres Bello, Campus La Casona, Fernndez Concha 700, Santiago (Chile)
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 01238 (United States)
We present high-contrast Magellan adaptive optics images of HD 7449, a Sun-like star with one planet and a long-term radial velocity (RV) trend. We unambiguously detect the source of the long-term trend from 0.6–2.15 μm at a separation of ∼0.″54. We use the object’s colors and spectral energy distribution to show that it is most likely an M4–M5 dwarf (mass ∼0.1–0.2 M{sub ⊙}) at the same distance as the primary and is therefore likely bound. We also present new RVs measured with the Magellan/MIKE and Planet Finder Spectrograph spectrometers and compile these with archival data from CORALIE and HARPS. We use a new Markov chain Monte Carlo procedure to constrain both the mass (>0.17 M{sub ⊙} at 99% confidence) and semimajor axis (∼18 AU) of the M dwarf companion (HD 7449B). We also refine the parameters of the known massive planet (HD 7449Ab), finding that its minimum mass is 1.09{sub −0.19}{sup +0.52} M{sub J}, its semimajor axis is 2.33{sub −0.02}{sup +0.01} AU, and its eccentricity is 0.8{sub −0.06}{sup +0.08}. We use N-body simulations to constrain the eccentricity of HD 7449B to ≲0.5. The M dwarf may be inducing Kozai oscillations on the planet, explaining its high eccentricity. If this is the case and its orbit was initially circular, the mass of the planet would need to be ≲1.5 M{sub J}. This demonstrates that strong constraints on known planets can be made using direct observations of otherwise undetectable long-period companions.
- OSTI ID:
- 22887030
- Journal Information:
- Astrophysical Journal, Vol. 818, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Since 2009, the country of publication for this journal is the UK.; ISSN 0004-637X
- Country of Publication:
- United Kingdom
- Language:
- English
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