TY - JOUR
T1 - Characterizing the cool KOIs. III. KOI 961
T2 - A small star with large proper motion and three small planets
AU - Muirhead, Philip S.
AU - Johnson, John Asher
AU - Apps, Kevin
AU - Carter, Joshua A.
AU - Morton, Timothy D.
AU - Fabrycky, Daniel C.
AU - Pineda, John Sebastian
AU - Bottom, Michael
AU - Rojas-Ayala, Bárbara
AU - Schlawin, Everett
AU - Hamren, Katherine
AU - Covey, Kevin R.
AU - Crepp, Justin R.
AU - Stassun, Keivan G.
AU - Pepper, Joshua
AU - Hebb, Leslie
AU - Kirby, Evan N.
AU - Howard, Andrew W.
AU - Isaacson, Howard T.
AU - Marcy, Geoffrey W.
AU - Levitan, David
AU - Diaz-Santos, Tanio
AU - Armus, Lee
AU - Lloyd, James P.
PY - 2012/3/10
Y1 - 2012/3/10
N2 - We characterize the star KOI 961, an M dwarf with transit signals indicative of three short-period exoplanets discovered by the Kepler mission. We proceed by comparing KOI 961 to Barnard's Star, a nearby, well-characterized mid-M dwarf. We compare colors, optical and near-infrared spectra, and find remarkable agreement between the two, implying similar effective temperatures and metallicities. Both are metal-poor compared to the Solar neighborhood, have low projected rotational velocity, high absolute radial velocity, large proper motion, and no quiescent Hα emission - all of which are consistent with being old M dwarfs. We combine empirical measurements of Barnard's Star and expectations from evolutionary isochrones to estimate KOI 961's mass (0.13 ± 0.05 M ⊙), radius (0.17 ± 0.04 R ⊙), and luminosity (2.40 × 10-3.0 ± 0.3 L ⊙). We calculate KOI 961's distance (38.7 ± 6.3 pc) and space motions, which, like Barnard's Star, are consistent with a high scale-height population in the Milky Way. We perform an independent multi-transit fit to the public Kepler light curve and significantly revise the transit parameters for the three planets. We calculate the false-positive probability for each planet candidate, and find a less than 1% chance that any one of the transiting signals is due to a background or hierarchical eclipsing binary, validating the planetary nature of the transits. The best-fitting radii for all three planets are less than 1R ⊕, with KOI 961.03 being Mars-sized (RP = 0.57 ± 0.18 R ⊕), and they represent some of the smallest exoplanets detected to date.
AB - We characterize the star KOI 961, an M dwarf with transit signals indicative of three short-period exoplanets discovered by the Kepler mission. We proceed by comparing KOI 961 to Barnard's Star, a nearby, well-characterized mid-M dwarf. We compare colors, optical and near-infrared spectra, and find remarkable agreement between the two, implying similar effective temperatures and metallicities. Both are metal-poor compared to the Solar neighborhood, have low projected rotational velocity, high absolute radial velocity, large proper motion, and no quiescent Hα emission - all of which are consistent with being old M dwarfs. We combine empirical measurements of Barnard's Star and expectations from evolutionary isochrones to estimate KOI 961's mass (0.13 ± 0.05 M ⊙), radius (0.17 ± 0.04 R ⊙), and luminosity (2.40 × 10-3.0 ± 0.3 L ⊙). We calculate KOI 961's distance (38.7 ± 6.3 pc) and space motions, which, like Barnard's Star, are consistent with a high scale-height population in the Milky Way. We perform an independent multi-transit fit to the public Kepler light curve and significantly revise the transit parameters for the three planets. We calculate the false-positive probability for each planet candidate, and find a less than 1% chance that any one of the transiting signals is due to a background or hierarchical eclipsing binary, validating the planetary nature of the transits. The best-fitting radii for all three planets are less than 1R ⊕, with KOI 961.03 being Mars-sized (RP = 0.57 ± 0.18 R ⊕), and they represent some of the smallest exoplanets detected to date.
KW - planetary systems
KW - stars: fundamental parameters
KW - stars: individual (Barnard's Star, KOI 961)
KW - stars: late-type
KW - stars: low-mass
UR - http://www.scopus.com/inward/record.url?scp=84859726936&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84859726936&partnerID=8YFLogxK
U2 - 10.1088/0004-637X/747/2/144
DO - 10.1088/0004-637X/747/2/144
M3 - Article
AN - SCOPUS:84859726936
SN - 0004-637X
VL - 747
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 144
ER -