TY - JOUR

T1 - A Second Planet Transiting LTT 1445A and a Determination of the Masses of Both Worlds

AU - Winters, Jennifer G.

AU - Cloutier, Ryan

AU - Medina, Amber A.

AU - Irwin, Jonathan M.

AU - Charbonneau, David

AU - Astudillo-Defru, Nicola

AU - Bonfils, Xavier

AU - Howard, Andrew W.

AU - Isaacson, Howard

AU - Bean, Jacob L.

AU - Seifahrt, Andreas

AU - Teske, Johanna K.

AU - Eastman, Jason D.

AU - Twicken, Joseph D.

AU - Collins, Karen A.

AU - Jensen, Eric L. N.

AU - Quinn, Samuel N.

AU - Payne, Matthew J.

AU - Kristiansen, Martti H.

AU - Spencer, Alton

AU - Vanderburg, Andrew

AU - Zechmeister, Mathias

AU - Weiss, Lauren M.

AU - Wang, Sharon Xuesong

AU - Wang, Gavin

AU - Udry, Stephane

AU - Terentev, Ivan A.

AU - Stuermer, Julian

AU - Stefansson, Gudmundur

AU - Shporer, Avi

AU - Shectman, Stephen

AU - Sefako, Ramotholo

AU - Schwengeler, Hans Martin

AU - Schwarz, Richard P.

AU - Scarsdale, Nicholas

AU - Rubenzahl, Ryan A.

AU - Roy, Arpita

AU - Rosenthal, Lee J.

AU - Robertson, Paul

AU - Petigura, Erik A.

AU - Pepe, Francesco

AU - Omohundro, Mark

AU - Murphy, Joseph M. Akana

AU - Murgas, Felipe

AU - Mocnik, Teo

AU - Montet, Benjamin T.

AU - Mennickent, Ronald

AU - Mayo, Andrew W.

AU - Massey, Bob

AU - Lubin, Jack

AU - Lovis, Christophe

AU - Lewin, Pablo

AU - Kasper, David

AU - Kane, Stephen R.

AU - Jenkins, Jon M.

AU - Huber, Daniel

AU - Horne, Keith

AU - Hill, Michelle L.

AU - Gorrini, Paula

AU - Giacalone, Steven

AU - Fulton, Benjamin

AU - Forveille, Thierry

AU - Figueira, Pedro

AU - Fetherolf, Tara

AU - Dressing, Courtney

AU - Diaz, Rodrigo F.

AU - Delfosse, Xavier

AU - Dalba, Paul A.

AU - Dai, Fei

AU - Cortes, C. C.

AU - Crossfield, Ian J. M.

AU - Crane, Jeffrey D.

AU - Conti, Dennis M.

AU - Collins, Kevin

AU - Chontos, Ashley

AU - Butler, R. Paul

AU - Brown, Peyton

AU - Brady, Madison

AU - Behmard, Aida

AU - Beard, Corey

AU - Batalha, Natalie M.

AU - Almenara, Jose-Manuel

PY - 2022/4/1

Y1 - 2022/4/1

N2 - LTT 1445 is a hierarchical triple M-dwarf star system located at a distance of 6.86 pc. The primary star LTT 1445A (0.257 M-circle dot) is known to host the transiting planet LTT 1445Ab with an orbital period of 5.36 days, making it the second-closest known transiting exoplanet system, and the closest one for which the host is an M dwarf. Using Transiting Exoplanet Survey Satellite data, we present the discovery of a second planet in the LTT 1445 system, with an orbital period of 3.12 days. We combine radial-velocity measurements obtained from the five spectrographs, Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations, High Accuracy Radial Velocity Planet Searcher, High-Resolution Echelle Spectrometer, MAROON-X, and Planet Finder Spectrograph to establish that the new world also orbits LTT 1445A. We determine the mass and radius of LTT 1445Ab to be 2.87 +/- 0.25 M-circle plus and 1.304(-0.060)(+0.067) R-circle plus, consistent with an Earth-like composition. For the newly discovered LTT 1445Ac, we measure a mass of 1.54(-0.19)(+0.20) M-circle plus and a minimum radius of 1.15 R-circle plus, but we cannot determine the radius directly as the signal-to-noise ratio of our light curve permits both grazing and nongrazing configurations. Using MEarth photometry and ground-based spectroscopy, we establish that star C (0.161 M-circle dot) is likely the source of the 1.4 day rotation period, and star B (0.215 MY circle dot) has a likely rotation period of 6.7 days. We estimate a probable rotation period of 85 days for LTT 1445A. Thus, this triple M-dwarf system appears to be in a special evolutionary stage where the most massive M dwarf has spun down, the intermediate mass M dwarf is in the process of spinning down, while the least massive stellar component has not yet begun to spin down.

AB - LTT 1445 is a hierarchical triple M-dwarf star system located at a distance of 6.86 pc. The primary star LTT 1445A (0.257 M-circle dot) is known to host the transiting planet LTT 1445Ab with an orbital period of 5.36 days, making it the second-closest known transiting exoplanet system, and the closest one for which the host is an M dwarf. Using Transiting Exoplanet Survey Satellite data, we present the discovery of a second planet in the LTT 1445 system, with an orbital period of 3.12 days. We combine radial-velocity measurements obtained from the five spectrographs, Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations, High Accuracy Radial Velocity Planet Searcher, High-Resolution Echelle Spectrometer, MAROON-X, and Planet Finder Spectrograph to establish that the new world also orbits LTT 1445A. We determine the mass and radius of LTT 1445Ab to be 2.87 +/- 0.25 M-circle plus and 1.304(-0.060)(+0.067) R-circle plus, consistent with an Earth-like composition. For the newly discovered LTT 1445Ac, we measure a mass of 1.54(-0.19)(+0.20) M-circle plus and a minimum radius of 1.15 R-circle plus, but we cannot determine the radius directly as the signal-to-noise ratio of our light curve permits both grazing and nongrazing configurations. Using MEarth photometry and ground-based spectroscopy, we establish that star C (0.161 M-circle dot) is likely the source of the 1.4 day rotation period, and star B (0.215 MY circle dot) has a likely rotation period of 6.7 days. We estimate a probable rotation period of 85 days for LTT 1445A. Thus, this triple M-dwarf system appears to be in a special evolutionary stage where the most massive M dwarf has spun down, the intermediate mass M dwarf is in the process of spinning down, while the least massive stellar component has not yet begun to spin down.

KW - EARTH-SIZED PLANET

KW - SUPER-EARTH

KW - STELLAR ACTIVITY

KW - TERRESTRIAL PLANET

KW - RADIAL-VELOCITIES

KW - ERROR-CORRECTION

KW - M DWARFS

KW - NEARBY

KW - SYSTEM

KW - HARPS

U2 - 10.3847/1538-3881/ac50a9

DO - 10.3847/1538-3881/ac50a9

M3 - Journal article

VL - 163

JO - The Astronomical Journal

JF - The Astronomical Journal

SN - 0004-6256

IS - 4

M1 - 168

ER -