Browsing by Author "Mekarnia, Djamel"

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    Precise Transit and Radial-velocity Characterization of a Resonant Pair: The Warm Jupiter TOI-216c and Eccentric Warm Neptune TOI-216b
    (2021) Dawson, Rebekah I.; Huang, Chelsea X.; Brahm, Rafael; Collins, Karen A.; Hobson, Melissa J.; Jordan, Andres; Dong, Jiayin; Korth, Judith; Trifonov, Trifon; Abe, Lyu; Agabi, Abdelkrim; Bruni, Ivan; Butler, R. Paul; Barbieri, Mauro; Collins, Kevin I.; Conti, Dennis M.; Crane, Jeffrey D.; Crouzet, Nicolas; Dransfield, Georgina; Evans, Phil; Espinoza, Nestor; Gan, Tianjun; Guillot, Tristan; Henning, Thomas; Lissauer, Jack J.; Jensen, Eric L. N.; Sainte, Wenceslas Marie; Mekarnia, Djamel; Myers, Gordon; Nandakumar, Sangeetha; Relles, Howard M.; Sarkis, Paula; Torres, Pascal; Shectman, Stephen; Schmider, Francois-Xavier; Shporer, Avi; Stockdale, Chris; Teske, Johanna; Triaud, Amaury H. M. J.; Wang, Sharon Xuesong; Ziegler, Carl; Ricker, G.; Vanderspek, R.; Latham, David W.; Seager, S.; Winn, J.; Jenkins, Jon M.; Bouma, L. G.; Burt, Jennifer A.; Charbonneau, David; Levine, Alan M.; McDermott, Scott; McLean, Brian; Rose, Mark E.; Vanderburg, Andrew; Wohler, Bill
    TOI-216 hosts a pair of warm, large exoplanets discovered by the TESS mission. These planets were found to be in or near the 2:1 resonance, and both of them exhibit transit timing variations (TTVs). Precise characterization of the planets' masses and radii, orbital properties, and resonant behavior can test theories for the origins of planets orbiting close to their stars. Previous characterization of the system using the first six sectors of TESS data suffered from a degeneracy between planet mass and orbital eccentricity. Radial-velocity measurements using HARPS, FEROS, and the Planet Finder Spectrograph break that degeneracy, and an expanded TTV baseline from TESS and an ongoing ground-based transit observing campaign increase the precision of the mass and eccentricity measurements. We determine that TOI-216c is a warm Jupiter, TOI-216b is an eccentric warm Neptune, and that they librate in 2:1 resonance with a moderate libration amplitude of deg, a small but significant free eccentricity of for TOI-216b, and a small but significant mutual inclination of 12-39 (95% confidence interval). The libration amplitude, free eccentricity, and mutual inclination imply a disturbance of TOI-216b before or after resonance capture, perhaps by an undetected third planet.
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    TOI-199 b: A Well-characterized 100 day Transiting Warm Giant Planet with TTVs Seen from Antarctica
    (2023) Hobson, Melissa J.; Trifonov, Trifon; Henning, Thomas; Jordan, Andres; Rojas, Felipe; Espinoza, Nestor; Brahm, Rafael; Eberhardt, Jan; Jones, Matias I.; Mekarnia, Djamel; Kossakowski, Diana; Schlecker, Martin; Pinto, Marcelo Tala; Torres Miranda, Pascal Jose; Abe, Lyu; Barkaoui, Khalid; Bendjoya, Philippe; Bouchy, Francois; Buttu, Marco; Carleo, Ilaria; Collins, Karen A.; Colon, Knicole D.; Crouzet, Nicolas; Dragomir, Diana; Dransfield, Georgina; Gasparetto, Thomas; Goeke, Robert F.; Guillot, Tristan; Guenther, Maximilian N.; Howard, Saburo; Jenkins, Jon M.; Korth, Judith; Latham, David W.; Lendl, Monika; Lissauer, Jack J.; Mann, Christopher R.; Mireles, Ismael; Ricker, George R.; Saesen, Sophie; Schwarz, Richard P.; Seager, S.; Sefako, Ramotholo; Shporer, Avi; Stockdale, Chris; Suarez, Olga; Tan, Thiam-Guan; J. Triaud, Amaury H. M.; Ulmer-Moll, Solene; Vanderspek, Roland; Winn, Joshua N.; Wohler, Bill; Zhou, George
    We present the spectroscopic confirmation and precise mass measurement of the warm giant planet TOI-199 b. This planet was first identified in TESS photometry and confirmed using ground-based photometry from ASTEP in Antarctica including a full 6.5 hr long transit, PEST, Hazelwood, and LCO; space photometry from NEOSSat; and radial velocities (RVs) from FEROS, HARPS, CORALIE, and CHIRON. Orbiting a late G-type star, TOI-199 b has a 104.854-0.002+0.001day period, a mass of 0.17 +/- 0.02 M J, and a radius of 0.810 +/- 0.005 R J. It is the first warm exo-Saturn with a precisely determined mass and radius. The TESS and ASTEP transits show strong transit timing variations (TTVs), pointing to the existence of a second planet in the system. The joint analysis of the RVs and TTVs provides a unique solution for the nontransiting companion TOI-199 c, which has a period of 273.69-0.22+0.26days and an estimated mass of 0.28-0.01+0.02MJ . This period places it within the conservative habitable zone.
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    TOI-2525 b and c: A Pair of Massive Warm Giant Planets with Strong Transit Timing Variations Revealed by TESS
    (2023) Trifonov, Trifon; Brahm, Rafael; Jordan, Andres; Hartogh, Christian; Henning, Thomas; Hobson, Melissa J.; Schlecker, Martin; Howard, Saburo; Reichardt, Finja; Espinoza, Nestor; Lee, Man Hoi; Nesvorny, David; Rojas, Felipe I.; Barkaoui, Khalid; Kossakowski, Diana; Boyle, Gavin; Dreizler, Stefan; Kuerster, Martin; Heller, Rene; Guillot, Tristan; Triaud, Amaury H. M. J.; Abe, Lyu; Agabi, Abdelkrim; Bendjoya, Philippe; Crouzet, Nicolas; Dransfield, Georgina; Gasparetto, Thomas; Guenther, Maximilian N.; Marie-Sainte, Wenceslas; Mekarnia, Djamel; Suarez, Olga; Teske, Johanna; Butler, R. Paul; Crane, Jeffrey D.; Shectman, Stephen; Ricker, George R.; Shporer, Avi; Vanderspek, Roland; Jenkins, Jon M.; Wohler, Bill; Collins, Karen A.; Collins, Kevin I.; Ciardi, David R.; Barclay, Thomas; Mireles, Ismael; Seager, Sara; Winn, Joshua N.
    The K-type star TOI-2525 has an estimated mass of M = 0.849(-0.033)(+0.024) M-circle dot and radius of R = 0.785(-0.007)(+0.007) R-circle dot observed by the TESS mission in 22 sectors (within sectors 1 and 39). The TESS light curves yield significant transit events of two companions, which show strong transit timing variations (TTVs) with a semiamplitude of similar to 6 hr. We performed TTV dynamical and photodynamical light-curve analysis of the TESS data combined with radial velocity measurements from FEROS and PFS, and we confirmed the planetary nature of these companions. The TOI-2525 system consists of a transiting pair of planets comparable to Neptune and Jupiter with estimated dynamical masses of m(b) = 0.088(-0.004)(+0.005) and m(c) = 0.709(-0.033)(+0.034) M-Jup, radii of r(b) = 0.88(-0.02)(+0.02) and r(c) = 0.98(-0.02)(+0.02) R-Jup, and orbital periods of P-b = 23.288(-0.002)(+0.001) and P-c = 49.260(-0.001)(+0.001) days for the inner and outer planet, respectively. The period ratio is close to the 2:1 period commensurability, but the dynamical simulations of the system suggest that it is outside the mean-motion resonance (MMR) dynamical configuration. Object TOI-2525 b is among the lowest-density Neptune-mass planets known to date, with an estimated median density of rho(b) = 0.174(-0.015)(+0.016) g cm(-3). The TOI-2525 system is very similar to the other K dwarf systems discovered by TESS, TOI-2202 and TOI-216, which are composed of almost identical K dwarf primaries and two warm giant planets near the 2:1 MMR.