Browsing by Author "Armstrong, David J."

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    An ultrahot Neptune in the Neptune desert
    (2020) Jenkins, James S.; Diaz, Matias R.; Kurtovic, Nicolas T.; Espinoza, Nestor; Vines, Jose I.; Rojas, Pablo A. Pena; Brahm, Rafael; Torres, Pascal; Cortes-Zuleta, Pia; Soto, Maritza G.; Lopez, Eric D.; King, George W.; Wheatley, Peter J.; Winn, Joshua N.; Ciardi, David R.; Ricker, George; Vanderspek, Roland; Latham, David W.; Seager, Sara; Jenkins, Jon M.; Beichman, Charles A.; Bieryla, Allyson; Burke, Christopher J.; Christiansen, Jessie L.; Henze, Christopher E.; Klaus, Todd C.; McCauliff, Sean; Mori, Mayuko; Narita, Norio; Nishiumi, Taku; Tamura, Motohide; de Leon, Jerome Pitogo; Quinn, Samuel N.; Villasenor, Jesus Noel; Vezie, Michael; Lissauer, Jack J.; Collins, Karen A.; Collins, Kevin I.; Isopi, Giovanni; Mallia, Franco; Ercolino, Andrea; Petrovich, Cristobal; Jordan, Andres; Acton, Jack S.; Armstrong, David J.; Bayliss, Daniel; Bouchy, Francois; Belardi, Claudia; Bryant, Edward M.; Burleigh, Matthew R.; Cabrera, Juan; Casewell, Sarah L.; Chaushev, Alexander; Cooke, Benjamin F.; Eigmueller, Philipp; Erikson, Anders; Foxell, Emma; Gansicke, Boris T.; Gill, Samuel; Gillen, Edward; Guenther, Maximilian N.; Goad, Michael R.; Hooton, Matthew J.; Jackman, James A. G.; Louden, Tom; McCormac, James; Moyano, Maximiliano; Nielsen, Louise D.; Pollacco, Don; Queloz, Didier; Rauer, Heike; Raynard, Liam; Smith, Alexis M. S.; Tilbrook, Rosanna H.; Titz-Weider, Ruth; Turner, Oliver; Udry, Stephane; Walker, Simon. R.; Watson, Christopher A.; West, Richard G.; Palle, Enric; Ziegler, Carl; Law, Nicholas; Mann, Andrew W.
    About 1 out of 200 Sun-like stars has a planet with an orbital period shorter than one day: an ultrashort-period planet(1,2). All of the previously known ultrashort-period planets are either hot Jupiters, with sizes above 10 Earth radii (R-circle plus), or apparently rocky planets smaller than 2 R-circle plus. Such lack of planets of intermediate size (the `hot Neptune desert') has been interpreted as the inability of low-mass planets to retain any hydrogen/ helium (H/He) envelope in the face of strong stellar irradiation. Here we report the discovery of an ultrashort-period planet with a radius of 4.6 R-circle plus and a mass of 29 M-circle plus, firmly in the hot Neptune desert. Data from the Transiting Exoplanet Survey Satellite(3) revealed transits of the bright Sun-like star LTT 9779 every 0.79 days. The planet's mean density is similar to that of Neptune, and according to thermal evolution models, it has a H/He-rich envelope constituting 9.0(-2.9)(+2.7) % of the total mass. With an equilibrium temperature around 2,000 K, it is unclear how this `ultrahot Neptune' managed to retain such an envelope. Follow-up observations of the planet's atmosphere to better understand its origin and physical nature will be facilitated by the star's brightness (V-mag = 9.8).
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    Author correction: An ultrahot Neptune in the Neptune desert
    (2020) Jenkins, James S.; Díaz, Matías R.; Kurtovic, Nicolás T.; Espinoza, Néstor; Vines, Jose I.; Peña Rojas, Pablo A.; Brahm, Rafael; Torres, Pascal; Cortés Zuleta, Pía ; Soto, Maritza G.; López, Eric D.; King, George W.; Wheatley, Peter J.; Winn, Joshua N.; Ciardi, David R.; Ricker, George; Vanderspek, Roland; Latham, David W.; Seager, Sara; Jenkins, Jon M.; Beichman, Charles A.; Bieryla, Allyson; Burke, Christopher J.; Christiansen , Jessie L.; Henze, Christopher E.; Klaus, Todd C.; McCaulif, Sean; Mori, Mayuko; Narita, Norio; Nishiumi, Taku; Tamura, Motohide; Pitogo de Leon, Jerome; Quinn, Samuel N.; Villaseñor, Jesus Noel; Vezie, Michael; Lissauer, Jack J.; Collins, Karen A.; Collins, Kevin I.; Isopi, Giovanni; Mallia, Franco; Ercolino, Andrea; Petrovich, Cristobal; Jordán, Andrés; Acton, Jack S.; Armstrong, David J.; Bayliss, Daniel; Bouchy, François; Belardi, Claudia; Bryant, Edward M.; Burleigh, Matthew R.; Cabrera, Juan; Casewell, Sarah L.; Chaushev, Alexander; Cooke, Benjamin F.; Eigmüller, Philipp; Erikson, Anders; Foxell, Emma; Gänsicke, Boris T.; Gill, Samuel; Gillen, Edward; Günther, Maximilian N.; Goad, Michael R.; Hooton, Matthew J.; Jackman, James A. G.; Louden, Tom; McCormac, James; Moyano, Maximiliano; Nielsen, Louise D.; Pollacco, Don; Queloz, Didier; Rauer, Heike; Raynard, Liam; Smith, Alexis M. S.; Tilbrook, Rosanna H.; Titz Weider, Ruth; Turner, Oliver; Udry, Stéphane; Walker, Simon R.; Watson, Christopher A.; West, Richard G.; Palle, Enric; Ziegler, Carl; Law, Nicholas; Mann, Andrew W.
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    TESS spots a mini- interior to a hot saturn in the TOI-2000 system
    (2023) Sha, Lizhou; Vanderburg, Andrew M.; Huang, Chelsea X.; Armstrong, David J.; Brahm, Rafael; Giacalone, Steven; Wood, Mackenna L.; Collins, Karen A.; Nielsen, Louise D.; Hobson, Melissa J.; Ziegler, Carl; Howell, Steve B.; Torres-Miranda, Pascal; Mann, Andrew W.; Zhou, George; Delgado-Mena, Elisa; Rojas, Felipe, I; Abe, Lyu; Trifonov, Trifon; Adibekyan, Vardan; Sousa, Sergio G.; Fajardo-Acosta, Sergio B.; Guillot, Tristan; Howard, Saburo; Littlefield, Colin; Hawthorn, Faith; Schmider, Francois-Xavier; Eberhardt, Jan; Tan, Thiam-Guan; Osborn, Ares; Schwarz, Richard P.; Strom, Paul; Jordan, Andres; Wang, Gavin; Henning, Thomas; Massey, Bob; Law, Nicholas; Stockdale, Chris; Furlan, Elise; Srdoc, Gregor; Wheatley, Peter J.; Navascues, David Barrado; Lissauer, Jack J.; Stassun, Keivan G.; Ricker, George R.; Vanderspek, Roland K.; Latham, David W.; Winn, Joshua N.; Seager, Sara; Jenkins, Jon M.; Barclay, Thomas; Bouma, Luke G.; Christiansen, Jessie L.; Guerrero, Natalia; Rose, Mark E.
    Hot jupiters (P < 10 d, M > 60 M.) are almost always found alone around their stars, but four out of hundreds known have inner companion planets. These rare companions allow us to constrain the hot jupiter's formation history by ruling out high-eccentricity tidal migration. Less is known about inner companions to hot Saturn-mass planets. We report here the discovery of the TOI-2000 system, which features a hot Saturn-mass planet with a smaller inner companion. The mini-neptune TOI-2000 b (2.70 +/- 0.15 R-circle plus, 11.0 +/- 2.4 M.) is in a 3.10-d orbit, and the hot saturn TOI-2000 c (8.14(+0.31) (-0.30) R-circle plus, 81.7(-4.6)(+4.7) M.) is in a 9.13-d orbit. Both planets transit their host star TOI-2000 (TIC 371188886, V = 10.98, TESS magnitude = 10.36), a metal-rich ([Fe/H] = 0.439 (+0.041)(-0.043)) G dwarf 173 pc away. TESS observed the two planets in sectors 9-11 and 36-38, and we followed up with groundbased photometry, spectroscopy, and speckle imaging. Radial velocities from CHIRON, FEROS, and HARPS allowed us to confirm both planets by direct mass measurement. In addition, we demonstrate constraining planetary and stellar parameters with MIST stellar evolutionary tracks through Hamiltonian Monte Carlo under the PYMC framework, achieving higher sampling efficiency and shorter run time compared to traditional Markov chain Monte Carlo. Having the brightest host star in the V band among similar systems, TOI-2000 b and c are superb candidates for atmospheric characterization by the JWST, which can potentially distinguish whether they formed together or TOI-2000 c swept along material during migration to form TOI-2000 b.
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    NGTS-11 b (TOI-1847 b): A Transiting Warm Saturn Recovered from a TESS Single-transit Event
    (2020) Gill, Samuel; Wheatley, Peter J.; Cooke, Benjamin F.; Jordan, Andres; Nielsen, Louise D.; Bayliss, Daniel; Anderson, David R.; Vines, Jose, I; Lendl, Monika; Acton, Jack S.; Armstrong, David J.; Bouchy, Francois; Brahm, Rafael; Bryant, Edward M.; Burleigh, Matthew R.; Casewell, Sarah L.; Eigmueller, Philipp; Espinoza, Nestor; Gillen, Edward; Goad, Michael R.; Grieves, Nolan; Gunther, Maximilian N.; Henning, Thomas; Hobson, Melissa J.; Hogan, Aleisha; Jenkins, James S.; McCormac, James; Moyano, Maximiliano; Osborn, Hugh P.; Pollacco, Don; Queloz, Didier; Rauer, Heike; Raynard, Liam; Rojas, Felipe; Sarkis, Paula; Smith, Alexis M. S.; Pinto, Marcelo Tala; Tilbrook, Rosanna H.; Udry, Stephane; Watson, Christopher A.; West, Richard G.
    We report the discovery of NGTS-11 b (=TOI-1847b), a transiting Saturn in a 35.46 day orbit around a mid K-type star (T-eff = 5050 +/- 80 K). We initially identified the system from a single-transit event in a TESS full-frame image light curve. Following 79 nights of photometric monitoring with an NGTS telescope, we observed a second full transit of NGTS-11 b approximately one year after the TESS single-transit event. The NGTS transit confirmed the parameters of the transit signal and restricted the orbital period to a set of 13 discrete periods. We combined our transit detections with precise radial-velocity measurements to determine the true orbital period and measure the mass of the planet. We find NGTS-11 b has a radius of 0.817 +/-(0.028)(0.032) R-Jup, a mass of 0.344 +/-(0.092)(0.073) M-Jup, and an equilibrium temperature of just 435 +/-(34)(32) K, making it one of the coolest known transiting gas giants. NGTS-11 b is the first exoplanet to be discovered after being initially identified as a TESS single-transit event, and its discovery highlights the power of intense photometric monitoring in recovering longer-period transiting exoplanets from single-transit events.
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    The Next Generation Transit Survey (NGTS)
    (2018) Wheatley, Peter J.; West, Richard G.; Goad, Michael R.; Jenkins, James S.; Pollacco, Don L.; Queloz, Didier; Rauer, Heike; Udry, Stephane; Watson, Christopher A.; Chazelas, Bruno; Eigmueller, Philipp; Lambert, Gregory; Genolet, Ludovic; McCormac, James; Walker, Simon; Armstrong, David J.; Bayliss, Daniel; Bento, Joao; Bouchy, Francois; Burleigh, Matthew R.; Cabrera, Juan; Casewell, Sarah L.; Chaushev, Alexander; Chote, Paul; Csizmadia, Szilard; Erikson, Anders; Faedi, Francesca; Foxell, Emma; Gansicke, Boris T.; Gillen, Edward; Grange, Andrew; Gunther, Maximilian N.; Hodgkin, Simon T.; Jackman, James; Jordán Colzani, Andrés Cristóbal; Loude, Tom; Metrailler, Lionel; Moyano, Maximiliano; Nielsen, Louise D.; Osborn, Hugh P.; Poppenhaeger, Katja; Raddi, Roberto; Raynard, Liam; Smith, Alexis M. S.; Soto, Maritza; Titz-Weider, Ruth
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    Three Saturn-mass planets transiting F-type stars revealed with TESS and HARPS TOI-615b, TOI-622b, and TOI-2641b
    (2023) Psaridi, Angelica; Bouchy, Francois; Lendl, Monika; Akinsanmi, Babatunde; Stassun, Keivan G.; Smalley, Barry; Armstrong, David J.; Howard, Saburo; Ulmer-Moll, Solene; Grieves, Nolan; Barkaoui, Khalid; Rodriguez, Joseph E.; Bryant, Edward M.; Suarez, Olga; Guillot, Tristan; Evans, Phil; Attia, Omar; Wittenmyer, Robert A.; Yee, Samuel W.; Collins, Karen A.; Zhou, George; Galland, Franck; Parc, Lena; Udry, Stephane; Figueira, Pedro; Ziegler, Carl; Mordasini, Christoph; Winn, Joshua N.; Seager, Sara; Jenkins, Jon M.; Twicken, Joseph D.; Brahm, Rafael; Jones, Matias, I; Abe, Lyu; Addison, Brett T.; Briceno, Cesar I.; Briegal, Joshua; Collins, Kevin; Daylan, Tansu; Eigmueller, Phillip M.; Furesz, Gabor; Guerrero, Natalia; Hagelberg, Janis; Heitzmann, Alexis X.; Hounsell, Rebekah; Huang, Chelsea M.; Krenn, Andreas W.; Law, Nicholas; Mann, Andrew; McCormac, James; Mekarnia, Djamel D.; Mounzer, Dany; Nielsen, Louise R.; Osborn, Ares; Reinarz, Yared A.; Sefako, Ramotholo; Steiner, Michal I.; Strom, Paul A.; Triaud, Amaury H. M. J.; Vanderspek, Roland; Vanzi, Leonardo; Vines, Jose; Watson, Christopher; Wright, Duncan; Zapata, Abner
    While the sample of confirmed exoplanets continues to grow, the population of transiting exoplanets around early-type stars is still limited. These planets allow us to investigate the planet properties and formation pathways over a wide range of stellar masses and study the impact of high irradiation on hot Jupiters orbiting such stars. We report the discovery of TOI-615b, TOI-622b, and TOI-2641b, three Saturn-mass planets transiting main sequence, F-type stars. The planets were identified by the Transiting Exoplanet Survey Satellite (TESS) and confirmed with complementary ground-based and radial velocity observations. TOI-615b is a highly irradiated (similar to 1277 F-circle dot) and bloated Saturn-mass planet (1.69(-0.06)(+0.05) R-Jup and 0.43(-0.08)(+0.09) M-Jup) in a 4.66 day orbit transiting a 6850 K star. TOI-622b has a radius of 0.82(-0.03)(+0.03) R-Jup and a mass of 0.30(-0.08)(+0.07) M-Jup in a 6.40 day orbit. Despite its high insolation flux (similar to 600 F-circle dot), TOI-622b does not show any evidence of radius inflation. TOI-2641b is a 0.39(-0.04)(+0.02) M-Jup planet in a 4.88 day orbit with a grazing transit (b = 1.04(-0.06)(+0.05)) that results in a poorly constrained radius of 1.61(-0.64)(+0.46) R-Jup. Additionally, TOI-615b is considered attractive for atmospheric studies via transmission spectroscopy with ground-based spectrographs and JWST. Future atmospheric and spin-orbit alignment observations are essential since they can provide information on the atmospheric composition, formation, and migration of exoplanets across various stellar types.