Browsing by Author "Nielsen, Louise D."

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    A Transiting Warm Giant Planet around the Young Active Star TOI-201
    (2021) Hobson, Melissa J.; Brahm, Rafael; Jordan, Andres; Espinoza, Nestor; Kossakowski, Diana; Henning, Thomas; Rojas, Felipe; Schlecker, Martin; Sarkis, Paula; Trifonov, Trifon; Thorngren, Daniel; Binnenfeld, Avraham; Shahaf, Sahar; Zucker, Shay; Ricker, George R.; Latham, David W.; Seager, S.; Winn, Joshua N.; Jenkins, Jon M.; Addison, Brett; Bouchy, Francois; Bowler, Brendan P.; Briegal, Joshua T.; Bryant, Edward M.; Collins, Karen A.; Daylan, Tansu; Grieves, Nolan; Horner, Jonathan; Huang, Chelsea; Kane, Stephen R.; Kielkopf, John; McLean, Brian; Mengel, Matthew W.; Nielsen, Louise D.; Okumura, Jack; Jones, Matias; Plavchan, Peter; Shporer, Avi; Smith, Alexis M. S.; Tilbrook, Rosanna; Tinney, C. G.; Twicken, Joseph D.; Udry, Stephane; Unger, Nicolas; West, Richard; Wittenmyer, Robert A.; Wohler, Bill; Torres, Pascal; Wright, Duncan J.
    We present the confirmation of the eccentric warm giant planet TOI-201 b, first identified as a candidate in Transiting Exoplanet Survey Satellite photometry (Sectors 1-8, 10-13, and 27-28) and confirmed using groundbased photometry from Next Generation Transit Survey and radial velocities from FEROS, HARPS, CORALIE, and MINERVA-Australis. TOI-201 b orbits a young (0.87(-0.49)(+0.46)) and bright (V = 9.07 mag) F-type star with a 52.9781 day period. The planet has a mass of 0.42(-0.03)(+0.05) M-J, a radius of 1.008(-0.015)(+0.012) R-J, and an orbital eccentricity of 0.28(-0.09)(+0.06); it appears to still be undergoing fairly rapid cooling, as expected given the youth of the host star. The star also shows long-term variability in both the radial velocities and several activity indicators, which we attribute to stellar activity. The discovery and characterization of warm giant planets such as TOI-201 b are important for constraining formation and evolution theories for giant planets.
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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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    HD 2685 b: a hot Jupiter orbiting an early F-type star detected by TESS
    (2019) Jones, Matias, I; Brahm, Rafael; Espinoza, Nestor; Wang, Songhu; Shporer, Avi; Henning, Thomas; Jordan, Andres; Sarkis, Paula; Paredes, Leonardo A.; Hodari-Sadiki, James; Henrys, Todd; Cruz, Bryndis; Nielsen, Louise D.; Bouchy, Francois; Pepe, Francesco; Segransan, Damien; Turner, Oliver; Udry, Stephane; Marmier, Maxime; Lovis, Christophe; Bakos, Gaspar; Osip, David; Suc, Vincent; Ziegler, Carl; Tokovinin, Andrei; Law, Nick M.; Mann, Andrew W.; Relles, Howard; Collins, Karen A.; Bayliss, Daniel; Sedaghati, Elyar; Latham, David W.; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Smith, Jeffrey C.; Davies, Misty; Tenenbaum, Peter; Dittmann, Jason; Vanderburg, Andrew; Christiansen, Jessie L.; Haworth, Kari; Doty, John; Furesz, Gabor; Laughlin, Greg; Matthews, Elisabeth; Crossfield, Ian; Howell, Steve; Ciardi, David; Gonzales, Erica; Matson, Rachel; Beichman, Charles; Schlieder, Joshua
    We report on the confirmation of a transiting giant planet around the relatively hot (T-eff = 6801 +/- 76 K) star HD 2685, whose transit signal was detected in Sector 1 data of NASA's TESS mission. We confirmed the planetary nature of the transit signal using Doppler velocimetric measurements with CHIRON, CORALIE, and FEROS, as well as using photometric data obtained with the Chilean-Hungarian Automated Telescope and the Las Cumbres Observatory. From the joint analysis of photometry and radial velocities, we derived the following parameters for HD 2685 b: P =4.12688(-0.00004)(+0.00005) days, e =0.091(-0.047)(+0.039), Mp = 1.17 +/- 0.12 M-J, and R-p =1.44 +/- 0.05 R-J. This system is a typical example of an inflated transiting hot Jupiter in a low-eccentricity orbit. Based on the apparent visual magnitude (V = 9.6 mag) of the host star, this is one of the brightest known stars hosting a transiting hot Jupiter, and it is a good example of the upcoming systems that will be detected by TESS during the two-year primary mission. This is also an excellent target for future ground- and space-based atmospheric characterization as well as a good candidate for measuring the projected spin-orbit misalignment angle through the Rossiter-McLaughlin effect.
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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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    TESS Delivers Five New Hot Giant Planets Orbiting Bright Stars from the Full-frame Images
    (2021) Rodriguez, Joseph E.; Quinn, Samuel N.; Zhou, George; Vanderburg, Andrew; Nielsen, Louise D.; Wittenmyer, Robert A.; Brahm, Rafael; Reed, Phillip A.; Huang, Chelsea X.; Vach, Sydney; Ciardi, David R.; Oelkers, Ryan J.; Stassun, Keivan G.; Hellier, Coel; Gaudi, B. Scott; Eastman, Jason D.; Collins, Karen A.; Bieryla, Allyson; Christian, Sam; Latham, David W.; Carleo, Ilaria; Wright, Duncan J.; Matthews, Elisabeth; Gonzales, Erica J.; Ziegler, Carl; Dressing, Courtney D.; Howell, Steve B.; Tan, Thiam-Guan; Wittrock, Justin; Plavchan, Peter; McLeod, Kim K.; Baker, David; Wang, Gavin; Radford, Don J.; Schwarz, Richard P.; Esposito, Massimiliano; Ricker, George R.; Vanderspek, Roland K.; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Addison, Brett; Anderson, D. R.; Barclay, Thomas; Beatty, Thomas G.; Berlind, Perry; Bouchy, Francois; Bowen, Michael; Bowler, Brendan P.; Brasseur, C. E.; Briceno, Cesar; Caldwell, Douglas A.; Calkins, Michael L.; Cartwright, Scott; Chaturvedi, Priyanka; Chaverot, Guillaume; Chimaladinne, Sudhish; Christiansen, Jessie L.; Collins, Kevin I.; Crossfield, Ian J. M.; Eastridge, Kevin; Espinoza, Nestor; Esquerdo, Gilbert A.; Feliz, Dax L.; Fenske, Tyler; Fong, William; Gan, Tianjun; Giacalone, Steven; Gill, Holden; Gordon, Lindsey; Granados, A.; Grieves, Nolan; Guenther, Eike W.; Guerrero, Natalia; Henning, Thomas; Henze, Christopher E.; Hesse, Katharine; Hobson, Melissa J.; Horner, Jonathan; James, David J.; Jensen, Eric L. N.; Jimenez, Mary; Jordan, Andres; Kane, Stephen R.; Kielkopf, John; Kim, Kingsley; Kuhn, Rudolf B.; Latouf, Natasha; Law, Nicholas M.; Levine, Alan M.; Lund, Michael B.; Mann, Andrew W.; Mao, Shude; Matson, Rachel A.; Mengel, Matthew W.; Mink, Jessica; Newman, Patrick; O'Dwyer, Tanner; Okumura, Jack; Palle, Enric; Pepper, Joshua; Quintana, Elisa V.; Sarkis, Paula; Savel, Arjun B.; Schlieder, Joshua E.; Schnaible, Chloe; Shporer, Avi; Sefako, Ramotholo; Seidel, Julia V.; Siverd, Robert J.; Skinner, Brett; Stalport, Manu; Stevens, Daniel J.; Stibbards, Caitlin; Tinney, C. G.; West, R. G.; Yahalomi, Daniel A.; Zhang, Hui
    We present the discovery and characterization of five hot and warm Jupiters-TOI-628 b (TIC 281408474; HD 288842), TOI-640 b (TIC 147977348), TOI-1333 b (TIC 395171208, BD+47 3521A), TOI-1478 b (TIC 409794137), and TOI-1601 b ( TIC 139375960)-based on data from NASA's Transiting Exoplanet Survey Satellite (TESS). The five planets were identified from the full-frame images and were confirmed through a series of photometric and spectroscopic follow-up observations by the TESS Follow-up Observing Program Working Group. The planets are all Jovian size (R-P = 1.01-1.77 R-J) and have masses that range from 0.85 to 6.33 M-J. The host stars of these systems have F and G spectral types (5595 <= T-eff <= 6460 K) and are all relatively bright (9.5 < V < 10.8, 8.2 < K < 9.3), making them well suited for future detailed characterization efforts. Three of the systems in our sample (TOI-640 b, TOI-1333 b, and TOI-1601 b) orbit subgiant host stars (log g < 4.1). TOI-640 b is one of only three known hot Jupiters to have a highly inflated radius (R-P > 1.7 R-J, possibly a result of its host star's evolution) and resides on an orbit with a period longer than 5 days. TOI-628 b is the most massive, hot Jupiter discovered to date by TESS with a measured mass of 6.31(-0.30)(+) (0.28) M-J and a statistically significant, nonzero orbital eccentricity of e = 0.074(-0.022)(+) (0.021). This planet would not have had enough time to circularize through tidal forces from our analysis, suggesting that it might be remnant eccentricity from its migration. The longest-period planet in this sample, TOI-1478 b (P = 10.18 days), is a warm Jupiter in a circular orbit around a near-solar analog. NASA's TESS mission is continuing to increase the sample of well-characterized hot and warm Jupiters, complementing its primary mission goals.
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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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    TOpI-2447 b / NGTS-29 b: a 69-day Saturn around a Solar analogue
    (2024) Gill, Samuel; Bayliss, Daniel; Ulmer-Moll, Solene; Wheatley, Peter J.; Brahm, Rafael; Anderson, David R.; Armstrong, David; Apergis, Ioannis; Alves, Douglas R.; Burleigh, Matthew R.; Butler, R. P.; Bouchy, Francois; Battley, Matthew P.; Bryant, Edward M.; Bieryla, Allyson; Crane, Jeffrey D.; Collins, Karen A.; Casewell, Sarah L.; Carleo, Ilaria; Claringbold, Alastair B.; Dalba, Paul A.; Dragomir, Diana; Eigmueller, Philipp; Eberhardt, Jan; Fausnaugh, Michael; Gunther, Maximilian N.; Grieves, Nolan; Goad, Michael R.; Gillen, Edward; Hagelberg, Janis; Hobson, Melissa; Hedges, Christina; Henderson, Beth A.; Hawthorn, Faith; Henning, Thomas; Jones, Matias, I; Jordan, Andres; Jenkins, James S.; Kunimoto, Michelle; Krenn, Andreas F.; Kendall, Alicia; Lendl, Monika; McCormac, James; Moyano, Maximiliano; Torres-Miranda, Pascal; Nielsen, Louise D.; Osborn, Ares; Otegi, Jon; Osborn, Hugh; Quinn, Samuel N.; Rodriguez, Joseph E.; Ramsay, Gavin; Schlecker, Martin; Shectman, Stephen A.; Seager, Sara; Tilbrook, Rosanna H.; Trifonov, Trifon; Teske, Johanna K.; Udry, Stephane; Vines, Jose, I; West, Richard R.; Wohler, Bill; Winn, Joshua N.; Wang, Sharon X.; Zhou, George; Zivave, Tafadzwa
    Discovering transiting exoplanets with relatively long orbital periods (>10 d) is crucial to facilitate the study of cool exoplanet atmospheres (T-eq < 700 K) and to understand exoplanet formation and inward migration further out than typical transiting exoplanets. In order to discover these longer period transiting exoplanets, long-term photometric, and radial velocity campaigns are required. We report the discovery of TOI-2447 b (=NGTS-29 b), a Saturn-mass transiting exoplanet orbiting a bright (T = 10.0) Solar-type star (T-eff = 5730 K). TOI-2447 b was identified as a transiting exoplanet candidate from a single transit event of 1.3 per cent depth and 7.29 h duration in TESS Sector 31 and a prior transit event from 2017 in NGTS data. Four further transit events were observed with NGTS photometry which revealed an orbital period of P = 69.34 d. The transit events establish a radius for TOI-2447 b of 0.865 +/- 0.010 R-J, while radial velocity measurements give a mass of 0.386 +/- 0.025 M-J. The equilibrium temperature of the planet is 414 K, making it much cooler than the majority of TESS planet discoveries. We also detect a transit signal in NGTS data not caused by TOI-2447 b, along with transit timing variations and evidence for a similar to 150 d signal in radial velocity measurements. It is likely that the system hosts additional planets, but further photometry and radial velocity campaigns will be needed to determine their parameters with confidence. TOI-2447 b/NGTS-29 b joins a small but growing population of cool giants that will provide crucial insights into giant planet composition and formation mechanisms.