Examinando por Autor "Henning, Thomas"

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    A New Sample of Warm Extreme Debris Disks from the ALLWISE Catalog
    (Institute of Physics, 2021-03-20) Moór, Attila; Ábrahám, Péter; Szabó, Gyula; Vida, Krisztián; Cataldi, Gianni; Derekas, Alíz; Henning, Thomas; Kinemuchi, Karen; Kóspál, Ágnes; Kovács, József; Pál, András; Sarkis, Paula; Seli, Bálint; Szabó, Zsófia M.; Takáts, Katalin
    Extreme debris disks (EDDs) are rare systems with peculiarly large amounts of warm dust that may stem from recent giant impacts between planetary embryos during the final phases of terrestrial planet growth. Here we report on the identification and characterization of six new EDDs. These disks surround F5-G9 type main-sequence stars with ages >100 Myr, have dust temperatures higher than 300 K, and fractional luminosities between 0.01 and 0.07. Using time-domain photometric data at 3.4 and 4.6 μm from the WISE all-sky surveys, we conclude that four of these disks exhibited variable mid-infrared (IR) emission between 2010 and 2019. Analyzing the sample of all known EDDs, now expanded to 17 objects, we find that 14 of them showed changes at 3-5 μm over the past decade, suggesting that mid-IR variability is an inherent characteristic of EDDs. We also report that wide-orbit pairs are significantly more common in EDD systems than in the normal stellar population. While current models of rocky planet formation predict that the majority of giant collisions occur in the first 100 Myr, we find that the sample of EDDs is dominated by systems older than this age. This raises the possibility that the era of giant impacts may be longer than we think, or that some other mechanism(s) can also produce EDDs. We examine a scenario where the observed warm dust stems from the disruption and/or collisions of comets delivered from an outer reservoir into the inner regions, and explore what role the wide companions could play in this process.
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    Early Release Science of the exoplanet WASP-39b with JWST NIRISS
    (Nature Research, 2023-02) Feinstein, Adina D.; Radica, Michael; Welbanks, Luis; Murray, Catriona Anne; Ohno, Kazumasa; Coulombe, Louis-Philippe; Espinoza, Néstor; Bean, Jacob L.; Teske, Johanna K.; Benneke, Björn; Line, Michael R.; Rustamkulov, Zafar; Saba, Arianna; Tsiaras, Angelos; Barstow, Joanna K.; Fortney, Jonathan J.; Gao, Peter; Knutson, Heather A.; MacDonald, Ryan J.; Mikal-Evans, Thomas; Rackham, Benjamin V.; Taylor, Jake; Parmentier, Vivien; Batalha, Natalie M.; Berta-Thompson, Zachory K.; Carter, Aarynn L.; Changeat, Quentin; dos Santos, Leonardo A.; Gibson, Neale P.; Goyal, Jayesh M.; Kreidberg, Laura; López-Morales, Mercedes; Lothringer, Joshua D.; Miguel, Yamila; Molaverdikhani, Karan; Moran, Sarah E.; Morello, Giuseppe; Mukherjee, Sagnick; Sing, David K.; Stevenson, Kevin B.; Wakeford, Hannah R.; Ahrer, Eva-Maria; Alam, Munazza K.; Alderson, Lili; Allen, Natalie H.; Batalha, Natasha E.; Bell, Taylor J.; Blecic, Jasmina; Brande, Jonathan; Caceres, Claudio; Casewell S.L.; Chubb, Katy L.; Crossfield, Ian J. M.; Crouzet, Nicolas; Cubillos, Patricio E.; Decin, Leen; Désert, Jean-Michel; Harrington, Joseph; Heng, Kevin; Henning, Thomas; Iro, Nicolas; Kempton, Eliza M.-R.; Kendrew, Sarah; Kirk, James; Krick, Jessica; Lagage, Pierre-Olivier; Lendl, Monika; Mancini, Luigi; Mansfield, Megan; May E.M.; Mayne N.J.; Nikolov, Nikolay K.; Palle, Enric; Petit dit de la Roche, Dominique J. M.; Piaulet, Caroline; Powell, Diana; Redfield, Seth; Rogers, Laura K.; Roman, Michael T.; Roy, Pierre-Alexis; Nixon, Matthew C.; Schlawin, Everett; Tan, Xianyu; Tremblin P.; Turner, Jake D.; Venot, Olivia; Waalkes, William C.; Wheatley, Peter J.; Zhang, Xi
    The Saturn-mass exoplanet WASP-39b has been the subject of extensive efforts to determine its atmospheric properties using transmission spectroscopy1–4. However, these efforts have been hampered by modelling degeneracies between composition and cloud properties that are caused by limited data quality5–9. Here we present the transmission spectrum of WASP-39b obtained using the Single-Object Slitless Spectroscopy (SOSS) mode of the Near Infrared Imager and Slitless Spectrograph (NIRISS) instrument on the JWST. This spectrum spans 0.6–2.8 μm in wavelength and shows several water-absorption bands, the potassium resonance doublet and signatures of clouds. The precision and broad wavelength coverage of NIRISS/SOSS allows us to break model degeneracies between cloud properties and the atmospheric composition of WASP-39b, favouring a heavy-element enhancement (‘metallicity’) of about 10–30 times the solar value, a sub-solar carbon-to-oxygen (C/O) ratio and a solar-to-super-solar potassium-to-oxygen (K/O) ratio. The observations are also best explained by wavelength-dependent, non-grey clouds with inhomogeneous coverageof the planet’s terminator. © 2023, The Author(s).
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    HD 213885b: A transiting 1-d-period super-Earth with an Earth-like composition around a bright (V = 7.9) star unveiled by TESS
    (Oxford University Press, 2020-01-01) Espinoza, Néstor; Brahm, Rafael; Henning, Thomas; Jordán, Andrés; Dorn, Caroline; Rojas, Felipe; Sarkis, Paula; Kossakowski, Diana; Schlecker, Martin; Díaz, Matías R.; Jenkins, James S.; Aguilera-Gomez, Claudia; Jenkins, Jon M.; Twicken, Joseph D.; Collins, Karen A.; Lissauer, Jack; Armstrong, David J.; Adibekyan, Vardan; Barrado, David; Barros, Susana C.C.; Battley, Matthew; Bayliss, Daniel; Bouchy, François; Bryant, Edward M.; Cooke, Benjamin F.; Olivier D.S.; Dumusque, Xavier; Figueira, Pedro; Giles, Helen; Lillo-Box, Jorge; Lovis, Christophe; Nielsen, Louise D.; Pepe, Francesco; Pollacco, Don; Santos, Nuno C.; Sousa, Sergio G.; Udry, Stéphane; Wheatley, Peter J.; Turner, Oliver; Marmier, Maxime; Ségransan, Damien; Ricker, George; Latham, David; Seager, Sara; Winn, Joshua N.; Kielkopf, John F.; Hart, Rhodes; Wingham, Geof; Jensen, Eric L.N.; Hełminiak, Krzysztof G.; Tokovinin A.; Briceño C.; Ziegler, Carl; Law, Nicholas M.; Mann, Andrew W.; Daylan, Tansu; Doty, John P.; Guerrero, Natalia; Boyd, Patricia; Crossfield, Ian
    We report the discovery of the 1.008-d, ultrashort period (USP) super-Earth HD 213885b (TOI-141b) orbiting the bright (V= 7.9) star HD 213885 (TOI-141, TIC 403224672), detected using photometry from the recently launched TESS mission. Using FEROS, HARPS, and CORALIE radial velocities, we measure a precise mass of 8.8 ±0.6M⊙ for this 1.74±0.05R⊙ exoplanet, which provides enough information to constrain its bulk composition - similar to Earth's but enriched in iron. The radius, mass, and stellar irradiation of HD 213885b are, given our data, very similar to 55 Cancri e, making this exoplanet a good target to perform comparative exoplanetology of short period, highly irradiated super-Earths. Our precise radial velocities reveal an additional 4.78-d signal which we interpret as arising from a second, non-transiting planet in the system, HD 213885c, whose minimum mass of 19.9 ± 1.4 M⊙ makes it consistent with being a Neptune-mass exoplanet. The HD 213885 system is very interesting from the perspective of future atmospheric characterization, being the second brightest star to host an USP transiting super-Earth (with the brightest star being, in fact, 55 Cancri). Prospects for characterization with present and future observatories are discussed.
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    No Clear, Direct Evidence for Multiple Protoplanets Orbiting LkCa 15: LkCa 15 bcd are Likely Inner Disk Signals
    (Institute of Physics Publishing, 2019-05-20) Currie, Thayne; Marois, Christian; Cieza, Lucas; Mulders, Gijs D.; Lawson, Kellen; Caceres, Claudio; Rodriguez-Ruiz, Dary; Wisniewski, John; Guyon, Olivier; Brandt, Timothy D.; Kasdin, N. Jeremy; Groff, Tyler D.; Lozi, Julien; Chilcote, Jeffrey; Hodapp, Klaus; Jovanovic, Nemanja; Martinache, Frantz; Skaf, Nour; Lyra, Wladimir; Tamura, Motohide; Asensio-Torres, Ruben; Dong, Ruobing; Grady, Carol; Gerard, Benjamin; Fukagawa, Misato; Hand, Derek; Hayashi, Masahiko; Henning, Thomas; Kudo, Tomoyuki; Kuzuhara, Masayuki; Kwon, Jungmi; McElwain, Michael W.; Uyama, Taichi
    Two studies utilizing sparse aperture-masking (SAM) interferometry and Hα differential imaging have reported multiple Jovian companions around the young solar-mass star, LkCa 15 (LkCa 15 bcd): the first claimed direct detection of infant, newly formed planets ("protoplanets"). We present new near-infrared direct imaging/spectroscopy from the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) system coupled with Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) integral field spectrograph and multi-epoch thermal infrared imaging from Keck/NIRC2 of LkCa 15 at high Strehl ratios. These data provide the first direct imaging look at the same wavelengths and in the same locations where previous studies identified the LkCa 15 protoplanets, and thus offer the first decisive test of their existence. The data do not reveal these planets. Instead, we resolve extended emission tracing a dust disk with a brightness and location comparable to that claimed for LkCa 15 bcd. Forward-models attributing this signal to orbiting planets are inconsistent with the combined SCExAO/CHARIS and Keck/NIRC2 data. An inner disk provides a more compelling explanation for the SAM detections and perhaps also the claimed Hα detection of LkCa 15 b. We conclude that there is currently no clear, direct evidence for multiple protoplanets orbiting LkCa 15, although the system likely contains at least one unseen Jovian companion. To identify Jovian companions around LkCa 15 from future observations, the inner disk should be detected and its effect modeled, removed, and shown to be distinguishable from planets. Protoplanet candidates identified from similar systems should likewise be clearly distinguished from disk emission through modeling.
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    Radial Velocity Survey for Planets around Young stars (RVSPY): Target characterisation and high-cadence survey
    (EDP Sciences, 2022-11-01) Zakhozhay, Olga V.; Launhardt, Ralf; Müller, Andre; Brems, Stefan S.; Eigenthaler, Paul; Gennaro, Mario; Hempel, Angela; Hempel, Maren; Henning, Thomas; Kennedy, Grant M.; Kim, Sam; Kürster, Martin; Lachaume, Régis; Manerikar, Yashodhan; Patel, Jayshil A.; Pavlov, Alexey; Reffert, Sabine; Trifonov, Trifon
    Context. The occurrence rate and period distribution of (giant) planets around young stars is still not as well constrained as for older main-sequence stars. This is mostly due to the intrinsic activity-related complications and the avoidance of young stars in many large planet search programmes. Yet, dynamical restructuring processes in planetary systems may last significantly longer than the actual planet formation phase and may well extend long into the debris disc phase, such that the planet populations around young stars may differ from those observed around main-sequence stars. Aims. We introduce our Radial Velocity Survey for Planets around Young stars (RVSPY), which is closely related to the NaCo-ISPY direct imaging survey, characterise our target stars, and search for substellar companions at orbital separations smaller than a few au from the host star. Methods. We used the FEROS spectrograph, mounted to the MPG/ESO 2.2 m telescope in Chile, to obtain high signal-to-noise spectra and time series of precise radial velocities (RVs) of 111 stars, most of which are surrounded by debris discs. Our target stars have spectral types between early F and late K, a median age of 400 Myr, and a median distance of 45 pc. During the initial reconnaissance phase of our survey, we determined stellar parameters and used high-cadence observations to characterise the intrinsic stellar activity, searched for hot companions with orbital periods of up to 10 days, and derived the detection thresholds for longer-period companions. In our analysis we, have included archival spectroscopic data, spectral energy distribution, and data for photometric time series from the TESS mission. Results. For all target stars we determined their basic stellar parameters and present the results of the high-cadence RV survey and activity characterisation. We have achieved a median single-measurement RV precision of 6 m sa 1 and derived the short-term intrinsic RV scatter of our targets (median 23 m sa 1), which is mostly caused by stellar activity and decays with an age from >100 m sa 1 at <20 Myr to [removed]500 Myr. We analysed time series periodograms of the high-cadence RV data and the shape of the individual cross-correlation functions. We discovered six previously unknown close companions with orbital periods between 10 and 100 days, three of which are low-mass stars, and three are in the brown dwarf mass regime. We detected no hot companion with an orbital period [removed]