Article
Astronomy & Astrophysics
Samuel A. Beiler, Katelyn N. Allers, Michael Cushing, Jacqueline Faherty, Mark Marley, Andrew Skemer
Summary: We conducted a spectroscopic study on eight young L dwarfs in the L-band (2.98-3.96 μm) with spectral types ranging from L2 to L7. Our analysis focused on the evolution of the Q-branch of methane absorption feature and the impact of including the L-band data on atmoshperic models. We found that the Q-branch feature first appears between L3 and L6 and that the addition of the L band causes a drop in effective temperature and requires thick clouds and higher vertical mixing rates in the models.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Mikhail Lipatov, Timothy D. Brandt, Natasha E. Batalha
Summary: The rotational speed and axis inclination of giant planets and brown dwarfs have significant effects on their spectral shape and total flux. Understanding these effects is important for studying the physical properties of stars and planets, and can help calculate the corresponding adjustment factors.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Sophie Dubber, Beth Biller, Loic Albert, Michael Liu, Jessy Jose, Zhoujian Zhang, Wen-Ping Chen, Bhavana Lalchand, Belinda Damian, Tanvi Sharma, Katelyn Allers
Summary: We have spectroscopically confirmed nine M5 or later Serpens Core candidate members using CFHT WIRCam photometry and IRTF SpeX spectroscopy. The latest of these candidates is best fit by an L0 spectral standard, suggesting a mass of about 0.01-0.035M (solar mass). If confirmed as cluster members, they would be among the lowest mass objects ever discovered in the Serpens Core. We performed analysis on the physical properties of the sample and discussed the likely membership of the candidate Serpens Core members.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Samrat Ghosh, Soumen Mondal, Somnath Dutta, Ramkrishna Das, Santosh Joshi, Sneh Lata, Dhrimadri Khata, Alik Panja
Summary: This study explores optical I-band photometric variability in the young star-forming region IC 348, detecting new photometric variability in 22 young M dwarfs, including 6 BDs. Among the 22 variables, 11 M dwarfs show hour-scale periodic variability. Interestingly, an optical flare was observed in a young M2.75 dwarf.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Samuel Pearson, Aleks Scholz, Paula S. Teixeira, Koraljka Muzic, Victor Almendros-Abad
Summary: Based on spectroscopic observations of 68 candidates in NGC 2264, researchers confirmed 13 brown dwarfs and 19 M-type stars, with ages predominantly younger than the known cluster population, indicating distinct formation processes. The estimated total of 200-600 brown dwarfs in NGC 2264 suggests a star-to-brown dwarf ratio between 2.5:1 and 7.5:1, with a consistent substellar mass function slope of alpha = 0.43(-0.56)(+0.41) across various young clusters, indicating a uniformity in substellar mass functions within star-forming environments.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Sophie Dubber, Beth Biller, Katelyn Allers, Jessy Jose, Loic Albert, Blake Pantoja, Clemence Fontanive, Michael Liu, Zhoujian Zhang, Wen-Ping Chen, Bhavana Lalchand, Belinda Damian, Tanvi Sharma
Summary: Using CFHT photometry and IRTF spectroscopy, low-mass candidate members of Serpens South and Serpens Core were identified using the W-band method. Young, low-mass Serpens candidate members were reported with masses less than 0.12 solar masses. Additionally, a binary system was discovered with components separated by approximately 45AU, each with spectral types and masses within a specific range. The analysis also discussed the impact of dust attenuation and reddened background stars on the reliability of the findings.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Genaro Suarez, Stanimir Metchev
Summary: Analysis of archival spectra from the Spitzer Space Telescope shows that silicate absorption in the 8-11 micron region is common in L-type dwarfs. This absorption is caused by silicate-rich clouds and is strongest in L4-L6 dwarfs. A comparison of low and high surface gravity dwarfs reveals that the silicate absorption feature is sensitive to gravity, with young atmospheres showing broader and redder profiles. This is the first spectroscopic evidence for gravity-dependent sedimentation of dust condensates in ultracool atmospheres.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Genaro Suarez, Stanimir Metchev
Summary: This study presents a uniform analysis of mid-infrared spectra of M5-T9 dwarfs obtained with the Spitzer Infrared Spectrograph. The results show the presence of water absorption in all spectra, with increasing strength towards later spectral types. Methane and ammonia are observed at specific spectral types, while silicate absorption is found to be present in L dwarfs but can be absent in some cases. The study also identifies a positive correlation between silicate absorption strength and near-infrared color, supporting the idea of variations in silicate cloud thickness leading to color scatter in L dwarfs. The observations further confirm the presence of silicate condensate clouds in L dwarf atmospheres and provide observational evidence for their emergence and sedimentation between effective temperatures of approximately 2000 and 1300 K.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
P. A. Miles-Paez
Summary: This study investigates the photometric properties of the M7.5 equal-mass binary VHS J1256-1257AB and finds that their light curves exhibit periodic modulation and stochastic variability, with rotation periods of 2.0782 hours and 2.1342 hours. The fluxes of the equally bright VHS J1256-1257A and B alternate between phase and anti-phase states, explaining the observed photometric variability in their combined light.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Elspeth K. H. Lee, Xianyu Tan, Shang-Min Tsai
Summary: Researchers investigate the connection between the 3D atmospheric dynamics and time-dependent chemistry in brown dwarfs, and explore its impact on spectral variability. By coupling a miniature kinetic chemistry module to a general circulation model, they simulate the chemical structures and spectral signatures of brown dwarf atmospheres. Their findings reveal non-equilibrium chemical behavior and localized storm regions that contribute to the dynamic nature of brown dwarf atmospheres.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Renae E. Wall, Mukremin Kilic, P. Bergeron, Nathan D. Leiphart
Summary: We analyze 14,001 DA white dwarfs using a detailed model atmosphere and ultraviolet photometry from the GALEX mission. Our findings show no major systematic differences between optical and optical + UV data in determining best-fitting parameters. The GALEX FUV and NUV data significantly improve model fits for hotter white dwarfs with UV peak spectral energy distributions. Our study identifies 89 new outliers based on GALEX UV data, highlighting the need for follow-up observations to confirm their nature.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Yapeng Zhang, Ignas A. G. Snellen, Paul Molliere
Summary: This study aims to investigate the relationship between atmospheric characteristics and formation pathways by measuring the carbon isotope ratio of a young, isolated brown dwarf. The findings show a difference in isotopologue ratio compared to super-Jupiters, suggesting potential variations in formation pathways.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Nolan Grieves, Francois Bouchy, Monika Lendl, Theron Carmichael, Ismael Mireles, Avi Shporer, Kim K. McLeod, Karen A. Collins, Rafael Brahm, Keivan G. Stassun, Sam Gill, Luke G. Bouma, Tristan Guillot, Marion Cointepas, Leonardo A. Dos Santos, Sarah L. Casewell, Jon M. Jenkins, Thomas Henning, Louise D. Nielsen, Angelica Psaridi, Stephane Udry, Damien Segransan, Jason D. Eastman, George Zhou, Lyu Abe, Abelkrim Agabi, Gaspar Bakos, David Charbonneau, Kevin Collins, Knicole D. Colon, Nicolas Crouzet, Georgina Dransfield, Phil Evans, Robert F. Goeke, Rhodes Hart, Jonathan M. Irwin, Eric L. N. Jensen, Andres Jordan, John F. Kielkopf, David W. Latham, Wenceslas Marie-Sainte, Djamel Mekarnia, Peter Nelson, Samuel N. Quinn, Don J. Radford, David R. Rodriguez, Pamela Rowden, Francois-Xavier Schmider, Richard P. Schwarz, Jeffrey C. Smith, Chris Stockdale, Olga Suarez, Thiam-Guan Tan, Amaury H. M. J. Triaud, William Waalkes, Geof Wingham
Summary: We report the discovery of five transiting companions near the hydrogen-burning mass limit in close orbits around main sequence stars originally identified by the Transiting Exoplanet Survey Satellite (TESS). These companions have small orbital periods, masses between 77 and 98 Earth masses, and radii between 0.81 and 1.66 Jupiter radii. The findings provide valuable insights for testing formation models of rare objects and distinguishing between brown dwarfs and hydrogen-burning main sequence stars.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
R. E. Ryan, P. Thorman, C. Aganze, A. J. Burgasser, S. H. Cohen, N. P. Hathi, B. Holwerda, N. Pirzkal, R. A. Windhorst
Summary: In this study, a self-consistent model of the Milky Way is presented to reproduce the observed distributions and total velocity dispersion of brown dwarfs. The results suggest that brown dwarfs likely form via similar processes as main-sequence stars. Wide-field infrared imaging or low-resolution spectroscopic surveys are recommended for further refinement of these conclusions.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Theron W. Carmichael
Summary: This study presents updates on the substellar mass-radius diagram for 11 transiting brown dwarfs (BDs) and low-mass stars published before Gaia DR3. By re-analyzing these systems, it is found that when using Gaia DR3's parallax measurements, seven BDs show significant differences or improved uncertainty in their radius estimation. This has important implications for testing substellar evolutionary models. The remaining four BDs show consistent mass-radius estimates with their pre-Gaia DR3 measurements. Among these, AD 3116b is a known member of the Praesepe cluster at an age of 600 Myr. Additionally, the previously smallest known transiting BDs, KOI-205b and KOI-415b, are not as small as previously thought, resulting in a relatively sparse region for the mass-radius diagram of the oldest BDs.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Ch. Helling, M. Worters, D. Samra, K. Molaverdikhani, N. Iro
Summary: Ultra-hot Jupiter HAT-P-7b has a significant day-night temperature difference, leading to distinct surface features and the potential formation of an ionosphere. Certain ions and atoms can be used as spectral tracers, and lightning may occur within the clouds of HAT-P-7b. The atmosphere of HAT-P-7b may couple to a global, large-scale magnetic field, with lightning potentially occurring on the nightside.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Geosciences, Multidisciplinary
Gregory Cesana, Andrew S. Ackerman, Ann M. Fridlind, Israel Silber, Maxwell Kelley
Summary: A new study shows that accounting for precipitation in climate models can significantly influence cloud phase partitioning and cloud feedback, which has previously been neglected in the majority of CMIP models. This finding suggests that making climate models precipitation-aware could further enhance their cloud feedback and increase their climate sensitivity.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Astronomy & Astrophysics
O. Herbort, P. Woitke, Ch Helling, A. L. Zerkle
Summary: Clouds are an important component of planetary atmospheres, and understanding their formation and composition is crucial for observing and understanding surface conditions. Researchers have developed a chemical equilibrium model to study condensates and cloud formation in the atmospheres of rocky exoplanets. The study identified 72 thermally stable cloud condensates, with a consistent sequence of condensation that is independent of crust composition, surface pressure, and temperature. Water is a common cloud condensate, but its base depends on the hydration level of the crust.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Ignas A. G. Snellen, F. Snik, M. Kenworthy, S. Albrecht, G. Anglada-Escude, I Baraffe, P. Baudoz, W. Benz, J-L Beuzit, B. Biller, J. L. Birkby, A. Boccaletti, R. van Boekel, J. de Boer, Matteo Brogi, L. Buchhave, L. Carone, M. Claire, R. Claudi, B-O Demory, J-M Desert, S. Desidera, B. S. Gaudi, R. Gratton, M. Gillon, J. L. Grenfell, O. Guyon, T. Henning, S. Hinkley, E. Huby, M. Janson, C. Helling, K. Heng, M. Kasper, C. U. Keller, O. Krause, L. Kreidberg, N. Madhusudhan, A-M Lagrange, R. Launhardt, T. M. Lenton, M. Lopez-Puertas, A-L Maire, N. Mayne, V Meadows, B. Mennesson, G. Micela, Y. Miguel, J. Milli, M. Min, E. de Mooij, D. Mouillet, M. N'Diaye, V D'Orazi, E. Palle, I Pagano, G. Piotto, D. Queloz, H. Rauer, I Ribas, G. Ruane, F. Selsis, A. Sozzetti, D. Stam, C. C. Stark, A. Vigan, Pieter de Visser
Summary: The White Paper recommends ESA to play a proactive role in developing a global collaborative effort to construct a large high-contrast imaging space telescope for characterizing Earth-like planets in the habitable zones of nearby Sun-like stars and searching for extraterrestrial biological activity.
EXPERIMENTAL ASTRONOMY
(2022)
Article
Geochemistry & Geophysics
Mason Neuman, Astrid Holzheid, Katharina Lodders, Bruce Fegley, Bradley L. Jolliff, Piers Koefoed, Heng Chen, Kun Wang
Summary: The study conducted twenty heating experiments to investigate the behavior of K, Cu, and Zn evaporation and isotopic fractionation from basaltic melts at high temperatures. Results show that Zn is the most volatile element followed by Cu and K. However, partitioning of Zn into spinel layers affects the Zn isotope fractionation factor. Higher temperatures and lower oxygen fugacities promote evaporation, and the experimentally determined fractionation factors for K and Cu are significantly larger than the apparent observed fractionation factors from lunar basalts.
GEOCHIMICA ET COSMOCHIMICA ACTA
(2022)
Article
Astronomy & Astrophysics
Aaron David Schneider, Ludmila Carone, Leen Decin, Uffe Grae Jorgensen, Paul Molliere, Robin Baeyens, Sven Kiefer, Christiane Helling
Summary: Simulations with a 3D general circulation model suggest that the observed radius inflation in hot Jupiters may be driven by the downward advection of energy from the photosphere into deeper layers. The study compares the dynamical heat transport in a non-inflated hot Jupiter and a canonical inflated hot Jupiter, and finds differences in the deep temperature profile and flow structures between the two planets.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Meteorology & Atmospheric Sciences
Larissa S. Nazarenko, Nick Tausnev, Gary L. Russell, David Rind, Ron L. Miller, Gavin A. Schmidt, Susanne E. Bauer, Maxwell Kelley, Reto Ruedy, Andrew S. Ackerman, Igor Aleinov, Michael Bauer, Rainer Bleck, Vittorio Canuto, Gregory Cesana, Ye Cheng, Thomas L. Clune, Ben I. Cook, Carlos A. Cruz, Anthony D. Del Genio, Gregory S. Elsaesser, Greg Faluvegi, Nancy Y. Kiang, Daehyun Kim, Andrew A. Lacis, Anthony Leboissetier, Allegra N. LeGrande, Ken K. Lo, John Marshall, Elaine E. Matthews, Sonali McDermid, Keren Mezuman, Lee T. Murray, Valdar Oinas, Clara Orbe, Carlos Perez Garcia-Pando, Jan P. Perlwitz, Michael J. Puma, Anastasia Romanou, Drew T. Shindell, Shan Sun, Kostas Tsigaridis, George Tselioudis, Ensheng Weng, Jingbo Wu, Mao-Sung Yao
Summary: This paper presents the response of the GISS-E2.1 climate models to anthropogenic forcing in the 21st century Shared Socioeconomic Pathways emission scenarios. The study finds that global mean warming ranges from 1.5 degrees C to 5.2 degrees C by the year 2100, depending on the emission scenario. Changes in surface air temperature, precipitation, sea ice area, and Atlantic overturning stream function are also observed.
JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS
(2022)
Article
Geosciences, Multidisciplinary
F. Tornow, A. S. Ackerman, A. M. Fridlind, B. Cairns, E. C. Crosbie, S. Kirschler, R. H. Moore, D. Painemal, C. E. Robinson, C. Seethala, M. A. Shook, C. Voigt, E. L. Winstead, L. D. Ziemba, P. Zuidema, A. Sorooshian
Summary: Recent aircraft measurements show that entrainment from the free troposphere has a significant impact on cloud condensation nucleus concentrations in the marine boundary layer, reducing regional albedo.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Astronomy & Astrophysics
Aaron David Schneider, Ludmila Carone, Leen Decin, Uffe Grae Jorgensen, Christiane Helling
Summary: Studying ultra-hot Jupiter WASP-76 b, it is concluded that the coupling between radiation and dynamics alone cannot explain the abnormally large radii of inflated hot gas giants.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Geochemistry & Geophysics
Piers Koefoed, Olga Pravdivtseva, Ryan Ogliore, Yun Jiang, Katharina Lodders, Mason Neuman, Kun Wang
Summary: The impact hypothesis is the favored model for the formation of CB chondrites, and this study further investigates their formation mechanisms using elemental and K isotope compositions. The results suggest the presence of differentiated precursor material and significant fractionation, possibly due to partial melting and evaporation processes.
GEOCHIMICA ET COSMOCHIMICA ACTA
(2022)
Article
Meteorology & Atmospheric Sciences
Mikhail D. D. Alexandrov, Alexander Marshak, Brian Cairns, Andrew S. S. Ackerman
Summary: We generalize the binary-value Markovian model to a continuous-value model for describing 1D fields of cloud optical thickness (COT), and demonstrate its ability to generate various cloud-field types through statistical simulation based on actual cloud observations.
JOURNAL OF THE ATMOSPHERIC SCIENCES
(2022)
Article
Environmental Sciences
Frank Rensen, Yamila Miguel, Mantas Zilinskas, Amy Louca, Peter Woitke, Christiane Helling, Oliver Herbort
Summary: This research updates the gas phase and condensation equilibrium chemistry of Jupiter's deep atmosphere based on Galileo and Juno data. The results show increased abundances of oxygen, nitrogen, carbon and sulfur, leading to higher concentrations of ammonia, water, methane and hydrogen sulfide. The study also reveals the importance of oxygen enrichment in determining the formation of liquid water clouds. Furthermore, new gas phase species, such as CN- and (NaCN)2, and new condensates, such as H3PO4 (s) and LiCl (s), are found in the atmosphere of Jupiter.
Article
Geosciences, Multidisciplinary
Patrick Barth, Eva E. Stueken, Christiane Helling, Lukas Rossmanith, Yuqian Peng, Wendell Walters, Mark Claire
Summary: Based on the results of spark discharge experiments, lightning-driven nitrogen fixation may have played a significant role in the development of Earth's earliest ecosystems, similar to modern times.
Article
Environmental Sciences
Michael S. Diamond, Pablo E. Saide, Paquita Zuidema, Andrew S. Ackerman, Sarah J. Doherty, Ann M. Fridlind, Hamish Gordon, Calvin Howes, Jan Kazil, Takanobu Yamaguchi, Jianhao Zhang, Graham Feingold, Robert Wood
Summary: Smoke from southern Africa affects the transition between stratocumulus and cumulus clouds, producing aerosol radiative effects that are crucial for understanding cloud evolution.
ATMOSPHERIC CHEMISTRY AND PHYSICS
(2022)
Article
Geosciences, Multidisciplinary
Israel Silber, Robert C. Jackson, Ann M. Fridlind, Andrew S. Ackerman, Scott Collis, Johannes Verlinde, Jiachen Ding
Summary: Climate models play a crucial role in understanding Earth's atmosphere, and the ground-based lidar and radar instrument simulator EMC2 facilitates direct comparison of model outputs with observations, providing a lightweight and flexible framework.
GEOSCIENTIFIC MODEL DEVELOPMENT
(2022)
