Article
Astronomy & Astrophysics
K. Kosak, R. Kiefer, A-M Broomhall
Summary: This study investigates the variation of pseudo-mode frequencies with solar activity during the solar cycle. The results show that acoustic oscillation frequencies are correlated with the solar cycle, while pseudo-mode frequencies vary in antiphase. The analysis is based on data from different instruments, and the findings reveal differences in the frequency variations between the instruments.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Igor P. Lopin
Summary: The study investigates axisymmetric magnetohydrodynamic wave modes in the model of a coronal magnetic tube, revealing two families of modes and discussing their properties in twisted and untwisted magnetic fields.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
I Lopin
Summary: This study examines the kink oscillations of a curved coronal slab with finite plasma-beta, simulating a loop arcade. The study finds two surface modes, namely the faster mode and slower mode, in the model. As the internal plasma-beta becomes finite and increases, the phase speed of the faster mode increases, while that of the slower mode decreases.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
I Lopin, I Nagorny
Summary: In this work, we study the impact of curvature on slow-mode oscillations in coronal loop arcade using a theoretical approach. By solving a set of magnetohydrodynamic equations, we derive the dispersion relation that governs the compressible MHD modes in a simple model of curved coronal magnetic structures. Our findings reveal the existence of a band of slow body modes and a single hybrid slow mode in coronal loops under typical circumstances, which exhibit radial kink-like displacements and accompanying longitudinal oscillations. These mode properties can explain the observed Doppler shift, intensity oscillations, and spatial displacements in arcade loops.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
David Korda, Michal Svanda
Summary: This study aims to construct a model of flows in average supergranular cells using a consistent time-distance inverse methodology. By analyzing travel-time maps of over 10^4 individual supergranular cells, near-surface divergent horizontal flows and upward vertical flows were discovered. However, systematic errors affected the accuracy of vertical flow estimates, while a longitudinal flow pattern was found to align well with the model of solar rotation in subsurface layers.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Kyuhyoun Cho, Jongchul Chae, Maria S. Madjarska
Summary: The analysis of umbral flashes in merging sunspots suggests that the subsurface of the umbra is an environment where convection can occur more easily than the convergent interface, supporting the cluster model. Further studies based on umbral velocity oscillations in the lower atmosphere are needed for more concrete results.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
K. Mandal, S. M. Hanasoge, L. Gizon
Summary: This study successfully extends the methodology to measure even azimuthal orders of Rossby waves in the Sun, adding credibility to the mode-coupling methodology in helioseismology. The results indicate significant power close to the theoretical dispersion relation for sectoral Rossby modes, with maximum power occurring at mode t = 8.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
David Korda, Michal Svanda, Thierry Roudier
Summary: The study aims to suppress the negative effects of magnetic fields on solar oscillations and measure plasma properties near active regions. This is done through new averaging geometries, a non-linear approach to travel-time measurements, and a consistent inversion method. The new methodology successfully reconstructs surface horizontal flows near active regions and helps understand the depth structure and physical conditions contributing to the evolution of these regions.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
S. N. Breton, R. A. Garcia, J. Ballot, V Delsanti, D. Salabert
Summary: This article introduces the peakbagging methods for extracting stellar oscillation mode parameters and presents a new Python 3 open-source MCMC framework called apollinaire. The apollinaire module allows for the analysis of helio- and asteroseismic observations and demonstrates its precision and reliability through comparisons with other peakbagging codes.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Rene Kiefer, Anne-Marie Broomhall
Summary: The study investigates the energy supply rates of solar p modes throughout the solar activity cycle and finds that these rates are anticorrelated with the level of solar activity. Different mode frequency and harmonic degrees show varying strengths of anticorrelation with the solar activity level.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
T. Mehta, K. Jain, S. C. Tripathy, R. Kiefer, D. Kolotkov, A-M Broomhall
Summary: In this study, we investigated the relationship between the solar cycle and the presence and periodicity of the Quasi-Biennial Oscillation (QBO). Using helioseismic techniques and solar activity proxies, we found that the presence of the QBO varied significantly between solar cycles. The QBO presence was reduced in Cycle 24 compared to Cycle 23, and it was not dependent on the depth or frequency of the p-mode.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Souvik Das, Ahmed Atteya, Pralay Kumar Karmakar
Summary: A recently developed gravito-electrostatic sheath model is used to study the helioseismic oscillation features in the bi-fluidic solar plasma system. The model reveals the evolution of both dispersive and non-dispersive features of the modified gravito-electrostatic sheath mode fluctuations. Different spectral profiles show important features of the perturbations. The stability of the system depends on various parameters and the dispersive features are more pronounced in the self-gravitational domains.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Dan Yang, Laurent Gizon, Helene Barucq
Summary: This study aims to improve helioseismic holography for detecting active regions on the far side of the Sun and enhancing space weather forecasts. By using a clear problem formulation, an accurate forward solver in the frequency domain, and better understanding of noise properties, the method was improved. Active regions on the far side can be detected with high confidence by measuring and averaging phase shifts between the ingression and egression wave fields. The improvements in active region detection rate and false discovery rate are attributed to the use of a complete Green’s function and all available observations on the front side.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
J. Philidet, L. Gizon
Summary: This study investigates the impact of turbulent motions on the inertial modes in the Sun's convective zone. The results suggest that the stochastic excitation mechanism by turbulent convection explains the observed mode amplitudes reasonably well. However, the complex power spectra of the modes make the interpretation of the observations challenging.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Yuto Bekki, Robert H. Cameron, Laurent Gizon
Summary: The study focuses on detecting and characterizing modes present in nonlinear numerical simulations of solar convection, highlighting equatorial Rossby modes and columnar convective modes. These modes are compared to linear models and solar observations, providing insights into their amplitudes and impact on heat and angular momentum transport.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Daniel Huber, Timothy R. White, Travis S. Metcalfe, Ashley Chontos, Michael M. Fausnaugh, Cynthia S. K. Ho, Vincent Van Eylen, Warrick H. Ball, Sarbani Basu, Timothy R. Bedding, Othman Benomar, Diego Bossini, Sylvain Breton, Derek L. Buzasi, Tiago L. Campante, William J. Chaplin, Jorgen Christensen-Dalsgaard, Margarida S. Cunha, Morgan Deal, Rafael A. Garcia, Antonio Garcia Munoz, Charlotte Gehan, Lucia Gonzalez-Cuesta, Chen Jiang, Cenk Kayhan, Hans Kjeldsen, Mia S. Lundkvist, Stephane Mathis, Savita Mathur, Mario J. P. F. G. Monteiro, Benard Nsamba, Jia Mian Joel Ong, Erika Pakstiene, Aldo M. Serenelli, Victor Silva Aguirre, Keivan G. Stassun, Dennis Stello, Sissel Norgaard Stilling, Mark Lykke Winther, Tao Wu, Thomas Barclay, Tansu Daylan, Maximilian N. Gunther, J. J. Hermes, Jon M. Jenkins, David W. Latham, Alan M. Levine, George R. Ricker, Sara Seager, Avi Shporer, Joseph D. Twicken, Roland K. Vanderspek, Joshua N. Winn
Summary: The analysis of the first 20 second cadence light curves obtained by the TESS space telescope during its extended mission showed improved precision compared to 2 minute data for bright stars. This improvement enabled the detection of oscillations in solar analogs and recharacterization of a transiting exoplanet, showing the strong potential of TESS 20 second cadence data for stellar astrophysics and exoplanet science.
ASTRONOMICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
A. Moya, L. M. Sarro, E. Delgado-Mena, W. J. Chaplin, V Adibekyan, S. Blanco-Cuaresma
Summary: Dating stars using chemical abundances is a significant challenge with implications for various astrophysical fields. By employing Bayesian inference techniques and accurate observations, researchers have made progress in estimating the ages of FGK stars. Results show good agreement with other reliable sources and benchmarks, indicating the potential of using chemical abundances for stellar dating.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Hong-peng Lu, Hui Tian, Li-yun Zhang, Christoffer Karoff, He-chao Chen, Jian-rong Shi, Zhen-yong Hou, Ya-jie Chen, Yu Xu, Yu-chuan Wu, Dong-tao Cao, Jiang-tao Wang
Summary: This study successfully detected three stellar CME candidates by analyzing the asymmetries of H alpha line profiles and found that the H alpha lines of these candidates exhibit blue-wing or red-wing enhancements. This indicates the existence of stellar CMEs in main-sequence stars.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Tomomi Otani, Ted von Hippel, Derek Buzasi, T. D. Oswalt, Alexander Stone-Martinez, Patrice Majewski
Summary: Accurate stellar ages are crucial for studying the star formation history and chemical evolution of the Milky Way, as well as constraining models of exoplanet formation. Gyrochronology, which relates stellar rotation to age, is a promising method for determining the age of main-sequence stars within a certain mass range. However, there is a lack of sufficient testing for older and lower mass stars. Binary stars can be used to expand and enhance the empirical testing of gyrochronology models.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Travis S. Metcalfe, Adam J. Finley, Oleg Kochukhov, Victor See, Thomas R. Ayres, Keivan G. Stassun, Jennifer L. van Saders, Catherine A. Clark, Diego Godoy-Rivera, Ilya V. Ilyin, Marc H. Pinsonneault, Klaus G. Strassmeier, Pascal Petit
Summary: The rotation rates of main-sequence stars slow over time due to the loss of angular momentum to magnetized stellar winds. This phenomenon is influenced by various factors such as the strength and morphology of the magnetic field, mass-loss rate, and stellar properties. Observations of different stars reveal a transition in magnetic morphology and a decrease in the rate of angular momentum loss as stars age.
ASTROPHYSICAL JOURNAL LETTERS
(2022)
Article
Astronomy & Astrophysics
Warrick H. Ball, Andrea Miglio, William J. Chaplin, Keivan G. Stassun, Rafael Garcia, Lucia Gonzalez-Cuesta, Savita Mathur, Thierry Appourchaux, Othman Benomar, Derek L. Buzasi, Chen Jiang, Cenk Kayhan, Sibel Ortel, Zeynep Celik Orhan, Mutlu Yildiz, J. M. Joel Ong, Sarbani Basu
Summary: Binary stars can provide important constraints on stellar physics, and the 12 Bootis system is particularly promising. By studying the oscillations and light curves of this system, we have obtained new constraints on its properties.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Emily Hatt, Martin B. Nielsen, William J. Chaplin, Warrick H. Ball, Guy R. Davies, Timothy R. Bedding, Derek L. Buzasi, Ashley Chontos, Daniel Huber, Cenk Kayhan, Yaguang Li, Timothy R. White, Chen Cheng, Travis S. Metcalfe, Dennis Stello
Summary: TESS mission provides photometric light curves for stars across nearly the entire sky, enabling the application of asteroseismology to a pool of potential solar-like oscillators unprecedented in size. The aim of this study is to create a catalogue of solar-like oscillators observed by TESS in the 120-s and 20-s cadence modes, focusing on stars oscillating at frequencies above the TESS 30-min cadence Nyquist frequency. Using a new probabilistic detection algorithm, a catalogue of 4177 solar-like oscillators is produced, reporting the asteroseismic parameters v(max) and Delta v for 98% of the total star count.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Geography, Physical
Sabrina Gjodvad Kaiser Kudsk, Mads Faurschou Knudsen, Christoffer Karoff, Claudia Baittinger, Stergios Misios, Jesper Olsen
Summary: This study investigates solar variability between 650 CE and 1900 based on new and published C-14 records. It identifies a Maunder-type minimum in 656-707 CE and suggests a potential prolongation of the 11-year solar cycle before the onset of major solar minima. The study also reviews the impact of near-Earth supernova events on C-14 production rates.
QUATERNARY SCIENCE REVIEWS
(2022)
Article
Astronomy & Astrophysics
Maria Pia Di Mauro, Raffaele Reda, Savita Mathur, Rafael A. A. Garcia, Derek L. L. Buzasi, Enrico Corsaro, Othman Benomar, Lucia Gonzalez Cuesta, Keivan G. G. Stassun, Serena Benatti, Valentina D'Orazi, Luca Giovannelli, Dino Mesa, Nicolas Nardetto
Summary: In this study, we present the analysis results of the photometric data collected by the Transiting Exoplanet Survey Satellite for GJ 504, a well-studied solar-like star hosting a planet. The fundamental parameters of this star have been debated for the past decade. Our analysis reveals that the high level of magnetic activity in this star suppresses the amplitude of acoustic modes. Measurements of the stellar rotational period and the main magnetic cycle confirm previous findings and indicate that the star is in the early main-sequence phase of its evolution.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
A. R. G. Santos, S. Mathur, R. A. Garcia, A. -m. Broomhall, R. Egeland, A. Jimenez, D. Godoy-Rivera, S. N. Breton, Z. R. Claytor, T. S. Metcalfe, M. S. Cunha, L. Amard
Summary: The photometric time series of solar-like stars are used to study their rotation and magnetic activity. This study investigates the behavior and strength of photometric magnetic activity of Kepler solar-like stars compared to the Sun. The amplitude of the variability of magnetic activity is strongly correlated with its mean value, similar to observations of chromospheric activity emission and magnetic field strength. KIC 8006161 is found to be among the most active stars due to its high metallicity.
ASTRONOMY & ASTROPHYSICS
(2023)
Article
Astronomy & Astrophysics
Chen Jiang, Tao Wu, Adina D. Feinstein, Keivan G. Stassun, Timothy R. Bedding, Dimitri Veras, Enrico Corsaro, Derek L. Buzasi, Dennis Stello, Yaguang Li, Savita Mathur, Rafael A. Garcia, Sylvain N. Breton, Mia S. Lundkvist, Przemyslaw J. Mikolajczyk, Charlotte Gehan, Tiago L. Campante, Diego Bossini, Stephen R. Kane, Jia Mian Joel Ong, Mutlu Yildiz, Cenk Kayhan, Zeynep celik Orhan, Sibel Ortel, Xinyi Zhang, Margarida S. Cunha, Bruno Lustosa de Moura, Jie Yu, Daniel Huber, Jian-wen Ou, Robert A. Wittenmyer, Laurent Gizon, William J. Chaplin
Summary: The Transiting Exoplanet Survey Satellite (TESS) mission has detected solar-like oscillations in the giant star HD 76920, allowing for detailed asteroseismic analysis. By utilizing TESS data, improved measurements of the stellar parameters and updated parameters of the planet have been determined. It is confirmed that the planet will be engulfed by the stellar envelope within about 100 Myr.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Travis S. Metcalfe, Klaus G. Strassmeier, Ilya V. Ilyin, Jennifer L. van Saders, Thomas R. Ayres, Adam J. Finley, Oleg Kochukhov, Pascal Petit, Victor See, Keivan G. Stassun, Sandra V. Jeffers, Stephen C. Marsden, Julien Morin, Aline A. Vidotto
Summary: During the first half of their main-sequence lifetimes, stars lose angular momentum rapidly through magnetic braking. Recent observations show that this process becomes less efficient when stars reach a critical value of the Rossby number. Using new spectropolarimetry measurements and reanalyzing published data, researchers find that the angular momentum loss rate drops significantly between two stars of different ages. The study provides new insights into the nature and timing of weakened magnetic braking.
ASTROPHYSICAL JOURNAL LETTERS
(2023)
Article
Geosciences, Multidisciplinary
Christoffer Karoff, Angel Liduvino Vara-Vela
Summary: Over the past decade, there has been a significant and unexplained increase in methane emissions, which could contribute to accelerated climate change. The primary source of this increase is believed to be agriculture, although oil and gas production as well as wetlands are also potential contributors. To accurately measure methane emissions, space-based remote sensing is the most effective method. Through the analysis of three years of data, it was discovered that methane concentrations are highest over croplands and lowest over shrublands, consistent with expectations. However, it was surprising to find lower than average methane concentrations over wetlands, which are typically considered a major source of methane emissions.
FRONTIERS IN EARTH SCIENCE
(2023)
Article
Astronomy & Astrophysics
Travis S. Metcalfe, Derek Buzasi, Daniel Huber, Marc H. Pinsonneault, Jennifer L. van Saders, Thomas R. Ayres, Sarbani Basu, Jeremy J. Drake, Ricky Egeland, Oleg Kochukhov, Pascal Petit, Steven H. Saar, Victor See, Keivan G. Stassun, Yaguang Li, Timothy R. Bedding, Sylvain N. Breton, Adam J. Finley, Rafael A. Garcia, Hans Kjeldsen, Martin B. Nielsen, J. M. Joel Ong, Jakob L. Rorsted, Amalie Stokholm, Mark L. Winther, Catherine A. Clark, Diego Godoy-Rivera, Ilya V. Ilyin, Klaus G. Strassmeier, Sandra V. Jeffers, Stephen C. Marsden, Aline A. Vidotto, Sallie Baliunas, Willie Soon
Summary: This study characterizes the fundamental properties of the bright star lambda Ser and examines its evolutionary pathway. Solar-like oscillations were detected, and precise asteroseismic properties were derived. The large-scale magnetic field morphology and chromospheric activity were analyzed using spectropolarimetric data and time series measurements. The star's rotational history and wind braking torque were also estimated. However, the interpretation of lambda Ser's properties is limited by the uncertainty in stellar age.
ASTRONOMICAL JOURNAL
(2023)
