Results 41 to 50 of about 1,834 (171)

The California-Kepler Survey. XI. A Survey of Chromospheric Activity through the Lens of Precise Stellar Properties

The Astrophysical Journal
Surveys of exoplanet host stars are valuable tools for assessing population level trends in exoplanets, and their outputs can include stellar ages, activity, and rotation periods.
Howard Isaacson, Stephen R. Kane, Brad Carter, Andrew W. Howard, Lauren Weiss, Erik A. Petigura, Benjamin Fulton   +6 more
doaj   +1 more source

Space Weather Impact of Three Solar Flares Observed by the POEMAS Telescope at 45 and 90 GHz

Journal of Geophysical Research: Space Physics, Volume 130, Issue 11, November 2025.
Abstract Solar flares are often associated with coronal mass ejections (CMEs) that, when directed toward Earth, can disrupt the magnetosphere and impact space weather. In this study, we investigate three long‐duration solar flares observed in 2012 by the POlarization Emission of Millimeter Activity at the Sun (POEMAS) telescopes at 45 and 90 GHz.
Adriana Valio, Karla F. Lopez, José Luis Gamonal Valenzuela, Ruben M. Romero Ramírez, Dougas F. da Silva   +4 more
wiley   +1 more source

Extrasolar planets, stellar winds and chromospheric hotspots [PDF]

Monthly Notices of the Royal Astronomical Society: Letters, 2006
Abstract Recent observations have shown what is believed to be planet-induced chromospheric activity on stars with hot Jupiters. We present a model of the magnetic interaction between a planet and a star with a dipolar magnetic field. Reconnection between the fields of the star and planet accelerates electrons along the field lines that ...
T. McIvor, M. Jardine, V. Holzwarth
openaire   +1 more source

The Near-infrared Ca ii Triplet as a Stellar Activity Indicator: A Library and Comparative Study

The Astrophysical Journal Supplement Series
We have established and released a new stellar index library of the Ca ii triplet, which serves as an indicator for characterizing the chromospheric activity of stars.
Xin Huang, Yuji He, Zhongrui Bai, Hailong Yuan, Mingkuan Yang, Ming Zhou, Yiqiao Dong, Mengxin Wang, Han He, Jinghua Zhang, Yaoquan Chu, Yongheng Zhao, Yong Zhang, Haotong Zhang   +13 more
doaj   +1 more source

The High-energy Spectrum of the Young Planet Host V1298 Tau

The Astronomical Journal, 2023
V1298 Tau is a young pre-main-sequence star hosting four known exoplanets that are prime targets for transmission spectroscopy with current-generation instruments. This work pieces together observations from the NICER X-ray telescope, the Space Telescope
Girish M. Duvvuri, P. Wilson Cauley, Fernando Cruz Aguirre, Roy Kilgard, Kevin France, Zachory K. Berta-Thompson, J. Sebastian Pineda   +6 more
doaj   +1 more source

Solar Flare Activity, 1937–2024: Introducing the New Hemispheric Solar Flare Index (hSFI) in the Context of 2024's Major Solar Storm Events

Space Weather, Volume 23, Issue 11, November 2025.
Abstract A new daily composite of the solar flare index (SFI) and the hemispherically‐resolved versions (hSFI) are presented for 1937 to 2024. The data set confirms that the northern hemisphere (NH) dominated solar flare activity during Solar Cycles 17 to 21, but that the southern hemisphere has dominated from Solar Cycle 22 to present.
V. M. Velasco Herrera, W. Soon, S. Knoška, A. Özgüç, G. Velasco Herrera, H. Yeşilyaprak, N. Babynets, M. Švanda, J. Muraközy, S. Qiu, D. Riveros‐Rosas, R. Connolly, M. Connolly, A. Tlatov, L. Cappellotto   +14 more
wiley   +1 more source

Physical Parameters and Activity Properties of K-type Stars Based on the LAMOST Spectral Survey

The Astrophysical Journal Supplement Series
K-type stars are important objects of our Galaxy. It is interesting to determine the stellar physical parameters and magnetic activity properties of K-type stars.
Zhiruo Zhang, Li-yun Zhang, Tianhao Su, Xianming L. Han, Prabhakar Misra, Qingfeng Pi, Hongpeng Lu   +6 more
doaj   +1 more source

Comparison of Solar Imaging Feature Extraction Methods in the Context of Space Weather Prediction With Deep Learning‐Based Models

Journal of Geophysical Research: Machine Learning and Computation, Volume 2, Issue 3, September 2025.
Abstract Recently, many machine learning‐based models have been developed to predict geomagnetic activity several days in advance directly from space‐borne solar imaging. To better understand and improve these models, we compare dimensionality reduction techniques to extract abstract features from solar images for space weather‐related downstream tasks.
Maria Tahtouh, Guillerme Bernoux, Antoine Brunet, Denis Standarovski, Gautier Nguyen, Angélica Sicard   +5 more
wiley   +1 more source

Predicting Photospheric Ultraviolet Emission from Stellar Evolutionary Models

The Astrophysical Journal
Stellar ultraviolet (UV) emission serves as a crucial indicator for estimating magnetic activity and evaluating the habitability of exoplanets orbiting stars.
Song Wang, Xue Li, Henggeng Han, Jifeng Liu   +3 more
doaj   +1 more source

Deriving the Coronal Separatrix‐Web With the WSA Model

Journal of Geophysical Research: Space Physics, Volume 130, Issue 8, August 2025.
Abstract We demonstrate a new capability of the Wang‐Sheeley‐Arge (WSA) model to routinely derive the coronal separatrix web (S‐web) as a standard data product. We describe our methodology for deriving the squashing factor (Q $Q$) and we use Carrington rotation (CR) 2109 to illustrate the validation of our output with that derived from the POT3D model.
Samantha Wallace, Aleida K. Higginson, David G. Simpson, Nicholeen M. Viall, Peter Wyper, C. Nick Arge   +5 more
wiley   +1 more source