Results 51 to 60 of about 173,010 (211)

The California Legacy Survey. VI. The Fate of Activity Cycles in Sun-like Stars

The Astronomical Journal
We analyze the spectra of 91 solar-type G- and K-type main-sequence dwarfs in the solar neighborhood to assess activity trends with stellar properties.
Howard Isaacson, Stephen R. Kane, Brad Carter, Andrew W. Howard   +3 more
doaj   +1 more source

Basal Chromospheric Flux and Maunder Minimum-type Stars: The quiet-Sun Chromosphere as a Universal Phenomenon

, 2012
Aims: We demonstrate the universal character of the quiet-Sun chromosphere among inactive stars (solar-type and giants). By assessing the main physical processes, we shed new light on some common observational phenomena.
Baliunas, Brandenburg, Buchholz, Cuntz, Cuntz, Duncan, Hall, Hauschildt, J. H. M. M. Schmitt, Judge, Judge, Judge, Judge, K.-P. Schröder, Keppens, Konstantinova-Antova, M. Cuntz, M. I. Pérez Martínez, M. Mittag, Mittag, Pasquini, Pevtsov, Pérez Martínez, Rammacher, Riethmüller, Schmitt, Schrijver, Schrijver, Schrijver, Schrijver, Schröder, Schröder, Schröder, Schwarzschild, Strassmeier, Stȩpień, Suzuki, Vögler, White, Wöger   +39 more
core   +1 more source

Quasi‐Periodic Pulsations in Ionospheric TEC Synchronized With Solar Flare EUV Emission

Journal of Geophysical Research: Space Physics, Volume 130, Issue 4, April 2025.
Abstract The extreme ultraviolet (EUV) and X‐ray radiation emitted during solar flares has been shown to significantly increase the electron density of the Earth's ionosphere. During flares, quasi‐periodic pulsations in X‐ray flux originating in the corona have previously been linked to subsequent pulsations in the Earth's ionospheric D‐region. Similar
Aisling N. O’Hare, Susanna Bekker, Laura A. Hayes, Ryan O. Milligan   +3 more
wiley   +1 more source

Relations of Rotation and Chromospheric Activity to Stellar Age for FGK Dwarfs from Kepler and LAMOST

The Astrophysical Journal Supplement Series
The empirical relations between rotation period, chromospheric activity, and age can be used to estimate stellar age. To calibrate these relations, we present a catalog, including the masses and ages of 52,321 FGK dwarfs, 47,489 chromospheric activity ...
Lifei Ye, Shaolan Bi, Jinghua Zhang, Tiancheng Sun, Liu Long, Zhishuai Ge, Tanda Li, Xianfei Zhang, Xunzhou Chen, Yaguang Li, Jianzhao Zhou, Maosheng Xiang   +11 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

Multi‐Source Forecast of Solar Cycle Flare Activity Using the Novel Informer‐Based Models

Space Weather, Volume 23, Issue 4, April 2025.
Abstract Solar flares, the significant indicators of solar activity, have an impact on Earth's satellites and communication systems. Accurate prediction of solar flare events is crucial for mitigating these effects. In this work, we use multiple data sources, including Geostationary Operational Environmental Satellites soft X‐ray flare flux and the ...
Jie Cao, Tingting Xu, Linhua Deng, Miao Wan, Xinhua Zhao, Yang Peng, Xueliang Zhou, Wenhua Wang, Lidong Huang, Wencheng Wang, Lei Yang, Weihong Zhou   +11 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

Cepheid limb darkening, angular diameter corrections, and projection factor from static spherical model stellar atmospheres

, 2012
Context. One challenge for measuring the Hubble constant using Classical Cepheids is the calibration of the Leavitt Law or period-luminosity relationship.
Baade, Barmby, Barnes, Benedict, Bonanos, Burki, C.-C. Ngeow, Claret, Claret, Claret, Clement, Davis, Fouqué, Freedman, Getting, Gieren, Gieren, Gieren, Gray, Groenewegen, H. R. Neilson, Hindsley, J. Storm, Kanbur, Keller, Kervella, Kervella, Kovács, Kurucz, Leavitt, Lester, Marengo, Marengo, Marengo, Marengo, Mourard, Mérand, Mérand, Mérand, N. Nardetto, Nardetto, Nardetto, Nardetto, Nardetto, Neilson, Neilson, Neilson, Neilson, Neilson, Neilson, Ngeow, Ngeow, P. Fouqué, Parsons, Pietrzyński, Riess, Riess, Sabbey, Sasselov, Sasselov, Sasselov, Storm, Storm, Turner, van Leeuwen, Wesselink, Windmark   +66 more
core   +3 more sources

Building Reliable Models of M Dwarf Chromospheres: The Spectral Diagnostics [PDF]

, 2000
As part of an ongoing project to study how reliable are the chromospheric models constructed semiempirically to fit the chromospheric spectrum of cold stars, in this paper we study how changes in the assumed chromospheric structure of dM and dMe stars ...
Mauas, Pablo Jacobo David
core   +1 more source

First Global Machine Learning Model to Predict the Rate of TEC Index (ROTI) Response to X‐Class Solar Flares

Space Weather, Volume 23, Issue 3, March 2025.
Abstract Solar flares are bursts of electromagnetic radiation originating in the Sun's atmosphere. Solar flares cause a rapid increase in ionization in the ionosphere, resulting in radio signal interference. This paper aims to predict the ionospheric response to the solar flare of various characteristics in all latitudes around the dayside ionosphere ...
A. Mahmoudian, F. Ghorbali, M. Vazifehkhah Hafteh   +2 more
wiley   +1 more source