Results 61 to 70 of about 173,010 (211)

Magnetic Activity in M-type Stars Based on LAMOST DR11 and TESS Observations

The Astrophysical Journal Supplement Series
We have used 898,351 M-type stellar spectra released by Large Sky Area Multi-Object Fiber Spectroscopic Telescope DR11 to calculate the equivalent width of the Ca II infrared triplet (IRT) lines, the residual chromospheric emission, and the parameter ${R}
Linfeng Ren, Li-yun Zhang, Xianming L. Han, Tianhao Su, Wenjie Li, Yinpeng Wang, Prabhakar Misra   +6 more
doaj   +1 more source

Three-dimensional hydrodynamical CO5BOLD model atmospheres of red giant stars VI. First chromosphere model of a late-type giant

, 2017
Although observational data unequivocally point out to the presence of chromospheres in red giant stars, no attempts have been made so far to model them using 3D hydrodynamical model atmospheres.
Klevas, Jonas, Kucinskas, Arunas, Ludwig, Hans-Gunter, Wedemeyer, Sven   +3 more
core   +1 more source

Stellar activity with LAMOST – II. Chromospheric activity in open clusters [PDF]

Monthly Notices of the Royal Astronomical Society, 2018
We use the LAMOST spectra of member stars in Pleiades, M34, Praesepe, and Hyades to study how chromospheric activity vary as a function of mass and rotation at different age. We measured excess equivalent widths of H$ $, H$ $, and Ca~{\sc ii} K based on estimated chromospheric contributions from old and inactive field dwarfs, and excess luminosities ...
Fang, Xiang-Song, Zhao, Gang, Zhao, Jing-Kun, Kumar, Yerra Bharat   +3 more
openaire   +2 more sources

First Observations of a Geomagnetic Superstorm With a Sub‐L1 Monitor

Space Weather, Volume 23, Issue 3, March 2025.
Abstract Forecasting the geomagnetic effects of solar coronal mass ejections (CMEs) is currently an unsolved problem. CMEs, responsible for the largest values of the north‐south component of the interplanetary magnetic field, are the key driver of intense and extreme geomagnetic activity.
E. Weiler, C. Möstl, E. E. Davies, A. M. Veronig, U. V. Amerstorfer, T. Amerstorfer, J. Le Louëdec, M. Bauer, N. Lugaz, V. Haberle, H. T. Rüdisser, S. Majumdar, M. Reiss   +12 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

Wavelet Analysis of Stellar Chromospheric Activity Variations

The Astrophysical Journal, 1997
Observations of chromospheric activity variations for some lower main-sequence stars from the Mount Wilson Observatory's HK project reveal a cyclic behavior comparable to the sunspot cycle. Even in the relatively short interval that they have been observed, those stars show stellar cycles and other features, like grand minima. The quasi-periodic nature
P. Frick, S. L. Baliunas, D. Galyagin, D. Sokoloff, W. Soon   +4 more
openaire   +1 more source

Decent Estimate of CME Arrival Time From a Data‐Assimilated Ensemble in the Alfvén Wave Solar Atmosphere Model (DECADE‐AWSoM)

Space Weather, Volume 23, Issue 1, January 2025.
Abstract Forecasting the arrival time of Earth‐directed coronal mass ejections (CMEs) via physics‐based simulations is an essential but challenging task in space weather research due to the complexity of the underlying physics and limited remote and in situ observations of these events. Data assimilation techniques can assist in constraining free model
Hongfan Chen, Nishtha Sachdeva, Zhenguang Huang, Bart van der Holst, Ward Manchester IV, Aniket Jivani, Shasha Zou, Yang Chen, Xun Huan, Gabor Toth   +9 more
wiley   +1 more source

Far-ultraviolet Emission Line Investigation of Flares on AU Mic

The Astrophysical Journal
The role of nonthermal proton energy transportation during solar and stellar flares is largely unknown; a better understanding of this physical process will allow us to rectify longstanding deficiencies in flare models.
Adalyn Gibson, Adam F. Kowalski, Adina D. Feinstein   +2 more
doaj   +1 more source

Hubble Space Telescope Constraints on the Winds and Astrospheres of Red Giant Stars [PDF]

, 2016
We report on an ultraviolet spectroscopic survey of red giants observed by the Hubble Space Telescope, focusing on spectra of the Mg II h & k lines near 2800 A in order to study stellar chromospheric emission, winds, and astrospheric absorption. We focus
Harper, Graham M., Müller, Hans-Reinhard, Wood, Brian E.   +2 more
core   +3 more sources

Plant‐Based Biosynthesis of Metal and Metal Oxide Nanoparticles: An Update on Antimicrobial and Anticancer Activity

ChemBioEng Reviews, Volume 11, Issue 6, December 2024.
When it comes to finding novel ways to battle newly developing pathogenic strains and illnesses, nanoparticles are the first line of defense. Plant‐based nanoparticles are showing more significance over chemically or physically synthesized nanoparticles. Several plant species and their constituent parts have found several applications in medicine. They
Shruti Nandkishor Tanwar, Yatish R. Parauha, Yogesh There, Hendrik C. Swart, Sanjay J. Dhoble   +4 more
wiley   +1 more source