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131 and 304 Å Emission Variability Increases Hours Prior to Solar Flare Onset
Mason, E. I.; Uritsky, Vadim M.; Kniezewski, Kara L. +1 more
Thermal changes in coronal loops are well studied, both in quiescent active regions and in flaring scenarios. However, relatively little attention has been paid to loop emission in the hours before the onset of a solar flare; here, we present the findings of a study of over 50 off-limb flares of Geostationary Operational Environmental Satellite cl…
The counter-rotating stellar core of NGC 4494
Morelli, L.; Corsini, E. M.; Pizzella, A. +2 more
Context. Kinematically decoupled cores (KDCs) are often found in the centers of early-type galaxies. Aims. We aim to investigate the kinematics, structure, and stellar populations of the KDC residing in the early-type galaxy NGC 4494 to understand its formation. Methods. We used long-slit spectroscopic data obtained with the FORS2 instrument on th…
Inferring the dust emission at submillimeter and millimeter wavelengths using neural networks
Ristorcelli, I.; Ysard, N.; Noriega-Crespo, A. +3 more
Context. The Planck mission provided all-sky dust emission maps in the submillimeter (submm) to millimeter (mm) range at an angular resolution of 5'. In addition, some specific sources can be observed at long wavelengths and higher resolution using ground-based telescopes. These observations are limited to small scales and are sometimes not delive…
Online Catalog of Activity Events of Solar Cycle 24 Related to Active Regions
Tsvetkov, Tsvetan; Petrov, Nikola; Nakeva, Yoana
We present a statistical study on the relationship of solar dynamic events (solar flares and coronal mass ejections) with active regions during Solar Cycle 24 (December 2008–December 2019). Combining data from NOAA Space Weather Prediction Center and observations of Large Angle and Spectrometric Coronagraph (LASCO) onboard the Solar and Heliospher…
Deriving physical parameters of unresolved star clusters. VIII. Limits of aperture photometry for star cluster studies
Stonkutė, Rima; Vansevičius, Vladas; Kriščiūnas, Eimantas +2 more
Context. Recently, it has been noticed that the discrepancies in the integrated colour indices (CIs) between star clusters and models are mostly due to the projection of bright stars in the apertures. In order to reduce this problem, the method of adaptive aperture photometry has been proposed. This method has been applied to star clusters from th…
X-ray plasma flow and turbulence in the colliding winds of WR140
Hamaguchi, Kenji; Miyamoto, Asca; Sugawara, Yasuharu +5 more
We analyse the XMM-Newton RGS spectra of Wolf-Rayet (WR) 140, an archetype long-period eccentric WR+O colliding wind binary. We evaluate the spectra of O and Fe emission lines and find that the plasmas emitting these lines have the largest approaching velocities with the largest velocity dispersions between phases 0.935 and 0.968 where the inferio…
SOFIA/upGREAT far-infrared spectroscopy of bright rimmed pillars in IC 1848
Wiesemeyer, Helmut; Güsten, Rolf; Seo, Youngmin +4 more
Using the upGREAT instrument on SOFIA, we imaged the [C II] 158 µm fine structure line emission in bright-rimmed pillars located at the southern edge of the IC 1848 H II region, and carried out pointed observations of the [O I] 63 and 145 µm fine structure lines toward selected positions. The observations are used to characterize the morphology, v…
Time Variation of the Solar Tachocline
Basu, Sarbani; Korzennik, Sylvain G.; Andrade de Aguiar, Wesley Antônio Machado
We have used solar oscillation frequencies and frequency splittings obtained over solar cycles 23 and 24 and the rising phase of solar cycle 25 to investigate whether the tachocline properties (the change in the rotation rate across the tachocline. i.e., the jump, the width, and the position) show any time variation. We confirm that the change in …
MK-like spectral classification for hot subdwarf stars with LAMOST spectra
Lei, Zhenxin; Zou, Xuan
An MK-like spectral classification has been conducted for 1224 hot subdwarf stars with LAMOST DR9 low-resolution spectra. The whole sample was divided into four categories according to the spectral line characteristics: He-normal, He-weak, He-strong C, and He-strong. Each selected spectrum was assigned a spectral class, a luminosity class, and a h…
A Special Kind of Interplanetary Coronal Mass Ejection
Zhao, G. Q.; Zhao, Y.; Li, H. B. +3 more
It is generally believed that coronal mass ejections (CMEs) have magnetic flux rope structures because of their helical shapes. However, only about 30%–40% of interplanetary CMEs (ICMEs) have a local magnetic flux rope structure. The usual explanations are that the spacecraft only crossed the flank of the ropes and failed to detect the complete ma…