Search Publications
On the Use of Field RR Lyrae As Galactic Probes: IV. New Insights Into and Around the Oosterhoff Dichotomy
Salaris, M.; Lemasle, B.; Zoccali, M. +30 more
We discuss the largest and most homogeneous spectroscopic data set of field RR Lyrae variables (RRLs) available to date. We estimated abundances using both high-resolution and low-resolution (ΔS method) spectra for fundamental (RRab) and first overtone (RRc) RRLs. The iron abundances for 7941 RRLs were supplemented with similar estimates that are …
A Study of the Photometric and Spectroscopic Variations of the Prototypical FU Orionis-type Star V1057 Cyg
Cseh, B.; Kriskovics, L.; Pál, A. +19 more
Among the low-mass pre-main sequence stars, a small group called FU Orionis-type objects (FUors) are notable for undergoing powerful accretion outbursts. V1057 Cyg, a classical example of an FUor, went into outburst around 1969-1970, after which it faded rapidly, making it the fastest-fading FUor known. Around 1995, a more rapid increase in fading…
Stellar Superflares Observed Simultaneously with Kepler and XMM-Newton
Kolotkov, Dmitrii Y.; Kuznetsov, Alexey A.
Solar and stellar flares are powerful events that produce intense radiation across the electromagnetic spectrum. Multiwavelength observations are highly important for understanding the nature of flares, because different flare-related processes reveal themselves in different spectral ranges. To study the correlation between thermal and nonthermal …
Visual Explanation of a Deep Learning Solar Flare Forecast Model and Its Relationship to Physical Parameters
Moon, Yong-Jae; Lim, Daye; Lee, Harim +2 more
In this study, we present a visual explanation of a deep learning solar flare forecast model and its relationship to physical parameters of solar active regions (ARs). For this, we use full-disk magnetograms at 00:00 UT from the Solar and Heliospheric Observatory/Michelson Doppler Imager and the Solar Dynamics Observatory/Helioseismic and Magnetic…
Evidence for a Cosmic-Ray Gradient in the IM Lup Protoplanetary Disk
Seifert, Richard A.; Cleeves, L. Ilsedore; Adams, Fred C. +1 more
Protoplanetary disk evolution is strongly impacted by ionization from the central star and local environment, which collectively have been shown to drive chemical complexity and are expected to impact the transport of disk material. Nonetheless, ionization remains a poorly constrained input to many detailed modeling efforts. We use new and archiva…
Dynamical Stellar Masses of Pre-main-sequence Stars in Lupus and Taurus Obtained with ALMA Surveys in Comparison with Stellar Evolutionary Models
Koch, Patrick M.; Yen, Hsi-Wei; Testi, Leonardo +3 more
We analyzed archival molecular line data of pre-main-sequence (PMS) stars in the Lupus and Taurus star-forming regions obtained with ALMA surveys with an integration time of a few minutes per source. We stacked the data of 13CO and C18O (J = 2-1 and 3-2) and CN (N = 3-2, J = 7/2-5/2) lines to enhance the signal-to-noise ratio…
M17 MIR: A Massive Protostar with Multiple Accretion Outbursts
Chen, Zhiwei; Chen, Xuepeng; Haas, Martin +3 more
We report the discovery of a massive protostar M17 MIR embedded in a hot molecular core in M17. The multiwavelength data obtained during 1993-2019 show significant mid-IR (MIR) variations, which can be split into three stages: the decreasing phase during 1993.03-mid-2004, the quiescent phase from mid-2004 to mid-2010, and the rebrightening phase f…
Millimeter-sized Dust Grains Surviving the Water-sublimating Temperature in the Inner 10 au of the FU Ori Disk
Chen, Wen Ping; Liu, Sheng-Yuan; Takami, Michihiro +11 more
Previous observations have shown that the ≲10 au, ≳400 K hot inner disk of the archetypal accretion outburst young stellar object, FU Ori, is dominated by viscous heating. To constrain dust properties in this region, we have performed radio observations toward this disk using the Karl G. Jansky Very Large Array in 2020 June-July, September, and No…
Hinode/EIS Coronal Magnetic Field Measurements at the Onset of a C2 Flare
Landi, E.; Li, W.; Hutton, R. +1 more
We study Hinode/EIS observations of an active region taken before, during, and after a small C2.0 flare in order to monitor the evolution of the magnetic field and its relation to the flare event. We find that while the flare left the active region itself unaltered, the event included a large magnetic field enhancement (MFE), which consisted of a …
Global Distribution of the Solar Wind Speed Reconstructed from Improved Tomographic Analysis of Interplanetary Scintillation Observations between 1985 and 2019
Kojima, Masayoshi; Tokumaru, Munetoshi; Fujiki, Ken'ichi +1 more
Computer-assisted tomography (CAT) for interplanetary scintillation (IPS) observations enables the determination of the global distribution of solar wind speed. We compared solar wind speeds derived from the CAT analysis of IPS observations between 1985 and 2019 with in situ observations conducted by the near-Earth and Ulysses spacecraft. From thi…