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Effects of Coronal Density and Magnetic Field Distributions on a Global Solar EUV Wave
Wang, Rui; Yang, Zhongwei; Liu, Ying D. +4 more
We investigate a global extreme-ultraviolet (EUV) wave associated with a coronal mass ejection (CME)-driven shock on 2017 September 10. The EUV wave is transmitted by north- and south-polar coronal holes (CHs), which is observed by the Solar Dynamics Observatory (SDO) and Solar Terrestrial Relations Observatory A (STEREO-A) from opposite sides of …
Origin of Radio-quiet Coronal Mass Ejections in Flare Stars
Mullan, D. J.; Paudel, R. R.
Type II radio bursts are observed in the Sun in association with many coronal mass ejections (CMEs). In view of this association, there has been an expectation that, by scaling from solar flares to the flares that are observed on M dwarfs, radio emission analogous to solar type II bursts should be detectable in association with M dwarf flares. How…
Discovery of an Intermediate-luminosity Red Transient in M51 and Its Likely Dust-obscured, Infrared-variable Progenitor
Williams, Robert E.; Kulkarni, S. R.; Tinyanont, Samaporn +49 more
We present the discovery of an optical transient (OT) in Messier 51, designated M51 OT2019-1 (also ZTF 19aadyppr, AT 2019abn, ATLAS19bzl), by the Zwicky Transient Facility (ZTF). The OT rose over 15 days to an observed luminosity of M r = -13 (νL ν = 9 × 106 L ⊙), in the luminosity gap between novae …
Metal-poor Stars Observed with the Automated Planet Finder Telescope. II. Chemodynamical Analysis of Six Low-metallicity Stars in the Halo System of the Milky Way
Zhao, Gang; Placco, Vinicius M.; Li, Haining +2 more
In this work, we study the chemical compositions and kinematic properties of six metal-poor stars with [Fe/H] < -2.5 in the Galactic halo. From high-resolution (R ∼ 110,000) spectroscopic observations obtained with the Lick/Automated Planet Finder, we determined individual abundances for up to 23 elements, to quantitatively evaluate our sample.…
Transition from Circular-ribbon to Parallel-ribbon Flares Associated with a Bifurcated Magnetic Flux Rope
Ding, M. D.; Guo, Y.; Zhong, Z. +2 more
Magnetic flux ropes play a key role in triggering solar flares in the solar atmosphere. In this paper, we investigate the evolution of NOAA Active Region 12268 within 36 hr from 2015 January 29 to 30, during which a flux rope was formed and three M-class and three C-class flares were triggered without coronal mass ejections. During the evolution o…
Constraining Compact Object Formation with 2M0521
Breivik, Katelyn; Andrews, Jeff J.; Chatterjee, Sourav
We show that the recently discovered binary 2M05215658+4359220 (2M0521), comprising a giant star (GS) orbiting a suspected black hole (BH) in an ∼80 day orbit, may be instrumental in shedding light on uncertain BH-formation physics and can be a test case for studying wind accretion models. Using binary population synthesis with a realistic prescri…
CG X-1: An Eclipsing Wolf-Rayet ULX in the Circinus Galaxy
Soria, Roberto; Liu, Jifeng; Walton, Dominic J. +7 more
We investigated the time-variability and spectral properties of the eclipsing X-ray source Circinus Galaxy X-1 (GG X-1), using Chandra, XMM-Newton and ROSAT. We phase-connected the light curves observed over 20 yr, and we obtained a best-fitting period P = (25,970.0 ± 0.1) s ≈ 7.2 hr, and a period derivative \dot{P}/P=(10.2+/- 4.6)× {10}-7
Single-spacecraft Identification of Flux Tubes and Current Sheets in the Solar Wind
Servidio, Sergio; Pecora, Francesco; Greco, Antonella +3 more
A novel technique is presented for describing and visualizing the local topology of the magnetic field using single-spacecraft data in the solar wind. The approach merges two established techniques: the Grad-Shafranov (GS) reconstruction method, which provides a plausible regional two-dimensional magnetic field surrounding the spacecraft trajector…
Asteroseismology of Massive Stars with the TESS Mission: The Runaway β Cep Pulsator PHL 346 = HN Aqr
Gazeas, Kosmas; Bowman, Dominic M.; Ricker, George R. +21 more
We report an analysis of the first known β Cep pulsator observed by the Transiting Exoplanet Survey Satellite (TESS) mission, the runaway star PHL 346 = HN Aqr. The star, previously known as a singly periodic pulsator, has at least 34 oscillation modes excited, 12 of those in the g-mode domain and 22 p modes. Analysis of archival data implies that…
Deep ATCA and VLA Radio Observations of Short-GRB Host Galaxies. Constraints on Star Formation Rates, Afterglow Flux, and Kilonova Radio Flares
Palazzi, E.; Greiner, J.; Hunt, L. K. +6 more
We report the results of an extensive radio-continuum observing campaign of host galaxies of short gamma-ray bursts (GRBs). The goal of this survey was to search for optically obscured star formation, possibly indicative of a population of young short-GRB progenitors. Our sample comprises the hosts and host-galaxy candidates of 16 short-GRBs from …