Search Publications
The Magnetic Environment of a Stealth Coronal Mass Ejection
Long, David M.; Démoulin, Pascal; Green, Lucie M. +4 more
Interest in stealth coronal mass ejections (CMEs) is increasing due to their relatively high occurrence rate and space weather impact. However, typical CME signatures such as extreme-ultraviolet dimmings and post-eruptive arcades are hard to identify and require extensive image processing techniques. These weak observational signatures mean that l…
Simultaneous ALMA-Hinode-IRIS Observations on Footpoint Signatures of a Soft X-Ray Loop-like Microflare
Shimojo, Masumi; Shimizu, Toshifumi; Abe, Masashi
Microflares have been considered to be among the major energy input sources to form active solar corona. To investigate the response of the low atmosphere to events, we conducted an Atacama Large Millimeter/submillimeter Array (ALMA) observation at 3 mm, coordinated with Interface Region Imaging Spectrograph (IRIS) and Hinode observations, on 2017…
Sagittarius B1: A Patchwork of H II Regions and Photodissociation Regions
Kaufman, Michael J.; Colgan, Sean W. J.; Simpson, Janet P. +2 more
Sgr B1 is a luminous H II region in the Galactic center immediately next to the massive star-forming giant molecular cloud Sgr B2 and apparently connected to it from their similar radial velocities. In 2018 we showed from SOFIA FIFI-LS observations of the [O III] 52 and 88 µm lines that there is no central exciting star cluster and that the …
Numerical MHD Simulations of the 3D Morphology and Kinematics of the 2017 September 10 CME-driven Shock from the Sun to Earth
Shen, Fang; Feng, Xueshang; Zhang, Man +8 more
A global, three-dimensional (3D) numerical simulation model has been employed to study the 3D morphology and kinematics of the large shock driven by the 2017 September 10 coronal mass ejection (CME). Based on actual solar observations, which include the photospheric magnetic field and the CME's speed and source location, the simulation result is d…
X-Ray AGB Stars in the 4XMM-DR9 Catalog: Further Evidence for Companions
Guerrero, M. A.; Ortiz, R.
Single AGB stars are not normally expected to be X-ray emitters due to the lack of a corona capable of powering a hot plasma. Therefore, the detection of X-ray emission in AGB stars by the ROSAT, Chandra, and XMM-Newton observatories has been interpreted as evidence for binarity. The number of X-ray-emitting AGB stars is, however, very small, and …
Deciphering the Deep Origin of Active Regions via Analysis of Magnetograms
McIntosh, Scott W.; Chatterjee, Subhamoy; Dikpati, Mausumi +5 more
In this work, we derive magnetic toroids from surface magnetograms by employing a novel optimization method, based on the trust region reflective algorithm. The toroids obtained in this way are combinations of Fourier modes (amplitudes and phases) with low longitudinal wavenumbers. The optimization also estimates the latitudinal width of the toroi…
GECKO Optical Follow-up Observation of Three Binary Black Hole Merger Events: GW190408_181802, GW190412, and GW190503_185404
Lee, Chung-Uk; Kim, Seung-Lee; Im, Myungshin +12 more
We present optical follow-up observation results of three binary black hole merger (BBH) events, GW190408_181802, GW190412, and GW190503_185404, which were detected by the Advanced LIGO and Virgo gravitational wave (GW) detectors. Electromagnetic (EM) counterparts are generally not expected for BBH merger events. However, some theoretical models s…
From Formation to Disruption: Observing the Multiphase Evolution of a Solar Flare Current Sheet
Chitta, L. P.; Cheng, X.; Priest, E. R.
A current sheet, where magnetic energy is liberated through reconnection and converted to other forms, is thought to play the central role in solar flares, the most intense explosions in the heliosphere. However, the evolution of a current sheet and its subsequent role in flare-related phenomena such as particle acceleration is poorly understood. …
Extreme Variability of the V488 Persei Debris Disk
Rieke, G. H.; Gáspár, András; Melis, Carl +1 more
V488 Persei is the most extreme debris disk known in terms of the fraction of the stellar luminosity it intercepts and reradiates. The infrared output of its disk is extremely variable, similar in this respect to the most variable disk known previously, that around ID8 in NGC 2547. We show that the variations are likely to be due to collisions of …
Lower-luminosity Obscured AGN Host Galaxies Are Not Predominantly in Major-merging Systems at Cosmic Noon
Kirkpatrick, Allison; Kocevski, Dale D.; Heckman, Timothy +15 more
For over 60 yr, the scientific community has studied actively growing central supermassive black holes (active galactic nuclei, AGNs), but fundamental questions on their genesis remain unanswered. Numerical simulations and theoretical arguments show that black hole growth occurs during short-lived periods (~107-108 yr) of pow…