Search Publications
Evidence for the First Extragalactic Hydrogen Recombination Line Maser in NGC 253
Jiménez-Serra, Izaskun; Martín-Pintado, Jesús; Rico-Villas, Fernando +1 more
We present the first evidence for extragalactic hydrogen recombination line maser emission in the H26α transition toward the inner 13.5 pc nuclear region of the starburst galaxy NGC 253 using the Atacama Large Millimeter/submillimeter Array data. In regions with complex continuum emission (dust, free-free, and synchrotron) we propose to use the re…
Flare Energy Release at the Magnetic Field Polarity Inversion Line during the M1.2 Solar Flare of 2015 March 15. I. Onset of Plasma Heating and Electron Acceleration
Zimovets, I. V.; Meshalkina, N. S.; Sharykin, I. N. +1 more
We present the study of the SOL2015-03-15 M1.2 flare, revealing acceleration of electrons and plasma heating in the sheared twisted magnetic structure at the polarity inversion line (PIL). The purpose is to make an analysis of nonthermal electron dynamics and plasma heating in the highly stressed magnetic loops interacting at the PIL by using X-ra…
Influence of Earth-directed Coronal Mass Ejections on the Sun’s Shadow Observed by the Tibet-III Air Shower Array
Zhang, Yi; Yang, Z.; Liu, C. +79 more
We examine the possible influence of Earth-directed coronal mass ejections (ECMEs) on the Sun’s shadow in the 3 TeV cosmic-ray intensity observed by the Tibet-III air shower (AS) array. We confirm a clear solar-cycle variation of the intensity deficit in the Sun’s shadow during ten years between 2000 and 2009. This solar-cycle variation is overall…
Tackling the Saturation of Oxygen: The Use of Phosphorus and Sulfur as Proxies within the Neutral Interstellar Medium of Star-forming Galaxies
Aloisi, A.; James, B.
The abundance of oxygen in galaxies is widely used in furthering our understanding of galaxy formation and evolution. Unfortunately, direct measurements of O/H in the neutral gas are extremely difficult to obtain, as the only O I line available within the Hubble Space Telescope (HST) UV wavelength range (1150-3200 Å) is often saturated. As such, p…
NGC 7793 P9: An Ultraluminous X-Ray Source Evolved from a Canonical Black Hole X-Ray Binary
Kong, Albert K. H.; Hu, Chin-Ping; Ng, C. -Y. +1 more
Transient ultraluminous X-ray sources (ULXs) provide an important link bridging transient low-mass X-ray binaries and ULXs. Here we report the first discovery of both a canonical sub-Eddington outburst and an ultraluminous super-Eddington outburst from an unusual transient ULX, NGC 7793 P9, with a variability factor higher than 103. Its…
Brightening and Darkening of the Extended Solar Corona during the Superflares of September 2017
West, Matthew J.; Podladchikova, O.; D'Huys, Elke +3 more
On 2017 September 6 and 10, the strongest X9.3 and X8.2 flares of the decade occurred in the active region NOAA Active Region 12673. During these flares, the Sun Watcher with Active Pixels and Image Processing (SWAP) telescope on board the Project for Onboard Autonomy 2 (PROBA2) satellite registered the unusual alternate brightening and darkening …
Extraplanar H II Regions in Spiral Galaxies. II. In Situ Star Formation in the Interstellar Thick Disk of NGC 4013
Savage, Blair D.; Lehner, Nicolas; Howk, J. Christopher +3 more
We present observations of an Hα-emitting knot in the thick disk of NGC 4013, demonstrating it is an H II region surrounding a cluster of young hot stars z = 860 pc above the plane of this edge-on spiral galaxy. With LBT/MODS spectroscopy we show that this H II region has an Hα luminosity ∼4-7 times that of the Orion nebula, with an implied ionizi…
Resonant Scattering Effect on the Soft X-Ray Line Emission from the Hot Interstellar Medium. I. Galactic Bulges
Wang, Q. Daniel; Chen, Yang; Zhang, Shuinai +2 more
Diffuse soft X-ray line emission is commonly used to trace the thermal and chemical properties of the hot interstellar medium, as well as its content, in nearby galaxies. Although resonant-line scattering complicates the interpretation of the emission, it also offers an opportunity to measure the kinematics of the medium. We have implemented a dir…
The Influence of Stellar Spin on Ignition of Thermonuclear Runaways
Galloway, Duncan K.; Kuulkers, Erik; Chenevez, Jérôme +8 more
Runaway thermonuclear burning of a layer of accumulated fuel on the surface of a compact star provides a brief but intense display of stellar nuclear processes. For neutron stars accreting from a binary companion, these events manifest as thermonuclear (type-I) X-ray bursts, and recur on typical timescales of hours to days. We measured the burst r…
Transport of Internetwork Magnetic Flux Elements in the Solar Photosphere
Rempel, Matthias; Bellot Rubio, Luis R.; Gošić, Milan +2 more
The motions of small-scale magnetic flux elements in the solar photosphere can provide some measure of the Lagrangian properties of the convective flow. Measurements of these motions have been critical in estimating the turbulent diffusion coefficient in flux-transport dynamo models and in determining the Alfvén wave excitation spectrum for corona…