Search Publications
Investigating the Origins of Two Extreme Solar Particle Events: Proton Source Profile and Associated Electromagnetic Emissions
Vainio, Rami; Valtonen, Eino; Pohjolainen, Silja +13 more
We analyze the high-energy particle emission from the Sun in two extreme solar particle events in which protons are accelerated to relativistic energies and can cause a significant signal even in the ground-based particle detectors. Analysis of a relativistic proton event is based on modeling of the particle transport and interaction, from a near-…
Cassini microwave observations provide clues to the origin of Saturn's C ring
Nicholson, P. D.; Hedman, M. M.; Janssen, M. A. +6 more
Despite considerable study, Saturn's rings continue to challenge current theories for their provenance. Water ice comprises the bulk of Saturn's rings, yet it is the small fraction of non-icy material that is arguably more valuable in revealing clues about the system's origin and age. Herein, we present new measurements of the non-icy material fra…
Global ULF waves generated by a hot flow anomaly
Zhao, L. L.; Zhang, H.; Zong, Q. G.
Hot flow anomalies (HFAs), which are frequently observed near Earth's bow shock, are phenomena resulting from the interaction between interplanetary discontinuities and Earth's bow shock. Such transient phenomena upstream the bow shock can cause significant deformation of the bow shock and the magnetosphere, generating traveling convection vortice…
The Evolution and Physical Parameters of WN3/O3s: A New Type of Wolf-Rayet Star
Massey, Philip; Hillier, D. John; Morrell, Nidia +1 more
As part of a search for Wolf-Rayet (WR) stars in the Magellanic Clouds, we have discovered a new type of WR star in the Large Magellanic Cloud (LMC). These stars have both strong emission lines, as well as He II and Balmer absorption lines and spectroscopically resemble a WN3 and O3V binary pair. However, they are visually too faint to be WN3+O3V …
The β Pictoris association low-mass members: Membership assessment, rotation period distribution, and dependence on multiplicity
Lanzafame, A. C.; Messina, S.; Zhang, L. +6 more
Context. Low-mass members of young loose stellar associations and open clusters exhibit a wide spread of rotation periods. Such a spread originates from the distributions of masses and initial rotation periods. However, multiplicity can also play a significant role.
Aims: We aim to investigate the role played by physical companions in multipl…
Mpc-scale diffuse radio emission in two massive cool-core clusters of galaxies
Babul, Arif; Bertoldi, Frank; Bonafede, Annalisa +4 more
Radio haloes are diffuse synchrotron sources on scales of ∼1 Mpc that are found in merging clusters of galaxies, and are believed to be powered by electrons re-accelerated by merger-driven turbulence. We present measurements of extended radio emission on similarly large scales in two clusters of galaxies hosting cool cores: Abell 2390 and Abell 22…
The 2014 X-Ray Minimum of η Carinae as Seen by Swift
Gull, T. R.; Corcoran, M. F.; Madura, T. I. +10 more
We report on Swift X-ray Telescope observations of Eta Carinae (η Car), an extremely massive, long-period, highly eccentric binary obtained during the 2014.6 X-ray minimum/periastron passage. These observations show that η Car may have been particularly bright in X-rays going into the X-ray minimum state, while the duration of the 2014 X-ray minim…
Observations of Ellerman bomb emission features in He I D3 and He I 10 830 Å
Joshi, Jayant; Leenaarts, Jorrit; Libbrecht, Tine +2 more
Context. Ellerman bombs (EBs) are short-lived emission features, characterised by extended wing emission in hydrogen Balmer lines. Until now, no distinct signature of EBs has been found in the He I 10 830 Å line, and conclusive observations of EBs in He I D3 have never been reported.
Aims: We aim to study the signature of EBs in ne…
Star formation towards the Galactic H II region RCW 120. Herschel observations of compact sources
Abergel, A.; Bernard, J. -P.; Hill, T. +16 more
Context. The expansion of H II regions can trigger the formation of stars. An overdensity of young stellar objects is observed at the edges of H II regions but the mechanisms that give rise to this phenomenon are not clearly identified. Moreover, it is difficult to establish a causal link between H II -region expansion and the star formation obser…
Stationary waves and slowly moving features in the night upper clouds of Venus
Hueso, R.; Sánchez-Lavega, A.; Kouyama, T. +9 more
At the cloud top level of Venus (65-70 km altitude) the atmosphere rotates 60 times faster than the underlying surface—a phenomenon known as superrotation1,2. Whereas on Venus's dayside the cloud top motions are well determined3,4,5,6 and Venus general circulation models predict the mean zonal flow at the upper clouds to be s…