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On the linear theory of oblique magnetospheric chorus excitation
Bespalov, P. A.; Savina, O. N.
Some aspects of the theory of generation of magnetospheric chorus are discussed. An original approach to solving the problem of oblique chorus generation near the Gendrin angle is outlined and partially realized within the framework of a beam pulsed amplifier mechanism. Parameters of the resonance electron beam in the chorus excitation region are …
Analysis of the disc components of our galaxy via kinematic and spectroscopic procedures
Bilir, S.; Karaali, S.; Plevne, O. +1 more
We used the spectroscopic and astrometric data provided from the GALactic Archaeology with HERMES (GALAH) Data Release (DR2) and Gaia DR2, respectively, for a large sample of stars to investigate the behaviour of the [α/Fe] abundances via two procedures, that is, kinematically and spectroscopically. With the kinematical procedure, we investigated …
Tomography of the Solar Corona with the Wide-Field Imager for the Parker Solar Probe
Vourlidas, Angelos; Howard, Russell A.; van der Holst, Bart +4 more
The Wide-field Imager for the Parker Solar Probe (PSP/WISPR) comprises two telescopes that record white-light total brightness [B ] images of the solar corona. Their fields of view cover a widely changing range of heliocentric heights over the 24 highly eccentric orbits planned for the mission. In this work, the capability of PSP/WISPR data to car…
He II Emission from Wolf-Rayet Stars as a Tool for Measuring Dust Reddening
Leitherer, Claus; Faisst, Andreas; Lee, Janice C.
We calibrated a technique to measure dust attenuation in star-forming galaxies. The technique utilizes the stellar-wind lines in Wolf-Rayet stars, which are widely observed in galaxy spectra. The He II 1640 and 4686 features are recombination lines whose ratio is largely determined by atomic physics. Therefore they can serve as a stellar dust prob…
Primeval very low-mass stars and brown dwarfs - V. A halo L3 subdwarf with prograde eccentric orbit in the Galactic plane
Burgasser, A. J.; Zhang, Z. H.; Smith, L. C.
VVV J12564163-6202039 is an L subdwarf located in the Galactic plane (b = 0{^{circ}.}831) discovered by its high proper motion (1.1 arcsec yr-1). We obtained an optical to near-infrared spectrum of it with the X-shooter on the Very Large Telescope, and re-classified it as an sdL3 subdwarf. Its best-fitting BT-Dusty model spec…
Direct Measurement of Low-Energy Electron Foreshock Beams
Soucek, Jan; Píša, David; Santolík, Ondrej
Electrostatic plasma waves above and below the local electron plasma frequency represent a characteristic feature of the foreshock region. These waves are known to be generated by electron beams originating from the bow shock and their spectrum varies from narrowband intense waves close to foreshock edge to weaker broadband emissions further downs…
Galactic halo age estimated from LAMOST DR4 and Gaia DR1
Yuan, Hai-Bo; Huang, Yang; Chen, Bing-Qiu +8 more
The stellar halo is one of the major components in the Milky Way. Research on its age can provide critical constraints on the origin of the stellar halo and further on the formation of our Galaxy. So far, different approaches and samples have been used to estimate the age of the Galactic halo. In our previous paper, we carefully selected 63 field …
Stellar Occultation by Comet 67P/Churyumov-Gerasimenko Observed with Rosetta's Alice Far-ultraviolet Spectrograph
Parker, Joel Wm.; Bertaux, Jean-Loup; Stern, S. Alan +13 more
Following our previous detection of ubiquitous {{{H}}}2{{O}} and {{{O}}}2 absorption against the far-ultraviolet continuum of stars located near the nucleus of Comet 67P/Churyumov-Gerasimenko, we present a serendipitously observed stellar occultation that occurred on 2015 September 13, approximately one month after the comet’…
A SCUBA-2 selected Herschel-SPIRE dropout and the nature of this population
Andreani, P.; Yun, M. S.; Clements, D. L. +19 more
Dusty star-forming galaxies (DSFGs) detected at z > 4 provide important examples of the first generations of massive galaxies. However, few examples with spectroscopic confirmation are currently known, with Hershel struggling to detect significant numbers of z > 6 DSFGs. NGP6_D1 is a bright 850 µm source (12.3 ± 2.5 mJy) with no counte…
Axisymmetric density waves in Saturn's rings
Nicholson, P. D.; Hedman, M. M.
Density waves in Saturn's rings are usually tightly wrapped spiral patterns generated by resonances with either Saturn's moons or structures inside the planet. However, between the Barnard and Bessel Gaps in the Cassini Division (i.e. between 120 240 and 120 300 km from Saturn's spin axis), there are density variations that appear to form an axisy…