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Whistler Fan Instability Driven by Strahl Electrons in the Solar Wind
Bale, S. D.; Krasnoselskikh, V.; Mozer, F. S. +3 more
We present a theoretical analysis of electron heat flux inhibition in the solar wind when a significant portion of the heat flux is carried by strahl electrons. We adopt core-strahl velocity distribution functions typical for the solar wind at 0.3-4 au to demonstrate that strahl electrons are capable of generating highly oblique whistler waves at …
The Type II-plateau Supernova 2017eaw in NGC 6946 and Its Red Supergiant Progenitor
Van Dyk, Schuyler D.; Filippenko, Alexei V.; Kelly, Patrick L. +31 more
We present extensive optical photometric and spectroscopic observations, from 4 to 482 days after explosion, of the Type II-plateau (II-P) supernova (SN) 2017eaw in NGC 6946. SN 2017eaw is a normal SN II-P intermediate in properties between, for example, SN 1999em and SN 2012aw and the more luminous SN 2004et, also in NGC 6946. We have determined …
The refractory-to-ice mass ratio in comets
Blum, J.; Gundlach, B.; Mottola, S. +6 more
We review the complex relationship between the dust-to-gas mass ratio usually estimated in the material lost by comets, and the refractory-to-ice mass ratio inside the nucleus, which constrains the origin of comets. Such a relationship is dominated by the mass transfer from the perihelion erosion to fallout over most of the nucleus surface. This m…
WASP-4b Arrived Early for the TESS Mission
Dai, F.; Winn, J. N.; Jenkins, J. M. +21 more
The Transiting Exoplanet Survey Satellite (TESS) recently observed 18 transits of the hot Jupiter WASP-4b. The sequence of transits occurred 81.6 ± 11.7 s earlier than had been predicted, based on data stretching back to 2007. This is unlikely to be the result of a clock error, because TESS observations of other hot Jupiters (WASP-6b, 18b, and 46b…
A quantitative analysis of systematic differences in the positions and proper motions of Gaia DR2 with respect to VLBI
Petrov, L.; Kovalev, Y. Y.; Plavin, A. V.
We have analysed the differences in positions of 9081 matched sources between the Gaia Data Release 2 (DR2) and very long baseline interferometry (VLBI) catalogues. The median position uncertainty of matched sources in the VLBI catalogue is a factor of two larger than the median position uncertainty in Gaia DR2. There are 9 per cent matched source…
ALMA 200 pc Resolution Imaging of Smooth Cold Dusty Disks in Typical z ∼ 3 Star-forming Galaxies
Daddi, E.; Elbaz, D.; Franco, M. +14 more
We present high-fidelity, 30 mas (200 pc) resolution ALMA rest-frame 240 µm observations of cold dust emission in three typical main-sequence star-forming galaxies (SFGs) at z ∼ 3 in the Hubble Ultra-Deep Field (HUDF). The cold dust is distributed within the smooth disklike central regions of star formation 1-3 kpc in diameter, despite their…
No evidence for intermediate-mass black holes in the globular clusters ω Cen and NGC 6624
Dreizler, S.; Usher, C.; Kamann, S. +8 more
We compare the results of a large grid of N-body simulations with the surface brightness and velocity dispersion profiles of the globular clusters ω Cen and NGC 6624. Our models include clusters with varying stellar-mass black hole retention fractions and varying masses of a central intermediate-mass black hole (IMBH). We find that an ∼ 45 000 M
Two new free-floating or wide-orbit planets from microlensing
Kaspi, Shai; Maoz, Dan; Han, Cheongho +57 more
Planet formation theories predict the existence of free-floating planets that have been ejected from their parent systems. Although they emit little or no light, they can be detected during gravitational microlensing events. Microlensing events caused by rogue planets are characterized by very short timescales tE (typically below two da…
Searching for Highly Magnified Stars at Cosmological Distances: Discovery of a Redshift 0.94 Blue Supergiant in Archival Images of the Galaxy Cluster MACS J0416.1-2403
Filippenko, Alexei V.; Foley, Ryan J.; Kelly, Patrick L. +12 more
Individual highly magnified stars have been recently discovered at lookback times of more than half the age of the universe, in lensed galaxies that straddle the critical curves of massive galaxy clusters. Having established their detectability, it is now important to carry out systematic searches for them in order to establish their frequency, an…
The evolutionary status of Cataclysmic Variables: eclipse modelling of 15 systems
Knigge, C.; Gänsicke, B. T.; Dhillon, V. S. +13 more
We present measurements of the component masses in 15 Cataclysmic Variables (CVs) - 6 new estimates and 9 improved estimates. We provide new calibrations of the relationship between superhump period excess and mass ratio, and use this relation to estimate donor star masses for 225 superhumping CVs. With an increased sample of donor masses we revis…