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On Solutions of the PFSS Model With GONG Synoptic Maps for 2006-2018
Nikolić; , L.
The potential field source surface (PFSS) model is widely used to derive the magnetic field of the solar corona. The only free parameter in the PFSS model is the radius of the so-called source surface, where magnetic field lines are forced to open. The radius of this surface is typically set to 2.5 solar radii in research and operational PFSS nume…
Six new rapidly oscillating Ap stars in the Kepler long-cadence data using super-Nyquist asteroseismology
Huber, Daniel; Bedding, Timothy R.; Howard, Andrew W. +6 more
We perform a search for rapidly oscillating Ap stars in the Kepler long-cadence data, where true oscillations above the Nyquist limit of 283.21 µHz can be reliably distinguished from aliases as a consequence of the barycentric time corrections applied to the Kepler data. We find evidence for rapid oscillations in six stars: KIC 6631188, KIC …
A three-dimensional map of the hot Local Bubble using diffuse interstellar bands
Javadi, Atefeh; van Loon, Jacco Th.; Khosroshahi, Habib G. +2 more
The Solar System is located within a low-density cavity known as the Local Bubble1-3, which appears to be filled with an X-ray-emitting gas at a temperature of 106 K (ref. 4). Such conditions are too harsh for typical interstellar atoms and molecules to survive2,3. The diffuse interstellar bands (DIBs), …
Dark disk substructure and superfluid dark matter
Alexander, Stephon; Bramburger, Jason J.; McDonough, Evan
Dark matter substructure has the potential to discriminate between broad classes of dark matter models. With this in mind, we construct novel solutions to the equations of motion governing condensate dark matter candidates, namely axion Bose-Einstein condensates and superfluids. These solutions are highly compressed along one axis and thus have a …
The fifth main-sequence magnetic B-type star showing coherent radio emission: Is this really a rare phenomenon?
Wade, Gregg A.; Chandra, Poonam; Das, Barnali +1 more
We report the discovery of intense, highly directional radio emission from the Bp star HD 35298, which we interpret as the consequence of Electron Cyclotron Maser Emission (ECME). The star was observed with the Giant Metrewave Radio Telescope near the rotational phases of both magnetic nulls in band 4 (550-750 MHz) and one of the nulls in band 5 (…
Interstellar Dust in the Solar System
Postberg, Frank; Altobelli, Nicolas; Sterken, Veerle J. +2 more
Interstellar dust from the Local Interstellar Cloud was detected unambiguously for the first time in 1992 (Grün et al. in Nature 362:428-430, 1993). Since then, great progress has been made in observing local interstellar dust in the Solar System using a variety of methods that, all together, provide complementary views of the dust particles from …
Discovery of a Double Blue Straggler Sequence in M15: New Insight into the Core-collapse Process
Knigge, C.; Dalessandro, E.; Beccari, G. +8 more
In this paper we report the discovery of a double blue straggler star (BSS) sequence in the core of the core-collapsed cluster M15 (NGC 7078). We performed a detailed photometric analysis of the extremely dense core of the cluster using a set of images secured with the Advanced Camera for Survey in the High Resolution Channel mode on board the Hub…
X-ray time lags in AGN: inverse-Compton scattering and spherical corona model
Chainakun, P.; Young, A. J.; Hancock, S. +1 more
We develop a physically motivated, spherical corona model to investigate the frequency-dependent time lags in active galactic nucleus (AGN). The model includes the effects of Compton up-scattering between the disc ultraviolet (UV) photons and coronal electrons, and the subsequent X-ray reverberation from the disc. The time lags are associated with…
Quasar lenses in the south: searches over the DES public footprint
Agnello, Adriano; Spiniello, Chiara
We have scanned 5000 deg2 of Southern Sky to search for strongly lensed quasars with five methods, all source oriented, but based on different assumptions and selection criteria. We present a list of high-grade candidates from each method (totalling 98 unique, new candidates), to facilitate follow-up spectroscopic campaigns, including t…
The Enigmatic (Almost) Dark Galaxy Coma P: Distance Measurement and Stellar Populations from HST Imaging
McQuinn, Kristen B. W.; Cannon, John M.; Dolphin, Andrew E. +9 more
We present Hubble Space Telescope (HST) observations of the low surface brightness (SB) galaxy Coma P. This system was first discovered in the Arecibo Legacy Fast ALFA H I survey and was cataloged as an (almost) dark galaxy because it did not exhibit any obvious optical counterpart in the available survey data (e.g., Sloan Digital Sky Survey). Sub…