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Magnetars and axion-like particles: probes with the hard X-ray spectrum
Sinha, Kuver; Guo, Huai-Ke; Fortin, Jean-François +2 more
Quiescent hard X-ray and soft gamma-ray emission from neutron stars constitute a promising frontier to explore axion-like-particles (ALPs). ALP production in the core peaks at energies of a few keV to a few hundreds of keV; subsequently, the ALPs escape and convert to photons in the magnetosphere. The emissivity goes as T6 while the con…
591 High-velocity Stars in the Galactic Halo Selected from LAMOST DR7 and Gaia DR2
Zhao, Gang; Xiang, Maosheng; Ting, Yuan-Sen +14 more
In this paper, we report 591 high-velocity star candidates (HiVelSCs) selected from over 10 million spectra of Data Release 7 (DR7) of the Large Sky Area Multi-object Fiber Spectroscopic Telescope and the second Gaia data release, with three-dimensional velocities in the Galactic rest frame larger than 445 km s-1. We show that at least …
From Pseudostreamer Jets to Coronal Mass Ejections: Observations of the Breakout Continuum
Antiochos, Spiro K.; Lynch, Benjamin J.; Kumar, Pankaj +3 more
The magnetic breakout model, in which reconnection in the corona leads to destabilization of a filament channel, explains numerous features of eruptive solar events, from small-scale jets to global-scale coronal mass ejections (CMEs). The underlying multipolar topology, pre-eruption activities, and sequence of magnetic-reconnection onsets (first b…
The effect of stellar multiplicity on protoplanetary discs: a near-infrared survey of the Lupus star-forming region
Ansdell, Megan; Pérez, Sebastián; Gonzalez-Ruilova, Camilo +9 more
We present results from a near-infrared (NIR) adaptive optics (AO) survey of pre-main-sequence stars in the Lupus molecular cloud with NACO at the Very Large Telescope (VLT) to identify (sub)stellar companions down to ~20-au separation and investigate the effects of multiplicity on circumstellar disc properties. We observe for the first time in th…
First constraints on the AGN X-ray luminosity function at z 6 from an eROSITA-detected quasar
Georgakakis, A.; Salvato, M.; Buchner, J. +19 more
Context. High-redshift quasars signpost the early accretion history of the Universe. The penetrating nature of X-rays enables a less absorption-biased census of the population of these luminous and persistent sources compared to optical/near-infrared colour selection. The ongoing SRG/eROSITA X-ray all-sky survey offers a unique opportunity to unco…
Primordial black holes and secondary gravitational waves from string inspired general no-scale supergravity
Gong, Yungui; Wu, Lina; Li, Tianjun
The formation of primordial black hole (PBH) dark matter and the generation of scalar induced secondary gravitational waves (SIGWs) have been studied in the generic no-scale supergravity inflationary models. By adding an exponential term to the Kähler potential, the inflaton experiences a period of ultraslow-roll and the amplitude of primordial po…
UV line-driven disc wind as the origin of UltraFast Outflows in AGN
Done, Chris; Mizumoto, Misaki; Odaka, Hirokazu +2 more
UltraFast Outflows (UFOs) are observed in some active galactic nuclei (AGN), with blueshifted and highly ionized Fe-K absorption features. AGN typically have an ultraviolet (UV-) bright accretion flow, so UV line driving is an obvious candidate for launching these winds. However this mechanism requires material with UV opacity, in apparent conflic…
Dark matter properties through cosmic history
Kopp, Michael; Skordis, Constantinos; Thomas, Daniel B. +1 more
We perform the first test of dark matter (DM) stress-energy evolution through cosmic history, using cosmic microwave background measurements supplemented with baryon acoustic oscillation data and the Hubble Space Telescope key project data. We constrain the DM equation of state (EoS) in 8 redshift bins, and its sound speed and (shear) viscosity in…
A β Cephei pulsator and a changing orbital inclination in the high-mass eclipsing binary system VV Orionis
Bowman, D. M.; Southworth, John; Pavlovski, K.
We present an analysis of the high-mass eclipsing binary system VV Ori based on photometry from the TESS satellite. The primary star (B1 V, 9.5 $\, {\rm M}_\odot$) shows β Cephei pulsations and the secondary (B7 V, 3.8 $\, {\rm M}_\odot$) is possibly a slowly pulsating B star. We detect 51 significant oscillation frequencies, including two multipl…
Reconstructing the Extreme Ultraviolet Emission of Cool Dwarfs Using Differential Emission Measure Polynomials
Loyd, R. O. Parke; Kowalski, Adam F.; Redfield, Seth +16 more
Characterizing the atmospheres of planets orbiting M dwarfs requires understanding the spectral energy distributions of M dwarfs over planetary lifetimes. Surveys like MUSCLES, HAZMAT, and FUMES have collected multiwavelength spectra across the spectral type's range of Teff and activity, but the extreme ultraviolet (EUV, 100-912 Å) flux…