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The Nature of 500 micron Risers III: a small complete sample
Pérez-Fournon, I.; Clements, D. L.; Riechers, D. +4 more
Herschel surveys have found large numbers of sources with red far-IR colours, and spectral energy distributions (SEDs) rising from 250 to 500 µm: 500 risers. The nature and role of these sources is not fully understood. We here present Submillimeter Array (SMA) interferometric imaging at 200 GHz of a complete sample of five 500 risers with F500 &g…
Exploring the case for hard-X-ray beaming in NGC 6946 X-1
Soria, Roberto; Middleton, Matthew J.; Roberts, Timothy P. +5 more
In order to understand the nature of super-Eddington accretion we must explore both the emission emerging directly from the inflow and its impact on the surroundings. In this paper, we test whether we can use the optical line emission of spatially resolved, ionized nebulae around ultraluminous X-ray sources (ULXs) as a proxy for their X-ray lumino…
The response of the cometary ionosphere to space weather forcing
Timar, Aniko; Nemeth, Zoltan; Burch, James L.
The Rosetta spacecraft observed the temporal evolution of the ion populations within the ionosphere of comet 67P/Churyumov-Gerasimenko. A striking feature of the ion spectrum is represented by the so-called medium-energy ion peaks, which recurrently emerge from the low-energy ion background with their energy levels typically reaching 50 to 1000 eV…
AstroSat/UVIT Study of the Diffuse Ultraviolet Radiation in the Dwarf Galaxy Holmberg II
Shalima, P.; Gogoi, Rupjyoti; Bordoloi, Olag Pratim +4 more
We present measurements of diffuse ultraviolet (UV) emission in the dwarf irregular galaxy Holmberg II obtained with the Ultra Violet Imaging Telescope (UVIT) instrument onboard AstroSat, India's first multiwavelength space mission. With a spatial resolution of 1.″2–1.″6, these are the highest resolution UV observations of the galaxy to date. We f…
Escape Velocity Mass of A1063
Miller, Christopher J.; Kremin, Anthony; Rodriguez, Alexander +1 more
We measure the radius–velocity phase-space edge profile of A1063 using galaxy redshifts from Karman et al. and Mercurio et al. Combined with a cosmological model and after accounting for interlopers and sampling effects, we infer the escape velocity profile. Using the Poisson equation, we then directly constrain the gravitational potential profile…
Constraints on the parameters of keV-scale mass annihilating dark matter obtained with SRG/ART-XC observations
Burenin, R. A.; Krivonos, R. A.; Zakharov, E. I. +2 more
In this paper we present new constraints on the velocity-independent cross section of keV-scale mass annihilating dark matter particles obtained with SRG/ART-XC after 4 full-sky surveys. These constraints are derived from observations of the Milky Way Halo, 33 Local Group spheroidal dwarf (dSph) galaxies and separately for the dSph galaxy Ursa Maj…
Classification of Wolf–Rayet Stars Using Ensemble-based Machine Learning Algorithms
Das, Ramkrishna; Bhattacharya, Rajorshi; Lewis, Megan O. +2 more
We develop a robust machine learning classifier model utilizing the eXtreme-Gradient Boosting (XGB) algorithm for improved classification of Galactic Wolf–Rayet (WR) stars based on IR colors and positional attributes. For our study, we choose an extensive data set of 6555 stellar objects (from 2MASS and AllWISE data releases) lying in the Milky Wa…
X-Ray Observations of the Enigmatic Wolf–Rayet System θ Mus: Two's Company but Three's a Crowd
Skinner, Stephen L.; Zhekov, Svetozar A.; Güdel, Manuel +1 more
θ Mus is a remarkable spectroscopic binary (SB) consisting of a carbon-type Wolf–Rayet star and OV companion (WC6+O6–7V) in a ≈19 days orbit. In addition an O-supergiant is visually detected at a small offset of 46 mas and if gravitationally bound to the SB system would have an orbital period of many decades. θ Mus is X-ray bright and a nonthermal…
Early Evolution of Earth-Directed Coronal Mass Ejections in the Vicinity of Coronal Holes
Dumbović, Mateja; Temmer, Manuela; Vršnak, Bojan +3 more
We investigate the deflection and rotation behaviour of 49 Earth-directed coronal mass ejections (CMEs) spanning the period from 2010 to 2020 aiming to understand the potential influence of coronal holes (CHs) on their trajectories. Our analysis incorporates data from coronagraphic observations captured from multiple vantage points, as well as ext…
The AllWISE Catalog as an Infrared Celestial Reference Frame in the Gaia Era
Liu, N.; Zhu, Z.; Liu, J. -C. +3 more
The launch of Gaia in 2013 December ushered in a new era of space astrometry, allowing for fundamental reference research at an unprecedented level of precision. The international celestial reference frames in the radio band and the Gaia celestial reference frame in the optical band have been established and are consistent within several microarcs…