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VLBI astrometry of radio stars to link radio and optical celestial reference frames: observing strategies
Sun, Yan; Zhang, Bo; Chen, Wen +12 more
The Gaia celestial reference frame (Gaia-CRF) will benefit from a close assessment with independent methods, such as Very Long Baseline Interferometry (VLBI) measurements of radio stars at bright magnitudes. However, obtaining full astrometric parameters for each radio star through VLBI measurements demands a significant amount of observation time…
Photometric Completeness Modelled with Neural Networks
Speagle, Joshua S.; Harris, William E.
In almost any study involving optical/near-infrared photometry, understanding the completeness of detection and recovery is an essential part of the work. The recovery fraction is, in general, a function of several variables including magnitude, color, background sky noise, and crowding. We explore how completeness can be modeled, with the use of …
NuSTAR and Swift observations of two supergiant fast X-ray transients: AX J1841.0-0536 and SAX J1818.6-1703
Romano, P.; Ferrigno, C.; Bozzo, E.
Supergiant fast X-ray transients are wind-fed binaries hosting neutron star accretors, which display a peculiar variability in the X-ray domain. Different models have been proposed to explain this variability and the strength of the compact object magnetic field is generally considered a key parameter to discriminate among possible scenarios. We p…
N2H+(1-0) as a tracer of dense gas in and between spiral arms
Moore, T. J. T.; Clark, P. C.; Ragan, S. E. +2 more
Recent advances in identifying giant molecular filaments in Galactic surveys allow us to study the interstellar material and its dense, potentially star forming phase on scales comparable to resolved extragalactic clouds. Two large filaments detected in the 13CO/C18O(J = 3-2) Heterodyne Inner Milky Way Plane Survey (CHIMPS) s…
Low-Frequency Solar Radio Type II Bursts And Their Association With Space Weather Events During The Ascending Phase Of Solar Cycle 25
Ndacyayisenga, Theogene; Uwamahoro, Jean; Uwamahoro, Jean Claude +5 more
Type II solar radio bursts are signatures of the coronal shocks and, therefore, particle acceleration events in the solar atmosphere and interplanetary space. Type II bursts can serve as a proxy to provide early warnings of incoming solar storm disturbances, such as geomagnetic storms and radiation storms, which may further lead to ionospheric eff…
Magnetic Field in the Earth's Magnetosheath: Models Versus Observations
Vandas, M.; Romashets, E.
Magnetic field measurements in the Earth's magnetosheath are compared with four analytical models, namely Kobel and Flückiger (1994), (https://doi.org/10.1029/94ja01778), Romashets and Vandas (2019), (https://doi.org/10.1029/2018ja026006), Vandas and…
Singular Spectrum Analysis of Exoplanetary Transits
Sajadian, Sedighe; Fatheddin, Hossein
Transit photometry is currently the most efficient and sensitive method for detecting extrasolar planets (exoplanets) and a large majority of confirmed exoplanets have been detected with this method. The substantial success of space-based missions such as NASA's Kepler/K2 and Transiting Exoplanet Survey Satellite has generated a large and diverse …
The first high-redshift cavity power measurements of cool-core galaxy clusters with the International LOFAR Telescope
Botteon, A.; van Weeren, R. J.; Röttgering, H. J. A. +3 more
Radio-mode feedback associated with the active galactic nuclei (AGNs) at the cores of galaxy clusters injects a large amount of energy into the intracluster medium (ICM), offsetting radiative losses through X-ray emission. This mechanism prevents the ICM from rapidly cooling down and fueling extreme starburst activity as it accretes onto the centr…
Visual Orbits of Wolf–Rayet Stars. I. The Orbit of the Dust-producing Wolf–Rayet Binary WR 137 Measured with the CHARA Array
Moffat, Anthony F. J.; Monnier, John D.; Schaefer, Gail H. +19 more
Classical Wolf–Rayet (W-R) stars are the descendants of massive OB stars that have lost their hydrogen envelopes and are burning helium in their cores prior to exploding as Type Ib/c supernovae. The mechanisms for losing their hydrogen envelopes are either through binary interactions or through strong stellar winds potentially coupled with episodi…
Classification of circular polarization Stokes profiles in a sunspot using k-means clustering
Mathew, Shibu K.; Raja Bayanna, A.; Louis, Rohan Eugene
The magnetic and velocity fields in sunspots are highly structured on small spatial scales which are encoded in the Stokes profiles. The Stokes profiles are in turn, derived from a sequence of polarization modulations on the incoming light that are imaged using an analyser-detector combination. Our aim is to identify Stokes profiles in a sunspot w…