Search Publications
S-index periodicity detection based on multiple random spectral observations
Shen, Yu-Fu
The solar magnetic activity cycle has a profound impact on our lives, yet its underlying causes remain elusive. While similar cycles have been observed in other stars, these results are scarce due to the significant challenge posed by the length of time required for observation. Continuous observation over an extended period is a luxury, making it…
The Challenge of Measuring Asteroid Masses with Gaia DR2 Astrometry
Murray, Zachary
The Gaia second data release (DR2) contains high-accuracy astrometric measurements of thousands of solar system bodies. These measurements raise the possibility of determining asteroid masses by modeling scattering events between massive objects observed by Gaia. In this paper, we identify promising encounters between small asteroids that occur du…
A New Method Linking the Solar Wind Speed to the Coronal Magnetic Field
Pinto, Rui F.; Bemporad, Alessandro; Casti, Marta +2 more
The release and acceleration of the solar wind is still an outstanding question. There are several aspects related to this phenomenon that still need to be investigated, and one of these is the identification of the region within the inner corona where the larger fraction of acceleration occurs. To address this matter, it is necessary to have reli…
EPIC 206197016: A very hot white dwarf orbited by a strongly irradiated red dwarf
Fossati, L.; Zejda, M.; Paunzen, E. +7 more
Context. Very precise satellite photometry has revealed a large number of variable stars whose variability is caused either by surface spots or by binarity. Detailed studies of such variables provide insights into the physics of these objects.
Aims: We study the nature of the periodic light variability of the white dwarf EPIC 206197016 that w…
Disentangling the nature of the prototype radio weak BL Lac. Contemporaneous multifrequency observations of WISE J141046.00+740511.2
Masetti, N.; Chavushyan, V.; Acosta-Pulido, J. A. +13 more
Context. The γ-ray emitting source WISE J141046.00+740511.2 has been associated with a Fermi-LAT detection by crossmatching with Swift/XRT data. It has shown all the canonical observational characteristics of a BL Lac source, including a power-law, featureless optical spectrum. However, it was only recently detected at radio frequencies and its ra…
A new method to determine X-ray luminosity functions of AGN and their evolution with redshift
Page, Mat J.; Alqasim, Ahlam
Almost all massive galaxies today are understood to contain supermassive black holes (SMBH) at their centres. SMBHs grew by accreting material from their surroundings, emitting X-rays as they did so. X-ray luminosity functions (XLFs) of active galactic nuclei (AGN) have been extensively studied in order to understand the AGN population's cosmologi…
Abundance analysis of a nitrogen-rich extreme-helium hot subdwarf from the SALT survey
Dorsch, M.; Jeffery, C. S.; Scott, L. J. A. +2 more
We have performed a detailed spectral analysis of the helium-rich hot subdwarf EC 20187-4939, using data obtained in the SALT survey of helium-rich hot subdwarfs. We have measured its effective temperature, surface gravity, and chemical abundances from the spectrum. Its radius has also been determined by fitting the spectral energy distribution us…
Space Weather Disturbances in Non-Stormy Times: Occurrence of dB/dt Spikes During Three Solar Cycles
Gunell, H.; Hamrin, M.; Opgenoorth, H. +8 more
Spatio-temporal variations of ionospheric currents cause rapid magnetic field variations at ground level and Geomagnetically Induced Currents (GICs) that can be harmful for human infrastructure. The risk for large excursions in the magnetic field time derivative, "dB/dt spikes", is known to be high during geomagnetic storms and substorms. However,…
Statistical Signatures of Nanoflare Activity. III. Evidence of Enhanced Nanoflaring Rates in Fully Convective stars as Observed by the NGTS
Mathioudakis, M.; Wheatley, P. J.; Goad, M. R. +11 more
Previous examinations of fully convective M-dwarf stars have highlighted enhanced rates of nanoflare activity on these distant stellar sources. However, the specific role the convective boundary, which is believed to be present for spectral types earlier than M2.5V, plays on the observed nanoflare rates is not yet known. Here, we utilize a combina…
Looking ahead to the sky with the Square Kilometre Array: simulating flux densities and resolved radio morphologies of 0 < z < 2.5 star-forming galaxies
Daddi, Emanuele; Franco, Maximilien; Cibinel, Anna +4 more
SKA-MID surveys will be the first in the radio domain to achieve clearly sub-arcsecond resolution at high sensitivity over large areas, opening new science applications for galaxy evolution. To investigate the potential of these surveys, we create simulated SKA-MID images of a ~0.04 deg2 region of GOODS-North, constructed using multi-ba…