Search Publications
Properties of High-Frequency Type II Radio Bursts and Their Relation to the Associated Coronal Mass Ejections
Gopalswamy, N.; Yashiro, S.; Mäkelä, P. +3 more
Solar radio bursts are often early indicators of space weather events such as coronal mass ejections (CMEs). In this study, we determined the properties of a sample of 40 high-starting-frequency (≥ 150 MHz) type II radio bursts and the characteristics of the associated CMEs such as width, location and speed during 2010-2016. The high starting freq…
The Galactic neutron star population - I. An extragalactic view of the Milky Way and the implications for fast radio bursts
Lyman, J. D.; Groot, P. J.; Nelemans, G. +2 more
A key tool astronomers have to investigate the nature of extragalactic transients is their position on their host galaxies. Galactocentric offsets, enclosed fluxes, and the fraction of light statistic are widely used at different wavelengths to help infer the nature of transient progenitors. Motivated by the proposed link between magnetars and fas…
Unsupervised Machine Learning for the Identification of Preflare Spectroscopic Signatures
De Pontieu, Bart; Sainz Dalda, Alberto; Woods, Magnus M.
The study of the preflare environment is of great importance to understanding what drives solar flares. k-means clustering, an unsupervised machine-learning technique, has the ability to cluster large data set in a way that would be impractical or impossible for a human to do. In this paper we present a study using k-means clustering to identify p…
NGC 1261: An r-process enhanced globular cluster from the Gaia-Enceladus event
McWilliam, Andrew; Koch-Hansen, Andreas J.; Hansen, Camilla J.
Our Milky Way (MW) has witnessed a series of major accretion events in the past. One of the later additions, the Gaia-Enceladus merger, has contributed a considerable mass to the inner Galaxy, but also generously donated to the outer halo. So far, associations with present-day MW globular clusters (GCs) have been chiefly based on their kinematics …
DH Type II Radio Bursts During Solar Cycles 23 and 24: Frequency-Dependent Classification and Their Flare-CME Associations
Joshi, Bhuwan; Cho, Kyung-Suk; Patel, Binal D. +1 more
We present the characteristics of DH type II bursts for the Solar Cycles 23 and 24. The bursts are classified according to their end frequencies into three categories: Low-Frequency Group (LFG; 20 kHz ≤ f ≤ 200 kHz), Medium-Frequency Group (MFG; 200 kHz <f ≤1 MHz), and High-Frequency Group (HFG; 1 MHz <f ≤16 MHz). We find that the sources fo…
A first glimpse at the Galactic plane with the ASKAP: the SCORPIO field
Umana, G.; Michałowski, M. J.; Kothes, R. +25 more
In the broad context of the Australian Square Kilometer Array Pathfinder (ASKAP) early-science phase and preparation for the related surveys, we report the first radio observations towards the Galactic plane. The targeted field was chosen to encompass the entire SCORPIO survey, one of the several pathfinder projects for the Evolutionary Map of the…
Repeated pattern of gamma-ray flares in the light curve of the blazar 3C 279
Larionov, V. M.; Blinov, D.; Jorstad, S. G. +10 more
The optical polarization plane of some blazars occasionally exhibits smooth hundred degree long rotations. Multiple theoretical models have been proposed to explain the nature of such events. A deterministic origin of these rotations, however, remains uncertain. We aim to find repeating patterns of flares in gamma-ray light curves of blazars, whic…
A revised cone model and its application to non-radial prominence eruptions
Zhang, Q. M.
Context. The traditional cone models achieve great success in studying the geometrical and kinematic properties of halo coronal mass ejections (CMEs).
Aims: In this Letter, a revised cone model is proposed to investigate the properties of CMEs as a result of non-radial prominence eruptions.
Methods: The cone apex is located at the source…
Decoding the morphological evolution of open clusters
Hu, Qingshun; Zhang, Yu; Esamdin, Ali
Context. The properties of open clusters such as metallicity, age, and morphology are useful tools in studies of the dynamic evolution of open clusters. The morphology of open clusters can help us better understand the evolution of such structures.
Aims: We aim to analyze the morphological evolution of 1256 open clusters by combining the shap…
Wind-luminosity evolution in NLS1 AGN 1H 0707-495
Fabian, Andrew C.; Walton, Dominic J.; Guainazzi, Matteo +7 more
Ultrafast outflows (UFOs) have been detected in the high-quality X-ray spectra of a number of active galactic nuclei (AGNs) with fairly high accretion rates and are thought to significantly contribute to the AGN feedback. After a decade of dedicated study, their launching mechanisms and structure are still not well understood, but variability tech…