Search Publications
S and VV Corona Australis: Spectroscopic Variability in Two Young Binary Star Systems
Edwards, Suzan; Schaefer, Gail H.; Prato, L. +2 more
We used high-resolution near-infrared spectroscopy from the NIRSPEC instrument on the Keck II telescope, taken over multiple epochs spanning five years, to examine two young binary T Tauri star systems, S Corona Australis and VV Corona Australis. The stars in these 1″-2″ separation systems have optically thick circumstellar disks and high extincti…
On the Possible Mechanism of GLE Initiation
Gan, W. Q.; Rodríguez-Pacheco, J.; Li, Y. P. +2 more
With the goal of understanding the initiations of solar energetic particle (SEP) (MeV) and ground-level enhancement (GLE) (GeV) particles, we have studied relative timings at approximately the Sun between temporal evolutions of the particles and some electromagnetic radiation components representing flares and shocks. Results show that GLE onsets …
Runaways and shells around the CMa OB1 association
Montmerle, T.; Gregorio-Hetem, J.; Santos-Silva, T. +1 more
Context. The origin of the arc-shaped Sh 2-296 nebula is still unclear. Mainly due to its morphology, the nebula has been suggested to be a 0.5 Myr old supernova remnant (SNR) that could be inducing star formation in the CMa OB1 association. This means that the region might be an excellent laboratory for investigating the influence of massive star…
Multi-waveband detection of quasi-periodic pulsations in a stellar flare on EK Draconis observed by XMM-Newton
Broomhall, A. -M.; Rosen, S. R.; Pye, J. P. +2 more
Context. Quasi-periodic pulsations (QPPs) are time variations in the energy emission during a flare that are observed on both the Sun and other stars and thus have the potential to link the physics of solar and stellar flares.
Aims: We characterise the QPPs detected in an X-ray flare on the solar analogue, EK Draconis, which was observed by X…
OGLE-2015-BLG-1670Lb: A Cold Neptune beyond the Snow Line in the Provisional WFIRST Microlensing Survey Field
Han, Cheongho; Udalski, Andrzej; Lee, Chung-Uk +56 more
We present the analysis of the microlensing event OGLE-2015-BLG-1670, detected in a high-extinction field very close to the Galactic plane. Due to the dust extinction along the line of sight, this event was too faint to be detected before it reached the peak of magnification. The microlensing light-curve models indicate a high-magnification event …
SHALOS: Statistical Herschel-ATLAS lensed objects selection
Bonavera, L.; González-Nuevo, J.; Herranz, D. +7 more
Context. The statistical analysis of large sample of strong lensing events can be a powerful tool to extract astrophysical or cosmological valuable information. Their selection using submillimetre galaxies has been demonstrated to be very effective with more than ∼200 proposed candidates in the case of Herschel-ATLAS data and several tens in the c…
Properties of High-Energy Solar Particle Events Associated with Solar Radio Emissions
Valtonen, Eino; Pohjolainen, Silja; Ameri, Dheyaa
We have analysed 58 high-energy proton events and 36 temporally related near-relativistic electron events from the years 1997 - 2015 for which the velocity dispersion analysis of the first-arriving particles gave the apparent path lengths between 1 and 3 AU. We investigated the dependence of the characteristics of the proton events on the associat…
A magnetic white dwarf with five H α components
Bergeron, P.; Kilic, Mukremin; Vanderbosch, Z. +3 more
G183-35 is an unusual white dwarf that shows an H α line split into five components, instead of the usual three components seen in strongly magnetic white dwarfs. Potential explanations for the unusual set of lines include a double degenerate system containing two magnetic white dwarfs and/or rotational modulation of a complex magnetic field struc…
An Efficient Spectral Selection of M Giants Using XGBoost
Luo, A. -Li; Yi, Zhenping; Chen, Zesheng +4 more
In optical bands, the spectra of M giants often overlap with those of M dwarfs due to their similarities, especially for low or moderate resolution spectra. Traditionally, several feature indices, such as Na I, CaH, TiO5, and K I, are used to distinguish between M giants and M dwarfs. However, these features are selected by experience based on a s…
Vertical position of the Sun with γ-rays
Siegert, Thomas
We illustrate a method for estimating the vertical position of the Sun above the Galactic plane by γ-ray observations. Photons of γ-ray wavelengths are particularly well suited for geometrical and kinematic studies of the Milky Way because they are not subject to extinction by interstellar gas or dust. Here, we use the radioactive decay line of