Search Publications
Caldera Collapse as the Trigger of Chaos and Fractured Craters on the Moon and Mars
Massironi, Matteo; Rossi, Angelo Pio; Pozzobon, Riccardo +3 more
Chaotic terrains are broad regions on Mars characterized by the disruption of the basaltic bedrock into polygonal blocks separated by deep fractures. To date, the proposed genetic scenarios often involve the occurrence of subsurface ice or liquid H2O. Nevertheless, similar features also occur within some craters on the Moon, namely floo…
The Initial-Final Mass Relation for Hydrogen-deficient White Dwarfs
Bolte, Michael; Williams, Kurtis A.; Barnett, Joseph W. +1 more
The initial-final mass relation represents the total mass lost by a star during the entirety of its evolution from the zero age main sequence to the white-dwarf cooling track. The semiempirical initial-final mass relation (IFMR) is largely based on observations of DA white dwarfs, the most common spectral type of white dwarf and the simplest atmos…
Chemical Analysis of Two Extremely Metal-poor Stars HE 2148-2039 and HE 2155-2043
Goswami, Aruna; Purandardas, Meenakshi
We present elemental abundance results for HE 2148-2039 and HE 2155-2043 based on a detailed high-resolution spectroscopic analysis. The high-resolution Subaru/High Dispersion Spectrograph (HDS) spectra used for our analysis have a resolution of R ∼ 60,000. Although limited information based on photometry and low-resolution spectroscopy is availab…
Hubble Space Telescope imaging of the extremely metal-poor globular cluster EXT8 in Messier 31
Romanowsky, Aaron J.; Brodie, Jean P.; Larsen, Søren S.
We recently found the globular cluster (GC) EXT8 in M 31 to have an extremely low metallicity of [Fe/H] = −2.91 ± 0.04 using high-resolution spectroscopy. Here we present a colour-magnitude diagram (CMD) for EXT8, obtained with the Wide Field Camera 3 on board the Hubble Space Telescope. Compared with the CMDs of metal-poor Galactic GCs, we find t…
Spectroscopic and photometric observations of dwarf nova superoutbursts by the 3.8 m telescope Seimei and the Variable Star Network
Ruiz, Javier; Maehara, Hiroyuki; Namekata, Kosuke +58 more
We present spectroscopic and photometric observations of 17 dwarf-nova superoutbursts obtained by KOOLS-IFU mounted on the 3.8 m telescope Seimei at the Okayama Observatory of Kyoto University and through the Variable Star Network collaboration (VSNET). Our spectroscopic observations for six outbursts were performed within 1 d of their optical pea…
Energetic particle evolution during coronal mass ejection passage from 0.3 to 1 AU
Mitchell, D. G.; McComas, D. J.; Bale, S. D. +21 more
We provide analysis of a coronal mass ejection (CME) that passed over Parker Solar Probe (PSP) on January 20, 2020 when the spacecraft was at just 0.32 AU. The Integrated Science Investigation of the Sun instrument suite measures energetic particle populations associated with the CME before, during, and after its passage over the spacecraft. We ob…
Cooling Models for the Most Massive White Dwarfs
Schwab, Josiah
We present a set of ultramassive white dwarf models, focused on masses above 1.3 M⊙. Given the uncertainties about the formation and compositions of such objects, we construct parameterized model sequences, guided by evolutionary calculations including both single star and double white dwarf merger formation channels. We demonstrate tha…
Particle-In-Cell Simulations of Electrostatic Solitary Waves in Asymmetric Magnetic Reconnection
Wang, Shui; Lu, Quanming; Gao, Xinliang +5 more
Electrostatic solitary waves (ESWs) are ubiquitously observed in magnetic reconnection. In this study, two-dimensional (2-D) particle-in-cell (PIC) simulations are performed to investigate the characteristics of ESWs in asymmetric magnetic reconnection. ESWs with bipolar structures of the parallel electric field can be generated near the separatri…
Similar but different: the varied landscape of Onfp/Oef stars variability
Nazé, Yaël; Rauw, Gregor
The Oef category gathers rapidly rotating and evolved O-stars displaying a centrally reversed He II λ 4686 emission line. The origin of the variability of their photospheric and wind spectral lines is debated, with rotational modulation or pulsations as the main contenders. To shed new light on this question, we analysed high-quality and high-cade…
The ACTIONFINDER: An Unsupervised Deep Learning Algorithm for Calculating Actions and the Acceleration Field from a Set of Orbit Segments
Famaey, Benoit; Ibata, Rodrigo; Monari, Giacomo +1 more
We introduce the ACTIONFINDER, a deep learning algorithm designed to transform a sample of phase-space measurements along orbits in a static potential into action and angle coordinates. The algorithm finds the mapping from positions and velocities to actions and angles in an unsupervised way, by using the fact that points along the same orbit have…