Search Publications
On the Migration Origin of the Hercules Moving Group with GAIA, LAMOST, APOGEE, and GALAH Surveys
Wu, Yaqian; Zhao, Jingkun; Yoon, Suk-Jin +3 more
Using Gaia DR3 data and the wavelet transformation technique, we study the substructures of the Hercules moving group (HMG): Hercules 1 (H1) and Hercules 2 (H2). Spectroscopic survey data from LAMOST, APOGEE, and GALAH are used to obtain metallicities and ages of stars belonging to the HMG. Our analysis leads to several key findings as follows: (a…
The effect of variations in the magnetic field direction from turbulence on kinetic-scale instabilities
Verscharen, Daniel; Chen, Christopher H. K.; Opie, Simon +2 more
At kinetic scales in the solar wind, instabilities transfer energy from particles to fluctuations in the electromagnetic fields while restoring plasma conditions towards thermodynamic equilibrium. We investigate the interplay between background turbulent fluctuations at the small-scale end of the inertial range and kinetic instabilities acting to …
The Influence of the Galactic Bar on the Dynamics of Globular Clusters
Carraro, Giovanni; Korchagin, Vladimir; Tkachenko, Roman +2 more
We make use of recent estimates for the parameters of the Milky Way's halo globular clusters and study the influence of the galactic bar on the dynamics of these clusters by computing their orbits. We use both an axisymmetric and non-axisymmetric galactic potentials, which include the rotating elongated bar/bulge structure. We account for observat…
Coronal height constraint in IRAS 13224-3809 and 1H 0707-495 by the random forest regressor
Chainakun, P.; Young, A. J.; Luangtip, W. +1 more
We develop a random forest regressor (RFR) machine learning model to trace the coronal evolution in two highly variable active galactic nuclei (AGNs) IRAS 13224-3809 and 1H 0707-495 observed with XMM-Newton, by probing the X-ray reverberation features imprinted on their power spectral density (PSD) profiles. Simulated PSDs in the form of a power l…
NGC 4388: a test case for relativistic disc reflection and Fe K fluorescence features
LaMassa, S.; Yaqoob, Tahir; Tzanavaris, P.
We present a new analysis of the Suzaku X-ray spectrum of the Compton-thin Seyfert 2 galaxy NGC 4388. The spectrum above ~2 keV can be described by a remarkably simple and rather mundane model, consisting of a uniform, neutral spherical distribution of matter, with a radial column density of $2.58\pm 0.02 \times 10^{23} \ \rm cm^{-2}$, and an Fe a…
An Extremely Massive White Dwarf Escaped from the Hyades Star Cluster
El-Badry, Kareem; Rodriguez, Antonio C.; van Roestel, Jan +5 more
We searched the Gaia DR3 database for ultramassive white dwarfs with kinematics consistent with having escaped the nearby Hyades open cluster, identifying three such candidates. Two of these candidates have masses estimated from Gaia photometry of approximately 1.1 solar masses; their status as products of single-stellar evolution that have escape…
New evidence about HW Vir's circumbinary planets from Hipparcos-Gaia astrometry and a reanalysis of the eclipse timing variations using nested sampling
Triaud, Amaury H. M. J.; Kervella, Pierre; Baycroft, Thomas A.
The post common-envelope eclipsing binary HW Virginis (HW Vir) has had many circumbinary companions proposed based on eclipse timing variations. Each proposed solution has lacked in predictability and orbital stability, leaving the origin of the eclipse timing variations an active area of research. Leveraging the catalogue of Hipparcos and Gaia pr…
Near-IR photometry of the small Uranian satellites with Keck at phase angles 0-2°
de Pater, Imke; Moeckel, Chris; Paradis, Samuel
We present photometric measurements of the seven brightest small inner moons of Uranus (Puck, Belinda, Rosalind, Portia, Juliet, Desdemona and Cressida) obtained with the Keck II telescope at 1.6 and 2 . 2 µm at phase angles of 0.026∘ and 0.36∘ in October-November 2019. We also applied our new calibration technique to the August 2015 data at…
The Differential Assembly History of the Centers and Outskirts of Main-sequence Galaxies at z 2.3
Giavalisco, Mauro; Ji, Zhiyuan; Cutler, Sam E. +1 more
We present a study of spatially resolved star formation histories (SFHs) for 60 z ~ 2.3 main-sequence, star-forming galaxies selected from the MOSDEF spectroscopic survey in the GOODS-N field, with median stellar mass $\mathrm{log}({M}_{\star }/{M}_{\odot })$ = 9.75 and spanning the range $8.6\lt \mathrm{log}({M}_{\star }/{M}_{\odot })\lt 11.5$ . …
Multiple stellar populations found outside the tidal radius of NGC 1851 via Gaia DR3 XP spectra
Milone, Antonino P.; Lagioia, Edoardo P.; Marino, Anna F. +6 more
Aims: Ancient galactic globular clusters (GCs) have long fascinated astronomers due to their intriguing multiple stellar populations (MPs), which are characterized by variations in light element abundances. Among these clusters, type II GCs stand out as they exhibit stars with large differences in heavy-element chemical abundances. These enig…