Search Publications
A speckle-imaging search for close and very faint companions to the nearest and brightest Wolf-Rayet stars
Moffat, Anthony F. J.; Howell, Steve B.; Shara, Michael M. +4 more
Gravitationally bound companions to stars enable determinations of their masses, and offer clues to their formation, evolution, and dynamical histories. So motivated, we have carried out a speckle imaging survey of eight of the nearest and brightest Wolf-Rayet (WR) stars to directly measure the frequency of their resolvable companions, and to sear…
New globular cluster candidates in the M81 group
Bell, Eric F.; Monachesi, Antonela; Bailin, Jeremy +7 more
The study of outer halo globular cluster (GC) populations can give insight into galaxy merging, GC accretion, and the origin of GCs. We use archival Subaru Hyper Suprime-Cam (HSC) data in concert with space-based GALEX, IRAC, and Gaia EDR3 data to select candidate GCs in the outer halo of the M81 group for confirmation and future study. We use a s…
Lessons from the Magellanic System and its modeling
Hammer, Francois; Wang, Jianling; Yang, Yanbin
The prominent Magellanic Stream that dominates the H I sky provides a tantalizing number of observations that potentially constrains the Magellanic Clouds and the Milky Way (MW) outskirts. Here we show that the 'ram-pressure plus collision' model naturally explain these properties, and is able to predict some of the most recent observations made a…
Measurement of redshift-space two- and three-point correlation of Lyα absorbers at 1.7 < z < 3.5: implications on evolution of the physical properties of IGM
Srianand, Raghunathan; Gaikwad, Prakash; Maitra, Soumak
We present redshift-space two-point (ξ), three-point (ζ), and reduced three-point (Q) correlation of Lyα absorbers (Voigt profile components having H I column density, NH I > 1013.5 cm-2) over three redshift bins spanning 1.7 < z < 3.5 using high-resolution spectra of 292 quasars. We detect posi…
A machine learning approach to photometric metallicities of giant stars
Sanders, Jason L.; Fallows, Connor P.
Despite the advances provided by large-scale photometric surveys, stellar features - such as metallicity - generally remain limited to spectroscopic observations often of bright, nearby low-extinction stars. To rectify this, we present a neural network approach for estimating the metallicities and distances of red giant stars with 8-band photometr…
No globular cluster progenitors in Milky Way satellite galaxies
Bovy, Jo; Boldrini, Pierre
In order to find the possible progenitors of Milky Way (MW) globular clusters, we perform orbit integrations to track the orbits of 170 Galactic globular clusters and the 11 classical MW satellite galaxies backwards in time for 11 Gyr in an MW-plus-satellites potential including the response of the MW to the infall of the Large Magellanic Cloud an…
The escape of globular clusters from the satellite dwarf galaxies of the Milky Way
Haghi, Hosein; Zonoozi, Akram Hasani; Khalaj, Pouria +2 more
Using numerical simulations, we have studied the escape of globular clusters (GCs) from the satellite dwarf spheroidal galaxies (dSphs) of the Milky Way (MW). We start by following the orbits of a large sample of GCs around dSphs in the presence of the MW potential field. We then obtain the fraction of GCs leaving their host dSphs within a Hubble …
The impact of stellar clustering on the observed multiplicity of super-earth systems: outside-in cascade of orbital misalignments initiated by stellar flybys
Rodet, Laetitia; Lai, Dong
A recent study suggests that the observed multiplicity of super-Earth (SE) systems is correlated with stellar overdensities: field stars in high phase-space density environments have an excess of single-planet systems compared to stars in low-density fields. This correlation is puzzling as stellar clustering is expected to influence mostly the out…
Improved hydrodynamic pulsation models for the pulsating extreme helium star V652 Herculis
Saio, Hideyuki; Jeffery, C. Simon; Montañés-Rodríguez, Pilar
New non-linear hydrodynamic models have been constructed to simulate the radial pulsations observed in the extreme helium star V652 Her. These use a finer zoning to allow higher radial resolution than in previous simulations. Models incorporate updated OPAL and OP opacity tables and adopt a composition based on the best atmospheric analyses to dat…
Doubling of minute-long quasi-periodic pulsations from super-flares on a low-mass star
Ramsay, Gavin; Irawati, Puji; Dhillon, Vik S. +5 more
Using the ULTRASPEC instrument mounted on the 2.4-m Thai National Telescope, we observed two large flares, each with a total energy close to 1034 erg with sub-second cadence. A combination of a wavelet analysis, a Fourier transform plus an empirical mode decomposition, reveals quasi-periodic pulsations (QPPs) that exhibit an apparent do…