Search Publications
Luminosity Models and Density Profiles for Nuclear Star Clusters for a Nearby Volume-limited Sample of 29 Galaxies
Pechetti, Renuka; Neumayer, Nadine; Kacharov, Nikolay +3 more
Nuclear star clusters (NSCs) are dense stellar clusters that are found at the centers of a majority of galaxies. In this paper, we study the density profiles for 29 galaxies in a volume-limited survey within 10 Mpc to characterize their NSCs. These galaxies span a 3 × 108-8 × 1010 M⊙ and a wide range of Hubble type…
A New Class of Roche Lobe-filling Hot Subdwarf Binaries
Duev, Dmitry A.; Szkody, Paula; Littlefair, S. P. +30 more
We present the discovery of the second binary with a Roche lobe-filling hot subdwarf transferring mass to a white dwarf (WD) companion. This 56 minute binary was discovered using data from the Zwicky Transient Facility. Spectroscopic observations reveal an He-sdOB star with an effective temperature of Teff = 33,700 ± 1000 K and a surfac…
HAZMAT VI: The Evolution of Extreme Ultraviolet Radiation Emitted from Early M Stars
Loyd, R. O. Parke; Peacock, Sarah; Barman, Travis +4 more
Quantifying the evolution of stellar extreme ultraviolet (EUV, 100-1000 Å) emission is critical for assessing the evolution of planetary atmospheres and the habitability of M dwarf systems. Previous studies from the HAbitable Zones and M dwarf Activity across Time (HAZMAT) program showed the far- and near-UV (FUV, NUV) emission from M stars at var…
SCExAO/CHARIS Direct Imaging Discovery of a 20 au Separation, Low-mass Ratio Brown Dwarf Companion to an Accelerating Sun-like Star
Currie, Thayne; Kwon, Jungmi; Tamura, Motohide +27 more
We present the direct imaging discovery of a substellar companion to the nearby Sun-like star, HD 33632 Aa, at a projected separation of ∼20 au, obtained with SCExAO/CHARIS integral field spectroscopy complemented by Keck/NIRC2 thermal infrared imaging. The companion, HD 33632 Ab, induces a 10.5σ astrometric acceleration on the star as detected wi…
A Relationship between Stellar Age and Spot Coverage
Morris, Brett M.
We investigate starspot distributions consistent with space-based photometry of F, G, and K stars in six stellar associations ranging in age from 10 Myr to 4 Gyr. We show that a simple light-curve statistic called the "smoothed amplitude" is proportional to stellar age as t-1/2, following a Skumanich-like spin-down relation. We marginal…
A Deep CFHT Optical Search for a Counterpart to the Possible Neutron Star-Black Hole Merger GW190814
Safi-Harb, Samar; Drout, Maria R.; Moon, Dae-Sik +10 more
We present a wide-field optical imaging search for electromagnetic counterparts to the likely neutron star-black hole (NS-BH) merger GW190814/S190814bv. This compact binary merger was detected through gravitational waves by the LIGO/Virgo interferometers, with masses suggestive of an NS-BH merger. We imaged the LIGO/Virgo localization region using…
The Variable and Non-variable X-Ray Absorbers in Compton-thin Type II Active Galactic Nuclei
Nikutta, Robert; Laha, Sibasish; Markowitz, Alex G. +3 more
We have conducted an extensive X-ray spectral variability study of a sample of 20 Compton-thin type II galaxies using broadband spectra from XMM-Newton, Chandra, and Suzaku. The aim is to study the variability of the neutral intrinsic X-ray obscuration along the line of sight and investigate the properties and location of the dominant component of…
Spitzer Follow-up of Extremely Cold Brown Dwarfs Discovered by the Backyard Worlds: Planet 9 Citizen Science Project
Debes, John H.; Kiman, Rocio; Meisner, Aaron M. +38 more
We present Spitzer follow-up imaging of 95 candidate extremely cold brown dwarfs discovered by the Backyard Worlds: Planet 9 citizen science project, which uses visually perceived motion in multiepoch Wide-field Infrared Survey Explorer (WISE) images to identify previously unrecognized substellar neighbors to the Sun. We measure Spitzer [3.6]-[4.5…
Detection of Strong Epicyclic Density Spikes in the GD-1 Stellar Stream: An Absence of Evidence for the Influence of Dark Matter Subhalos?
Martin, Nicolas; Malhan, Khyati; Famaey, Benoit +3 more
The density variations in thin stellar streams may encode important information on the nature of dark matter. For instance, if dark matter aggregates into massive subhalos, these perturbers are expected to scatter stars out of dynamically cold stellar streams, possibly leading to detectable gaps in those structures. Here, we reexamine the density …
Ubiquitous Molecular Outflows in z > 4 Massive, Dusty Galaxies. I. Sample Overview and Clumpy Structure in Molecular Outflows on 500 pc Scales
Gonzalez, Anthony H.; Phadke, Kedar A.; Aravena, Manuel +14 more
Massive galaxy-scale outflows of gas are one of the most commonly invoked mechanisms to regulate the growth and evolution of galaxies throughout the universe. While the gas in outflows spans a large range of temperatures and densities, the cold molecular phase is of particular interest because molecular outflows may be capable of suppressing star …