Search Publications
A "Hyperburst" in the MAXI J0556-332 Neutron Star: Evidence for a New Type of Thermonuclear Explosion
Homan, Jeroen; Wijnands, Rudy; Degenaar, Nathalie +5 more
The study of transiently accreting neutron stars provides a powerful means to elucidate the properties of neutron star crusts. We present extensive numerical simulations of the evolution of the neutron star in the transient low-mass X-ray binary MAXI J0556-332. We model nearly 20 observations obtained during the quiescence phases after four differ…
NuSTAR Observations of Intrinsically X-Ray Weak Quasar Candidates: An Obscuration-only Scenario
Stern, D.; Alexander, D. M.; Bauer, F. E. +6 more
We utilize recent NuSTAR observations (co-added depth ≈55-120 ks) of PG 1001+054, PG 1254+047, and PHL 1811 to constrain their hard X-ray (≳5 keV) weakness and spectral shapes and thus to investigate the nature of their extreme X-ray weakness. These quasars showed very weak soft X-ray emission, and they were proposed to be intrinsically X-ray weak…
Extreme Variation in Star Formation Efficiency across a Compact, Starburst Disk Galaxy
Bolatto, A. D.; Fisher, D. B.; Glazebrook, K. +4 more
We report on the internal distribution of star formation efficiency in IRAS 08339+6517 (hereafter IRAS08), using ~200 pc resolution CO(2 - 1) observations from NOEMA. The molecular gas depletion time changes by 2 orders-of-magnitude from disk-like values in the outer parts to less than 108 yr inside the half-light radius. This translate…
The Stellar-age Dependence of X-Ray Emission from Normal Star-forming Galaxies in the GOODS Fields
Williams, Benjamin F.; Brandt, William N.; Luo, Bin +11 more
The Chandra Deep Field-South and North surveys (CDFs) provide unique windows into the cosmic history of X-ray emission from normal (nonactive) galaxies. Scaling relations of normal-galaxy X-ray luminosity (L X) with star formation rate (SFR) and stellar mass (M ⋆) have been used to show that the formation rates of low-mass an…
Embedded Young Massive Star Clusters in the Antennae Merger
Johnson, Kelsey; He, Hao; Wilson, Christine +3 more
The properties of young massive clusters (YMCs) are key to understanding the star formation mechanism in starburst systems, especially mergers. We present Atacama Large Millimeter/submillimeter Array high-resolution (~10 pc) continuum (100 and 345 GHz) data of YMCs in the overlap region of the Antennae galaxy. We identify six sources in the overla…
Dynamical Masses of the Primary Be Star and Secondary sdB Star in the Single-lined Binary κ Dra (B6 IIIe)
Gies, Douglas R.; Wang, Luqian; Klement, Robert +16 more
Because many classical Be stars may owe their nature to mass and angular-momentum transfer in a close binary, the present masses, temperatures, and radii of their components are of high interest for comparison to stellar evolution models. Object κ Dra is a 61.5 day single-lined binary with a B6 IIIe primary. With the CHARA Array instruments MIRC/M…
Stars That Approach within One Parsec of the Sun: New and More Accurate Encounters Identified in Gaia Data Release 3
Bailer-Jones, C. A. L.
Close encounters of stars to the Sun could affect life on Earth through gravitational perturbations of comets in the Oort cloud or exposure to ionizing radiation. By integrating orbits through the Galactic potential, I identify which of 33 million stars in Gaia DR3 with complete phase space information come close to the Sun. 61 stars formally appr…
NuSTAR Observations of AGNs with Low Observed X-Ray to [O III] Luminosity Ratios: Heavily Obscured AGNs or Turned-off AGNs?
Stern, Daniel; García, Javier A.; Malkan, Matthew A. +2 more
Type 2 active galactic nuclei (AGNs) show signatures of accretion onto a supermassive black hole through strong, high-ionization, narrow emission lines extended on scales of hundreds to thousands of parsecs, but they lack the broad emission lines from close in to the black hole that characterize type 1 AGNs. The lack of broad emission could indica…
Accretion Disk Outflow during the X-Ray Flare of the Super-Eddington Active Nucleus of I Zwicky 1
Ho, Luis C.; Ricci, Claudio; Li, Ruancun +1 more
We present a detailed X-ray spectral analysis of the narrow-line Seyfert 1 galaxy I Zwicky 1, for which a sequence of X-ray flares were detected during a long, simultaneous observation acquired with XMM-Newton and NuSTAR. We determine the key parameters of the inner accretion disk and hot corona in the context of the disk reflection model, which s…
The Effect of Current on Magnetic Null Topology during Turbulent Reconnection
Wang, Z.; Cao, J. B.; Liu, Y. Y. +5 more
Using data from the Cluster mission and the First-Order Taylor Expansion method, we investigate the spiral magnetic nulls nested in the diffusion region of turbulent reconnection in the magnetotail. We particularly focus on the relation between the magnetic null topologies and currents, which can be decomposed into a component perpendicular to spi…