Search Publications
SDSS J075101.42+291419.1: A Super-Eddington Accreting Quasar with Extreme X-Ray Variability
Brandt, W. N.; Luo, B.; Gallagher, S. C. +6 more
We report the discovery of extreme X-ray variability in a type 1 quasar: SDSS J075101.42+291419.1. It has a black hole (BH) mass of 1.6 × 107 M ⊙ measured from reverberation mapping, and the BH is accreting with a super-Eddington accretion rate. Its XMM-Newton observation in 2015 May reveals a flux drop by a factor of ∼22 wit…
EVR-CB-001: An Evolving, Progenitor, White Dwarf Compact Binary Discovered with the Evryscope
Law, Nicholas M.; Kupfer, Thomas; Glazier, Amy +7 more
We present EVR-CB-001, the discovery of a compact binary with an extremely low-mass (0.21 ± 0.05M ⊙) helium core white dwarf progenitor (pre-He WD) and an unseen low-mass (0.32 ± 0.06M ⊙) helium white dwarf (He WD) companion. He WDs are thought to evolve from the remnant helium-rich core of a main-sequence star stripped durin…
Variable Stars in Terzan 5: Additional Evidence of Multi-age and Multi-iron Stellar Populations
Dalessandro, E.; Massari, D.; Contreras Ramos, R. +7 more
Terzan 5 is a complex stellar system in the Galactic bulge, harboring stellar populations (SPs) with very different iron content (Δ[Fe/H] ∼ 1 dex) and with ages differing by several gigayears. Here we present an investigation of its variable stars. We report on the discovery and characterization of three RR Lyrae stars. For these newly discovered …
The Origin of the Late-time Luminosity of Supernova 2011dh
Maund, Justyn R.
Due to the small amount of hydrogen (≤0.1 M ⊙) remaining on the surface of their progenitors, SNe IIb are sensitive probes of the mass-loss processes of massive stars toward the ends of their lives, including the role of binarity. We report late-time Hubble Space Telescope observations of SN 2011dh in M51, and a brief period of rebright…
A Trio of Massive Black Holes Caught in the Act of Merging
Shen, Yue; Nyland, Kristina; Li, Zhiyuan +6 more
We report the discovery of SDSS J0849+1114 as the first known triple Type 2 Seyfert nucleus. It represents three active black holes that are identified from new spatially resolved optical slit spectroscopy using the Dual Imaging Spectrograph on the 3.5 m telescope at the Apache Point Observatory. We also present new complementary observations incl…
RELICS: High-resolution Constraints on the Inner Mass Distribution of the z = 0.83 Merging Cluster RXJ0152.7-1357 from Strong Lensing
Ouchi, Masami; Mahler, Guillaume; Bradač, Maruša +37 more
Strong gravitational lensing (SL) is a powerful means of mapping the distribution of dark matter. In this work, we perform an SL analysis of the prominent X-ray cluster RXJ0152.7-1357 (z = 0.83, also known as CL0152.7-1357) in Hubble Space Telescope images, taken in the framework of the Reionization Lensing Cluster Survey (RELICS). On top of a pre…
An Inner Disk in the Large Gap of the Transition Disk SR 24S
Benisty, Myriam; Pinilla, Paola; Harsono, Daniel +3 more
We report new Atacama Large Millimeter/submillimeter Array (ALMA) Band 3 observations at 2.75 mm of the transition disk around SR 24S, with an angular resolution of ∼0.″11 × 0.″09 and a peak signal-to-noise ratio of ∼24. We detect an inner disk and a mostly symmetric ring-like structure that peaks at ∼0.″32, which is ∼37 au at a distance of ∼114.4…
The Extremely High Dark Matter Halo Concentration of the Relic Compact Elliptical Galaxy Mrk 1216
Barth, Aaron J.; Buote, David A.
Spatially compact stellar profiles and old stellar populations have established compact elliptical galaxies (CEGs) as local analogs of the high-redshift “red nuggets” thought to represent the progenitors of today’s early-type galaxies (ETGs). To address whether the structure of the dark matter (DM) halo in a CEG also reflects the extremely quiesce…
The Structure of the Orion Nebula in the Direction of θ 1 Ori C
Abel, N. P.; O'Dell, C. R.; Ferland, G. J.
We have used existing optical emission and absorption lines, [C II] emission lines, and H I absorption lines to create a new model for a central column of material near the Trapezium region of the Orion Nebula. This was necessary because recent high spectral resolution spectra of optical emission lines and imaging spectra in the [C II] 158 µ…
Efficient Calculation of Non-local Thermodynamic Equilibrium Effects in Multithreaded Hydrodynamic Simulations of Solar Flares
Warren, Harry P.; Crump, Nicholas A.; Bradshaw, Stephen J. +1 more
Understanding the dynamics of the chromosphere is crucial to understanding energy transport across the solar atmosphere. The chromosphere is optically thick at many wavelengths and described by non-local thermodynamic equilibrium (NLTE), making it difficult to interpret observations. Furthermore, there is considerable evidence that the atmosphere …