Search Publications
Strong and Rapid X-Ray Variability of the Super-Eddington Accreting Quasar SDSS J081456.10+532533.5
Brandt, W. N.; Garmire, Gordon P.; Luo, Bin +6 more
We report strong and rapid X-ray variability found from the super-Eddington accreting quasar SDSS J081456.10+532533.5 at z = 0.1197. It has a black hole mass of 2.7 × 107 M ⊙ and a dimensionless accretion rate of ≈4 measured from reverberation-mapping observations. It showed weak X-ray emission in the 2021 February Chandra ob…
Denoising Diffusion Probabilistic Models to Predict the Density of Molecular Clouds
Xu, Duo; Tan, Jonathan C.; Hsu, Chia-Jung +1 more
We introduce the state-of-the-art deep-learning denoising diffusion probabilistic model as a method to infer the volume or number density of giant molecular clouds (GMCs) from projected mass surface density maps. We adopt magnetohydrodynamic simulations with different global magnetic field strengths and large-scale dynamics, i.e., noncolliding and…
Photometric Calibrations of M-dwarf Metallicity with Markov Chain Monte Carlo and Bayesian Inference
Caballero, J. A.; Montes, D.; Duque-Arribas, C. +3 more
Knowledge of stellar atmospheric parameters (T eff, $\mathrm{log}g$ , [Fe/H]) of M dwarfs can be used to constrain both theoretical stellar models and Galactic chemical evolutionary models, and guide exoplanet searches, but their determination is difficult due to the complexity of the spectra of their cool atmospheres. In our ongoing ef…
The X-Ray Binary-star Cluster Connection in Late-type Galaxies
Chandar, Rupali; Maccarone, Thomas J.; Thilker, David A. +3 more
We conduct one of the largest systematic investigations of bright X-ray binaries (XRBs) in both young star clusters and ancient globular clusters (GCs) using a sample of six nearby star-forming galaxies. Combining complete CXO X-ray source catalogs with optical Physics at High Angular Resolution in Nearby Galaxies-Hubble Space Telescope cluster ca…
Environmental Impacts on the Rest-frame UV Size and Morphology of Star-forming Galaxies at z 2
Koyama, Yusei; Kodama, Tadayuki; Shimakawa, Rhythm +1 more
We report the measurement of rest-frame UV size and morphology of Hα-emission-selected star-forming galaxies (HAEs) in four protoclusters at z ~ 2 (PKS 1138-262, USS 1558-003, PHz G237.0+42.5, and CC 2.2) using archival Hubble Space Telescope Advanced Camera Survey (HST/ACS) F814W data. We compare the measurement of 122 HAEs in protoclusters detec…
Multiwavelength Characterization of the High-mass X-Ray Binary Population of M33
Williams, Benjamin F.; Eracleous, Michael; Dalcanton, Julianne J. +12 more
We present multiwavelength characterization of 65 high-mass X-ray binary (HMXB) candidates in M33. We use the Chandra ACIS survey of M33 (ChASeM33) catalog to select hard X-ray point sources that are spatially coincident with UV-bright point-source optical counterparts in the Panchromatic Hubble Andromeda Treasury: Triangulum Extended Region catal…
A New Physical Picture for Active Galactic Nuclei Lacking Optical Emission Lines
Ellison, Sara L.; Faber, S. M.; Salim, Samir +2 more
In this work, we use ~500 low-redshift (z ~ 0.1) X-ray active galactic nuclei (AGNs) observed by XMM-Newton and the Sloan Digital Sky Survey (SDSS) to investigate the prevalence and nature of AGNs that apparently lack optical emission lines ("optically dull AGNs"). Although one quarter of spectra appear absorption-line dominated in visual assessme…
Mass Distribution for Single-lined Hot Subdwarf Stars in LAMOST
Németh, Péter; Yang, Yong; Zhao, Jingkun +4 more
Masses for 664 single-lined hot subdwarf stars identified in LAMOST were calculated by comparing synthetic fluxes from spectral energy distribution with observed fluxes from a Virtual Observatory service. Three groups of hot subdwarf stars were selected from the whole sample according to their parallax precision to study the mass distributions. We…
The Radio Parallax of the Crab Pulsar: A First VLBI Measurement Calibrated with Giant Pulses
Deller, Adam T.; Kirsten, Franz; van Kerkwijk, Marten H. +2 more
We use four observations with the European very long baseline interferometry (VLBI) network to measure the first precise radio parallax of the Crab Pulsar. We found two in-beam extragalactic sources just outside the Crab Nebula, with one bright enough to use as a background reference source in our data. We use the Crab Pulsar's giant pulses to det…
Understanding the Deflection of the "Cartwheel CME": Data Analysis and Modeling
Vourlidas, Angelos; Balmaceda, Laura A.; Cécere, Mariana +1 more
We study the low corona evolution of the "Cartwheel" coronal mass ejection (CME; 2008 April 9) by reconstructing its three-dimensional path and modeling it with magnetohydrodynamic simulations. This event exhibited a double deflection that has been reported and analyzed in previous works but whose underlying cause remained unclear. The Cartwheel C…