Search Publications
Exploring Changes in Quasar Spectral Energy Distributions across C IV Parameter Space
Gallagher, Sarah C.; Richards, Gordon T.; Shemmer, Ohad +4 more
We examine the UV/X-ray properties of 1378 quasars in order to link empirical correlations to theoretical models of the physical mechanisms dominating quasars as a function of mass and accretion rate. The clarity of these correlations is improved when (1) using C IV broad emission line equivalent width (EQW) and blueshift (relative to systemic) va…
The Obscured Fraction of Quasars at Cosmic Noon
Sawicki, Marcin; Schramm, Malte; Gwyn, Stephen +6 more
Statistical studies of X-ray selected active galactic nuclei (AGN) indicate that the fraction of obscured AGN increases with increasing redshift, and the results suggest that a significant part of the accretion growth occurs behind obscuring material in the early universe. We investigate the obscured fraction of highly accreting X-ray AGN at aroun…
The Relation between the Mass Accretion Rate and the Disk Mass in Class I Protostars
Kóspál, Ágnes; Fiorellino, Eleonora; Cruz-Sáenz de Miera, Fernando +5 more
Evidence of a relation between the mass accretion rate and the disk mass is established for young, Class II pre-main-sequence stars. This observational result opened an avenue to test theoretical models and constrain the initial conditions of disk formation, fundamental in the understanding of the emergence of planetary systems. However, it is bec…
K2 Photometry on Oscillation Mode Variability: The New Pulsating Hot B Subdwarf Star EPIC 220422705
Ma, Xiao-Yu; Zong, Weikai; Fu, Jian-Ning +4 more
We present an analysis of oscillation mode variability in the hot B subdwarf star EPIC 220422705, a new pulsator discovered from ~78 days of K2 photometry. The high-quality light curves provide a detection of 66 significant independent frequencies, from which we identified nine incomplete potential triplets and three quintuplets. Those g- and p-mu…
Simultaneous Observations of Chromospheric Evaporation and Condensation during a C-class Flare
Li, Dong; Hong, Zhenxiang; Ning, Zongjun
We explored simultaneous observations of chromospheric evaporation and condensation during the impulsive phase of a C6.7 flare on 2019 May 9. The solar flare was simultaneously observed by multiple instruments, i.e., the New Vacuum Solar Telescope (NVST), the Interface Region Imaging Spectrograph, the Atmospheric Imaging Assembly (AIA), Fermi, the…
X-Ray Reverberation Mapping of Ark 564 Using Gaussian Process Regression
Ingram, Adam; Reynolds, Christopher S.; García, Javier A. +15 more
Ark 564 is an extreme high-Eddington narrow-line Seyfert 1 galaxy, known for being one of the brightest, most rapidly variable soft X-ray active galactic nuclei (AGN), and for having one of the lowest temperature coronae. Here, we present a 410 ks NuSTAR observation and two 115 ks XMM-Newton observations of this unique source, which reveal a very …
Rapid Bursts of Magnetically Gated Accretion in the Intermediate Polar V1025 Cen
Garnavich, Peter; Littlefield, Colin; Szkody, Paula +5 more
Magnetically gated accretion has emerged as a proposed mechanism for producing extremely short, repetitive bursts of accretion onto magnetized white dwarfs in intermediate polars (IPs), but this phenomenon has not been detected previously in a confirmed IP. We report the 27 day TESS light curve of V1025 Cen, an IP that shows a remarkable series of…
Grain Alignment in the Circumstellar Shell of IRC+10° 216
Sandin, Christer; Soam, Archana; Hoang, Thiem +7 more
Dust-induced polarization in the interstellar medium (ISM) is due to asymmetric grains aligned with an external reference direction, usually the magnetic field. For both the leading alignment theories, the alignment of the grain's angular momentum with one of its principal axes and the coupling with the magnetic field requires the grain to be para…
ALMA Uncovers Highly Filamentary Structure toward the Sgr E Region
Mills, E. A. C.; Anderson, L. D.; Battersby, C. +7 more
We report on the discovery of linear filaments observed in the CO(1-0) emission for a ~2' field of view toward the Sgr E star-forming region, centered at (l, b) = (358.°720, 0.°011). The Sgr E region is thought to be at the turbulent intersection of the "far dust lane" associated with the Galactic bar and the Central Molecular Zone (CMZ). This reg…
Constraining the CME Core Heating and Energy Budget with SOHO/UVCS
Reeves, Katharine K.; Raymond, John C.; Shen, Chengcai +4 more
We describe the energy budget of a coronal mass ejection (CME) observed on 1999 May 17 with the Ultraviolet Coronagraph Spectrometer (UVCS). We constrain the physical properties of the CME's core material as a function of height along the corona by using the spectra taken by the single-slit coronagraph spectrometer at heliocentric distances of 2.6…