Search Publications
A Multiepoch X-Ray Study of the Nearby Seyfert 2 Galaxy NGC 7479: Linking Column Density Variability to the Torus Geometry
Ajello, M.; Marchesi, S.; Torres-Albà, N. +3 more
Active galactic nuclei are powered by accreting supermassive black holes, surrounded by a torus of obscuring material. Recent studies have shown how the torus structure, formerly thought to be homogeneous, appears to be "patchy": the detection of variability in the line-of-sight hydrogen column density, in fact, matches the description of an obscu…
An Improved Magnetohydrodynamic Simulation of the 2006 December 13 Coronal Mass Ejection of NOAA Active Region 10930
Fan, Yuhong
We present a magnetohydrodynamic simulation of the coronal mass ejection on 2006 December 13 in the emerging δ-sunspot NOAA Active Region 10930, improving upon a previous simulation by Fan as follows. (1) Incorporate an ambient solar wind instead of using a static potential magnetic field extrapolation as the initial state. (2) In addition to impo…
Testing High-energy Emission Models for Blazars with X-Ray Polarimetry
Liodakis, Ioannis; Peirson, Abel L.; Romani, Roger W.
Both leptonic and hadronic emission processes may contribute to blazar jet emission; which dominates in blazars' high-energy emission component remains an open question. Some intermediate synchrotron peaked blazars transition from their low- to high-energy emission components in the X-ray band making them excellent laboratories to probe both compo…
Photometric and Spectroscopic Study of the EXor-like Eruptive Young Star Gaia19fct
Pál, András; Lee, Jeong-Eun; Ábrahám, Péter +19 more
Gaia19fct is one of the Gaia-alerted eruptive young stars that has undergone several brightening events. We conducted monitoring observations using multifilter optical and near-infrared photometry, as well as near-infrared spectroscopy, to understand the physical properties of Gaia19fct and investigate whether it fits into the historically defined…
A Light-curve Analysis of the X-Ray Flash First Observed in Classical Novae
Kato, Mariko; Hachisu, Izumi; Saio, Hideyuki
An X-ray flash, expected in a very early phase of a nova outburst, was at last detected with the SRG/eROSITA in the classical nova YZ Reticuli 2020. The observed flash timescale, luminosity, and blackbody temperature substantially constrain the nova model. We present light-curve models of the X-ray flash for various white dwarf (WD) masses and mas…
Probability of Forming Gaps in the GD-1 Stream by Close Encounters of Globular Clusters
Hattori, Kohei; Doke, Yuka
One of the most intriguing properties of the GD-1 stellar stream is the existence of three gaps. If these gaps were formed by close encounters with dark matter subhalos, the GD-1 stream opens an exciting window through which we can see the size, mass, and velocity distributions of the dark matter subhalos in the Milky Way. However, in order to use…
HAZMAT. VIII. A Spectroscopic Analysis of the Ultraviolet Evolution of K Stars: Additional Evidence for K Dwarf Rotational Stalling in the First Gigayear
Loyd, R. O. Parke; Jackman, James A. G.; Barman, Travis +7 more
Efforts to discover and characterize habitable zone planets have primarily focused on Sun-like stars and M dwarfs. K stars, however, provide an appealing compromise between these two alternatives that has been relatively unexplored. Understanding the ultraviolet (UV) environment around such stars is critical to our understanding of their planets, …
DUVET: Spatially Resolved Observations of Star Formation Regulation via Galactic Outflows in a Starbursting Disk Galaxy
Fielding, Drummond; Cameron, Alex J.; Kacprzak, Glenn G. +14 more
We compare 500 pc scale, resolved observations of ionized and molecular gas for the z ~ 0.02 starbursting disk galaxy IRAS08339+6517, using measurements from KCWI and NOEMA. We explore the relationship of the star-formation-driven ionized gas outflows with colocated galaxy properties. We find a roughly linear relationship between the outflow mass …
On the Formation of Solar Wind and Switchbacks, and Quiet Sun Heating
Tripathi, Durgesh; Upendran, Vishal
The solar coronal heating in quiet Sun (QS) and coronal holes (CHs), including solar wind formation, are intimately tied by magnetic field dynamics. Thus, a detailed comparative study of these regions is needed to understand the underlying physical processes. CHs are known to have subdued intensity and larger blueshifts in the corona. This work in…
Revisiting a Disky Origin for the Faint Branch of the Sagittarius Stellar Stream
Errani, Raphaël; Famaey, Benoit; Ibata, Rodrigo +2 more
We investigate ways to produce the bifurcation observed in the stellar stream of the Sagittarius dwarf galaxy (Sgr). Our method consists of running N-body simulations of Sgr falling into the Milky Way for the last 3 Gyr, with added test particles on disk orbits that span a wide range of initial positions, energies, and angular momenta. We find tha…