Search Publications
Structure of a Quasi-parallel Shock Front
Zhang, Tielong; Gedalin, Michael; Walker, Simon N. +2 more
The aim of this study is to compare observations of the magnetic field structure of observed quasi-parallel collisionless shock fronts with the results obtained analytically. A two-fluid analytic model of the shock front structure was derived under the assumptions that the shock is stationary and planar. The ion and electron kinetic pressures were…
Point-source Contribution to the Diffuse X-Ray Background below 1 keV and Its Effect on Our Understanding of the Circumgalactic Medium
Gupta, Anjali; Galeazzi, Massimiliano; Ursino, Eugenio +4 more
We studied the spectral signature of different components of the diffuse X-ray background (DXB), including Local Hot Bubble, solar wind charge exchange, galactic halo, and typically unresolved point sources (galaxies and active galactic nuclei), in the direction of the Chandra Deep Field South using the 4 Ms XMM-Newton survey and Chandra 4 Ms Sour…
Observations of Multiphase, High-velocity, Shocked Gas in the Vela Supernova Remnant
Ritchey, Adam M.
We present an analysis of high-resolution far-UV archival spectra obtained with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope of the star HD 75309, which probes high-velocity shocked gas in the Vela supernova remnant (SNR). We examine high-velocity features from intrinsically strong absorption lines of O I, Si II, Si II*, …
Population of X-Ray Sources in the Intermediate-age Cluster NGC 3532: a Test Bed for Machine-learning Classification
Kargaltsev, Oleg; Chen, Steven; Yang, Hui +4 more
Open clusters are thought to be the birthplace of most stars in the galaxy. Thus, they are excellent laboratories for investigating stellar evolution, and X-ray properties of various types of stars (including binary stars, evolved stars, and compact objects). In this work, we investigate the population of X-ray sources in the nearby 300 Myr old op…
The [O III] Profiles of Far-infrared Active and Inactive Optically Selected Green Valley Galaxies
Pović, Mirjana; Väisänen, Petri; Márquez, Isabel +8 more
We present a study of the [O III] λ5007 line profile in a subsample of eight active galactic nuclei (AGNs) and six non-AGNs in the optically selected green valley at z < 0.5 using long-slit spectroscopic observations obtained with the 11 m Southern African Large Telescope. Gaussian decomposition of the line profile was performed to study its di…
G 68-34: A Double-lined M-dwarf Eclipsing Binary in a Hierarchical Triple System
Charbonneau, David; Pass, Emily K.
Using high-resolution spectra from the Tillinghast Reflector Echelle Spectrograph and photometry from sector 56 of the Transiting Exoplanet Survey Satellite, we report that the nearby M dwarf G 68-34 is a double-lined eclipsing binary. The pair is spin-orbit synchronized with a period of 0.655 days. The light curve shows significant spot modulatio…
Nonthermal X-Rays from Pulsation-driven Shocks in Cepheids
Drake, Jeremy J.; Evans, Nancy Remage; Fraschetti, Federico +1 more
Rapid X-ray phase-dependent flux enhancement in the archetype classical Cepheid star δ Cep was observed by XMM-Newton and Chandra. We jointly analyze thermal and nonthermal components of the time-resolved X-ray spectra prior to, during, and after the enhancement. A comparison of the timescales of shock particle acceleration and energy losses is co…
Investigations of Flaring Plasma Parameters during an M-class Flare Using the Differential Evolution Method and XSM/Chandrayaan-2 Observations
Awasthi, Arun Kumar; Sylwester, Barbara; Sylwester, Janusz +2 more
We employ the differential evolution (DE) method to analyze observations from the Solar X-Ray Monitor on board the Chandrayaan-2 spacecraft. DE belongs to the family of evolutionary algorithms that find solutions using mechanisms inspired by biological processes. This approach enables us to simultaneously calculate the distribution of the differen…
Detecting and Characterizing Young Quasars. III. The Impact of Gravitational Lensing Magnification
Hennawi, Joseph F.; Belli, Sirio; Tacchella, Sandro +8 more
We test the impact of gravitational lensing on the lifetime estimates of seven high-redshift quasars at redshift z ≳ 6. The targeted quasars are identified by their small observed proximity zone sizes, which indicate extremely short quasar lifetimes (t Q ≲ 105yr). However, these estimates of quasar lifetimes rely on the ass…
Magellanic System Stars Identified in SMACS J0723.3-7327 James Webb Space Telescope Early Release Observations Images
Holwerda, Benne W.; Koekemoer, Anton M.; Pirzkal, Nor +23 more
We identify 71 distant stars in James Webb Space Telescope/NIRCam early release observations (ERO) images of the field of galaxy cluster SMACS J0723.3-7327 (SMACS 0723). Given the relatively small (~10°) angular separation between SMACS 0723 and the Large Magellanic Cloud (LMC), it is likely that these stars are associated with the LMC outskirts o…