Search Publications
The Missing Link? Discovery of Pulsations in the Nitrogen-rich PG 1159 Star PG 1144+005
Jones, David; Handler, Gerald; Sowicka, Paulina +1 more
Up to 98% of all single stars will eventually become white dwarfs-stars that link the history and future evolution of the Galaxy, and whose previous evolution is engraved in their interiors. Those interiors can be studied using asteroseismology, utilizing stellar pulsations as seismic waves. The pulsational instability strips of DA and DB white dw…
X-Ray Constraints on the Hot Gas Content of Early-type Galaxies in Virgo
Jones, Christine; Li, Zhiyuan; Hou, Meicun +2 more
We present a systematic study of the diffuse hot gas around early-type galaxies (ETGs) residing in the Virgo cluster, based on archival Chandra observations. Our representative sample consists of 79 galaxies with low-to-intermediate stellar masses (M* ≈ 109-11 M⊙), a mass range that has not been extensively explore…
Tracing the Ionization Structure of the Shocked Filaments of NGC 6240
Kewley, Lisa J.; Heckman, Timothy M.; Calzetti, Daniela +14 more
We study the ionization and excitation structure of the interstellar medium in the late-stage gas-rich galaxy merger NGC 6240 using a suite of emission-line maps at ~25 pc resolution from the Hubble Space Telescope, Keck/NIRC2 with Adaptive Optics, and the Atacama Large Millimeter/submillimeter Array (ALMA). NGC 6240 hosts a superwind driven by in…
Surveying the Giant H II Regions of the Milky Way with SOFIA. III. W49A
Lim, Wanggi; Karnath, Nicole; De Buizer, James M. +2 more
We present our third set of results from our mid-infrared imaging survey of Milky Way Giant H II regions with our detailed analysis of W49A, one of the most distant, yet most luminous, GH II regions in the Galaxy. We used the FORCAST instrument on the Stratospheric Observatory For Infrared Astronomy (SOFIA) to obtain 20 and 37 µm images of t…
Forward Modeling Helioseismic Signatures of One- and Two-cell Meridional Circulation
Kosovichev, Alexander G.; Pipin, Valery V.; Stejko, Andrey M.
Using a 3D global solver of the linearized Euler equations, we model acoustic oscillations over background velocity flow fields of single-cell meridional circulation with deep and shallow return flows as well as double-cell meridional circulation with strong and weak reversals. The velocities are generated using a mean-field hydrodynamic and dynam…
Influence of Heliolatitudinal Anisotropy of Solar FUV/EUV Emissions on Lyα Helioglow: SOHO/SWAN Observations and WawHelioGlow Modeling
Bzowski, M.; Kubiak, M. A.; Strumik, M.
Observations of the Sun's surface suggest a nonuniform radiated flux as related to the presence of bright active regions and darker coronal holes. The variations of the FUV/EUV source radiation can be expected to affect the Lyα backscatter glow measured by spaceborne instruments. In particular, inferring the heliolatitudinal structure of the solar…
AstroSat Study of the Globular Cluster NGC 2298: Probable Evolutionary Scenarios of Hot Horizontal Branch Stars
Sahu, Snehalata; Chung, Chul; Subramaniam, Annapurni +3 more
We present the far-UV (FUV) photometry of images acquired with UVIT on AstroSat to probe the horizontal branch (HB) population of the Galactic globular cluster NGC 2298. UV-optical color-magnitude diagrams (CMDs) are constructed for member stars in combination with Hubble Space Telescope UV Globular Cluster Survey data for the central region and G…
Constraining the Origin of the Puzzling Source HESS J1640-465 and the PeVatron Candidate HESS J1641-463 Using Fermi-Large Area Telescope Observations
Grondin, M. -H.; Lemoine-Goumard, M.; Clark, C. J. +6 more
There are only a few very-high-energy sources in our Galaxy that might accelerate particles up to the knee of the cosmic-ray spectrum. To understand the mechanisms of particle acceleration in these PeVatron candidates, Fermi-Large Area Telescope (LAT) and High-Energy Stereoscopic System (H.E.S.S.) observations are essential to characterize their γ…
X-Ray Evidence Against the Hypothesis that the Hyperluminous z = 6.3 Quasar J0100+2802 is Lensed
Connor, Thomas; Stern, Daniel; Bañados, Eduardo +1 more
The z = 6.327 quasar SDSS J010013.02+280225.8 (hereafter J0100+2802) is believed to be powered by a black hole more massive than 1010 M ⊙, making it the most massive black hole known in the first billion years of the universe. However, recent high-resolution ALMA imaging shows four structures at the location of this quasar, p…
Associated Molecular and Atomic Clouds with X-Ray Shell of Superbubble 30 Doradus C in the LMC
Filipović, M. D.; Aharonian, F.; Rowell, G. +20 more
30 Doradus C is a superbubble that emits the brightest non-thermal X- and TeV gamma-rays in the Local Group. To explore the detailed connection between the high-energy radiation and the interstellar medium, we have carried out new CO and HI observations using the Atacama Large Millimeter/Submillimeter Array (ALMA), Atacama Submillimeter Telescope …