Search Publications
Constraints on the Abundance of 0.01 c Stellar Engines in the Milky Way
Lingam, Manasvi; Loeb, Abraham
Stellar engines are hypothesized megastructures that extract energy from the host star, typically with the purpose of generating thrust and accelerating the stellar system. We explore the maximum potential speeds that could be realizable by stellar engines, and determine that speeds up to ∼0.1 c might perhaps be attainable under optimal conditions…
The Role of Peak Temperatures in Solar X-Ray Flare Associations with CME Speeds and Widths and in Flare Size Distributions
Kahler, S. W.; Ling, A. G.
Recently, we reported that solar X-ray flares with relatively low peak (0.05-0.3 nm)/(0.1-0.8 nm) ratios R, a proxy for peak flare temperature T, were preferentially associated not only with solar energetic (E > 10 MeV) particle (SEP) events, but also with fast (Vcme ≥ 1000 km s-1) coronal mass ejections (CMEs) that produc…
Geometric Support for Dark Matter by an Unaligned Einstein Ring in A3827
Broadhurst, Tom; Oguri, Masamune; Chen, Mandy C. +4 more
The nondetection of dark matter (DM) particles in increasingly stringent laboratory searches has encouraged alternative gravity theories where gravity is sourced only from visible matter. Here, we consider whether such theories can pass a two-dimensional test posed by gravitational lensing—to reproduce a particularly detailed Einstein ring in the …
Stellar Variability in a Forming Massive Star Cluster
Andersen, Morten; Cheng, Yu; Tan, Jonathan
We present a near-infrared (NIR) variability analysis for a 6' × 6' region, which encompasses the massive protocluster G286.21+0.17. The total sample comprises more than 5000 objects, of which 562 show signs of a circumstellar disk based on their infrared colors. The data includes Hubble Space Telescope observations taken in two epochs separated b…
The Energetics of Launching the Most Powerful Jets in Quasars: A Study of 3C 82
Berton, Marco; Zeimann, Greg; Hill, Gary J. +5 more
3C 82 at a redshift of 2.87 is the most distant 3C (Third Cambridge Catalogue) quasar. Thus, it is a strong candidate to have the most-luminous radio lobes in the universe. 3C 82 belongs to the class of compact steep-spectrum radio sources. We use single-dish and interferometric radio observations in order to model the plasma state of these powerf…
An Observational Test of Solar Plasma Heating by Magnetic Flux Cancellation
Park, Sung-Hong
Recent observations suggest that magnetic flux cancellation may play a crucial role in heating the Sun's upper atmosphere (chromosphere, transition region, corona). Here, we intended to validate an analytic model for magnetic reconnection and consequent coronal heating, driven by a pair of converging and canceling magnetic flux sources of opposite…
A Radio Pinwheel Emanating from WR 147
Toalá, Jesús A.; Carrasco-González, Carlos; Rodríguez, Luis F. +2 more
Wolf-Rayet (WR) stars are evolved massive stars, presumably on their way to becoming supernovae. They are characterized by high luminosities and fast and dense stellar winds. We have detected signs of a radio continuum pinwheel associated with WR 147, a nitrogen-rich WR star with spectral subtype WN8. These structures are known to exist around a h…
Galaxy Cluster Mass Estimates in the Presence of Substructure
Mateo, Mario; Olszewski, Edward W.; Miller, Christopher J. +3 more
We develop and implement a model to analyze the internal kinematics of galaxy clusters that may contain subpopulations of galaxies that do not independently trace the cluster potential. The model allows for substructures within the cluster environment and disentangles cluster members from contaminating foreground and background galaxies. We estima…
Inferring Contributions from Unresolved Point Sources to Diffuse Emissions Measured in UV Sky Surveys: General Method and SOHO/SWAN Case Study
Bzowski, M.; Kubiak, M. A.; Kowalska-Leszczynska, I. +1 more
In observations of diffuse emissions like, e.g., the Lyα heliospheric glow, contributions to the observed signal from point sources (e.g., stars) are considered to be a contamination. There are relatively few bright point sources that are usually properly resolved and can be subtracted or masked. We present results of an analysis of the distributi…
Termination Shock as a Source of Unusual Solar Radio Bursts
Chernov, Gennady; Fomichev, Valery
Using centimeter-wave and decimeter-wave solar radio spectral observations of the flares of 2003 November 18 and 2004 September 12, we have discussed two type-II-like bursts at the meter waves. The radio bursts show that the ordinary frequency drift from high to low frequencies slows down and stops, and a frequency drift from low to high frequenci…