Search Publications
On Estimating the High-energy Cutoff in the X-Ray Spectra of Black Holes via Reflection Spectroscopy
Steiner, James F.; McClintock, Jeffrey E.; Wilms, Jörn +3 more
The fundamental parameters describing the coronal spectrum of an accreting black hole are the slope Γ of the power-law continuum and the energy Ecut at which it rolls over. Remarkably, this latter parameter can be accurately measured for values as high as 1 MeV by modeling the spectrum of X-rays reflected from a black hole accretion dis…
A Hard X-Ray Study of the Ultraluminous X-Ray Source NGC 5204 X-1 with NuSTAR and XMM-Newton
Harrison, F. A.; Stern, D.; Fabian, A. C. +16 more
We present the results from coordinated X-ray observations of the ultraluminous X-ray source NGC 5204 X-1 performed by the Nuclear Spectroscopic Telescope Array and XMM-Newton in early 2013. These observations provide the first detection of NGC 5204 X-1 above 10 {keV}, extending the broadband coverage to 0.3-20 {keV}. The observations were carried…
A Circular-ribbon Solar Flare Following an Asymmetric Filament Eruption
Liu, Yang; Liu, Chang; Wang, Haimin +6 more
The dynamic properties of flare ribbons and the often associated filament eruptions can provide crucial information on the flaring coronal magnetic field. This Letter analyzes the GOES-class X1.0 flare on 2014 March 29 (SOL2014-03-29T17:48), in which we found an asymmetric eruption of a sigmoidal filament and an ensuing circular flare ribbon. Init…
Local H i Emissivity Measured with Fermi-LAT and Implications for Cosmic-Ray Spectra
Casandjian, Jean-Marc
Cosmic-ray (CR) electrons and nuclei interact with the Galactic interstellar gas and produce high-energy γ-rays. The γ-ray emission rate per hydrogen atom, called emissivity, provides a unique indirect probe of the CR flux. We present the measurement and the interpretation of the emissivity in the solar neighborhood for γ-ray energy from 50 MeV to…
Spatially Extended Na I D Resonant Emission and Absorption in the Galactic Wind of the Nearby Infrared-Luminous Quasar F05189-2524
Veilleux, Sylvain; Rupke, David S. N.
Emission from metal resonant lines has recently emerged as a potentially powerful probe of the structure of galactic winds at low and high redshift. In this work, we present only the second example of spatially resolved observations of Na i D emission from a galactic wind in a nearby galaxy (and the first 3D observations at any redshift). F05189-2…
An Extreme Starburst in the Core of a Rich Galaxy Cluster at z = 1.7
Muzzin, Adam; Smith, Matthew W. L.; Yee, H. K. C. +19 more
We have discovered an optically rich galaxy cluster at z = 1.7089 with star formation occurring in close proximity to the central galaxy. The system, SpARCS104922.6+564032.5, was detected within the Spitzer Adaptation of the red-sequence Cluster Survey, and confirmed through Keck-MOSFIRE spectroscopy. The rest-frame optical richness of Ngal
Kepler’s Supernova: An Overluminous Type Ia Event Interacting with a Massive Circumstellar Medium at a Very Late Phase
Maeda, Yoshitomo; Katsuda, Satoru; Petre, Robert +7 more
We have analyzed XMM-Newton, Chandra, and Suzaku observations of three similarly aged, ejecta-dominated supernova remnants (SNRs), Kepler's SNR, Tycho's SNR, and SNR 0509-67.5, to investigate the properties of the SN ejecta and the circumstellar medium (CSM). By simply comparing the X-ray spectra, we find that line intensity ratios of iron-group e…
How Important Are Electron Beams in Driving Chromospheric Evaporation in the 2014 March 29 Flare?
Krucker, Säm; Kleint, Lucia; Battaglia, Marina +1 more
We present high spatial resolution observations of chromospheric evaporation in the flare SOL2014-03-29T17:48. Interface Region Imaging Spectrograph observations of the Fe xxi λ 1354.1 line indicate evaporating plasma at a temperature of 10 MK along the flare ribbon during the flare peak and several minutes into the decay phase with upflow velocit…
A Radio-Polarisation and Rotation Measure Study of the Gum Nebula and Its Environment
Gaensler, B. M.; Carretti, E.; Bernardi, G. +7 more
The Gum Nebula is 36°-wide shell-like emission nebula at a distance of only ∼450 pc. It has been hypothesized to be an old supernova remnant, fossil H ii region, wind-blown bubble, or combination of multiple objects. Here we investigate the magneto-ionic properties of the nebula using data from recent surveys: radio-continuum data from the NRAO VL…
Gamma-Ray Flaring Activity from the Gravitationally Lensed Blazar PKS 1830-211 Observed by Fermi LAT
Troja, E.; Caraveo, P. A.; Bechtol, K. +125 more
The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope routinely detects the MeV-peaked flat-spectrum radio quasar PKS 1830-211 (z = 2.507). Its apparent isotropic γ-ray luminosity (E > 100 MeV), averaged over ~3 years of observations and peaking on 2010 October 14/15 at 2.9 × 1050 erg s-1, makes it am…