Search Publications
Chandra View of the Warm-hot Intergalactic Medium toward 1ES 1553+113: Absorption-line Detections and Identifications. I.
Piro, L.; Shull, J. M.; Barcons, X. +14 more
We present the first results from our pilot 500 ks Chandra Low Energy Transmission Grating Large Program observation of the soft X-ray brightest source in the z >~ 0.4 sky, the blazar 1ES 1553+113, aimed to secure the first uncontroversial detections of the missing baryons in the X-rays. We identify a total of 11 possible absorption lines, with…
The Exceptional Soft X-Ray Halo of the Galaxy Merger NGC 6240
Zezas, A.; Elvis, M.; Pellegrini, S. +5 more
We report on a recent ~150 ks long Chandra observation of the ultraluminous infrared galaxy merger NGC 6240, which allows a detailed investigation of the diffuse galactic halo. Extended soft X-ray emission is detected at the 3σ confidence level over a diamond-shaped region with projected physical size of ~110 × 80 kpc, and a single-component therm…
Nonlinear Force-free Magnetic Field Fitting to Coronal Loops with and without Stereoscopy
Aschwanden, Markus J.
We developed a new nonlinear force-free magnetic field (NLFFF) forward-fitting algorithm based on an analytical approximation of force-free and divergence-free NLFFF solutions, which requires as input a line-of-sight magnetogram and traced two-dimensional (2D) loop coordinates of coronal loops only, in contrast to stereoscopically triangulated thr…
Determination of an Upper Limit for the Water Outgassing Rate of Main-belt Comet P/2012 T1 (PANSTARRS)
Hartogh, P.; Teyssier, D.; Biver, N. +8 more
A new Main-Belt Comet (MBC) P/2012 T1 (PANSTARRS) was discovered on 2012 October 6, approximately one month after its perihelion, by the Pan-STARRS1 survey based in Hawaii. It displayed cometary activity upon its discovery with one hypothesis being that the activity was driven by sublimation of ices; as a result, we searched for emission assumed t…
The Emission Measure Distribution of Impulsive Phase Flare Footpoints
Fletcher, L.; Hannah, I. G.; Milligan, R. O. +1 more
The temperature distribution of the emitting plasma is a crucial constraint when studying the heating of solar flare footpoints. However, determining this for impulsive phase footpoints has been difficult in the past due to insufficient spatial resolution to resolve the footpoints from the loop structures, and a lack of spectral and temporal cover…
Short-term Variability of X-Rays from Accreting Neutron Star Vela X-1. I. Suzaku Observations
Makishima, Kazuo; Takahashi, Tadayuki; Odaka, Hirokazu +3 more
We have analyzed the time variability of the wide-band X-ray spectrum of Vela X-1, the brightest wind-fed accreting neutron star, on a short timescale of 2 ks by using Suzaku observations with an exposure of 100 ks. During the observation, the object showed strong variability, including several flares and so-called "low states," in which the X-ray…
The Mid-infrared Emission of Narrow-line Active Galactic Nuclei: Star Formation, Nuclear Activity, and Two Populations Revealed by Wise
Burtscher, Leonard; Lutz, Dieter; Rosario, David J. +3 more
We explore the nature of the long-wavelength mid-infrared (MIR) emission of a sample of 13,000 local Type II (narrow-line) active galactic nuclei (AGNs) from the Sloan Digital Sky Survey (SDSS) using 12 µm and 22 µm photometry from the WISE all-sky survey. In combination with FIRST 1.4 GHz photometry, we show that AGNs divide into two …
A High Resolution View of the Warm Absorber in the Quasar MR 2251-178
Turner, T. J.; Kraemer, S. B.; Crenshaw, D. M. +5 more
High resolution X-ray spectroscopy of the warm absorber in a nearby quasar, MR 2251-178 (z = 0.06398), is presented. The observations were carried out in 2011 using the Chandra High Energy Transmission Grating (HETG) and the XMM-Newton Reflection Grating Spectrometer, with net exposure times of approximately 400 ks each. A multitude of absorption …
Far-ultraviolet Observations of Outflows from Infrared-luminous Galaxies
Schaerer, Daniel; Leitherer, Claus; Chandar, Rupali +2 more
We obtained medium-resolution ultraviolet (UV) spectra between 1150 and 1450 Å of the four UV-bright, infrared-luminous starburst galaxies IRAS F08339+6517, NGC 3256, NGC 6090, and NGC 7552 using the Cosmic Origins Spectrograph on board the Hubble Space Telescope. The selected sightlines toward the starburst nuclei probe the properties of the rece…
Hard X-Ray Lags in Active Galactic Nuclei: Testing the Distant Reverberation Hypothesis with NGC 6814
Harrison, F. A.; Fabian, A. C.; Miller, J. M. +7 more
We present an X-ray spectral and temporal analysis of the variable active galaxy NGC 6814, observed with Suzaku during 2011 November. Remarkably, the X-ray spectrum shows no evidence for the soft excess commonly observed amongst other active galaxies, despite its relatively low level of obscuration, and is dominated across the whole Suzaku bandpas…