Search Publications
X-ray Emission from Optically Selected Radio-intermediate and Radio-loud Quasars
Brandt, W. N.; Schneider, D. P.; Miller, B. P. +3 more
We present the results of an investigation into the X-ray properties of radio-intermediate and radio-loud quasars (RIQs and RLQs, respectively). We combine large, modern optical (e.g., SDSS) and radio (e.g., FIRST) surveys with archival X-ray data from Chandra, XMM-Newton, and ROSAT to generate an optically selected sample that includes 188 RIQs a…
The First Measurement of the Adiabatic Index in the Solar Corona Using Time-dependent Spectroscopy of Hinode/EIS Observations
Del Zanna, Giulio; Van Doorsselaere, Tom; Nakariakov, Valery M. +3 more
We use observations of a slow magnetohydrodynamic wave in the corona to determine for the first time the value of the effective adiabatic index, using data from the Extreme-ultraviolet Imaging Spectrometer on board Hinode. We detect oscillations in the electron density, using the CHIANTI atomic database to perform spectroscopy. From the time-depen…
Two Components of the Solar Coronal Emission Revealed by Extreme-ultraviolet Spectroscopic Observations
Martínez-Sykora, Juan; De Pontieu, Bart; Wang, Xin +3 more
Recent spectroscopic observations have revealed the ubiquitous presence of blueward asymmetries of emission lines formed in the solar corona and transition region. These asymmetries are most prominent in loop footpoint regions, where a clear correlation of the asymmetry with the Doppler shift and line width determined from the single-Gaussian fit …
The Dark Matter Distribution in A383: Evidence for a Shallow Density Cusp from Improved Lensing, Stellar Kinematic, and X-ray Data
Treu, Tommaso; Ellis, Richard S.; Newman, Andrew B. +1 more
We extend our analyses of the dark matter (DM) distribution in relaxed clusters to the case of A383, a luminous X-ray cluster at z = 0.189 with a dominant central galaxy and numerous strongly lensed features. Following our earlier papers, we combine strong and weak lensing constraints secured with Hubble Space Telescope and Subaru imaging with the…
Constraints on the Heating of High-temperature Active Region Loops: Observations from Hinode and the Solar Dynamics Observatory
Winebarger, Amy R.; Warren, Harry P.; Brooks, David H.
We present observations of high-temperature emission in the core of a solar active region using instruments on Hinode and the Solar Dynamics Observatory (SDO). These multi-instrument observations allow us to determine the distribution of plasma temperatures and follow the evolution of emission at different temperatures. We find that at the apex of…
Emission Lines from the Gas Disk around TW Hydra and the Origin of the Inner Hole
Pascucci, I.; Najita, J.; Hollenbach, D. +1 more
We compare line emission calculated from theoretical disk models with optical to submillimeter wavelength observational data of the gas disk surrounding TW Hya and infer the spatial distribution of mass in the gas disk. The model disk that best matches observations has a gas mass ranging from ~10-4 to 10-5 M sun fo…
Fe-K Line Probing of Material Around the Active Galactic Nucleus Central Engine with Suzaku
Fukazawa, Yasushi; Ohno, Masanori; Nishino, Sho +6 more
We systematically analyzed the high-quality Suzaku data of 88 Seyfert galaxies, about 31% of which are Compton-thick active galactic nuclei (AGNs). We obtained a clear relation between the absorption column density and the equivalent width (EW) of the 6.4 keV line above 1023 cm-2, suggesting a wide-ranging column density of 1…
Evidence for Cold Accretion: Primitive Gas Flowing onto a Galaxy at z ~ 0.274
Tripp, Todd M.; Prochaska, J. Xavier; Lehner, Nicolas +5 more
We present UV and optical observations from the Cosmic Origins Spectrograph on the Hubble Space Telescope and Keck of a z = 0.27395 Lyman limit system (LLS) seen in absorption against the QSO PG1630+377. We detect H I absorption with log N(H I) = 17.06 ± 0.05 as well as Mg II, C III, Si III, and O VI in this system. The column densities are readil…
XRF 100316D/SN 2010bh and the Nature of Gamma-Ray Burst Supernovae
D'Avanzo, P.; Melandri, A.; Pian, E. +21 more
We present ground-based and Hubble Space Telescope optical and infrared observations of Swift XRF 100316D/SN 2010bh. It is seen that the optical light curves of SN 2010bh evolve at a faster rate than the archetype gamma-ray burst supernova (GRB-SN) 1998bw, but at a similar rate to SN 2006aj, an SN that was spectroscopically linked with XRF 060218,…
Spiraling Out of Control: Three-dimensional Hydrodynamical Modeling of the Colliding Winds in η Carinae
Corcoran, M. F.; Hamaguchi, K.; Pittard, J. M. +1 more
Three-dimensional adaptive mesh refinement hydrodynamical simulations of the wind-wind collision between the enigmatic supermassive star η Car and its mysterious companion star are presented which include radiative driving of the stellar winds, gravity, optically thin radiative cooling, and orbital motion. Simulations with static stars with a peri…