Search Publications
Unveiling Extragalactic Star Formation Using Radio Recombination Lines: An Expanded Very Large Array Pilot Study with NGC 253
Johnson, Kelsey E.; Chomiuk, Laura; Pisano, D. J. +3 more
Radio recombination lines (RRLs) are powerful, extinction-free diagnostics of the ionized gas in young, star-forming regions. Unfortunately, these lines are difficult to detect in external galaxies. We present the results of Expanded Very Large Array (EVLA) observations of the RRL and radio continuum emission at 33 GHz from NGC 253, a nearby nucle…
Channel morphometry, sediment transport, and implications for tectonic activity and surficial ages of Titan basins
Kirk, Randolph L.; Cartwright, Richard; Clayton, Jordan A.
Fluvial features on Titan and drainage basins on Earth are remarkably similar despite differences in gravity and surface composition. We determined network bifurcation ( R b) ratios for five Titan and three terrestrial analog basins. Tectonically-modified Earth basins have R b values greater than the expected range (3.0-5.0) …
The Remarkable γ-Ray Activity in the Gravitationally Lensed Blazar PKS 1830-211
Costa, E.; Barbiellini, G.; Longo, F. +34 more
We report the extraordinary γ-ray activity (E > 100 MeV) of the gravitationally lensed blazar PKS 1830-211 (z = 2.507) detected by AGILE between 2010 October and November. On October 14, the source experienced a factor of ~12 flux increase with respect to its average value and remained brightest at this flux level (~500 × 10-8 photon…
Local structure of directional discontinuities in the solar wind
Haaland, S. E.; Paschmann, G.; Teh, W. -L. +1 more
We examine local structures of three directional discontinuities (DDs) observed by Cluster in the solar wind, using reconstruction based on the ideal 2-D MHD equations in a steady state. In this novel application of the technique, our goals are the following: (1) to explain why the minimum variance analysis of the magnetic field (MVAB) often fails…
X-ray wind tomography of the highly absorbed HMXB IGR J17252-3616
Walter, R.; Manousakis, A.
Context. About ten persistently highly absorbed super-giant high-mass X-ray binaries (sgHMXB) have been discovered by INTEGRAL as bright hard X-ray sources lacking bright X-ray counterparts. Besides IGR J16318-4848, which has peculiar characteristics, the other members of this family share many properties with the classical wind-fed sgHMXB systems…
SAPS intensification during substorm recovery: A multi-instrument case study
Nishimura, Y.; Lyons, L. R.; Kellerman, A. C. +3 more
A case of the major intensification of the subauroral polarization stream (SAPS) during the substorm recovery phase is presented. The continuous high-time-resolution Doppler velocity measurements in the subauroral and auroral regions were conducted with the Unwin HF radar, and these are analyzed in the context of the simultaneous and coincident me…
A Jet Model for the Broadband Spectrum Of the Seyfert 1 Galaxy NGC 4051
Miller, Jon M.; Markoff, Sera; Maitra, Dipankar +1 more
Recent radio very long baseline interferometry observations of the ~ parsec-scale nuclear region of the narrow line Seyfert 1 galaxy NGC 4051 hint toward the presence of outflowing plasma. From available literature we have collected high-quality, high-resolution broadband spectral energy distribution (SED) data of the nuclear region of NGC 4051 sp…
A High Spatial Resolution Study of the λ = 3 mm Continuum of Orion-KL
Friedel, D. N.; Widicus Weaver, S. L.
Recent interferometric observations have called into question the traditional view of the Orion-KL region, which displays one of the most well-defined cases of chemical differentiation in a star-forming region. Previous lower-resolution images of Orion-KL show emission signatures for oxygen-bearing organic molecules toward the Orion Compact Ridge …
X-Ray Warm Absorption and Emission in the Polar-scattered Seyfert 1 Galaxy Mrk 704
Dewangan, Gulab C.; Laha, Sibasish; Kembhavi, Ajit K.
We present a detailed study of the ionized environment of the Seyfert 1 galaxy Mrk 704 using medium- and high-resolution X-ray spectra obtained with a long XMM-Newton observation. The 0.3-10 keV continuum, well described by a power law (Γ ≈ 1.86) and two blackbodies (kT ≈ 0.085 and 0.22 keV), is found to be affected by a neutral partial covering a…
Suzaku observation of the LINER NGC 4102
Esquej, P.; Ebrero, J.; Papadakis, I. +11 more
Context. Low-ionisation, nuclear emission-line region (LINER) nuclei are said to be different from other active galactic nuclei (AGN) due to the presence of complex absorbing structures along the line-of-sight and/or an inefficient mode of accretion onto the supermassive black hole. However, this is still open.
Aims: We investigate the broad …