Search Publications
Ultraviolet Emission-line Correlations in HST/COS Spectra of Active Galactic Nuclei: Single-epoch Black Hole Masses
Shull, J. Michael; Tilton, Evan M.
Effective methods of measuring supermassive black hole masses in active galactic nuclei (AGNs) are of critical importance to studies of galaxy evolution. While there has been much success in obtaining masses through reverberation mapping, the extensive observing time required by this method has limited the practicality of applying it to large samp…
RHESSI and TRACE Observations of Multiple Flare Activity in AR 10656 and Associated Filament Eruption
Kushwaha, Upendra; Joshi, Bhuwan; Veronig, Astrid M. +1 more
We present Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) and Transition Region and Coronal Explorer (TRACE) observations of multiple flare activity that occurred in the NOAA active region 10656 over a period of 2 hr on 2004 August 18. Out of four successive flares, three were class C events, and the final event was a major X1.8 sol…
Evolution of the 1919 Ejecta of V605 Aquilae
Sparks, William B.; Bond, Howard E.; Chesneau, O. +7 more
New imaging of V605 Aql, was obtained in 2009 with HST/WFPC2, which had a nova-like outburst in 1919, and is located at the center of the planetary nebula (PN), A58. This event has long been ascribed to a final helium shell flash, but it has been suggested recently that it may instead have been an ONe nova. The new images provide an 18 yr baseline…
Discovery of X-Ray Pulsation from the Geminga-like Pulsar PSR J2021+4026
Cheng, K. S.; Takata, J.; Wang, Y. +8 more
We report the discovery of an X-ray periodicity of ~265.3 ms from a deep XMM-Newton observation of the radio-quiet γ-ray pulsar, PSR J2021+4026, located at the edge of the supernova remnant G78.2+2.1 (γ-Cygni). The detected frequency is consistent with the γ-ray pulsation determined by the observation of the Fermi Gamma-ray Space Telescope at the …
Dark Matter Subhalos and the X-Ray Morphology of the Coma Cluster
Churazov, Eugene; Andrade-Santos, Felipe; Jones, Christine +4 more
Structure formation models predict that clusters of galaxies contain numerous massive subhalos. The gravity of a subhalo in a cluster compresses the surrounding intracluster gas and enhances its X-ray emission. We present a simple model, which treats subhalos as slow moving and gasless, for computing this effect. Recent weak lensing measurements b…
A Chandra X-Ray Study of the Interacting Binaries in the Old Open Cluster NGC 6791
Verbunt, Frank; Bedin, Luigi R.; Belloni, Tomaso +3 more
We present the first X-ray study of NGC 6791, one of the oldest open clusters known (8 Gyr). Our Chandra observation is aimed at uncovering the population of close interacting binaries down to L X ≈ 1 × 1030 erg s-1 (0.3-7 keV). We detect 86 sources within 8' of the cluster center, including 59 inside the half-mass…
Gradients of Stellar Population Properties and Evolution Clues in a Nearby Galaxy M101
Kong, Xu; Zou, Hu; Lin, Lin +5 more
Multiband photometric images from ultraviolet and optical to infrared are collected to derive spatially resolved properties of the nearby Scd-type galaxy M101. With evolutionary stellar population synthesis models, two-dimensional distributions and radial profiles of age, metallicity, dust attenuation, and star formation timescale in the form of t…
The XMM-Newton/EPIC X-Ray Light Curve Analysis of WR 6
Hamann, W. -R.; Oskinova, L. M.; Ignace, R. +4 more
We obtained four pointings of over 100 ks each of the well-studied Wolf-Rayet star WR 6 with the XMM-Newton satellite. With a first paper emphasizing the results of spectral analysis, this follow-up highlights the X-ray variability clearly detected in all four pointings. However, phased light curves fail to confirm obvious cyclic behavior on the w…
Unusual Filaments inside the Umbra
Sainz Dalda, A.; Kleint, L.
We analyze several unusual filamentary structures which appeared in the umbra of one of the sunspots in AR 11302. They do not resemble typical light bridges in morphology or in evolution. We analyze data from SDO/HMI to investigate their temporal evolution, Hinode/SP for photospheric inversions, IBIS for chromospheric imaging, and SDO/AIA for the …
The Origin of the 3.4 µm Feature in Wild 2 Cometary Particles and in Ultracarbonaceous Interplanetary Dust Particles
Matrajt, G.; Flynn, G.; Brownlee, D. +2 more
We analyzed two ultracarbonaceous interplanetary dust particles (IDPs) and two cometary Wild 2 particles with infrared spectroscopy. We characterized the carrier of the 3.4 µm band in these samples and compared its profile and the CH2/CH3 ratios to the 3.4 µm band in the diffuse interstellar medium (DISM), in the …