Search Publications
A Deep Chandra ACIS Study of NGC 4151. I. The X-ray Morphology of the 3 kpc Diameter Circum-nuclear Region and Relation to the Cold Interstellar Medium
Elvis, Martin; Zezas, Andreas; Schinnerer, Eva +6 more
We report on the imaging analysis of ~200 ks sub-arcsecond resolution Chandra Advanced CCD Imaging Spectrometer (ACIS-S) observations of the nearby Seyfert 1 galaxy NGC 4151. Bright, structured soft X-ray emission is observed to extend from 30 pc to 1.3 kpc in the southwest from the nucleus, much farther than seen in earlier X-ray studies. The ter…
X-ray Properties of Narrow-line Seyfert 1 Galaxies with Very Small Broadline Widths
Wang, T. G.; Yuan, W.; Zhou, H. Y. +2 more
Narrow-line Seyfert 1 galaxies (NLS1s) with very small broadline widths (say, FWHM(Hβ) lsim1200 km s-1) represent the extreme type of Seyfert 1 galaxies that have small black hole masses (M BH) and/or high Eddington ratios (L/L Edd). Here, we study the X-ray properties of a homogeneously and optically selected samp…
Multiwavelength Observations of A0620-00 in Quiescence
Prochaska, J. Xavier; Maccarone, Thomas J.; Danforth, Charles W. +17 more
We present contemporaneous X-ray, ultraviolet, optical, near-infrared, and radio observations of the black hole binary system, A0620-00, acquired in 2010 March. Using the Cosmic Origins Spectrograph on the Hubble Space Telescope, we have obtained the first FUV spectrum of A0620-00 as well as NUV observations with the Space Telescope Imaging Spectr…
Plasma Diagnostics of an EIT Wave Observed by Hinode/EIS and SDO/AIA
Temmer, M.; Veronig, A. M.; Vršnak, B. +4 more
We present plasma diagnostics of an Extreme-Ultraviolet Imaging Telescope (EIT) wave observed with high cadence in Hinode/Extreme-Ultraviolet Imaging Spectrometer (EIS) sit-and-stare spectroscopy and Solar Dynamics Observatory/Atmospheric Imaging Assembly imagery obtained during the HOP-180 observing campaign on 2011 February 16. At the propagatin…
Spatially and Spectrally Resolved Observations of a Zebra Pattern in a Solar Decimetric Radio Burst
Chen, Bin; Jing, Ju; Gary, D. E. +1 more
We present the first interferometric observation of a zebra-pattern radio burst with simultaneous high spectral (≈1 MHz) and high time (20 ms) resolution. The Frequency-Agile Solar Radiotelescope Subsystem Testbed (FST) and the Owens Valley Solar Array (OVSA) were used in parallel to observe the X1.5 flare on 2006 December 14. By using OVSA to cal…
New Constraints on Mass-dependent Disruption of Star Clusters in M51
Calzetti, Daniela; Schinnerer, Eva; Whitmore, Bradley C. +4 more
We use UBVI Hα images of the Whirlpool galaxy, M51, taken with the Advanced Camera for Surveys and WFPC2 cameras on the Hubble Space Telescope (HST) to select star clusters, and to estimate their masses and ages by comparing their observed colors with predictions from population synthesis models. We construct the mass function of intermediate-age …
Measuring Turbulence in the Interstellar Medium by Comparing N(H I; Lyα) and N(H I; 21 cm)
Lockman, Felix J.; Wakker, Bart P.; Brown, Jonathan M.
We present a study of the small-scale structure of the interstellar medium (ISM) in the Milky Way. We used HST STIS data to measure N(H I) in a pencil beam toward 59 active galactic nuclei and compared the results with the values seen at 9'-36' resolution in the same directions using radio telescopes (Green Bank Telescope, Green Bank 140-ft, and L…
Detection of Current Sheets and Magnetic Reconnections at the Turbulent Leading Edge of an Interplanetary Coronal Mass Ejection
Chian, Abraham C. -L.; Muñoz, Pablo R.
The relation between current sheets, turbulence, and magnetic reconnections at the leading edge of an interplanetary coronal mass ejection detected by four Cluster spacecraft on 2005 January 21 is studied. We report the observational evidence of two magnetically reconnected current sheets in the vicinity of a front magnetic cloud boundary layer wi…
Star Clusters in the Tidal Tails of Interacting Galaxies: Cluster Populations Across a Variety of Tail Environments
Bastian, N.; Konstantopoulos, I. S.; Gallagher, S. C. +17 more
We have searched for compact stellar structures within 17 tidal tails in 13 different interacting galaxies using F606W- and F814W-band images from the Wide Field Planetary Camera 2 on the Hubble Space Telescope. The sample of tidal tails includes a diverse population of optical properties, merging galaxy mass ratios, H I content, and ages. Combini…
Evolution of Currents of Opposite Signs in the Flare-productive Solar Active Region NOAA 10930
Tiwari, Sanjiv Kumar; Venkatakrishnan, P.; Ravindra, B. +1 more
Analysis of a time series of high spatial resolution vector magnetograms of the active region NOAA 10930 available from the Solar Optical Telescope SpectroPolarimeter on board Hinode revealed that there is a mixture of upward and downward currents in the two footpoints of an emerging flux rope. The flux emergence rate is almost the same in both th…