Search Publications
The Temporal Evolution of Coronal Loops Observed by GOES SXI
López Fuentes, M. C.; Klimchuk, J. A.; Mandrini, C. H.
We study the temporal evolution of coronal loops using data from the Solar X-Ray Imager (SXI) on board the Geosynchronous Operational Environmental Satellite 12 (GOES-12). This instrument provides continuous soft X-ray observations of the solar corona at a high temporal cadence permitting detailed study of the full lifetime of each of several coro…
Evidence of Stellar-driven Outflows from the Classical T Tauri Star RY Tau
Gómez de Castro, Ana I.; Verdugo, Eva
RY Tau is a rapidly rotating classical T Tauri star observed close to edge-on. The combination of new HST/STIS observations obtained in 2001 with HST/GHRS archive data from 1993 has allowed us to get, for the first time, information on the thermal structure and velocity of the wind. The repeated observations of the Si III] and C III] lines show a …
Determining the Source of Coronal Helicity through Measurements of Braiding and Spin Helicity Fluxes in Active Regions
Barnes, G.; Longcope, D. W.; Ravindra, B.
Magnetic helicity has become a valuable tool for understanding the energetics and dynamics of coronal magnetic fields. Recently, long time sequences of magnetograms have been used to measure the flux of helicity into active region coronae. We demonstrate how this helicity flux can be usefully decomposed into contributions of differing origin, call…
Discovery of an Extended Debris Disk around the F2 V Star HD 15745
Kalas, Paul; Fitzgerald, Michael P.; Graham, James R. +1 more
Using the Advanced Camera for Surveys aboard the Hubble Space Telescope, we have discovered dust-scattered light from the debris disk surrounding the F2 V star HD 15745. The circumstellar disk is detected between 2.0" and 7.5" radius, corresponding to 128-480 AU radius. The circumstellar disk morphology is asymmetric about the star, resembling a f…
The Remarkable X-Ray Spectrum of the Broad-Line Radio Galaxy 3C 445
Reeves, J. N.; Braito, V.; Sambruna, R. M.
We present the results of the analysis of an archival 15 ks XMM-Newton observation of the nearby (z=0.057) radio-loud source 3C 445, optically classified as a broad-line radio galaxy. While the RGS data are of insufficient quality to allow a meaningful analysis, the EPIC data show a remarkable X-ray spectrum. The 2-10 keV continuum is described by…
Deep Chandra and Multicolor HST Observations of the Jets of 3C 371 and PKS 2201+044
Maraschi, L.; Cheung, C. C.; Tavecchio, F. +3 more
This paper presents multiwavelength imaging and broadband spectroscopy of the relativistic jets in the two nearby radio galaxies 3C 371 and PKS 2201+044, acquired with Chandra, HST, VLA, and MERLIN. Radio polarization is also presented for 3C 371. The two sources stand out as ``intermediate'' between FR I and FR II type galaxies; their cores are c…
Spectropolarimetric Observations of the Ca II λ8498 and λ8542 in the Quiet Sun
Pietarila, A.; Socas-Navarro, H.; Bogdan, T.
The Ca II infrared triplet is one of the few magnetically sensitive chromospheric lines available for ground-based observations. We present spectropolarimetric observations of the 8498 and 8542 Å lines in a quiet Sun region near a decaying active region and compare the results with a simulation of the lines in a high plasma-β regime. Cluster analy…
Fe K Line Profile in Low-Redshift Quasars: Average Shape and Eddington Ratio Dependence
Ho, Luis C.; Terashima, Yuichi; Inoue, Hirohiko
We analyze X-ray spectra of 43 Palomar-Green quasars observed with XMM-Newton in order to investigate their mean Fe K line profile and its dependence on physical properties. The continuum spectra of 39 objects are well reproduced by a model consisting of a power law and a blackbody modified by Galactic absorption. The spectra of the remaining four…
Integral Field Spectroscopy of the Extended Emission-Line Region of 4C 37.43
Fu, Hai; Stockton, Alan
We present Gemini integral field spectroscopy and Keck II long-slit spectroscopy of the extended emission-line region (EELR) around the quasar 4C 37.43. The velocity structure of the ionized gas is complex and cannot be explained globally by a simple dynamical model. The spectra from the clouds are inconsistent with shock or ``shock + precursor'' …
The Nature of Optical Features in the Inner Region of the 3C 48 Host Galaxy
Fu, Hai; Stockton, Alan; Canalizo, Gabriela +1 more
The well-known quasar 3C 48 is the most powerful compact steep-spectrum radio-loud QSO at low redshifts. It also has two unusual optical features within the radius of the radio jet (~1"): (1) an anomalous, high-velocity narrow-line component, and (2) a bright continuum peak (3C 48A) ~1" northeast of the quasar. Both of these optical features have …