Search Publications
X-Ray and Optical Emission from Radio Hot Spots of Powerful Quasars
Maraschi, L.; Cheung, C. C.; Tavecchio, F. +4 more
In a survey with Chandra and HST of a sample of 17 radio sources with bright radio jets (16 powerful FR II and one nearby FR I), we detected X-ray and optical emission from a number of radio hot spots and lobes. Six hot spots on the near sides of powerful FR II galaxies (as determined from the jet asymmetry) were detected at X-rays, while none wer…
X-Ray Variability Characteristics of the Seyfert 1 Galaxy NGC 3783
Markowitz, A.
We have characterized the energy-dependent X-ray variability properties of the Seyfert 1 galaxy NGC 3783 using archival XMM-Newton and Rossi X-Ray Timing Explorer data. The high-frequency fluctuation power spectral density function (PSD) slope is consistent with flattening toward higher energies. Light-curve cross-correlation functions yield no si…
Properties of Remote Flare Ribbons Associated with Coronal Mass Ejections
Wang, Haimin
To understand the large-scale structure of flares and coronal mass ejections, we studied the motion and properties of remote flare ribbons of three major events: 2003 May 27 X1.3, 2000 November 24 X1.8, and 2000 November 25 X1.9 flares. The remote ribbons are in addition to the typical two-ribbon pairs in the flare cores. We found two common prope…
Nanodiamond Dust and the Far-Ultraviolet Quasar Break
Krongold, Yair; Morisset, Christophe; Binette, Luc +5 more
We explore the possibility that the steepening observed shortward of 1000 Å in the energy distribution of quasars may result from absorption by dust, being either intrinsic to the quasar environment or intergalactic. We find that a dust extinction curve consisting of nanodiamonds, composed of terrestrial cubic diamonds or with surface impurities a…
The Low Quiescent X-Ray Luminosity of the Transient X-Ray Burster EXO 1747-214
Kaaret, Philip; Gelino, Dawn M.; Tomsick, John A.
We report on X-ray and optical observations of the X-ray burster EXO 1747-214. This source is an X-ray transient, and its only known outburst was observed in 1984-1985 by the EXOSAT satellite. We reanalyzed the EXOSAT data to derive the source position, column density, and a distance upper limit using its peak X-ray burst flux. We observed the EXO…
Far-Ultraviolet Spectroscopy of the Dwarf Novae SS Cygni and WX Hydri in Quiescence
Blair, William P.; Kallman, Timothy R.; Long, Knox S. +3 more
We present time-resolved FUV spectra of the dwarf novae SS Cyg and WX Hyi in quiescence from observations using the Hopkins Ultraviolet Telescope on the Astro-1 and Astro-2 space shuttle missions and the Goddard High Resolution Spectrograph on the Hubble Space Telescope. Both dwarf novae are characterized by blue continua that extend to the Lyman …
Bulk Comptonization of the Cosmic Microwave Background by Extragalactic Jets as a Probe of Their Matter Content
Georganopoulos, Markos; Kazanas, Demosthenes; Perlman, Eric +1 more
We propose a method for estimating the composition, i.e., the relative amounts of leptons and protons, of extragalactic jets that exhibit X-ray-bright knots in their kiloparsec-scale jets. The method relies on measuring, or setting upper limits on, the component of the cosmic microwave background (CMB) radiation that is bulk Comptonized (BC) by co…
Search for 17 µm H2 Pure Rotational Emission from Circumstellar Disks
Onaka, T.; Kataza, H.; Sako, S. +5 more
We report the negative detection of the S(1) pure rotational line emission of molecular hydrogen at 17.035 µm for four young stars, HD 163296, MWC 863, CQ Tau, and LkCa 15, for which Infrared Space Observatory (ISO) observations detected the S(1) emission, with the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on the 8.2 m Subaru Tele…
Study of Hα Macrospicules in Coronal Holes: Magnetic Structure and Evolution in Relation to Photospheric Magnetic Setting
Wang, H.; Moore, R. L.; Jiang, Y. +2 more
Small-scale solar dynamic events such as spicules, macrospicules, and microflares may play an important role in the coronal heating and solar wind acceleration in coronal holes. In these regions, the network fields concentrated along edges of supergranules are probably the source of the fine-scale activity that may drive the heating and accelerati…
State Transition and Flaring Activity of IGR J17464-3213/H1743-322 with INTEGRAL SPI
Capitanio, F.; Ubertini, P.; Malzac, J. +4 more
IGR J17464-3213, already known as the HEAO 1 transient source H1743-322, has been detected during a state transition by INTEGRAL SPI. We describe the spectral evolution and flaring activity of IGR J17464-3213/H1743-322 from 2003 March 21 to 2003 April 22. During the first part, the source followed a continuous spectral softening, with the peak of …