Search Publications
XMM-Newton discovery of a Compton-thick AGN in the GPS galaxy Mkn 668
Guainazzi, M.; Siemiginowska, A.; Rodriguez-Pascual, P. +1 more
We report the XMM-Newton discovery of the first Compton-thick obscured AGN in a Broad Line Radio Galaxy, the Gigahertz Peaked-Spectrum source Mkn 668 (OQ+208). The remarkably flat 2-10 keV X-ray spectrum (observed photon index, Γ ≃ 0.7), with a prominent iron Kα fluorescent emission line, is a clear signature of a Compton-reflection dom…
Helicity Patterns of Coronal Mass Ejection-associated Active Regions
Zhang, Jun; Wang, Jingxiu; Zhou, Guiping
Coronal mass ejections (CMEs) are thought to originate from the overaccumulation of magnetic helicity. While recent studies have revealed the inability of active region (AR) fields to create enough helicity for CMEs, we have tried, on the other hand, to examine whether particular helicity patterns are retained by CME-associated ARs. Nine ARs, whos…
Radar signal simulation: Surface modeling with the Facet Method
Safaeinili, A.; Kofman, W.; Herique, A. +1 more
A major finding in exploration of Mars is the indication that a large quantity of water has been present on Mars. To discover the distribution of this quantity of water, the Mars Express spacecraft is carrying a spaceborne radar sounder, called Mars Advance Radar for Subsurface and Ionospheric Sounding (MARSIS), in order to map Mars subsurface die…
Composition of the local interstellar medium as diagnosed with pickup ions
Gloeckler, George; Geiss, Johannes
Pickup ions provide us with a powerful tool to probe remote regions in and beyond the heliosphere and determine the composition of the neutral gas in these regions. Interstellar pickup ions, observed inside the heliosphere at 3-5 AU from the Sun, are created by charge exchange and photoionization of the local interstellar gas that penetrates deep …
Filtration of interstellar H, O, N atoms through the heliospheric interface: Inferences on local interstellar abundances of the elements
Geiss, J.; Gloeckler, G.; Izmodenov, V. +1 more
In this Letter we report on our study of the filtration of interstellar atoms of hydrogen, oxygen and nitrogen in the interaction region between the solar wind and the local interstellar medium. The filtration has great importance for the determination of local interstellar abundances of these elements, which becomes now possible due to measuremen…
Period and light variations for the cool, overcontact binary BX Pegasi
Han, Wonyong; Kim, Ho-Il; Lee, Jae Woo +2 more
New charge-coupled device photometric observations of the W UMa-type binary BX Pegasi (BX Peg) were collected on four nights from 1999 October to 2000 September. The light curve was covered completely in each season. Seven new times of minimum light were determined. It was found that the orbital period of the system has varied recently in a sinuso…
Cassini between Earth and asteroid belt: first in-situ charge measurements of interplanetary grains
Kempf, S.; Krüger, H.; Srama, R. +9 more
Dust particles in interplanetary space are expected to charge up to an electrostatic potential of about +5 V mostly by the solar UV (Horányi, 1996, Annu. Rev. Astrophys. 34, 383). Since the dynamics of charged grains may be quite different from neutral particles, the knowledge of the grain charge Qd is highly desirable. In the last two …
First observation of a solar X-class flare in the submillimeter range with KOSMA
Miller, M.; Lüthi, T.; Magun, A.
We present the first solar flare observations with the KOSMA submillimeter telescope at 230 and 345 GHz. The GOES X2.0 flare on April 12, 2001 was also observed at millimeter and centimeter wavelengths, as well as in soft and hard X-rays. It exhibits both an impulsive phase of nonthermal gyrosynchrotron radiation and an extended phase of strong th…
Physical conditions in the planetary nebula NGC 6543
Liu, X. -W.; Wesson, R.
We present analysis of spectra and Hubble Space Telescope (HST) images of NGC 6543, the Cat's Eye Nebula. Using HST WFPC2 images taken in narrow-band filters isolating Hα and Hβ, we have produced an extinction map towards the nebula, and find that c(Hβ) is low, at ~0.1, and exhibits only very small spatial variations across the surface of the nebu…
Powerful, obscured active galactic nuclei among X-ray hard, optically dim serendipitous Chandra sources
Fabian, A. C.; Gandhi, P.; Johnstone, R. M. +1 more
We present a small sample of Chandra X-ray sources selected from the fields of ACIS observations which probe fluxes around the break in the hard band source counts. The targets of these fields include nine nearby galaxy clusters, one distant cluster and two powerful radio galaxy fields. The follow-up of this serendipitous sample was biased towards…