Search Publications
Magnetic turbulence in the plasma sheet
Balogh, A.; Zhang, T. L.; Klecker, B. +9 more
Small-scale magnetic turbulence observed by the Cluster spacecraft in the plasma sheet is investigated by means of a wavelet estimator suitable for detecting distinct scaling characteristics even in noisy measurements. The spectral estimators used for this purpose are affected by a frequency-dependent bias. The variances of the wavelet coefficient…
XMM-Newton observation of the relaxed cluster A478: Gas and dark matter distribution from 0.01R200 to 0.5R200
de Plaa, J.; Arnaud, M.; Pointecouteau, E. +1 more
We present an XMM-Newton mosaic observation of the hot (kT∼6.5 keV) and nearby (z=0.0881) relaxed cluster of galaxies A478. We derive precise gas density, gas temperature, gas mass and total mass profiles up to 12 arcmin (about half of the virial radius R200). The gas density profile is highly peaked towards the center and the surface b…
Tests of stellar model atmospheres by optical interferometry. VLTI/VINCI limb-darkening measurements of the M4 giant ψ Phe
Kervella, P.; Wittkowski, M.; Aufdenberg, J. P.
We present K-band interferometric measurements of the limb-darkened (LD) intensity profile of the M 4 giant star ψ Phoenicis obtained with the Very Large Telescope Interferometer (VLTI) and its commissioning instrument VINCI. High-precision squared visibility amplitudes in the second lobe of the visibility function were obtained employing two 8.2 …
Long-term spectral changes in the partial-covering candidate narrow-line Seyfert 1 galaxy 1H 0707-495
Brandt, W. N.; Vaughan, S.; Fabian, A. C. +3 more
We compare two XMM-Newton observations of the narrow-line Seyfert 1 galaxy 1H 0707-495, separated by two years, and discuss the results in terms of the partial-covering phenomenon. The second longer observation once again displays a sharp (<200 eV) spectral drop above 7 keV; however, in comparison with the first observation, the edge depth and …
Testing Lorentz Invariance with GRB 021206
Hurley, K.; Wunderer, C. B.; Boggs, Steven E. +1 more
Since the discovery of the cosmological origin of gamma-ray bursts (GRBs), there has been growing interest in using these transient events to probe the quantum gravity energy scale in the range 1016-1019 GeV, up to the Planck mass scale. This energy scale can manifest itself through a measurable modification in the electromag…
The Stellar Populations of Low-Luminosity Active Galactic Nuclei. II. Space Telescope Imaging Spectrograph Observations
Heckman, Timothy; Leitherer, Claus; Storchi-Bergmann, Thaisa +5 more
We present a study of the stellar populations of low-luminosity active galactic nuclei (LLAGNs). Our goal is to search for spectroscopic signatures of young and intermediate-age stars and to investigate their relationship with the ionization mechanism in LLAGNs. The method used is based on the stellar population synthesis of the optical continuum …
Highly Ionized High-Velocity Clouds toward PKS 2155-304 and Markarian 509
Shull, J. Michael; Giroux, Mark L.; Collins, Joseph A.
To gain insight into four highly ionized high-velocity clouds (HVCs) discovered by Sembach et al., we have analyzed data from the Hubble Space Telescope (HST) and Far Ultraviolet Spectroscopic Explorer (FUSE) for the PKS 2155-304 and Mrk 509 sight lines. We measure strong absorption in O VI and column densities of multiple ionization stages of sil…
The late-time light curve of the type Ia supernova 2000cx
Sollerman, J.; Lundqvist, P.; Spyromilio, J. +10 more
We have conducted a systematic and comprehensive monitoring programme of the type Ia supernova 2000cx at late phases using the VLT and HST. The VLT observations cover phases 360 to 480 days past maximum brightness and include photometry in the BVRIJH bands, together with a single epoch in each of U and K_s. While the optical bands decay by about 1…
Structure and kinematics of candidatedouble-barred galaxies
Moiseev, A. V.; Chavushyan, V. H.; Valdés, J. R.
Results of optical and NIR spectral and photometric observations of a sample of candidate double-barred galaxies are presented. Velocity fields and velocity dispersion maps of stars and ionized gas, continuum and emission-line images were constructed from integral-field spectroscopy observations carried out at the 6 m telescope (BTA) of SAO RAS, w…
Evolution of Solar Supergranulation
Toomre, Juri; De Rosa, Marc L.
The structure and evolution of solar supergranulation is studied using horizontal velocity fields, deduced from applying local correlation tracking (LCT) techniques to full-disk, line-of-sight Doppler velocity data observed by the Michelson Doppler Imager on board the Solar and Heliospheric Observatory spacecraft. Two 45° square regions of photosp…