Search Publications
The HELLAS2XMM Survey. I. The X-Ray Data and the logN-logS Relation
Fiore, F.; Vignali, C.; Molendi, S. +3 more
We present the first results from an XMM-Newton serendipitous medium-deep survey, which covers nearly 3 deg2. We detect a total of 1022, 495, and 100 sources, down to minimum fluxes of about 5.9×10-16, 2.8×10-15, and 6.2×10-15 ergs cm-2 s-1, in the 0.5-2, 2-10, and 4.5-10 keV bands,…
Discovery of an Ionized Fe K Edge in the z=3.91 Broad Absorption Line Quasar APM 08279+5255 with XMM-Newton
Schartel, N.; Hasinger, G.; Komossa, S.
Recent XMM-Newton observations of the high-redshift, lensed, broad absorption line (BAL) quasi-stellar object APM 08279+5255, one of the most luminous objects in the universe, allowed the detection of a high column density absorber (NH~1023 cm-2) in the form of a K-shell absorption edge of significantly ionized iro…
Variability of Southern T Tauri Stars. II. The Spectral Variability of the Classical T Tauri Star TW Hydrae
Alencar, Silvia H. P.; Batalha, Celso
We present the analysis of 42 spectra of the Classical T Tauri star TW Hya observed with the FEROS echelle spectrograph over 2 yr. We determined the rotational and radial velocities of TW Hya, obtaining vsini=5+/-2 km s-1 and vrad=12.5+/-0.5 km s-1. The star exhibits strong emission lines that show substantial vari…
Far Ultraviolet Spectroscopic Explorer and Space Telescope Imaging Spectrograph Observations of Intervening O VI Absorption Line Systems in the Spectrum of PG 0953+415
Savage, B. D.; Sembach, K. R.; Richter, P. +1 more
We present Far Ultraviolet Spectroscopic Explorer (FUSE) and Space Telescope Imaging Spectrograph (STIS) observations of the intergalactic medium toward the bright QSO PG 0953+415 (zem=0.239). The FUSE spectra extend from 905 to 1187 Å and have a resolution of 25 km s-1, while the STIS spectra cover 1150-1730 Å and have a res…
The Excitation and Metallicity of Galactic H II Regions from Infrared Space Observatory SWS Observations of Mid-Infrared Fine-Structure Lines
Pauldrach, A. W. A.; Feuchtgruber, Helmut; Lutz, Dieter +2 more
We present mid-infrared Infrared Space Observatory Short-Wavelength Spectrometer (ISO-SWS) observations of the fine-structure emissions lines [Ne II] 12.8 µm, [Ne III] 15.6 µm, [Ne III] 36.0 µm, [Ar II] 6.99 µm, [Ar III] 8.99 µm, [S III] 18.7 µm, [S III] 33.5 µm, and [S IV] 10.5 µm and the recombinat…
Rapid Changes of Magnetic Fields Associated with Six X-Class Flares
Moon, Yong-Jae; Qiu, Jiong; Denker, Carsten +5 more
In this paper, we present the results of the study of six X-class flares. We found significant changes in the photospheric magnetic fields associated with all of the events. For the five events in 2001, when coronagraph data were available, all were associated with halo coronal mass ejections. Based on the analyses of the line-of-sight magnetogram…
A Survey of Extended Radio Jets in Active Galactic Nuclei with Chandra and the Hubble Space Telescope: First Results
Maraschi, L.; Cheung, C. C.; Tavecchio, F. +5 more
We present the first results from an X-ray and optical survey of a sample of radio jets in active galactic nuclei with Chandra and the Hubble Space Telescope (HST). We focus here on the first six sources observed in X-ray, in four of which a bright X-ray jet was detected for the first time. In three out of the four cases, optical emission from the…
Cosmic Shear and Power Spectrum Normalization with the Hubble Space Telescope
Refregier, Alexandre; Rhodes, Jason; Groth, Edward J.
Weak lensing by large-scale structure provides a direct measurement of matter fluctuations in the universe. We report a measurement of this ``cosmic shear'' based on 271 Wide Field Planetary Camera 2 archival images from the Hubble Space Telescope Medium Deep Survey. Our measurement method and treatment of systematic effects were discussed in an e…
Tightly Correlated X-Ray/Hα-emitting Filaments in the Superbubble and Large-Scale Superwind of NGC 3079
Veilleux, Sylvain; Bland-Hawthorn, Joss; Cecil, Gerald
Using Chandra and HST, we show that X-ray and Hα filaments that form the 1.3 kpc diameter superbubble of NGC 3079 have strikingly similar patterns at ~0.8" resolution. This tight optical line/X-ray match seems to arise from cool disk gas that has been driven by the wind, with X-rays being emitted from upstream, standoff bow shocks or by conductive…
The Star Formation Rate Intensity Distribution Function: Implications for the Cosmic Star Formation Rate History of the Universe
Chen, Hsiao-Wen; Lanzetta, Kenneth M.; Pascarelle, Sebastian +2 more
We address the effects of cosmological surface brightness dimming on observations of faint galaxies by examining the distribution of ``unobscured'' star formation rate intensities versus redshift. We use the star formation rate intensity distribution function to assess the ultraviolet luminosity density versus redshift, based on our photometry and…