Search Publications
HST large-field weak lensing analysis of MS 2053-04: study of the mass distribution and mass-to-light ratio of X-ray luminous clusters at 0.22<z<0.83
van Dokkum, Pieter G.; Franx, Marijn; Hoekstra, Henk +1 more
We have detected the weak lensing signal induced by the cluster of galaxies MS 2053-04 (z=0.58) from a two-colour mosaic of six Hubble Space Telescope (HST) WFPC2 images. The best-fitting singular isothermal sphere model to the observed tangential distortion yields an Einstein radius rE=6.2+/-1.8arcsec, which corresponds to a velocity d…
X-ray sources in the starburst spiral galaxy M 83. Nuclear region and discrete source population
Soria, R.; Wu, K.
Chandra has resolved the starburst nuclear region of the face-on grand-design spiral M 83. Eighty-one point sources are detected (above 3.5-sigma ) in the ACIS S3 image, and 15 of them are within the inner 16\arcsec region of the galaxy. A point source with Lx ~ 3 x 1038 erg s-1 in the 0.3-8.0 keV band is found to …
Simultaneous X-ray spectroscopy of YY Gem with Chandra and XMM-Newton
Schmitt, J. H. M. M.; Burwitz, V.; Neuhäuser, R. +7 more
We report on a detailed study of the X-ray spectrum of the nearby eclipsing spectroscopic binary YY Gem. Observations were obtained simultaneously with both large X-ray observatories, XMM-Newton and Chandra. We compare the high-resolution spectra acquired with the Reflection Grating Spectrometer onboard XMM-Newton and with the Low Energy Transmiss…
Conversion of relativistic pair energy into radiation in the jets of active galactic nuclei
Vainio, R.; Schlickeiser, R.; Pohl, M. +3 more
It is generally accepted that relativistic jet outflows power the nonthermal emission from active galactic nuclei (AGN). The composition of these jets - leptonic versus hadronic - is still under debate. We investigate the microphysical details of the conversion process of the kinetic energy in collimated relativistic pair outflows into radiation t…
Ionized iron Kalpha lines in AGN X-ray spectra
Bianchi, S.; Matt, G.
The Equivalent Widths (EW) of the He- and H-like iron lines produced in photoionized, circumnuclear matter of AGN are calculated with respect to both the reflected and the total continua. We found that the EWs with respect to the total continuum may be as large as a few tens of eV, making them observable in bright Seyfert 1s by instruments on boar…
RU Cen and SX Cen: Two strongly depleted RV Tauri stars in binary systems. The RV Tauri photometric b phenomenon and binarity
Maas, T.; Van Winckel, H.; Waelkens, C.
We present a chemical abundance analysis on the basis of high signal-to-noise and high-resolution (lambda /Delta lambda ~ 48 000) optical spectra of two RV Tauri stars RU Cen and SX Cen. With an [Fe/H] = -1.9 and a [Zn/Fe] = +0.9 for RU Cen and a [Fe/H] = -1.1 and a [Zn/Fe] = +0.6 for SX Cen, both stars of spectroscopic class B display strong depl…
Saturn's F Ring: Kinematics and Particle Sizes from Stellar Occultation Studies
Nicholson, P. D.; Bosh, A. S.; Olkin, C. B. +1 more
The occultation of GSC5249-01240 by Saturn's rings was observed in a spectrally resolved mode using the Faint Object Spectrograph on the Hubble Space Telescope. By combining these data with other occultation data, we have determined the inclination of the F ring to be 0.0065±0.0014 deg. Our inclined F ring orbit model explains an abrupt decrease i…
The Infrared Space Observatory Deep Asteroid Search
Tedesco, Edward F.; Desert, François-Xavier
A total of six deep exposures (using the astronomical observation template CAM01 with a 6" pixel field of view) through the ISOCAM LW10 filter (IRAS band 1, i.e., 12 µm) were obtained on a ~15' square field centered on the ecliptic plane. Point sources were extracted using the technique described in 1999 by Désert et al. Two known asteroids …
Ultraviolet Hubble Space Telescope Snapshot Survey of 3CR Radio Source Counterparts at Low Redshift
Baum, Stefi A.; O'Dea, Christopher P.; Sparks, William B. +6 more
We present UV images of 27 3CR radio galaxies with redshifts z<0.1 that have been imaged with the Space Telescope Imaging Spectrograph (STIS) on board the Hubble Space Telescope (HST). The observations employed the NUV MAMA and broadband filters with peak sensitivity at 2200 Å. We find that the UV luminosities show approximately a factor of 10-…
The Most Violent Super-Active Regions in the 22nd and 23rd Cycles
Liu, Yang; Tian, Lirong; Wang, Jinxiu
We survey 14 super-active regions (SARs) in the 22nd cycle and 15 SARs in the 23rd cycle. Each produced major flares and major solar storms. Among them, the 25 most violent super active regions (VSARs) are selected based on five parameters: the largest area of sunspots, X-ray flare index (XRI), 10.7 cm radio flux, proton flux and geomagnetic A