Search Publications
The origin of crystalline silicates in the Herbig Be star HD 100546 and in comet Hale-Bopp
Waters, L. B. F. M.; Dominik, C.; de Koter, A. +1 more
We have investigated the spatial distribution, and the properties and chemical composition of the dust orbiting HD 100546. This system is remarkably different from other isolated Herbig Ae/Be stars in both the strength of the mid-IR excess and the composition of the circumstellar dust. To explain spectral features and the amount of mid-IR dust emi…
Hot coronal loop oscillations observed with SUMER: Examples and statistics
Solanki, S. K.; Curdt, W.; Innes, D. E. +3 more
We give an extensive overview of Doppler shift oscillations in hot active region loops obtained with SUMER. The oscillations have been detected in loops sampled 50-100 arcsec off the limb of the Sun in ultraviolet lines, mainly Fe Xix and Fe Xxi, with formation temperature greater than 6 MK. The spectra were recorded along a 300 arcsec slit placed…
The thermal radiation of the isolated neutron star RX J1856.5-3754 observed with Chandra and XMM-Newton
Haberl, F.; Burwitz, V.; Neuhäuser, R. +3 more
We present results of the analysis of data collected in 57-ks XMM-Newton and 505-ks Chandra observations of the nearby ( =~ 120 pc) isolated neutron star RX J1856.5-3754. We confirm most of the statements made by Burwitz et al. (\cite{Buretal01}) who discussed the original 55-ks Chandra data. Detailed spectral analysis of the combined X-ray and op…
Grain growth in the inner regions of Herbig Ae/Be star disks
Waters, L. B. F. M.; Dominik, C.; van Boekel, R. +4 more
We present new mid-infrared spectroscopy of the emission from warm circumstellar dust grains in Herbig Ae/Be stars. Our survey significantly extends the sample that was studied by Bouwman et al. (2001). We find a correlation between the strength of the silicate feature and its shape. We interpret this as evidence for the removal of small (0.1 mu m…
The ISO view of Palomar-Green quasars
Meisenheimer, K.; Krause, O.; Lemke, D. +8 more
Mining the ISO data archive we provide the complete ISO view of PG quasars containing 64 infrared spectral energy distributions between 5 and 200 mu m. About half of the sample was supplemented by MAMBO and SCUBA (sub-)millimetre data. Since the PG quasars were selected optically, the high infrared detection rate of more than 80% suggests that eve…
Clusters in the inner spiral arms of M 51: The cluster IMF and the formation history
Panagia, N.; Bastian, N.; Bik, A. +2 more
We present the results of an analysis of the HST-WFPC2 observations of the interacting galaxy M 51. From the observations in 5 broadband filters (UBVRI) and two narrowband filters (Hα and [OIII]) we study the cluster population in a region of 3.2 x 3.2 kpc2 in the inner spiral arms of M 51, at a distance of about 1 to 3 kpc from the nuc…
On the Lyalpha emission from gamma-ray burst host galaxies: Evidence for low metallicities
Fruchter, A. S.; Wijers, R. A. M. J.; Pedersen, H. +11 more
We report on the results of a search for Lyalpha emission from the host galaxy of the z=2.140 GRB 011211 and other galaxies in its surrounding field. We detect Lyalpha emission from the host as well as from six other galaxies in the field. The restframe equivalent width of the Lyalpha line from the GRB 011211 host is about 21 Å. This is the fifth …
Slow-mode standing waves observed by SUMER in hot coronal loops
Solanki, S. K.; Marsch, E.; Curdt, W. +2 more
We report the first detection of postflare loop oscillations seen in both Doppler shift and intensity. The observations were recorded in an Fe Xix line by the SUMER spectrometer on SOHO in the corona about 70 min after an M-class flare on the solar limb. The oscillation has a period of about 17 min in both the Doppler velocity and the intensity, b…
Dynamics of solar coronal loops. I. Condensation in cool loops and its effect on transition region lines
Peter, H.; Hansteen, V. H.; Müller, D. A. N.
We report numerical calculations of the condensation of plasma in short coronal loops, which have several interesting physical consequences. Firstly, we propose a connection between small, cool loops (T < 106 K), which constitute one of the basic components of the solar transition region, and prominences, in the sense that the same p…
The low-level radial velocity variability in Barnard's star (= GJ 699). Secular acceleration, indications for convective redshift, and planet mass limits
Kürster, M.; Hatzes, A. P.; Cochran, W. D. +6 more
We report results from 2 1/2 yr of high precision radial velocity (RV) monitoring of Barnard's star. The high RV measurement precision of the VLT-UT2+UVES of 2.65 m s-1 made the following findings possible. (1) The first detection of the change in the RV of a star caused by its space motion (RV secular acceleration). (2) An anti-correla…