Search Publications
X-ray emission from a metal depleted accretion shock onto the classical T Tauri star TW Hya
Schmitt, J. H. M. M.; Stelzer, B.
We present the X-ray spectrum of TW Hya observed at high and intermediate spectral resolution with the Reflection Grating Spectrometer (RGS) and the European Photon Imaging Camera (EPIC) onboard the XMM-Newton satellite. TW Hya is the first classical T Tauri star for which simultaneous X-ray data with both high spectral resolution and high sensiti…
Magnetic Doppler imaging of 53 Camelopardalis in all four Stokes parameters
Petit, P.; Piskunov, N.; Wade, G. A. +5 more
We present the first investigation of the structure of the stellar surface magnetic field using line profiles in all four Stokes parameters. We extract the information about the magnetic field geometry and abundance distributions of the chemically peculiar star 53 Cam by modelling time-series of high-resolution spectropolarimetric observations wit…
The dynamical mass of the young cluster W3 in NGC 7252. Heavy-weight globular cluster or ultra compact dwarf galaxy?
Saglia, R. P.; Bastian, N.; Maraston, C. +3 more
We have determined the dynamical mass of the most luminous stellar cluster known to date, i.e. object W3 in the merger remnant galaxy NGC 7252. The dynamical mass is estimated from the velocity dispersion measured with the high-resolution spectrograph UVES on VLT. Our result is the astonishingly high velocity dispersion of σ=45 ± 5 km s-1
X-ray flares reveal mass and angular momentum of the Galactic Center black hole
Grosso, N.; Porquet, D.; Predehl, P. +1 more
We have analysed the light curve of the two brightest X-ray flares from the Galactic Center black hole, one flare observed by XMM-Newton on October 3, 2002 (Porquet et al. \cite{P2003}), and the other flare observed by Chandra on October 26, 2000 (Baganoff et al. \cite{B2001}). The power density spectra show five distinct peaks at periods of ∼100 …
Hard X-ray view of the past activity of Sgr A* in a natural Compton mirror
Gilfanov, M. R.; Sunyaev, R. A.; Sazonov, S. Yu. +6 more
We report the association of the recently discovered hard X-ray source IGR J17475-2822 with the giant molecular cloud Sgr B2 in the Galactic Center region. The broad band (3-200 keV) spectrum of the source constructed from data of different observatories strongly supports the idea that the X-ray emission of Sgr B2 is Compton scattered and reproces…
Some empirical estimates of the H2 formation rate in photon-dominated regions
Boulanger, F.; Walmsley, C. M.; Habart, E. +2 more
We combine recent ISO observations of the vibrational ground state lines of H2 towards Photon-Dominated Regions (PDRs) with observations of vibrationally excited states made with ground-based telescopes in order to constrain the formation rate of H2 on grain surfaces under the physiconditions in the layers responsible for H
A multiwavelength study of solar flare waves. I. Observations and basic properties
Magdalenić, J.; Vršnak, B.; Hanslmeier, A. +2 more
Propagating wave-like disturbances associated with solar flares - commonly observed in the chromosphere as Moreton waves - have been known for several decades. Recently, the phenomenon has come back into focus prompted by the observation of coronal waves with the SOHO/EIT instrument (``EIT waves"). It has been suggested that they represent the ant…
Mapping ices in protostellar environments on 1000 AU scales. Methanol-rich ice in the envelope of Serpens SMM 4
van Dishoeck, E. F.; Pontoppidan, K. M.; Dartois, E.
We present VLT-ISAAC L-band spectroscopy toward 10 stars in SVS 4, a 30 arcsec×45 arcsec dense cluster of pre-main sequence stars deeply embedded in the Serpens star forming cloud. The ISAAC spectra are combined with archival imaging from UKIRT and ISOCAM to derive accurate extinctions toward the SVS 4 stars. The data are then used to construct a …
A multiwavelength study of solar flare waves. II. Perturbation characteristics and physical interpretation
Magdalenić, J.; Vršnak, B.; Hanslmeier, A. +2 more
The study of solar flare waves - globally propagating wave-like disturbances usually observed in Hα as Moreton waves - has recently come back into focus prompted by the observation of coronal waves in the EUV with the SOHO/EIT instrument (``EIT waves"), and in several additional wavelength channels. We study 12 flare wave events in order to determ…
Solar magnetic elements at 0.1 arcsec resolution. General appearance and magnetic structure
Hansteen, V. H.; Carlsson, M.; Berger, T. E. +6 more
New observations of solar magnetic elements in a remnant active region plage near disk center are presented. The observations were obtained at the recently commissioned Swedish 1-m Solar Telescope on La Palma. We examine a single 430.5 nm G-band filtergram that resolves ∼70 km (0.1 arcsec) structures and find new forms of magnetic structures in th…