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A possible association of the new VHE γ-ray source HESS J1825-137 with the pulsar wind nebula G18.0-0.7
Raux, J.; Ripken, J.; Funk, S. +96 more
We report on a possible association of the recently discovered very high-energy γ-ray source HESS J1825-137 with the pulsar wind nebula (commonly referred to as G 18.0 0.7) of the 2.1× 104 year old Vela-like pulsar PSR B1823 13. HESS J1825-137 was detected with a significance of 8.1σ in the Galactic Plane survey conducted with the HESS …
XMM-Newton observations of the Lockman Hole IV: spectra of the brightest AGN
Streblyanska, A.; Barcons, X.; Fabian, A. C. +5 more
This paper presents the results of a detailed X-ray spectral analysis of a sample of 123 X-ray sources detected with XMM-Newton in the Lockman Hole field. This is the deepest observation carried out with XMM-Newton with more that 600 ks of good EPIC-pn data. We have spectra with good signal to noise (>500 source counts) for all objects down to …
Chemical abundances in 43 metal-poor stars
Magain, P.; Gustafsson, B.; Asplund, M. +3 more
We have derived abundances of O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Ni, and Ba for 43 metal-poor field stars in the solar neighbourhood, most of them subgiants or turn-off-point stars with iron abundances [Fe/H] ranging from -0.4 to -3.0. About half of this sample has not been spectroscopically analysed in detail before. Effective temperatures…
INTEGRAL discovery of persistent hard X-ray emission from the Soft Gamma-ray Repeater SGR 1806-20
Hurley, K.; Götz, D.; Mereghetti, S. +1 more
We report the discovery of persistent hard X-ray emission extending up to 150 keV from the soft gamma-ray repeater SGR 1806-20 using data obtained with the INTEGRAL satellite in 2003-2004. Previous observations of hard X-rays from objects of this class were limited to short duration bursts and rare transient episodes of strongly enhanced luminosit…
Integrated spectrum of the planetary nebula NGC 7027
Barlow, M. J.; Zhang, Y.; Liu, X. -W. +2 more
We present deep optical spectra of the archetypal young planetary nebula (PN)
The evolution of planetary nebulae. III. Internal kinematics and expansion parallaxes
Steffen, M.; Schönberner, D.; Jacob, R.
A detailed theoretical study of the basic internal kinematics of planetary nebulae is presented, based on 1D radiation-hydrodynamics simulations of circumstellar envelopes around central stars of 0.595 and 0.696 M⊙. By means of observable quantities like radial surface-brightness distributions and emission-line profiles computed from th…
Optical novae: the major class of supersoft X-ray sources in M 31
Pietsch, W.; Haberl, F.; Greiner, J. +4 more
We searched for X-ray counterparts of optical novae detected in
A 3-5 µm VLT spectroscopic survey of embedded young low mass stars II. Solid OCN-
van Dishoeck, E. F.; Pontoppidan, K. M.; Fraser, H. J. +1 more
The 4.62 µm (2164.5 cm-1) “XCN” band has been detected in the M-band spectra of 34 deeply embedded young stellar objects (YSO's), observed with high signal-to-noise and high spectral resolution with the VLT-ISAAC spectrometer, providing the first opportunity to study the solid OCN- abundance toward a large number of low…
Sensitivity of spectral lines to temperature, velocity, and magnetic field
Bellot Rubio, L. R.; del Toro Iniesta, J. C.; Cabrera Solana, D.
We present an analytical and numerical study of the sensitivity of weak solar photospheric lines to temperature, velocity, and magnetic fields. Our investigation is based on the concept of response functions (Landi degl'Innocenti & Landi degl'Innocenti 1977; Ruiz Cobo & del Toro Iniesta 1994). Lines commonly used in solar spectropolarimetr…
Asphericity and clumpiness in the winds of Luminous Blue Variables
Vink, Jorick S.; Davies, Ben; Oudmaijer, René D.
We present the first systematic spectropolarimetric study of Luminous Blue Variables (LBVs) in the Galaxy and the Magellanic Clouds, in order to investigate the geometries of their winds. We find that at least half of our sample show changes in polarization across the strong Hα emission line, indicating that the light from the stars is intrinsical…