Search Publications
The VLT-FLAMES Tarantula Survey. IV. Candidates for isolated high-mass star formation in 30 Doradus
Crowther, P. A.; Bastian, N.; de Koter, A. +15 more
Whether massive stars (≳30 M⊙) can occasionally form in relative isolation (e.g. in clusters with M < 100 M⊙) or if they require a large cluster of lower-mass stars around them is a key test in the differentiation of star-formation theories as well as how the initial mass function of stars is sampled. Previous attempts to …
Nitrogen line spectroscopy in O-stars. III. The earliest O-stars
Puls, J.; Najarro, F.; Massey, P. +1 more
Context. The classification scheme proposed by Walborn et al. (2002, AJ, 123, 2754), based primarily on the relative strengths of the N ivλ4058 and N iiiλ4640 emission lines, has been used in a variety of studies to spectroscopically classify early O-type stars. Owing to the lack of a solid theoretical basis, this scheme has not yet been universal…
Are the strengths of solar cycles determined by converging flows towards the activity belts?
Schüssler, M.; Cameron, R. H.
It is proposed that the observed near-surface inflows towards the active regions and sunspot zones provide a nonlinear feedback mechanism that limits the amplitude of a Babcock-Leighton-type solar dynamo and determines the variation of the cycle strength. This hypothesis is tested with surface flux transport simulations including converging latitu…
Nanostructuration of carbonaceous dust as seen through the positions of the 6.2 and 7.7 µm AIBs
Dartois, E.; d'Hendecourt, L.; Brunetto, R. +7 more
Context. Carbonaceous cosmic dust is observed through infrared spectroscopy either in absorption or in emission. The details of the spectral features are believed to shed some light on its structure and finally enable the study of its life cycle.
Aims: The goal is to combine several analytical tools in order to decipher the intimate nanostruc…
Nitrogen hydrides in interstellar gas. II. Analysis of Herschel/HIFI observations towards W49N and G10.6 - 0.4 (W31C)
Menten, K. M.; Godard, B.; Persson, C. M. +14 more
As a part of the Herschel key programme PRISMAS, we have used the Herschel/HIFI instrument to observe interstellar nitrogen hydrides along the sight-lines towards eight high-mass star-forming regions in order to elucidate the production pathways leading to nitrogen-bearing species in diffuse gas. Here, we report observations towards W49N of the NH…
Dust and gas power spectrum in M 33 (HERM33ES)
Boquien, M.; Braine, J.; Calzetti, D. +18 more
Power spectra of deprojected images of late-type galaxies in gas or dust emission are very useful diagnostics of the dynamics and stability of their interstellar medium. Previous studies have shown that the power spectra can be approximated as two power laws, a shallow one on large scales (larger than 500 pc) and a steeper one on small scales, wit…
Characterization of new hard X-ray cataclysmic variables
Mukai, K.; de Martino, D.; Masetti, N. +5 more
Aims: We aim at characterizing a sample of nine new hard X-ray selected cataclysmic variable (CVs), to unambiguously identify them as magnetic systems of the intermediate polar (IP) type.
Methods: We performed detailed timing and spectral analysis by using X-ray, and simultaneous UV and optical data collected by XMM-Newton, complemented …
Nonthermal X-rays from low-energy cosmic rays: application to the 6.4 keV line emission from the Arches cluster region
Decourchelle, A.; Maurin, G.; Tatischeff, V.
Context. The iron Kα line at 6.4 keV provides a valuable spectral diagnostic in several fields of X-ray astronomy. The line often results from the reprocessing of external hard X-rays by a neutral or low-ionized medium, but it can also be excited by impacts of low-energy cosmic rays.
Aims: This paper aims to provide signatures allowing identi…
Benchmarking atomic data for the CHIANTI atomic database: coronal lines observed by Hinode EIS
Del Zanna, G.
The coronal lines that are observable in the Hinode EUV Imaging Spectrometer (EIS) wavelengths are assessed with new atomic data that have recently become available for a range of important ions. EIS spectral lines are identified based on their spatial variation across different solar regions, their wavelengths, and their intensities. Two off-limb…
Herschel/HIFI observations of O-rich AGB stars: molecular inventory
Menten, K. M.; Olofsson, H.; Marston, A. P. +17 more
Aims: Spectra, taken with the heterodyne instrument, HIFI, aboard the Herschel Space Observatory, of O-rich asymptotic giant branch (AGB) stars which form part of the guaranteed time key program HIFISTARS are presented. The aim of this program is to study the dynamical structure, mass-loss driving mechanism, and chemistry of the outflows from…