Search Publications
Fermi-LAT observations of the Sagittarius B complex
Aharonian, Felix; Yang, Rui-zhi; Jones, David I.
Aims: We use 5 years of Fermi-LAT data towards the Galactic-centre giant molecular cloud complex, Sagittarius B, to test questions of how well-mixed the Galactic component of cosmic rays are and what the level of the cosmic-ray sea in different parts of the Galaxy is.
Methods: We use dust-opacity maps from the Planck satellite to obtain …
Proton intensity spectra during the solar energetic particle events of May 17, 2012 and January 6, 2014
Dresing, N.; Heber, B.; Kühl, P. +4 more
Context. Ground-level enhancements (GLEs) are solar energetic particle events that show a significant intensity increase at energies that can be measured by neutron monitors. The most recent GLE-like events were recorded on May 17, 2012 and January 6, 2014. They were also measured by sophisticated instrumentation in space such as PAMELA and the El…
The high energy spectrum of 3C 273
Lähteenmäki, A.; Tramacere, A.; Walter, R. +4 more
Aims: The high energy spectrum of 3C 273 is usually understood in terms of inverse-Compton emission in a relativistic leptonic jet. This model predicts variability patterns and delays that could be tested with simultaneous observations from the radio to the GeV range.
Methods: The instruments IBIS, SPI, JEM-X on board INTEGRAL, PCA on bo…
Negatively charged nano-grains at 67P/Churyumov-Gerasimenko
Gombosi, T. I.; Burch, J. L.; Horányi, M.
Shortly after the Rosetta mission's rendezvous with 67P/Churyumov-Gerasimenko the RPC/IES instrument intermittently detected negative particles that were identified as singly charged nano-dust grains. These grains were recorded as a nearly mono-energetic beam of particles in the 200-500 eV range arriving from the direction of the comet. Occasional…
The role of massive halos in the star formation history of the Universe
Finoguenov, A.; Berta, S.; Magnelli, B. +21 more
Context. The most striking feature of the cosmic star formation history (CSFH) of the Universe is a dramatic drop in the star formation (SF) activity after z ~ 1.
Aims: In this work we investigate whether the very same process of assembly and growth of structures is one of the major drivers of the observed decline in the Universe's SF activit…
A census of variability in globular cluster M 68 (NGC 4590)
Surdej, J.; Arellano Ferro, A.; Steele, I. A. +34 more
Aims: We analyse 20 nights of CCD observations in the V and I bands of the globular cluster M 68 (NGC 4590) and use them to detect variable objects. We also obtained electron-multiplying CCD (EMCCD) observations for this cluster in order to explore its core with unprecedented spatial resolution from the ground.
Methods: We reduced our da…
Orbital elements of the material surrounding comet 67P/Churyumov-Gerasimenko
Jorda, L.; Lamy, P. L.; Lara, L. M. +44 more
Context. We investigate the dust coma within the Hill sphere of comet 67P/Churyumov-Gerasimenko.
Aims: We aim to determine osculating orbital elements for individual distinguishable but unresolved slow-moving grains in the vicinity of the nucleus. In addition, we perform photometry and constrain grain sizes.
Methods: We performed astrome…
Herschel observations of extreme OH/IR stars. The isotopic ratios of oxygen as a sign-post for the stellar mass
Waters, L. B. F. M.; Olofsson, H.; Blommaert, J. +10 more
Aims: The late stages of stellar evolution are mainly governed by the mass of the stars. Low- and intermediate-mass stars lose copious amounts of mass during the asymptotic giant branch (AGB) which obscure the central star making it difficult to study the stellar spectra and determine the stellar mass. In this study, we present observational …
Far-infrared study of K giants in the solar neighborhood: Connection between Li enrichment and mass-loss
Zhao, G.; Muthumariappan, C.; Bharat Kumar, Yerra +1 more
Context. A small group of red giant branch (RGB) stars are known to have anomalous Li enhancement whose origin is still not well understood. Some studies have proposed that the Li enhancement in RGB stars is correlated to their far-IR excess, a result of mass loss. Studies to confirm such a correlation have a significant bearing on our understandi…
B fields in OB stars (BOB): FORS 2 spectropolarimetric follow-up of the two rare rigidly rotating magnetosphere stars HD 23478 and HD 345439
Fossati, L.; Morel, T.; Przybilla, N. +7 more
Aims: Massive B-type stars with strong magnetic fields and fast rotation are very rare and pose a mystery for theories of star formation and magnetic field evolution. Only two such stars, called σ Ori E analogues, were known until recently. A team involved in APOGEE, one of the Sloan Digital Sky Survey III programs, announced the discovery of…