Institute For Weltraumforschung

Graz, Austria

Institute For Weltraumforschung

Graz, Austria
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Scholler M.,European Southern Observatory | Hubrig S.,Leibniz Institute for Astrophysics Potsdam | Fossati L.,Institute For Weltraumforschung | Fossati L.,University of Bonn | And 18 more authors.
Astronomy and Astrophysics | Year: 2017

Aims. The B fields in OB stars (BOB) Collaboration is based on an ESO Large Programme to study the occurrence rate, properties, and ultimately the origin of magnetic fields in massive stars. Methods. In the framework of this program, we carried out low-resolution spectropolarimetric observations of a large sample of massive stars using FORS 2 installed at the ESO VLT 8 m telescope. Results. We determined the magnetic field values with two completely independent reduction and analysis pipelines. Our in-depth study of the magnetic field measurements shows that differences between our two pipelines are usually well within 3σ errors. From the 32 observations of 28 OB stars, we were able to monitor the magnetic fields in CPD -57° 3509 and HD 164492C, confirm the magnetic field in HD 54879, and detect a magnetic field in CPD -62° 2124. We obtain a magnetic field detection rate of 6 ± 3% for the full sample of 69 OB stars observed with FORS 2 within the BOB program. For the preselected objects with a v sin i below 60 km s-1, we obtain a magnetic field detection rate of 5 ± 5%. We also discuss X-ray properties and multiplicity of the objects in our FORS 2 sample with respect to the magnetic field detections. © ESO, 2017.

Prattes G.,Institute For Weltraumforschung | Schwingenschuh K.,Institute For Weltraumforschung | Eichelberger H.U.,Institute For Weltraumforschung | Magnes W.,Institute For Weltraumforschung | And 8 more authors.
Natural Hazards and Earth System Science | Year: 2011

This work presents ground based Ultra Low Frequency (ULF) magnetic field measurements in the frequency range from 10-15 mHz from 1 January 2008 to 14 April 2009. In this time period a strong earthquake series hit the Italian Abruzzo region around L'Aquila with the main stroke of magnitude M = 6.3 on 6 April 2009. In the frame of the South European Geomagnetic Array (SEGMA), a European collaboration runs ULF fluxgate instruments providing continuously magnetic field data recorded in mid- and south Europe. The main scientific objective is the investigation of signal variations due to seismic activity and the discrimination between other natural and human influences. The SEGMA station closest to the L'Aquila earthquake epicenter is L'Aquila observatory located in the epicenter region. For the scientific analysis we extract the nighttime period from 22:00-02:00 UT and determine the power spectral density (PSD) of the horizontal (H) and vertical (Z) magnetic field components and the standardized polarization ratio (Z) over (H). To discriminate local emissions from global geomagnetic effects, data from three SEGMA stations in distances up to 630 km from the epicenter region are analyzed and further compared to the independent global geomagnetic ∑ Kp index. Apart from indirect ionospheric effects, electromagnetic noise could be originated in the lithosphere due to tectonic mechanisms in the earthquake focus. To estimate the amplitude of assumed lithospheric electromagnetic noise emissions causing anomalies in the PSD of the (Z) component, we consider magnetotelluric calculations of the electric crust conductivity in the L'Aquila region. Results found at L'Aquila observatory are interpreted with respect to the lithosphere electrical conductivity in the local observatory region, the ∑ Kp index, and further in a multi station analysis. Possible seismic related ULF anomalies occur ∼2 weeks before the main stroke. © 2011 Author(s).

Lichtenegger H.,Institute For Weltraumforschung | Iorio L.,R.A.U.M. | Iorio L.,International Institute for Theoretical Physics and Advanced Mathematics Einstein
European Physical Journal Plus | Year: 2011

The problem of absolute motion in the context of the twin paradox is discussed. It is shown that the various versions of the clock paradox feature some aspects which Mach might have appreciated. However, the ultimate cause of the behavior of the clocks must be attributed to the autonomous status of spacetime, thereby proving the relational program advocated by Mach as impracticable. © Società Italiana di Fisica / Springer-Verlag 2011.

Richter I.,TU Braunschweig | Auster H.-U.,TU Braunschweig | Berghofer G.,Institute For Weltraumforschung | Carr C.,Imperial College London | And 10 more authors.
Annales Geophysicae | Year: 2016

The European Space Agency's spacecraft ROSETTA has reached its final destination, comet 67P/Churyumov-Gerasimenko. Whilst orbiting in the close vicinity of the nucleus the ROSETTA magnetometers detected a new type of low-frequency wave possibly generated by a cross-field current instability due to freshly ionized cometary water group particles. During separation, descent and landing of the lander PHILAE on comet 67P/Churyumov-Gerasimenko, we used the unique opportunity to perform combined measurements with the magnetometers onboard ROSETTA (RPCMAG) and its lander PHILAE (ROMAP). New details about the spatial distribution of wave properties along the connection line of the ROSETTA orbiter and the lander PHILAE are revealed. An estimation of the observed amplitude, phase and wavelength distribution will be presented as well as the measured dispersion relation, characterizing the new type of low-frequency waves. The propagation direction and polarization features will be discussed using the results of a minimum variance analysis. Thoughts about the size of the wave source will complete our study. © 2016 Author(s).

Iorio L.,R.A.U.M. | Lichtenegger H.I.M.,Institute For Weltraumforschung | Ruggiero M.L.,Polytechnic University of Turin | Corda C.,Associazione Scientifica Galileo Galilei | Corda C.,Institute for Basic Research
Astrophysics and Space Science | Year: 2011

Recent years have seen increasing efforts to directly measure some aspects of the general relativistic grav-itomagnetic interaction in several astronomical scenarios in the solar system. After briefly overviewing the concept of gravitomagnetism from a theoretical point of view, we review the performed or proposed attempts to detect the Lense-Thirring effect affecting the orbital motions of natural and artificial bodies in the gravitational fields of the Sun, Earth, Mars and Jupiter. In particular, we will focus on the evaluation of the impact of several sources of systematic uncertainties of dynamical origin to realistically elucidate the present and future perspectives in directly measuring such an elusive relativistic effect. © Springer Science+Business Media B.V. 2010.

Cabrera J.,German Aerospace Center | Csizmadia Sz.,German Aerospace Center | Montagnier G.,University Pierre and Marie Curie | Fridlund M.,Leiden University | And 59 more authors.
Astronomy and Astrophysics | Year: 2015

Context. We present the discovery of two transiting extrasolar planets by the satellite CoRoT. Aims. We aim at a characterization of the planetary bulk parameters, which allow us to further investigate the formation and evolution of the planetary systems and the main properties of the host stars. Methods. We used the transit light curve to characterize the planetary parameters relative to the stellar parameters. The analysis of HARPS spectra established the planetary nature of the detections, providing their masses. Further photometric and spectroscopic ground-based observations provided stellar parameters (log g, Teff, vsini) to characterize the host stars. Our model takes the geometry of the transit to constrain the stellar density into account, which when linked to stellar evolutionary models, determines the bulk parameters of the star. Because of the asymmetric shape of the light curve of one of the planets, we had to include the possibility in our model that the stellar surface was not strictly spherical. Results. We present the planetary parameters of CoRoT-28b, a Jupiter-sized planet (mass 0.484 ± 0.087 MJup; radius 0.955 ± 0.066 RJup) orbiting an evolved star with an orbital period of 5.208 51 ± 0.000 38 days, and CoRoT-29b, another Jupiter-sized planet (mass 0.85 ± 0.20 MJup; radius 0.90 ± 0.16 RJup) orbiting an oblate star with an orbital period of 2.850 570 ± 0.000 006 days. The reason behind the asymmetry of the transit shape is not understood at this point. Conclusions. These two new planetary systems have very interesting properties and deserve further study, particularly in the case of the star CoRoT-29. © ESO, 2015.

Van Boekel R.,Max Planck Institute for Astronomy | Benneke B.,Massachusetts Institute of Technology | Heng K.,ETH Zurich | Hu R.,Massachusetts Institute of Technology | And 31 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

We present EclipseSim, a radiometric model for exoplanet transit spectroscopy that allows easy exploration of the fundamental performance limits of any space-based facility aiming to perform such observations. It includes a library of stellar model atmosphere spectra and can either approximate exoplanet spectra by simplified models, or use any theoretical or observed spectrum, to simulate observations. All calculations are done in a spectrally resolved fashion and the contributions of the various fundamental noise sources are budgeted separately, allowing easy assessment of the dominant noise sources, as a function of wavelength. We apply EclipseSimto the Exoplanet Characterization Observatory (EChO), a proposed mission dedicated to exoplanet transit spectroscopy that is currently in competition for the M3 launch slot of ESA's cosmic vision programme. We show several case studies on planets with sizes in the super-Earth to Jupiter range, and temperatures ranging from the temperate to the ≈1500K regime, demonstrating the power and versatility of EChO. EclipseSim is publicly available. © 2012 SPIE.

Villante U.,University of L'Aquila | De Lauretis M.,University of L'Aquila | De Paulis C.,University of L'Aquila | Francia P.,University of L'Aquila | And 11 more authors.
Natural Hazards and Earth System Science | Year: 2010

Several investigations reported the possible identification of anomalous geomagnetic field signals prior to earthquake occurrence. In the ULF frequency range, candidates for precursory signatures have been proposed in the increase in the noise background and polarization parameter (i.e. the ratio between the amplitude/power of the vertical component and that one of the horizontal component), in the changing characteristics of the slope of the power spectrum and fractal dimension, in the possible occurrence of short duration pulses. We conducted, with conventional techniques of data processing, a preliminary analysis of the magnetic field observations performed at L'Aquila during three months preceding the 6 April 2009 earthquake, focusing attention on the possible occurrence of features similar to those identified in previous events. Within the limits of this analysis, we do not find compelling evidence for any of the features which have been proposed as earthquake precursors: indeed, most of aspects of our observations (which, in some cases, appear consistent with previous findings) might be interpreted in terms of the general magnetospheric conditions and/or of different sources.

Schwingenschuh K.,Institute For Weltraumforschung | Prattes G.,Institute For Weltraumforschung | Delva M.,Institute For Weltraumforschung | Eichelberger H.U.,Institute For Weltraumforschung | And 7 more authors.
Proceedings of the 2012 ESA Workshop on Aerospace EMC 2012 | Year: 2012

Magnetic field measurements on planetary surfaces are disturbed by various internal and external sources. We discuss methods to reduce their influence on the quality of magnetic field experiments aboard surface stations. Our major emphasis is on terrestrial seismo-magnetic measurements, but magnetic cleanliness procedures for the ROSETTA lander magnetic field experiment is discussed too. We consider not only disturbing magnetic field sources as magnetized material or current loops but also environmental sources as the vibration of the magnetic field sensors and eddy currents in conducting material. © 2012 ESA.

Futaana Y.,Swedish Institute of Space Physics | Chaufray J.-Y.,French National Center for Scientific Research | Smith H.T.,Johns Hopkins University | Garnier P.,Hoffmann-La Roche | And 5 more authors.
Space Science Reviews | Year: 2011

Our understanding of the upper atmosphere of unmagnetized bodies such as Mars, Venus and Titan has improved significantly in this decade. Recent observations by in situ and remote sensing instruments on board Mars Express, Venus Express and Cassini have revealed characteristics of the neutral upper atmospheres (exospheres) and of energetic neutral atoms (ENAs). The ENA environment in the vicinity of the bodies is by itself a significant study field, but ENAs are also used as a diagnostic tool for the exosphere and the interaction with the upstream plasmas. Synergy between theoretical and modeling work has also improved considerably. In this review, we summarize the recent progress of our understanding of the neutral environment in the vicinity of unmagnetized planets. © 2011 Springer Science+Business Media B.V.

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