Search Publications
The intensity ratio variation of the Si IV 1394/1403 Å lines during solar flares. Resonance scattering and opacity effects
Ding, M. D.; Hong, J.; Yu, H. C.
Context. The Si IV lines at 1394 Å and 1403 Å form in the solar atmosphere at a temperature of ∼104.8 K. They are usually considered optically thin, but their opacity can be enhanced during solar flares. Traditionally, the intensity ratio of these lines are used as an indicator of the optical thickness. However, observations have shown …
The magnetic field clock angle departure in the Venusian magnetosheath and its response to IMF rotation
Xu, Qi; Zhang, Tielong; Rong, Zhaojin +4 more
We investigate the characteristics of interplanetary magnetic field (IMF) draping in the Venusian magnetosheath using both Venus Express (VEX) observations and magnetohydrodynamics simulations. The distributions of magnetosheath field clock angle illustrate the nearly symmetric morphology of draped magnetic field with respect to the solar wind ele…
Cometary dust collected by MIDAS on board Rosetta. I. Dust particle catalog and statistics
Bentley, M. S.; Mannel, T.; Longobardo, A. +5 more
Context. The Micro-Imaging Dust Analysis System (MIDAS) atomic force microscope (AFM) on board the Rosetta comet orbiter has been dedicated to the collection and 3D topographical investigation of cometary dust in the size range of a few hundreds of nanometers to tens of micrometers with a resolution down to a few nanometers.
Aims: We aim to c…
Multi-spacecraft observations of near-relativistic electron events at different radial distances
Rodríguez-Pacheco, J.; Wimmer-Schweingruber, R. F.; Gómez-Herrero, R. +11 more
Aims: We study the radial evolution of near-relativistic solar energetic electron (SEE) events observed by at least two spacecraft at different heliocentric distances and with small separation angles between their magnetic footpoints at the Sun.
Methods: We identified SEE events for which Solar Orbiter and either Wind or STEREO-A had a s…
Temporal and spatial association between microwaves and type III bursts in the upper corona
Reid, H.; Altyntsev, A. T.; Meshalkina, N. S. +2 more
One of the most important tasks in solar physics is the study of particles and energy transfer from the lower corona to the outer layers of the solar atmosphere. The most sensitive methods for detecting fluxes of non-thermal electrons in the solar atmosphere is observing their radio emission using modern large radioheliographs. We analyzed joint o…
The peculiar ejecta of the nova V1425 Aquilae
Schmidtobreick, L.; Celedón, L.; Tappert, C.
Many important details of the mechanisms underlying the ejection of material during a (classical) nova eruption are still not understood. Here we present optical spectroscopy and narrow-band images of the nova V1425 Aql, 23 yr after the nova eruption. We find that the ejecta consist of two significantly different components. The first resembles wh…
Determination of the eddy diffusion in the Venusian clouds from VeRa sulfuric acid observations
Sheng, Zheng; Dai, Longkang; Shao, Wencheng +1 more
Context. The vertical eddy diffusion coefficient (Kzz) characterizing the efficiency of vertical atmospheric mixing is essential for 1D planetary atmospheric modeling, but poorly constrained in the Venusian clouds, where our ability to observe tracer gases is limited. The Venusian clouds are mainly composed of H2SO4
Convective blueshift strengths for 242 evolved stars
Reiners, A.; Zechmeister, M.; Jeffers, S. V. +1 more
Context. With the advent of extreme precision radial velocity (RV) surveys, seeking to detect planets at RV semi-amplitudes of 10 cm s−1, intrinsic stellar variability is the biggest challenge to detecting small exoplanets. To overcome the challenge we must first thoroughly understand all facets of stellar variability. Among those, conv…
High-precision broadband linear polarimetry of early-type binaries. IV. The DH Cephei binary system in the open cluster of NGC 7380
Piirola, Vilppu; Berdyugin, Andrei V.; Sakanoi, Takeshi +2 more
Aims: DH Cephei is a well-known massive O+O-type binary system on the northern sky, situated at the center of young open cluster NGC 7380. Our high-precision multi-band polarimetry clearly reveals that variations of linear polarization in this system are synchronous with the phase of the orbital period. We used the observed variations of Stok…
Likelihood of the sky. Bayesian treatment of the geometric two-catalog matching problem
Schmitt, J. H. M. M.; Salvato, M.; Buchner, J. +4 more
Catalogs with celestial positions and uncertainties are among the primary data products of observational astronomy. Consequently, the (cross-)matching problem, namely, the question of how many (and which) pairs of positions pertain to the same celestial source, remains a central part of this scientific exploitation. We address the matching problem…