Search Publications
Clues to cometary circular polarization from studying the magnetic field in the vicinity of the nucleus of comet 67P/Churyumov-Gerasimenko
Kolokolova, Ludmilla; Hoang, Thiem; Goetz, Charlotte +4 more
Circular polarization in cometary continuum bands has been observed for more than 30 years. Recently, imaging data on circular polarization have been obtained for more than 10 comets using the 6-m Big Telescope Alt-azimuthal (BTA) telescope (Russia). However, despite the accumulation of significant amounts of data, the mechanisms that form circula…
Departure of High-temperature Iron Lines from the Equilibrium State in Flaring Solar Plasmas
Keenan, F. P.; Kawate, T.; Jess, D. B.
The aim of this study is to clarify if the assumption of ionization equilibrium and a Maxwellian electron energy distribution is valid in flaring solar plasmas. We analyze the 2014 December 20 X1.8 flare, in which the Fe xxi 187 Å, Fe xxii 253 Å, Fe xxiii 263 Å, and Fe xxiv 255 Å emission lines were simultaneously observed by the EUV Imaging Spect…
Overlooked wide companions of nearby F stars
Scholz, R. -D.
Aims: We checked a sample of 545 F stars within 50 pc for wide companions using existing near-infrared and optical sky surveys.
Methods: Applying the common proper motion (CPM) criterion, we detected wide companion candidates with 6-120 arcsec angular separations by visual inspection of multi-epoch finder charts and by searching in prope…
Detection of HF Toward PKS 1830-211, Search for Interstellar H2F+, and Laboratory Study of H2F+ and H2Cl+ Dissociative Recombination
Muller, S.; Black, J. H.; Miyamoto, Y. +7 more
We report extragalactic observations of two fluorine-bearing species, hydrogen fluoride (HF) and fluoronium (H2F+), in the z = 0.89 absorber in front of the lensed blazar PKS 1830-211 with the Atacama Large Millimeter/submillimeter Array. HF was detected toward both southwest and northeast images of the blazar, with column de…
Spectral variation in the supergiant fast X-ray transient SAX J1818.6-1703 observed by XMM-Newton and INTEGRAL
Hill, A. B.; Sidoli, L.; Bird, A. J. +6 more
We present the results of a 30 ks XMM-Newton observation of the supergiant fast X-ray transient (SFXT) SAX J1818.6-1703 - the first in-depth soft X-ray study of this source around periastron. INTEGRAL observations shortly before and after the XMM-Newton observation show the source to be in an atypically active state. Over the course of the XMM-New…
Running cosmological constant with observational tests
Geng, Chao-Qiang; Lee, Chung-Chi; Zhang, Kaituo
We investigate the running cosmological constant model with dark energy linearly proportional to the Hubble parameter, Λ = σH +Λ0, in which the ΛCDM limit is recovered by taking σ = 0. We derive the linear perturbation equations of gravity under the Friedmann-Lemaïtre-Robertson-Walker cosmology, and show the power spectra of the CMB tem…
Oxygen ion response to proton bursty bulk flows
Karlsson, Tomas; Nilsson, Hans; Gunell, Herbert +6 more
We have used Cluster spacecraft data from the years 2001 to 2005 to study how oxygen ions respond to bursty bulk flows (BBFs) as identified from proton data. We here define bursty bulk flows as periods of proton perpendicular velocities more than 100 km/s and a peak perpendicular velocity in the structure of more than 200 km/s, observed in a regio…
Constraining SN feedback: a tug of war between reionization and the Milky Way satellites
Lacey, Cedric G.; Hou, Jun; Frenk, Carlos. S. +1 more
Theoretical models of galaxy formation based on the cold dark matter cosmogony typically require strong feedback from supernova (SN) explosions in order to reproduce the Milky Way satellite galaxy luminosity function and the faint end of the field galaxy luminosity function. However, too strong a SN feedback also leads to the universe reionizing t…
X-ray and optical observations of four polars
Granzer, T.; Schwope, A. D.; Traulsen, I. +3 more
Aims: We investigate the temporal and spectral behaviour of four polar cataclysmic variables from the infrared to X-ray regimes, refine our knowledge of the physical parameters of these systems at different accretion rates, and search for a possible excess of soft X-ray photons.
Methods: We obtained and analysed four XMM-Newton X-ray obs…
Dust in a compact, cold, high-velocity cloud: A new approach to removing foreground emission
Kerp, J.; Lenz, D.; Flöer, L.
Context. Because isolated high-velocity clouds (HVCs) are found at great distances from the Galactic radiation field and because they have subsolar metallicities, there have been no detections of dust in these structures. A key problem in this search is the removal of foreground dust emission.
Aims: Using the Effelsberg-Bonn H I Survey and th…