Search Publications
A relationship between the solar rotation and activity in the period 1998-2006 analysed by tracing small bright coronal structures in SOHO-EIT images
Hanslmeier, A.; Wöhl, H.; Brajša, R. +4 more
Aims: The study aims to find a relationship between the rotation of the small bright coronal structures (SBCS) described by the solar rotation parameters and indices of solar activity on monthly and yearly temporal scales.
Methods: We analyse precise measurements of the solar differential rotation determined by tracing SBCS in SOHO-EIT i…
A comparison of preprocessing methods for solar force-free magnetic field extrapolation
Wiegelmann, T.; Valori, G.; Fuhrmann, M. +1 more
Context. Extrapolations of solar photospheric vector magnetograms into three-dimensional magnetic fields in the chromosphere and corona are usually done under the assumption that the fields are force-free. This condition is violated in the photosphere itself and a thin layer in the lower atmosphere above. The field calculations can be improved by …
X-ray study of HLX1: intermediate-mass black hole or foreground neutron star?
Soria, Roberto; Wu, Kinwah; Zampieri, Luca +1 more
We re-assess the XMM-Newton and Swift observations of HLX1 to examine the evidence for its identification as an intermediate-mass black hole. We show that the X-ray spectral and timing properties are equally consistent with an intermediate-mass black hole in a high state or with a foreground neutron star with a luminosity ∼ a few ×1032 …
Direct Measurements of Magnetic Twist in the Solar Corona
Longcope, D. W.; Malanushenko, A.; Yusuf, M. H.
In the present work, we study the evolution of magnetic helicity in the solar corona. We compare the rate of change of a quantity related to the magnetic helicity in the corona to the flux of magnetic helicity through the photosphere and find that the two rates are similar. This gives observational evidence that helicity flux across the photospher…
The last revolution of new comets: the role of stars and their detectability
Rickman, H.; Valsecchi, G. B.; Fouchard, M. +1 more
Context. This work is a follow-up of a previous study, where we simulated the dynamical evolution of the Oort Cloud over 5 Gyr with special attention to the injection of comets into observable orbits.
Aims: We wish to clarify how comet injection operates with two types of perturbers: Galactic tides and passing stars. We illustrate why attempt…
Search for cosmic strings in the COSMOS survey
Smoot, G. F.; Christiansen, J. L.; Albin, E. +4 more
We search the COSMOS survey for pairs of galaxies consistent with the gravitational lensing signature of a cosmic string. The COSMOS survey imaged 1.64 square degrees using the Advanced Camera for Surveys aboard the Hubble Space Telescope. Our technique includes estimates of the efficiency for finding the lensed galaxy pair. We find no evidence fo…
HD 5388 b is a 69 MJup companion instead of a planet
Queloz, D.; Sahlmann, J.; Ségransan, D. +1 more
We examined six exoplanet host stars with non-standard Hipparcos astrometric solution, which may be indicative of unrecognised orbital motion. Using Hipparcos intermediate astrometric data, we detected the astrometric orbit of HD 5388 at a significance level of 99.4% (2.7 σ). HD 5388 is a metal-deficient star and hosts a planet candidate with a mi…
Outflow in Overlooked Luminous Quasar: Subaru Observations of AKARI J1757+5907
Oyabu, Shinki; Matsuhara, Hideo; Toba, Yoshiki +5 more
We present Subaru observations of the newly discovered luminous quasar AKARI J1757+5907, which shows an absorption outflow in its spectrum. The absorption consists of 9 distinct troughs, and our analysis focuses on the troughs at ∼-1000 km s-1 for which we could measure accurate column densities of He I*, Fe II, and Mg II. We…
Multi-wavelength Probes of Obscuration Toward the Narrow-line Region in Seyfert Galaxies
Turner, T. J.; Kraemer, S. B.; Crenshaw, D. M. +4 more
We present a study of reddening and absorption toward the narrow line regions (NLRs) in active galactic nuclei (AGNs) selected from the Revised Shapley-Ames, 12 µm, and Swift/Burst Alert Telescope samples. For the sources in host galaxies with inclinations of b/a > 0.5, we find that the mean ratio of [O III] λ5007, from ground-based obser…
Spitzer Observations of Supernova Remnants. II. Physical Conditions and Comparison with HH7 and HH54
Yuan, Yuan; Neufeld, David A.
We have studied the shock-excited molecular regions associated with four supernova remnants (SNRs)—IC443C, W28, W44, and 3C391—and two Herbig-Haro objects—HH7 and HH54—using Spitzer's Infrared Spectrograph (IRS). The physical conditions within the observed areas (roughly ~1' × 1' in size) are inferred from spectroscopic data obtained from IRS and …