Search Publications
Deriving Stellar Inclination of Slow Rotators Using Stellar Activity
Dumusque, X.
Stellar inclination is an important parameter for many astrophysical studies. Although different techniques allow us to estimate stellar inclination for fast rotators, it becomes much more difficult when stars are rotating slower than ~2-2.5 km s-1. By using the new activity simulation SOAP 2.0 which can reproduce the photometric and sp…
A multiwavelength view on the dusty Wolf-Rayet star WR 48a★
Zhekov, Svetozar A.; Borissova, Jura; Hajduk, Marcin +5 more
We present results from the first attempts to derive various physical characteristics of the dusty Wolf-Rayet (WR) star WR 48a based on a multiwavelength view of its observational properties. This is done on the basis of new optical and near-infrared spectral observations and on data from various archives in the optical, radio and X-rays. The opti…
Can magnetopause reconnection drive Saturn's magnetosphere?
Coates, A. J.; Russell, C. T.; Dougherty, M. K. +3 more
While solar wind-driven compression of Saturn's magnetosphere is an important trigger of magnetospheric dynamics, the importance of magnetopause reconnection has been the subject of debate. Here we use Cassini observations at Saturn's magnetopause to address this open issue. Measured conditions at the boundary suggest a typical reconnection electr…
The soft X-ray spectrum of the luminous narrow line Seyfert galaxy PG 1211+143 - evidence for a second high-velocity outflow component
Pounds, K. A.
An XMM-Newton observation of the luminous Seyfert galaxy PG 1211+143 in 2001 revealed the first clear evidence for a highly ionized high-speed wind (in a non-broad absorption line active galactic nucleus), with a velocity of v ∼ 0.09c based on the identification of blueshifted absorption lines in both EPIC and Reflection Grating Spectrometer (RGS)…
Energization of planetary pickup ions in the solar system
Kallio, E.; Jarvinen, R.
We study the solar wind-induced ion escape from planetary atmospheres at different radial heliospheric distances in the solar system. We derive histograms of the gyroaveraged E×B velocities, energies, and Larmor radii of planetary ions in the solar wind at Mercury, Venus, Earth, and Mars. The statistical analysis is based on the interplanetary Pio…
Differential emission measure analysis of active region cores and quiet Sun for the non-Maxwellian κ-distributions
Dzifčáková, E.; Dudík, J.; Mackovjak, Š.
Context. The non-Maxwellian κ-distributions have been detected in the solar wind and can explain intensities of some transition region lines. Presence of such distributions in the outer layers of the solar atmosphere influences the ionization and excitation equilibrium and widens the line contribution functions. This behavior may be reflected on t…
Atmospheric parameters and carbon abundance for hot DB white dwarfs
Gänsicke, B. T.; Koester, D.; Provencal, J.
Atmospheric parameters for hot DB (helium atmosphere) white dwarfs near effective temperatures of 25 000 K are extremely difficult to determine from optical spectroscopy. The neutral He lines reach a maximum in this range and change very little with effective temperature and surface gravity. Moreover, an often unknown amount of hydrogen contaminat…
Mass Transport around Comets and its Impact on the Seasonal Differences in Water Production Rates
Altwegg, K.; Thomas, N.; Combi, M. R. +4 more
Comets are surrounded by a thin expanding atmosphere, and although the nucleus' gravity is small, some molecules and grains, possibly with the inclusion of ices, can get transported around the nucleus through scattering (atoms/molecules) and gravitational pull (grains). Based on the obliquity of the comet, it is also possible that volatile materia…
Long-Period Oscillations of Sunspots Observed by SOHO/MDI
Solov'ev, A. A.; Efremov, V. I.; Parfinenko, L. D. +1 more
We processed magnetograms that were obtained with the Michaelson Doppler Imager onboard the Solar and Heliospheric Observatory (SOHO/MDI). The results confirm the basic properties of long-period oscillations of sunspots that have previously been established and also reveal new properties. We show that the limiting (lowest) eigenmode of low-frequen…
Fresh exposures of hydrous Fe-bearing amorphous silicates on Mars
Weitz, Catherine M.; Bishop, Janice L.; Baker, Leslie L. +1 more
We have discovered relatively fresh exposures of a hydrated, amorphous material along the wall rock slopes in Coprates Chasma, Mars. Visible and near-infrared reflectance spectra extracted from the deposits exhibit broad absorptions around 1.42, 1.94, and 2.25 µm that are most consistent with laboratory spectra of nanophase hydrated Fe-rich alloph…