Search Publications
A Data-driven Model for the Global Coronal Evolution
Wu, S. T.; Feng, Xueshang; Jiang, Chaowei +2 more
This work is devoted to the construction of a data-driven model for the study of the dynamic evolution of the global corona that can respond continuously to the changing of the photospheric magnetic field. The data-driven model consists of a surface flux transport (SFT) model and a global three-dimensional (3D) magnetohydrodynamic (MHD) coronal mo…
Spacecraft VLBI and Doppler tracking: algorithms and implementation
Molera Calvés, G.; Gurvits, L. I.; Duev, D. A. +3 more
Aims: We present the results of several multi-station Very Long Baseline Interferometry (VLBI) experiments conducted with the ESA spacecraft Venus Express as a target. To determine the true capabilities of VLBI tracking for future planetary missions in the solar system, it is necessary to demonstrate the accuracy of the method for existing op…
Investigating Slim Disk Solutions for HLX-1 in ESO 243-49
Gehrels, N.; Braito, V.; Farrell, S. A. +7 more
The hyperluminous X-ray source HLX-1 in the galaxy ESO 243-49, currently the best intermediate-mass black hole (BH) candidate, displays spectral transitions similar to those observed in Galactic BH binaries, but with a luminosity 100-1000 times higher. We investigated the X-ray properties of this unique source by fitting multi-epoch data collected…
Analytic theory of Titan's Schumann resonance: Constraints on ionospheric conductivity and buried water ocean
Sotin, Christophe; Karkoschka, Erich; Berthelier, Jean-Jacques +6 more
This study presents an approximate model for the atypical Schumann resonance in Titan's atmosphere that accounts for the observations of electromagnetic waves and the measurements of atmospheric conductivity performed with the Huygens Atmospheric Structure and Permittivity, Wave and Altimetry (HASI-PWA) instrumentation during the descent of the Hu…
Observations of the nightside ionosphere of Mars by the Mars Express Radio Science Experiment (MaRS)
Hinson, D. P.; Witasse, O.; Withers, Paul +7 more
The vertical structure of the nightside ionosphere of Mars and its dependence on solar zenith angle are currently poorly determined, as is the importance of two key sources of nightside plasma, electron precipitation and transport of dayside plasma. We examined 37 electron density profiles of the ionosphere of Mars at solar zenith angles of 101°-1…
Pulsed Gamma Rays from the Original Millisecond and Black Widow Pulsars: A Case for Caustic Radio Emission?
Camilo, F.; Gargano, F.; Grove, J. E. +25 more
We report the detection of pulsed gamma-ray emission from the fast millisecond pulsars (MSPs) B1937+21 (also known as J1939+2134) and B1957+20 (J1959+2048) using 18 months of survey data recorded by the Fermi Large Area Telescope and timing solutions based on radio observations conducted at the Westerbork and Nançay radio telescopes. In addition, …
Accretion-related properties of Herbig Ae/Be stars. Comparison with T Tauris
Eiroa, C.; Montesinos, B.; Mora, A. +4 more
Context. The mass accretion rate M⊙;acc) is a key parameter that has not accurately been determined for a wide sample of Herbig Ae/Be (HAeBe) stars until recently.
Aims: We look for trends relating M⊙acc and the stellar ages (t), spectral energy distributions (SEDs), and disk masses for a sample of 38 HAeBe stars, compar…
On the masses of OJ287 black holes
Ciprini, S.; Lehto, H. J.; Valtonen, M. J.
Two multifrequency campaigns were carried out on OJ287 in 2005: in April when it was in its pre-outburst state, and in November during the main 12 yr cycle outburst. The wavelength coverage was from radio to X-rays. In the optical-to-ultraviolet range, the differential spectrum between the observations has a bremsstrahlung spectral shape, consiste…
Optical flux and spectral variability of blazars
Gupta, Alok C.; Wiita, Paul J.; Bachev, R. +9 more
We report the results of optical monitoring for a sample of 11 blazars including 10 BL Lacertae objects (BL Lacs) and one flat spectrum radio quasar (FSRQ). We have measured the multiband optical flux and colour variations in these blazars on intraday and short-term time-scales of months and have limited data for two more blazars. These photometri…
X-Ray and Multiwavelength Insights into the Nature of Weak Emission-line Quasars at Low Redshift
Brandt, W. N.; Hall, Patrick B.; Anderson, Scott F. +5 more
We report on the X-ray and multiwavelength properties of 11 radio-quiet quasars with weak or no emission lines identified by the Sloan Digital Sky Survey (SDSS) with redshift z = 0.4-2.5. Our sample was selected from the Plotkin et al. catalog of radio-quiet, weak-featured active galactic nuclei (AGNs). The distribution of relative X-ray brightnes…