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Observations of the Goldreich-Kylafis effect in star-forming regions with XPOL at the IRAM 30m telescope
Jan Forbrich, Helmut Wiesemeyer, Clemens Thum +2
The Goldreich-Kylafis (GK) effect causes certain molecular line emission to be weakly linearly polarized, e.g., in the presence of a magnetic field. Compared to polarized dust emis…
A new activity phase of the blazar 3C 454.3. Multifrequency observations by the WEBT and XMM-Newton in 2007-2008
C. M. Raiteri, M. Villata, V. M. Larionov +2
We present and analyse the WEBT multifrequency observations of 3C 454.3 in the 2007-2008 observing season, including XMM-Newton observations and near-IR spectroscopic monitoring, a…
Coordinated mm/sub-mm observations of Sagittarius A* in May 2007
D. Kunneriath, A. Eckart, S. Vogel +26
At the center of the Milky Way, with a distance of ~8 kpc, the compact source Sagittarius A* (SgrA*) can be associated with a super massive black hole of ~4x10^6 solar masses. SgrA…
Coordinated multi-wavelength observations of Sgr A*
A. Eckart, R. Schoedel, F. K. Baganoff +26
We report on recent near-infrared (NIR) and X-ray observations of Sagittarius A* (Sgr A*), the electromagnetic manifestation of the ~4x10^6 solar masses super-massive black hole (S…
Precessing planetary magnetospheres in SiO stars ? First detection of quasi-periodic polarization fluctuations in R Leo and V Cam
Helmut W. Wiesemeyer, Clemens Thum, Alain Baudry +1
The origin of magnetism around AGB stars is uncertain. If these stars drive a dynamo, it cannot be sufficient to generate a strong global field, otherwise the observed X-ray lumino…
The modulation of SiO maser polarization by Jovian planets
Helmut Wiesemeyer
Searching for planets in the atmosphere of AGB stars is difficult, due to confusion with the stellar wind and pulsations. The aim here is to provide a complementary strategy for pl…
XPOL - the correlation polarimeter at the IRAM 30m telescope
Clemens Thum, Helmut Wiesemeyer, Gabriel Paubert +2
XPOL, the first correlation polarimeter at a large millimeter telescope, uses a flexible digital correlator to measure all four Stokes parameters simultaneously, i.e. the total pow…
The high activity of 3C 454.3 in autumn 2007. Monitoring by the WEBT during the AGILE detection
C. M. Raiteri, M. Villata, W. P. Chen +5
The quasar-type blazar 3C 454.3 underwent a phase of high activity in summer and autumn 2007, which was intensively monitored in the radio-to-optical bands by the Whole Earth Blaza…
Large excess of heavy nitrogen in both hydrogen cyanide and cyanogen from comet 17P/Holmes
D. Bockelée-Morvan, N. Biver, E. Jehin +15
From millimeter and optical observations of the Jupiter-family comet 17P/Holmes performed soon after its huge outburst of October 24, 2007, we derive 14 N/15N = 139 +/- 26 in HCN,…
Full polarization study of SiO masers at 86 GHz
Fabrice Herpin, Alain Baudry, Clemens Thum +2
We study the polarization of the SiO maser emission in a representative sample of evolved stars in order to derive an estimate of the strength of the magnetic field, and thus deter…
The polarization of mm methanol masers
Helmut Wiesemeyer, Clemens Thum, Malcolm Walmsley
We present a survey of the polarization properties of mm-wavelength methanol masers, comprising both classes, and transitions from 84.5 to 157.0 GHz. Linear polarization is found i…
Numerical methods for non-LTE line radiative transfer: Performance and convergence characteristics
G. -J. van Zadelhoff, C. P. Dullemond, F. F. S. van der Tak +7
Comparison is made between a number of independent computer programs for radiative transfer in molecular rotational lines. The test models are spherically symmetric circumstellar e…