S. Strasser
Current Organizations / Institutes
The organizations/institutes from the scholar's latest article
Research Subjects
S. Strasser has a total of 23 co-authors. Here are the top co-authors by number of shared publications:
- John Darlington Landstreet
Armagh Observatory and Planetarium College Hill BT61 9DG Armagh Northern Ireland UK
3 shared publications - Pascal Petit
Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, CNRS, CNES, 14 avenue Édouard Belin, 31400 Toulouse, France
3 shared publications - Alexander W. Fullerton
Dept. of Physics & Astronomy University of Victoria P.O. Box 3055 V8W 3P6 Victoria BC Canada
2 shared publications - Gregg A. Wade
Department of Physics, Engineering Physics, and Astronomy, Queen’s University
2 shared publications A. R. Taylor
Department of Physics and Astronomy, University of Calgary, Calgary, AB T2N 1N4, Canada
1 shared publication- Anne J. Green
Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006, Australia
1 shared publication
Latest Publications
- Open Access
- 25 April 2006
- Published by EDP Sciences in Astronomy & Astrophysics
- Vol. 451 (1) , 195-206
The magnetic field and confined wind of the O star $\mathsf{\theta^1}$ Orionis CAstronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics
- 25 April 2006
- Published by EDP Sciences in Astronomy & Astrophysics
- Vol. 451 (1) , 195-206
Open AccessThe magnetic field and confined wind of the O star $\mathsf{\theta^1}$ Orionis CAstronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics
- Open Access
The magnetic field and confined wind of the O star $θ^1$~Orionis~C
In this paper we confirm the presence of a globally-ordered, kG-strength magnetic field in the photosphere of the young O star $\theta^1$~Orionis~C, and examine the properties of its optical line profile variations. A new series of high-resolution MuSiCoS Stokes $V$ and $I$ spectra has been acquired which samples approximately uniformly the rotational cycle of $\theta^1$~Orionis~C. Using the Least-Squares Deconvolution (LSD) multiline technique, we have succeeded in detecting variable Stokes $V$ Zeeman signatures associated with the LSD mean line profile. These signatures have been modeled to determine the magnetic field geometry. We have furthermore examined the profi le variations of lines formed in both the wind and photosphere using dynamic spectra. Based on spectrum synthesis fitting of the LSD profiles, we determine that the polar strength of the magnetic dipole component is $1150 \la B_{\rm d}\la 1800$~G and that the magnetic obliquity is $27\degr \la \beta \la 68\degr$, assuming $i=45\pm 20\degr$. The best-fit values for $i=45\degr$ are $B_{\rm d} = 1300 \pm 150 (1\sigma)$~G and $\beta = 50\degr \pm 6\degr (1\sigma)$. Our data confirm the previous detection of a magnetic field in this star, and furthermore demonstrate the sinusoidal variability of the longitudinal field and accurately determine the phases and intensities of the magnetic extrema. The analysis of ``photospheric'' and ``wind'' line profile variations supports previous reports of the optical spectroscopic characteristics, and provides evidence for infall of material within the magnetic equatorial plane.Open AccessThe magnetic field and confined wind of the O star $θ^1$~Orionis~C
In this paper we confirm the presence of a globally-ordered, kG-strength magnetic field in the photosphere of the young O star $\theta^1$~Orionis~C, and examine the properties of its optical line profile variations. A new series of high-resolution MuSiCoS Stokes $V$ and $I$ spectra has been acquired which samples approximately uniformly the rotational cycle of $\theta^1$~Orionis~C. Using the Least-Squares Deconvolution (LSD) multiline technique, we have succeeded in detecting variable Stokes $V$ Zeeman signatures associated with the LSD mean line profile. These signatures have been modeled to determine the magnetic field geometry. We have furthermore examined the profi le variations of lines formed in both the wind and photosphere using dynamic spectra. Based on spectrum synthesis fitting of the LSD profiles, we determine that the polar strength of the magnetic dipole component is $1150 \la B_{\rm d}\la 1800$~G and that the magnetic obliquity is $27\degr \la \beta \la 68\degr$, assuming $i=45\pm 20\degr$. The best-fit values for $i=45\degr$ are $B_{\rm d} = 1300 \pm 150 (1\sigma)$~G and $\beta = 50\degr \pm 6\degr (1\sigma)$. Our data confirm the previous detection of a magnetic field in this star, and furthermore demonstrate the sinusoidal variability of the longitudinal field and accurately determine the phases and intensities of the magnetic extrema. The analysis of ``photospheric'' and ``wind'' line profile variations supports previous reports of the optical spectroscopic characteristics, and provides evidence for infall of material within the magnetic equatorial plane. - Open Access
The Southern Galactic Plane Survey: HI Observations and Analysis
We describe the HI component of the Southern Galactic Plane Survey (SGPS). The SGPS is a large-scale project to image at arcminute resolution the HI spectral line and 21 cm continuum emission in parts of the plane of the Milky Way. The survey covers Galactic longitudes 253 deg < l < 358 deg and latitudes |b| <1.5 deg (SGPS I), plus a first quadrant extension covering 5 deg < l < 20 deg and |b| <1.5 deg (SGPS II). The survey combines data from the Australia Telescope Compact Array and the Parkes Radio Telescope for sensitivity to angular scales ranging from 2 arcminutes to several degrees. The combined data cover 325 sq-deg and have an rms sensitivity of 1.6 K. Here we describe the HI observations and data reduction in detail, and present examples from the final data products. The complete dataset is publicly available through the Australia Telescope National Facility's HI Surveys archive. This dataset provides an unprecedented view of the neutral component of interstellar hydrogen in the inner Milky Way.
Open AccessThe Southern Galactic Plane Survey: HI Observations and Analysis
We describe the HI component of the Southern Galactic Plane Survey (SGPS). The SGPS is a large-scale project to image at arcminute resolution the HI spectral line and 21 cm continuum emission in parts of the plane of the Milky Way. The survey covers Galactic longitudes 253 deg < l < 358 deg and latitudes |b| <1.5 deg (SGPS I), plus a first quadrant extension covering 5 deg < l < 20 deg and |b| <1.5 deg (SGPS II). The survey combines data from the Australia Telescope Compact Array and the Parkes Radio Telescope for sensitivity to angular scales ranging from 2 arcminutes to several degrees. The combined data cover 325 sq-deg and have an rms sensitivity of 1.6 K. Here we describe the HI observations and data reduction in detail, and present examples from the final data products. The complete dataset is publicly available through the Australia Telescope National Facility's HI Surveys archive. This dataset provides an unprecedented view of the neutral component of interstellar hydrogen in the inner Milky Way.
- 10 March 2004
- Published by American Astronomical Society in The Astrophysical Journal
- Vol. 603 (2) , 560-568
1420 MHz Continuum Absorption toward Extragalactic Sources in the Galactic Plane
We present a 21 cm emission-absorption study toward extragalactic sources in the Canadian Galactic Plane Survey (CGPS). We have analyzed H I spectra toward 437 sources with Sν ≥ 150 mJy, giving us a source density of 0.6 sources per square degree at arcminute resolution. We present the results of a first analysis of the H I temperatures, densities, and feature statistics. Particular emphasis is placed on five features with observed spin temperatures below 40 K. We find most spin temperatures in the range 40-300 K. A simple H I two-component model constrains the bulk of the cold component to temperatures (Tc) between 40 and 100 K. We find that Tc peaks in the Perseus arm region, and clearly drops off with Galactocentric radius R beyond that. The H I density follows this trend, ranging from a local value of 0.4 cm-3 to less than 0.1 cm-3 at R = 20 kpc. We find that H I emission alone on average traces about 75% of the total H I column density, as compared to the total inferred by the emission and absorption. Comparing the neutral hydrogen absorption to CO emission, no correlation is found in general, but all strong CO emission is accompanied by a visible H I spectral feature. Finally, the number of spectral H I absorption features per kiloparsec drops off exponentially with increasing R.
- 10 March 2004
- Published by American Astronomical Society in The Astrophysical Journal
- Vol. 603 (2) , 560-568
1420 MHz Continuum Absorption toward Extragalactic Sources in the Galactic Plane
We present a 21 cm emission-absorption study toward extragalactic sources in the Canadian Galactic Plane Survey (CGPS). We have analyzed H I spectra toward 437 sources with Sν ≥ 150 mJy, giving us a source density of 0.6 sources per square degree at arcminute resolution. We present the results of a first analysis of the H I temperatures, densities, and feature statistics. Particular emphasis is placed on five features with observed spin temperatures below 40 K. We find most spin temperatures in the range 40-300 K. A simple H I two-component model constrains the bulk of the cold component to temperatures (Tc) between 40 and 100 K. We find that Tc peaks in the Perseus arm region, and clearly drops off with Galactocentric radius R beyond that. The H I density follows this trend, ranging from a local value of 0.4 cm-3 to less than 0.1 cm-3 at R = 20 kpc. We find that H I emission alone on average traces about 75% of the total H I column density, as compared to the total inferred by the emission and absorption. Comparing the neutral hydrogen absorption to CO emission, no correlation is found in general, but all strong CO emission is accompanied by a visible H I spectral feature. Finally, the number of spectral H I absorption features per kiloparsec drops off exponentially with increasing R.
- 1 January 2004
- Published by Cambridge University Press (CUP) in Symposium - International Astronomical Union
- Vol. 215, 294-299
Surface Differential Rotation of Evolved Fast Rotators
Zeeman-Doppler Imaging enables one to estimate the short term temporal evolution of surface brightness and magnetic structures, under the effect of differential rotation. We present here spectropolarimetric observations secured between 1998 and 2002 for two evolved active stars: the K1 subgiant of the RS CVn system HR 1099 and the single FK Com giant HD 199178. Differential rotation is detected both from brightness and magnetic images, indicating that the rotational shear, roughly solar in magnitude for the single star, is significantly weaker in the binary system. This result suggests that tidal forces, rather than stellar evolution, could be responsible for the lower rotational shear and thus the longer spot lifetime reported for binary systems.
- 1 January 2004
- Published by Cambridge University Press (CUP) in Symposium - International Astronomical Union
- Vol. 215, 294-299
Surface Differential Rotation of Evolved Fast Rotators
Zeeman-Doppler Imaging enables one to estimate the short term temporal evolution of surface brightness and magnetic structures, under the effect of differential rotation. We present here spectropolarimetric observations secured between 1998 and 2002 for two evolved active stars: the K1 subgiant of the RS CVn system HR 1099 and the single FK Com giant HD 199178. Differential rotation is detected both from brightness and magnetic images, indicating that the rotational shear, roughly solar in magnitude for the single star, is significantly weaker in the binary system. This result suggests that tidal forces, rather than stellar evolution, could be responsible for the lower rotational shear and thus the longer spot lifetime reported for binary systems.