C. Schrijvers - Academia.edu (original) (raw)

Papers by C. Schrijvers

Research paper thumbnail of Line-profile variations of non-radial adiabatic pulsations of rotating stars. II. The diagnostic value of amplitude and phase diagrams derived from time series of spectra

Astronomy and Astrophysics

We use a model of a non-radially, adiabatically pulsating rotating star to generate time series o... more We use a model of a non-radially, adiabatically pulsating rotating star to generate time series of absorption line profiles. We analyse the spectral time series of a tesseral mode with pulsation parameters ℓ=2 and m=−1, to obtain amplitude and phase diagrams as a function of position in the line profile. We investigate whether the phase diagrams can be used to identify the pulsation parameters ℓ and |m| of this mode.

Research paper thumbnail of 3D active regions in the solar-type giant FK Comae

FK Com is a solar-type fast rotating giant star. The authors present results based on several dat... more FK Com is a solar-type fast rotating giant star. The authors present results based on several data sets obtained with the ESA-MUSICOS spectrograph (at INT) and with Aurelie spectrograph (at OHP) in 1997. Their observations of the Halpha Balmer line allow to start to understand the 3D structure, variability and evolution of the active regions that produce this spectral signature. The very broad emission is interpreted as extended active loops or prominences up to 3 stellar radii. The authors were able to analyse the contribution of phenomena with very different timescales, from flare to micro-flaring. These bursts of emission occur at all times in different active loops, due to loop excitation/recombination in the stressed magnetic field.

Research paper thumbnail of Apsidal motion and non-radial pulsations in psi 2 Ori

Astronomy & Astrophysics - ASTRON ASTROPHYS, 2001

We present a time series of high-resolution echelle spectra of the double-lined close binary psi ... more We present a time series of high-resolution echelle spectra of the double-lined close binary psi 2 Ori. The spectra sample the wavelength region of 3800-6800 Å. In the absorption lines of the early-B type primary we find clear evidence for non-radial pulsations with intermediate values of the modal degree l. Using a cross-correlation technique we derive the radial velocity of both components. We compare our orbital solution with those reported in the literature to derive the apsidal motion period in this system: 47.5 +/- 0.7 year. We analyse the absorption line profiles of the primary using Fourier techniques to derive apparent pulsation periods and l values of two detected modes with apparent frequencies f_1=10.48 c/d and f_2=10.73 c/d. We discuss whether the non-radial pulsations in this star are internally excited or due to tidal forcing. Comparing the pulsation frequencies with those expected for tidal forcing and for internally excited modes, we tentatively conclude that these ...

Research paper thumbnail of ??Centauri: An eccentric binary with two ??Cep-type components

Astronomy and Astrophysics, 2002

We introduce our observational study of the orbital motion and the intrinsic variability of the d... more We introduce our observational study of the orbital motion and the intrinsic variability of the double-lined spectroscopic binary beta Cen. Using 463 high signal-to-noise, high-resolution spectra obtained over a timespan of 12 years it is shown that the radial velocity of beta Cen varies with an orbital period of 357.0 days. We derive for the first time the orbital parameters of beta Cen and find a very eccentric orbit (e=0.81) and similar component masses with a mass ratio M1/M2=1.02. beta Cen forms a challenge for current evolution scenarios in close binaries and it is also a puzzle how a massive binary with such a large eccentricity could have formed in the first place. Both the primary and the secondary exhibit line-profile variations. A period analysis performed on the radial velocity variations of the primary after prewhitening the orbital motion leads to the detection of at least 3 pulsation frequencies while the star does not show any periodic photometric variability. Based on observations obtained with the ESO CAT/CES telescope and the Swiss Euler/CORALIE telescope, both situated at La Silla, Chile.

Research paper thumbnail of A high-resolution spectroscopy survey of β Cephei pulsations in bright stars

Astronomy and Astrophysics, 2006

We present preliminary results of our high-resolution (R≥50000

Research paper thumbnail of SCIAMACHY Level 1 data: calibration concept and in-flight calibration

Atmospheric Chemistry and Physics, 2006

The calibration of SCIAMACHY was thoroughly checked since the instrument was launched on-board EN... more The calibration of SCIAMACHY was thoroughly checked since the instrument was launched on-board EN-VISAT in February 2002. While SCIAMACHY's functional performance is excellent since launch, a number of technical difficulties have appeared, that required adjustments to the calibration. The problems can be separated into three types: (1) Those caused by the instrument and/or platform environment. Among these are the high water content in the satellite structure and/or MLI layer. This results in the deposition of ice on the detectors in channels 7 and 8 which seriously affects the retrievals in the IR, mostly because of the continuous change of the slit function caused by scattering of the light through the ice layer. Additionally a light leak in channel 7 severely hampers any retrieval from this channel.

Research paper thumbnail of Line-profile variations of non-radial adiabatic pulsations of rotating stars. II. The diagnostic value of amplitude and phase diagrams derived from time series of spectra

Astronomy and Astrophysics

We use a model of a non-radially, adiabatically pulsating rotating star to generate time series o... more We use a model of a non-radially, adiabatically pulsating rotating star to generate time series of absorption line profiles. We analyse the spectral time series of a tesseral mode with pulsation parameters ℓ=2 and m=−1, to obtain amplitude and phase diagrams as a function of position in the line profile. We investigate whether the phase diagrams can be used to identify the pulsation parameters ℓ and |m| of this mode.

Research paper thumbnail of 3D active regions in the solar-type giant FK Comae

FK Com is a solar-type fast rotating giant star. The authors present results based on several dat... more FK Com is a solar-type fast rotating giant star. The authors present results based on several data sets obtained with the ESA-MUSICOS spectrograph (at INT) and with Aurelie spectrograph (at OHP) in 1997. Their observations of the Halpha Balmer line allow to start to understand the 3D structure, variability and evolution of the active regions that produce this spectral signature. The very broad emission is interpreted as extended active loops or prominences up to 3 stellar radii. The authors were able to analyse the contribution of phenomena with very different timescales, from flare to micro-flaring. These bursts of emission occur at all times in different active loops, due to loop excitation/recombination in the stressed magnetic field.

Research paper thumbnail of Apsidal motion and non-radial pulsations in psi 2 Ori

Astronomy & Astrophysics - ASTRON ASTROPHYS, 2001

We present a time series of high-resolution echelle spectra of the double-lined close binary psi ... more We present a time series of high-resolution echelle spectra of the double-lined close binary psi 2 Ori. The spectra sample the wavelength region of 3800-6800 Å. In the absorption lines of the early-B type primary we find clear evidence for non-radial pulsations with intermediate values of the modal degree l. Using a cross-correlation technique we derive the radial velocity of both components. We compare our orbital solution with those reported in the literature to derive the apsidal motion period in this system: 47.5 +/- 0.7 year. We analyse the absorption line profiles of the primary using Fourier techniques to derive apparent pulsation periods and l values of two detected modes with apparent frequencies f_1=10.48 c/d and f_2=10.73 c/d. We discuss whether the non-radial pulsations in this star are internally excited or due to tidal forcing. Comparing the pulsation frequencies with those expected for tidal forcing and for internally excited modes, we tentatively conclude that these ...

Research paper thumbnail of ??Centauri: An eccentric binary with two ??Cep-type components

Astronomy and Astrophysics, 2002

We introduce our observational study of the orbital motion and the intrinsic variability of the d... more We introduce our observational study of the orbital motion and the intrinsic variability of the double-lined spectroscopic binary beta Cen. Using 463 high signal-to-noise, high-resolution spectra obtained over a timespan of 12 years it is shown that the radial velocity of beta Cen varies with an orbital period of 357.0 days. We derive for the first time the orbital parameters of beta Cen and find a very eccentric orbit (e=0.81) and similar component masses with a mass ratio M1/M2=1.02. beta Cen forms a challenge for current evolution scenarios in close binaries and it is also a puzzle how a massive binary with such a large eccentricity could have formed in the first place. Both the primary and the secondary exhibit line-profile variations. A period analysis performed on the radial velocity variations of the primary after prewhitening the orbital motion leads to the detection of at least 3 pulsation frequencies while the star does not show any periodic photometric variability. Based on observations obtained with the ESO CAT/CES telescope and the Swiss Euler/CORALIE telescope, both situated at La Silla, Chile.

Research paper thumbnail of A high-resolution spectroscopy survey of β Cephei pulsations in bright stars

Astronomy and Astrophysics, 2006

We present preliminary results of our high-resolution (R≥50000

Research paper thumbnail of SCIAMACHY Level 1 data: calibration concept and in-flight calibration

Atmospheric Chemistry and Physics, 2006

The calibration of SCIAMACHY was thoroughly checked since the instrument was launched on-board EN... more The calibration of SCIAMACHY was thoroughly checked since the instrument was launched on-board EN-VISAT in February 2002. While SCIAMACHY's functional performance is excellent since launch, a number of technical difficulties have appeared, that required adjustments to the calibration. The problems can be separated into three types: (1) Those caused by the instrument and/or platform environment. Among these are the high water content in the satellite structure and/or MLI layer. This results in the deposition of ice on the detectors in channels 7 and 8 which seriously affects the retrievals in the IR, mostly because of the continuous change of the slit function caused by scattering of the light through the ice layer. Additionally a light leak in channel 7 severely hampers any retrieval from this channel.