Pierre North - Academia.edu (original) (raw)

Papers by Pierre North

Research paper thumbnail of Book Review: Cosmic company. The search for life in the universe. Cambridge University Press, 2003, 161 pp., ISBN 0-521-82233-5

Orion: Zeitschrift für Amateur-Astronomie, Jun 1, 2005

Research paper thumbnail of Book Review: Les lois du monde. Notre environnement expliqué par la physique. Belin, Pour la science. 2003, 159 pp. ISBN 2-84245-059-0

Research paper thumbnail of Book Review: L'univers exploré, peu à peu expliqué. Odile Jacob, 2003, 335 pp., broché, ISBN 2-7381-1188-2

Orion: Zeitschrift für Amateur-Astronomie, Feb 1, 2006

Research paper thumbnail of Book Review: The scientific legacy of Fred Hoyle. Ed. by Douglas Gough. Cambridge University Press, 2005, 249 pp. ISBN 0-521-82448-6

Orion: Zeitschrift für Amateur-Astronomie, Apr 1, 2006

Research paper thumbnail of VizieR Online Data Catalog: Bp-Ap stars HR-diagram from Hipparcos data (Gomez+ 1998)

Research paper thumbnail of Gravitational Lensing: Strong, Weak and Micro: Swiss Society for Astrophysics and Astronomy

to Gravitational Lensing and Cosmology.- Strong Gravitational Lensing.- Weak Gravitational Lensin... more to Gravitational Lensing and Cosmology.- Strong Gravitational Lensing.- Weak Gravitational Lensing.- Gravitational Microlensing.

Research paper thumbnail of On the Binarity of the F0p Magnetic Stars ϒ Equ and 49 Cam

International Astronomical Union Colloquium, 1999

The magnetic field investigations of the rapidly-oscillating (ro)Ap starϒEqu show a very long mag... more The magnetic field investigations of the rapidly-oscillating (ro)Ap starϒEqu show a very long magnetic (rotational) period of about 74 years (Leroy et al. 1994; Bychkov & Shtol 1997). No significant changes of radial velocities were detected during the history of investigations of this star. Recently, Scholz et al. (1997) (hereafter S97) reported a rapid increase of radial velocity (RV) ofϒEqu from the mean value of -16.81 km s−1up to a maximum at -4.28 km s−1within the interval JD 2449608 – JD 2450356, and suggested thatϒEqu is a long-period binary star with high eccentricity. Such a probable discovery of binary motion ofϒEqu is very interesting, since it opens the possibility to compare asteroseismic parameters of the star with those obtained from the binary orbit.

Research paper thumbnail of Stellar Classification (Classification Stellaire)

Reports on Astronomy, 1997

Research paper thumbnail of Book Review: Planète rouge; Mars: mythes et explorations. Dunod (Coll. Quai des sciences), 2003, 224 pp., broché, ISBN 2-10-007260-9

Research paper thumbnail of Magnetically controlled circumstellar plasma in the helium-weak stars

Astronomy & Astrophysics, 2004

We report the discovery of variable C  line profiles in the magnetic helium-weak stars HD 14230... more We report the discovery of variable C  line profiles in the magnetic helium-weak stars HD 142301, HD 142990, and HD 144334, all of which are members of the Sco-Cen association, and the hot helium-weak star HD 175362. These stars display behavior that is similar to HD 5737 and HD 79158, two helium-weak stars for which magnetically confined plasma has previously been reported. The present study thus extends the C  survey to all of the stars for which strong radio emission has been detected. No C  absorption has been detected for two other Sco-Cen chemically peculiar stars, HD 144844 and 146001, nor has it been detected from archival spectra of HD 28843, HD 49333, or HD 124224. The reported detections are the first helium-weak stars that do not belong to the sn subclass that have been found to display such UV line profile variations. It appears that the restriction of this phenomenon to the extreme helium-weak subgroup was a selection effect and that the occurrence of magnetically trapped corotating plasma is more widespread among the upper main sequence magnetic spectrum variables. We show model calculations for the C  variability that clarify the plasmaspheric structure. Supporting Hα observations show no evidence of line profile variability for HD 142301 and HD 144334, while HD 142990 appears to have extremely weak emission at certain phases, and the profile of HD 124224 shows some changing asymmetry.

Research paper thumbnail of New Homogeneous v sin i Determinations for B Stars in Galactic Open Clusters

Symposium - International Astronomical Union, 2004

We present new observations of projected rotational velocities of main sequence B stars in the ga... more We present new observations of projected rotational velocities of main sequence B stars in the galactic clusters NGC 2439, NGC 3293, NGC 3766, NGC 4755, NGC 7160…

Research paper thumbnail of An up-to-date catalogue of the vilnius UPXYZVTS photometry

Research paper thumbnail of Evidence for no short time scale photometric variations in the Bp-Si star HD 29664

Astronomy & Astrophysics Supplement Series, 1987

ABSTRACT

Research paper thumbnail of VizieR Online Data Catalog: EWs of 31 giant stars of 10 open clusters (Smiljanic+, 2009)

VizieR Online Data Catalog, May 1, 2009

Research paper thumbnail of Photometric properties of AP stars in the Geneva system

Astronomy and Astrophysics, 1982

An examination of the properties in some photometric diagrams of more than 600 Ap stars measured ... more An examination of the properties in some photometric diagrams of more than 600 Ap stars measured in the Geneva photometric system confirm that the Balmer discontinuity is smaller than for normal stars, along with the link between a proposed peculiarity parameter and both rotational velocity and effective magnetic field. It is shown that the peculiarity parameter is sensitive to interstellar reddening, and it is found through examination of the standard deviations for visual magnitudes that cool CP 2 stars without Eu peculiarity have the greatest amplitudes. Rapid rotators have a mild peculiarity, while positive correlation exists for Si and SrCr stars.

Research paper thumbnail of Erratum) The nature of the F STR λ4077 stars. III. Spectroscopy of the barium dwarfs and other CP stars

Research paper thumbnail of Book Review: Intelligent life in the universe; from common origins to the future of humanity. Advances in Astrobiology and Biogeophysics, Springer-Verlag, 2003, 251 pp. ISBN 3-540-43988-9

Orion Zeitschrift Fur Amateur Astronomie, Oct 1, 2004

Research paper thumbnail of Stellar abundance patterns. What is the possible level of completeness today ?

Proceedings of the International Astronomical Union

We discuss the way of increasing of the number of chemical elements, investigated in stellar spec... more We discuss the way of increasing of the number of chemical elements, investigated in stellar spectra. We can reach it by using spectrum synthesis method, new atomic data and observation of stellar spectra with resolution comparable to solar spectral atlases. We show two examples of this kind researches. The first is the implementation of new atomic data to well known Przybylski's star. We show that the number of spectral lines, which can be identificated in the spectrum of this star can be significantly higher. The second example is the investigation of zeta Cyg. We found the abundances of 51 elements in the atmosphere of this mild barium star.

Research paper thumbnail of The nature of the F str λ4077 stars. II, Frequency, kinematics, metallicity, binarity and rotational velocities

Astronomy and Astrophysics, 1987

Fundamental characteristics of the F str λ4077 stars are investigated. Their frequency in the sol... more Fundamental characteristics of the F str λ4077 stars are investigated. Their frequency in the solar neighbourhood is estimated at about 1.4% of all main-sequence F stars. The space velocities are consistent with Population I membership, with the exception of one object (in a sample of 17) whose velocity is above 100 km/s. The binary frequency is higher than normal, and the rotational velocities are normal for the cooler stars but rather low for the hotter ones

Research paper thumbnail of The Gaia Mission

Gaia is a very ambitious mission of the European Space Agency. At the heart of Gaia lie the measu... more Gaia is a very ambitious mission of the European Space Agency. At the heart of Gaia lie the measurements of the positions, distances, space motions, brightnesses and astrophysical parameters of stars, which represent fundamental pillars of modern astronomical knowledge. We provide a brief description of the Gaia mission with an emphasis on binary stars. In particular, we summarize results of simulations, which estimate the number of binary stars to be processed to several tens of millions. We also report on the catalogue release scenarios. In the current proposal, the first results for binary stars will be available in 2017 (for a launch in 2013).

Research paper thumbnail of Book Review: Cosmic company. The search for life in the universe. Cambridge University Press, 2003, 161 pp., ISBN 0-521-82233-5

Orion: Zeitschrift für Amateur-Astronomie, Jun 1, 2005

Research paper thumbnail of Book Review: Les lois du monde. Notre environnement expliqué par la physique. Belin, Pour la science. 2003, 159 pp. ISBN 2-84245-059-0

Research paper thumbnail of Book Review: L'univers exploré, peu à peu expliqué. Odile Jacob, 2003, 335 pp., broché, ISBN 2-7381-1188-2

Orion: Zeitschrift für Amateur-Astronomie, Feb 1, 2006

Research paper thumbnail of Book Review: The scientific legacy of Fred Hoyle. Ed. by Douglas Gough. Cambridge University Press, 2005, 249 pp. ISBN 0-521-82448-6

Orion: Zeitschrift für Amateur-Astronomie, Apr 1, 2006

Research paper thumbnail of VizieR Online Data Catalog: Bp-Ap stars HR-diagram from Hipparcos data (Gomez+ 1998)

Research paper thumbnail of Gravitational Lensing: Strong, Weak and Micro: Swiss Society for Astrophysics and Astronomy

to Gravitational Lensing and Cosmology.- Strong Gravitational Lensing.- Weak Gravitational Lensin... more to Gravitational Lensing and Cosmology.- Strong Gravitational Lensing.- Weak Gravitational Lensing.- Gravitational Microlensing.

Research paper thumbnail of On the Binarity of the F0p Magnetic Stars ϒ Equ and 49 Cam

International Astronomical Union Colloquium, 1999

The magnetic field investigations of the rapidly-oscillating (ro)Ap starϒEqu show a very long mag... more The magnetic field investigations of the rapidly-oscillating (ro)Ap starϒEqu show a very long magnetic (rotational) period of about 74 years (Leroy et al. 1994; Bychkov & Shtol 1997). No significant changes of radial velocities were detected during the history of investigations of this star. Recently, Scholz et al. (1997) (hereafter S97) reported a rapid increase of radial velocity (RV) ofϒEqu from the mean value of -16.81 km s−1up to a maximum at -4.28 km s−1within the interval JD 2449608 – JD 2450356, and suggested thatϒEqu is a long-period binary star with high eccentricity. Such a probable discovery of binary motion ofϒEqu is very interesting, since it opens the possibility to compare asteroseismic parameters of the star with those obtained from the binary orbit.

Research paper thumbnail of Stellar Classification (Classification Stellaire)

Reports on Astronomy, 1997

Research paper thumbnail of Book Review: Planète rouge; Mars: mythes et explorations. Dunod (Coll. Quai des sciences), 2003, 224 pp., broché, ISBN 2-10-007260-9

Research paper thumbnail of Magnetically controlled circumstellar plasma in the helium-weak stars

Astronomy & Astrophysics, 2004

We report the discovery of variable C  line profiles in the magnetic helium-weak stars HD 14230... more We report the discovery of variable C  line profiles in the magnetic helium-weak stars HD 142301, HD 142990, and HD 144334, all of which are members of the Sco-Cen association, and the hot helium-weak star HD 175362. These stars display behavior that is similar to HD 5737 and HD 79158, two helium-weak stars for which magnetically confined plasma has previously been reported. The present study thus extends the C  survey to all of the stars for which strong radio emission has been detected. No C  absorption has been detected for two other Sco-Cen chemically peculiar stars, HD 144844 and 146001, nor has it been detected from archival spectra of HD 28843, HD 49333, or HD 124224. The reported detections are the first helium-weak stars that do not belong to the sn subclass that have been found to display such UV line profile variations. It appears that the restriction of this phenomenon to the extreme helium-weak subgroup was a selection effect and that the occurrence of magnetically trapped corotating plasma is more widespread among the upper main sequence magnetic spectrum variables. We show model calculations for the C  variability that clarify the plasmaspheric structure. Supporting Hα observations show no evidence of line profile variability for HD 142301 and HD 144334, while HD 142990 appears to have extremely weak emission at certain phases, and the profile of HD 124224 shows some changing asymmetry.

Research paper thumbnail of New Homogeneous v sin i Determinations for B Stars in Galactic Open Clusters

Symposium - International Astronomical Union, 2004

We present new observations of projected rotational velocities of main sequence B stars in the ga... more We present new observations of projected rotational velocities of main sequence B stars in the galactic clusters NGC 2439, NGC 3293, NGC 3766, NGC 4755, NGC 7160…

Research paper thumbnail of An up-to-date catalogue of the vilnius UPXYZVTS photometry

Research paper thumbnail of Evidence for no short time scale photometric variations in the Bp-Si star HD 29664

Astronomy & Astrophysics Supplement Series, 1987

ABSTRACT

Research paper thumbnail of VizieR Online Data Catalog: EWs of 31 giant stars of 10 open clusters (Smiljanic+, 2009)

VizieR Online Data Catalog, May 1, 2009

Research paper thumbnail of Photometric properties of AP stars in the Geneva system

Astronomy and Astrophysics, 1982

An examination of the properties in some photometric diagrams of more than 600 Ap stars measured ... more An examination of the properties in some photometric diagrams of more than 600 Ap stars measured in the Geneva photometric system confirm that the Balmer discontinuity is smaller than for normal stars, along with the link between a proposed peculiarity parameter and both rotational velocity and effective magnetic field. It is shown that the peculiarity parameter is sensitive to interstellar reddening, and it is found through examination of the standard deviations for visual magnitudes that cool CP 2 stars without Eu peculiarity have the greatest amplitudes. Rapid rotators have a mild peculiarity, while positive correlation exists for Si and SrCr stars.

Research paper thumbnail of Erratum) The nature of the F STR λ4077 stars. III. Spectroscopy of the barium dwarfs and other CP stars

Research paper thumbnail of Book Review: Intelligent life in the universe; from common origins to the future of humanity. Advances in Astrobiology and Biogeophysics, Springer-Verlag, 2003, 251 pp. ISBN 3-540-43988-9

Orion Zeitschrift Fur Amateur Astronomie, Oct 1, 2004

Research paper thumbnail of Stellar abundance patterns. What is the possible level of completeness today ?

Proceedings of the International Astronomical Union

We discuss the way of increasing of the number of chemical elements, investigated in stellar spec... more We discuss the way of increasing of the number of chemical elements, investigated in stellar spectra. We can reach it by using spectrum synthesis method, new atomic data and observation of stellar spectra with resolution comparable to solar spectral atlases. We show two examples of this kind researches. The first is the implementation of new atomic data to well known Przybylski's star. We show that the number of spectral lines, which can be identificated in the spectrum of this star can be significantly higher. The second example is the investigation of zeta Cyg. We found the abundances of 51 elements in the atmosphere of this mild barium star.

Research paper thumbnail of The nature of the F str λ4077 stars. II, Frequency, kinematics, metallicity, binarity and rotational velocities

Astronomy and Astrophysics, 1987

Fundamental characteristics of the F str λ4077 stars are investigated. Their frequency in the sol... more Fundamental characteristics of the F str λ4077 stars are investigated. Their frequency in the solar neighbourhood is estimated at about 1.4% of all main-sequence F stars. The space velocities are consistent with Population I membership, with the exception of one object (in a sample of 17) whose velocity is above 100 km/s. The binary frequency is higher than normal, and the rotational velocities are normal for the cooler stars but rather low for the hotter ones

Research paper thumbnail of The Gaia Mission

Gaia is a very ambitious mission of the European Space Agency. At the heart of Gaia lie the measu... more Gaia is a very ambitious mission of the European Space Agency. At the heart of Gaia lie the measurements of the positions, distances, space motions, brightnesses and astrophysical parameters of stars, which represent fundamental pillars of modern astronomical knowledge. We provide a brief description of the Gaia mission with an emphasis on binary stars. In particular, we summarize results of simulations, which estimate the number of binary stars to be processed to several tens of millions. We also report on the catalogue release scenarios. In the current proposal, the first results for binary stars will be available in 2017 (for a launch in 2013).