Chemical analysis of 24 dusty (pre-)main-sequence stars

Acke, B.; Waelkens, Christoffel

doi:10.1051/0004-6361:20041460

Cited by 64 publications

(125 citation statements)

References 49 publications

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“…We adopt the photospheric abundances from Acke & Waelkens (2004) and Folsom et al (2012). For overlapping sources, the surveys are largely consistent, but we adopt the Folsom et al values as the study is more consistent in the stellar parameter determination.…”

Section: The Elemental Abundancesmentioning

confidence: 99%

Fingerprints of giant planets in the photospheres of Herbig stars

Kama

Folsom

Pinilla

2015

A&A

110

152

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Around 2% of all A stars have photospheres depleted in refractory elements. This is hypothesised to arise from gas being accreted more efficiently than dust, but the specific processes and the origin of the material -circum-or interstellar -are not known. The same depletion is seen in 30% of young, disk-hosting Herbig Ae/Be stars. We investigate whether the chemical peculiarity originates in a circumstellar disk. Using a sample of systems for which both the stellar abundances and the protoplanetary disk structure are known, we find that stars hosting warm, flaring group I disks typically have Fe, Mg and Si depletions of 0.5 dex compared to the solar-like abundances of stars hosting cold, flat group II disks. The volatile, C and O, abundances in both sets are identical. Group I disks are generally transitional, having radial cavities depleted in millimetre-sized dust grains, while those of group II are usually not. Thus we propose that the depletion of heavy elements emerges as Jupiter-like planets block the accretion of part of the dust, while gas continues to flow towards the central star. We calculate gas to dust ratios for the accreted material and find values consistent with models of disk clearing by planets. Our results suggest that giant planets of ∼0.1 to 10 M Jup are hiding in at least 30% of Herbig Ae/Be disks.

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Section: The Elemental Abundancesmentioning

confidence: 99%

Fingerprints of giant planets in the photospheres of Herbig stars

Kama

Folsom

Pinilla

2015

A&A

110

152

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“…Certainly, the advantage of using high resolution spectropolarimeters such as ESPaDOnS at the Canada-France-Hawaii Bernacca & Perinotto (1970), c Grady et al (1996), d van den Ancker et al (1998), e Acke & Waelkens (2004), f Hamidouche et al (2008), g this work, h Dunkin et al (1997), i Hubrig et al (2007b), j Alencar et al (2003), k Royer et al (2007), l Mora et al (2001), m Slettebak (1982), n de la Reza & Pinzón (2004), o Beskrovnaya et al (2004), p Alecian et al (2008), q Landstreet et al (2008) Pontoppidan et al (2007b), aa Siebenmorgen et al (2000), bb Kessler-Silacci et al (2005), cc Okamoto et al (2004), dd Schütz et al (2005b), ee Dommanget & Nys (1994), f f Baines et al (2006), gg Corporon & Lagrange (1999), hh Stelzer et al (2006), ii Chen et al (2006a), j j Augereau et al (2001), kk Carmona et al (2007), ll Stecklum et al (1995), mm Reipurth & Zinnecker (1993), nn Roberge et al (2002), oo Grady et al (2007), pp Stauffer et al (1995), qq SIMBAD, rr Eisner et al (2004), ss Grady et al (2004), tt Pirzkal et al (1997), uu Schnerr et al (2007), vv Blondel et al (2006), ww van den Ancker et al (1997), xx Wade et al (2007), yy …”

Section: Observations and Data Reductionmentioning

confidence: 99%

Searching for a link between the magnetic nature and other observed properties of Herbig Ae/Be stars and stars with debris disks

Hubrig

Stelzer

Schöller

et al. 2009

A&A

100

149

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Context. Recently, evidence for the presence of weak magnetic fields in Herbig Ae/Be stars has been found in several studies. Aims. We seek to expand the sample of intermediate-mass pre-main sequence stars with circular polarization data to measure their magnetic fields, and to determine whether magnetic field properties in these stars are correlated with mass-accretion rate, disk inclination, companions, silicates, PAHs, or show a correlation with age and X-ray emission as expected for the decay of a remnant dynamo. Methods. Spectropolarimetric observations of 21 Herbig Ae/Be stars and six debris disk stars have been obtained at the European Southern Observatory with FORS 1 mounted on the 8 m Kueyen telescope of the VLT. With the GRISM 600B in the wavelength range 3250-6215 Å we were able to cover all hydrogen Balmer lines from Hβ to the Balmer jump. In all observations a slit width of 0. 4 was used to obtain a spectral resolving power of R ≈ 2000. Results. Among the 21 Herbig Ae/Be stars studied, new detections of a magnetic field were achieved in six stars. For three Herbig Ae/Be stars, we confirm previous magnetic field detections. The largest longitudinal magnetic field, B z = −454 ± 42 G, was detected in the Herbig Ae/Be star HD 101412 using hydrogen lines. No field detection at a significance level of 3σ was achieved in stars with debris disks. Our study does not indicate any correlation of the strength of the longitudinal magnetic field with disk orientation, disk geometry, or the presence of a companion. We also do not see any simple dependence on the mass-accretion rate. However, it is likely that the range of observed field values qualitatively supports the expectations from magnetospheric accretion models giving support for dipole-like field geometries. Both the magnetic field strength and the X-ray emission show hints of a decline with age in the range of ∼2-14 Myr probed by our sample, supporting a dynamo mechanism that decays with age. However, our study of rotation does not show any obvious trend of the strength of the longitudinal magnetic field with rotation period. Furthermore, the stars seem to obey the universal power-law relation between magnetic flux and X-ray luminosity established for the Sun and main-sequence active dwarf stars.

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“…The star HD 104237 has a mass of about 2.3 M (T eff = 8000 K), a luminosity of about 1.42 L (Böhm et al 2004) and an approximate age of 2 Myr (van den Ancker et al 1998), as well as a magnetic field of about 50 G (Donati et al 1997(Donati et al , 2000. It is an HAeBe star for which Acke & Waelkens (2004) found that Si, Cr and Fe abundances were solar, which agrees with our results since even the heavier 2.50W5E-14 model is roughly normal until 3 Myr (see Fig. 1).…”

Section: Comparison To Observationsmentioning

confidence: 99%

Abundance anomalies in pre-main-sequence stars

Vick

Michaud

Richer

et al. 2010

A&A

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Aims. The effects of atomic diffusion on internal and surface abundances of A and F pre-main-sequence stars with mass loss are studied in order to determine at what age the effects materialize, as well as to further understand the processes at play in HAeBe and young ApBp stars. Methods. Self-consistent stellar evolution models of 1.5 to 2.8 M with atomic diffusion (including radiative accelerations) for all species within the OPAL opacity database were computed and compared to observations of HAeBe stars. Results. Atomic diffusion in the presence of weak mass loss can explain the observed abundance anomalies of pre-main-sequence stars, as well as the presence of binary systems with metal rich primaries and chemically normal secondaries such as V380 Ori and HD 72106. This is in contrast to turbulence models which do not allow for abundance anomalies to develop on the pre-main-sequence. The age at which anomalies can appear depends on stellar mass. Conclusions. For A and F stars, the effects of atomic diffusion can modify both the internal and surface abundances before the onset of the main-sequence. The appearance of important surface abundance anomalies on the pre-main-sequence does not require mass loss, though the mass loss rate affects their amplitude. Observational tests are suggested to decipher the effects of mass loss from those of turbulent mixing. If abundance anomalies are confirmed in pre-main-sequence stars they would severely limit the role of turbulence in these stars.

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Chemical analysis of 24 dusty (pre-)main-sequence stars

Cited by 64 publications

References 49 publications

Fingerprints of giant planets in the photospheres of Herbig stars

Fingerprints of giant planets in the photospheres of Herbig stars

Searching for a link between the magnetic nature and other observed properties of Herbig Ae/Be stars and stars with debris disks

Abundance anomalies in pre-main-sequence stars

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