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Beuzit, Jean-Luc; Demailly, L.; Gendron, É.; Gigan, P.; Lacombe, F.; Rouan, D.; Hubin, N.; Bonaccini, D.; Prieto, Éric; Chazallet, Frédéric; Rabaud, Didier; Madec, Pierre-Yves; Rousset, G.; Hofmann, R.; Eisenhauer, F.

doi:10.1023/a:1007924901154

Cited by 27 publications

(21 citation statements)

References 4 publications

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“…The observations were performed with the ADONIS/ SHARPII+ system (Beuzit et al 1997) on the ESO 3.6 meter telescope at La Silla, Chile. This is an adaptive optics system coupled to an infrared camera with a NICMOS3 detector array.…”

Section: Observationsmentioning

confidence: 99%

The primordial binary population

Kouwenhoven

Brown²,

Zinnecker³

et al. 2005

A&A

182

263

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Abstract. We present the results of a near-infrared adaptive optics survey with the aim to detect close companions to Hipparcos members in the three subgroups of the nearby OB association Sco OB2: Upper Scorpius (US), Upper Centaurus Lupus (UCL) and Lower Centaurus Crux (LCC). We have targeted 199 A-type and late B-type stars in the K S band, and a subset also in the J and H band. We find 151 stellar components other than the target stars. A brightness criterion is used to separate these components into 77 background stars and 74 candidate physical companion stars. Out of these 74 candidate companions, 41 have not been reported before (14 in US; 13 in UCL; 14 in LCC). The angular separation between primaries and observed companion stars ranges from 0.22 to 12.4 . At the mean distance of Sco OB2 (130 pc) this corresponds to a projected separation of 28.6 AU to 1612 AU. Absolute magnitudes are derived for all primaries and observed companions using the parallax and interstellar extinction for each star individually. For each object we derive the mass from K S , assuming an age of 5 Myr for the US subgroup, and 20 Myr for the UCL and LCC subgroups. Companion star masses range from 0.10 M to 3.0 M . The mass ratio distribution follows f (q) = q −Γ with Γ = 0.33, which excludes random pairing. No close (ρ ≤ 3.75 ) companion stars or background stars are found in the magnitude range 12 mag ≤ K S ≤ 14 mag. The lack of stars with these properties cannot be explained by low-number statistics, and may imply a lower limit on the companion mass of ∼0.1 M . Close stellar components with K S > 14 mag are observed. If these components are very low-mass companion stars, a gap in the companion mass distribution might be present. The small number of close low-mass companion stars could support the embryoejection formation scenario for brown dwarfs. Our findings are compared with and complementary to visual, spectroscopic, and astrometric data on binarity in Sco OB2. We find an overall companion star fraction of 0.52 in this association. This is a lower limit since the data from the observations and from literature are hampered by observational biases and selection effects. This paper is the first step toward our goal to derive the primordial binary population in Sco OB2.

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Section: Observationsmentioning

confidence: 99%

The primordial binary population

Kouwenhoven

Brown²,

Zinnecker³

et al. 2005

A&A

182

263

View full text Add to dashboard Cite

show abstract

“…2 had been performed between 1993 and 1996 as part of a high angular resolution survey of visual binaries among HAeBe stars (Bouvier & Corporon 2001). MWC 147, Hen 3-1141, and HR 5999 were observed with the ADONIS adaptive optics (AO) system at ESO (Beuzit et al 1997) equipped with the SHARP IR camera (Hofmann et al 1995). AS 310, V373 Cep, BD+65 1637, and AS 477 were observed with the PUE'O AO system at CFHT (Rigaut et al 1998) equipped with the Monica IR camera (Nadeau et al 1994).…”

Section: High-resolution Near-ir Imagingmentioning

confidence: 99%

New X-ray detections of Herbig stars

Stelzer¹,

Robrade

Schmitt

et al. 2008

A&A

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Context. The interpretation of X-ray detections from Herbig Ae/Be stars is disputed as it is not clear whether these intermediate-mass pre-main sequence stars are able to drive a dynamo and ensuing phenomena of magnetic activity. Alternative X-ray production mechanisms, related to stellar winds, star-disk magnetospheres, or unresolved late-type T Tauri star companions have been proposed. Aims. The companion hypothesis can be tested by resolving Herbig stars in X-rays from their known visual secondaries. Furthermore, their global X-ray properties (such as detection rate, luminosity, temperature, variability) may give clues to the emission mechanism by comparison to other types of stars, e.g. similar-age but lower-mass T Tauri stars, similar-mass but more evolved main-sequence Aand B-type stars, and with respect to model predictions. Methods. In a series of papers we have been investigating high-resolution X-ray Chandra images of Herbig Ae/Be and main-sequence B-type stars where known close visual companions are spatially separated from the primaries. Results. Here we report on six as yet unpublished Chandra exposures from our X-ray survey of Herbig stars. The target list comprises six Herbig stars with known cool companions, and three other A/B-type stars that are serendipitously in the Chandra field-of-view. In this sample we record a detection rate of 100%; i.e. all A/B-type stars display X-ray emission at levels of log (L x /L bol ) ∼ −5... − 7. The analysis of hardness ratios confirms that HAeBes have hotter and/or more absorbed X-ray emitting plasma than more evolved B-type stars. Conclusions. Radiative winds are ruled out as an exclusive emission mechanism on the basis of the high X-ray temperatures. Confirming earlier results, the X-ray properties of Herbig Ae/Be stars are not vastly different from those of their late-type companion stars (if such are known). The diagnostics provided by the presently available data leave it open whether the hard X-ray emission of Herbig stars is due to young age or indicative of further coronally active low-mass companion stars. In the latter case, our detection statistics imply a high fraction of higher order multiple systems among Herbig stars.

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“…It delivers diffraction-limited images in the near-infrared (Beuzit et al 1997). Using a Shack-Hartman wave-front sensor, it usually analyzes the light at visible wavelengths, but during this observing run, we used RASOIR, a prototype of the infrared wave-front sensor of NAOS, the future adaptive optics system of the VLT (see Appendix A).…”

Section: Campaignmentioning

confidence: 99%

Adaptive optics $\vec{L}$-band observations of the Galactic Center region

Clénet

Rouan

Gendron

et al. 2001

A&A

Self Cite

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Abstract. L-band adaptive optics observations of the Galactic Center region have been performed in June 1999and May 2000 at La Silla with the 3.6 m telescope, using the ADONIS adaptive optics system. In June 1999, we used a dedicated infrared wave-front sensor, RASOIR. This paper reports on the photometry and astrometry of more than 40 stars. Thanks to additional adaptive optics K-band observations made at CFHT, colour-magnitude diagrams have been constructed to identify individual sources with various types of stars known in this region (AGB, LPV, WC9, WN9/WN10, Ofpe/WN9, YSO). The so-called "cool slash" stars (Ofpe/WN9) appear to be numerous in the field and an estimation of the extinction coefficient towards the Galactic Center from the colours of these intrinsically weakly absorbed stars leads to AK = 2.7, which is among the lowest published values.

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Cited by 27 publications

References 4 publications

The primordial binary population

The primordial binary population

New X-ray detections of Herbig stars

Adaptive optics $\vec{L}$-band observations of the Galactic Center region

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