A 25 micron search for Vega-like disks around main-sequence stars with
ISO

Laureijs, R. J.; Muizon, M. Jourdain de; Leech, K.; Siebenmorgen, R.; Dominik, C.; Habing, H. J.; Trams, N. R.; Kessler, Martin

doi:10.1051/0004-6361:20020366

Cited by 54 publications

(62 citation statements)

References 9 publications

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“…These increased sizes relative to Altair indicate to us that Alderamin is slightly evolved, perhaps being more adequately classified as an A7 IV; this finding is consistent with an age of 0.82 Gyr for Alderamin, as quoted by Rieke et al (2005). This same study found only marginal evidence for excess flux at 24 m, indicates that there is negligible excess at 2.2 m, and is consistent with the 25 m null result of Laureijs et al (2002). These results are evidence that the observations presented here examine the photosphere of the star alone and are not contaminated by contributions from a circumstellar disk.…”

Section: Discussionsupporting

confidence: 87%

First Results from the CHARA Array. III. Oblateness, Rotational Velocity, and Gravity Darkening of Alderamin

Belle

Ciardi

Brummelaar

et al. 2006

ApJ

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We present observations of the A7 IV-V star Alderamin ( Cep, HR 8162, HD 203280) from the Georgia State University CHARA Array. These infrared interferometric angular size measurements indicate a noncircular projected disk brightness distribution for this known rapid rotator. The interferometric observations are modeled as arising from an elongated rigid atmosphere, with apparent polar and equatorial radii of r p ¼ 0:6753 þ0:0119 À0:0135 and r e ¼ 0:8767 þ0:0293 À0:0183 mas, respectively, for a difference of 201 AE 32 as, and with an axial ratio of r e /r p ¼ 1:298 AE 0:051. Using the Hipparcos distance of 14:96 AE 0:11 pc, these angular measures translate to 2:18 AE 0:05 and 2:82 AE 0:10 R . The inclination of Alderamin to the line of sight indicated by this modeling is effectively edge-on (i ¼ 88:2 þ1:8 À13:3 deg). The star has a true rotational velocity of 283 AE 10 km s À1 ($83% of breakup velocity) and a polar temperature of roughly 8400 K. Significantly, a necessary aspect of this modeling is a determination of the gravity-darkening coefficient, which at a value of ¼ 0:084 þ0:026 À0:049 is consistent with a convective photosphere, as expected for an A7 IV-V star. Our detailed characterization of this object allows us to investigate various scenarios for the angular momentum history of Alderamin and the appropriateness of certain stellar evolution models.

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Section: Discussionsupporting

confidence: 87%

First Results from the CHARA Array. III. Oblateness, Rotational Velocity, and Gravity Darkening of Alderamin

Belle

Ciardi

Brummelaar

et al. 2006

ApJ

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“…HD 128620: α Centauri A, astrometric binary, P = 81.2 years, masses 1.17 (A) and 1.09 (B) solar masses (Pourbaix et al 1999 Endl et al (2002) find no radial velocity variation compatible with stellar or substellar companions. Low HK flux, but Hα flux higher than solar suggests age of less than 1 Gyr, which is corroborated by detection of infrared excess compatible with Vega-like disk (Laureijs et al 2002). Probably a young star.…”

mentioning

confidence: 58%

Astrobiologically Interesting Stars Within 10 Parsecs of the Sun

2006

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The existence of life based on carbon chemistry and water oceans relies upon planetary properties, chiefly climate stability, and stellar properties, such as mass, age, metallicity and Galactic orbits. The latter can be well constrained with present knowledge. We present a detailed, up-to-date compilation of the atmospheric parameters, chemical composition, multiplicity and degree of chromospheric activity for the astrobiologically interesting solar-type stars within 10 parsecs of the Sun. We determine their state of evolution, masses, ages and space velocities, and produce an optimized list of candidates that merit serious scientific consideration by the future space-based interferometry probes aimed at directly detecting Earth-sized extrasolar planets and seeking spectroscopic infrared biomarkers as evidence of photosynthetic life. The initially selected stars number 33 solar-type within the population of 182 stars (excluding late M-dwarfs) closer than 10 pc. A comprehensive and detailed data compilation for these objects is still essentially lacking: a considerable amount of recent data has so far gone unexplored in this context. We present 13 objects as the nearest "biostars", after eliminating multiple stars, young, chromospherically active, hard X-ray emitting stars, and low metallicity objects. Three of these "biostars", HD 1581, 109358 and 115617, closely reproduce most of the solar properties and are considered as premier targets. We show that approximately 7% of the nearby stars are optimally interesting targets for exobiology.

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“…A planet (2.10 AU semi-major half axis, M = 0.91 M Jup ) was recently discovered (Mayor 2003). -HD 38678 (alias ζ Lep) shows excess emission around 25 µm (Laureijs et al 2002) and 60 µm (Habing et al 2001) measured with ISOPHOT. Based on photometry and a marginally resolved emission at 17.9 µm, obtained with the Keck I telescope, Chen & Jura (2001) conclude that the dust may reside within 6 AU distance to the star and is likely being replenished by collisions of larger bodies.…”

Section: Observed Sourcesmentioning

confidence: 99%

“…These objects are now classified as Vega-type and their infrared excess is attributed to the thermal re-emission of dust particles at a temperature between 50 and 125 K (Backman & Paresce 1993;Laureijs et al 2002).…”

Section: Introductionmentioning

confidence: 99%

Mid-IR observations of circumstellar disks

Schütz¹,

Meeus

Sterzik

2005

A&A

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Abstract. We present spectral energy distributions and new N-band photometry and spectroscopy for a sample of six main sequence stars and one post-MS object using the ESO TIMMI2 camera at La Silla observatory (Chile). All objects are thought to possess circumstellar material and for the majority of the targets this is their first N-band spectroscopic observation. The emission spectra (observed in three cases), modelled with a mixture of silicates consisting of different grain sizes and composition, confirm the suspected presence of disks around these targets. The most important discovery is that HD 113766, a young Vega-type star, is host to highly processed dust which is probably second generation. It is the first time a Vega-type star with such highly evolved dust has been observed. Silicate emission of basically unevolved dust is seen in case of the post-MS object HD 41511 and the Vega-type star HD 172555. In addition, to study the cold dust, we observed a subsample at 1200 µm with the bolometer array SIMBA at the SEST in La Silla but we only got upper limits for those five objects. This shows that these Vega-type stars have a smaller amount of dust than their precursors, the T Tauri and Herbig Ae/Be stars.

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A 25 micron search for Vega-like disks around main-sequence stars with ISO

Cited by 54 publications

References 9 publications

First Results from the CHARA Array. III. Oblateness, Rotational Velocity, and Gravity Darkening of Alderamin

First Results from the CHARA Array. III. Oblateness, Rotational Velocity, and Gravity Darkening of Alderamin

Astrobiologically Interesting Stars Within 10 Parsecs of the Sun

Mid-IR observations of circumstellar disks

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