Das Weltbild des Mittelalters

Knapp, Fritz Peter

doi:10.1007/978-3-642-18959-3_6

Cited by 13 publications

(54 citation statements)

References 1 publication

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“…11, indicates that source 318 is very unlikely to be a background star. However, its fluxes and colours are consistent with an early T dwarf (most consistent with type T3) located in the foreground at a distance of ∼130 pc (using data from Knapp et al 2004). The T‐dwarf space density in the 800–1400 K range is believed be 0.01–0.06 pc −3 (Burgasser 2004) and the volume of space at d < 130 pc in our 26 arcmin 2 survey area is 1.5 pc 3 .…”

Section: Resultsmentioning

confidence: 53%

“…This is unsurprising since the dusty model represents the limiting case of high dust opacity. In the K versus ( H − K ) diagram we overplot the observed colours of field stars and brown dwarfs as a dashed line, using data from Knapp et al (2004), Leggett et al (2001), Dahn et al (2002) and Tokunaga (2000). The colour transformations of Carpenter (2003) were used to convert to the MKO photometric system.…”

Section: Resultsmentioning

confidence: 99%

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A deep survey of brown dwarfs in Orion with Gemini

Lucas

Roche

Tamura

2005

Monthly Notices of the Royal Astronomical Society

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We report the results of a deep near infrared (JHK) survey of the outer parts of the Trapezium Cluster with Gemini South/Flamingos. 396 sources were detected in a 26 arcmin 2 area, including 138 brown dwarf candidates, defined as M< 0.075M ⊙ for an assumed age of 1 Myr. Only 33 of the brown dwarf candidates are planetary mass candidates (PMCs) with estimated masses in the range 0.003 150 AU) binary companions. This result has modest statistical significance (96%) in our data but is supported at 93% confidence by analysis of an completely independent sample taken from the Subaru data of Kaifu et al.(2000). There is a statistically very significant excess of both stars and brown dwarfs with small separations from each other (< 6 arcsec or 2600 AU). This appears to be due to the presence of small N subgroups, which are likely to be dynamically unstable in the long term. Hence these results are consistent with the 'ejected stellar embryo' hypothesis for brown dwarf formation (Reipurth & Clarke 2001). We also report the discovery of two new bipolar nebulae, which are interpreted as Class I protostars.

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Section: Resultsmentioning

confidence: 53%

Section: Resultsmentioning

confidence: 99%

A deep survey of brown dwarfs in Orion with Gemini

Lucas

Roche

Tamura

2005

Monthly Notices of the Royal Astronomical Society

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“…Various combinations of low resolution NIR spectra (Leggett et al 2000;Geballe et al 2002;Knapp et al 2004) for 2MASS J15074769-1627386 (L5.5 8 ), SDSS J023617.93+004855.0 (L6.5), Gliese 584C (L8), SDSS J015141.69+124429.6 (T1), SDSS J125453.90-012247.4 (T2) and SDSS J175032.96+175903.9 (T3.5) were made after scaling the spectra to match the component HST fluxes. Figure 2 demonstrates how an L6.5+T2 combination provides an excellent match to spectral energy distribution of SDSS 0423−0414, particularly CH 4 and H 2 O band strengths.…”

Section: Discussionmentioning

confidence: 99%

“…It has been surmised that the L/T transition may be modulated by a rapid evolution of photospheric condensate dust clouds, as opposed to the gradual sinking of these clouds as predicted by atmospheric models (e.g., Ackerman & Marley (2001)). Burgasser et al (2002a) have proposed that these clouds break apart, creating bright regions analogous to Jupiter's 5 µm hot spots (Westphal et al 1974 Knapp et al (2004) postulate a phase of "rapid rainout". Tsuji & Nakajima (2003), however, argue that the 1 µm brightening arises from variations in secondary parameters, such as age or metallicity.…”

Section: Introductionmentioning

confidence: 99%

SDSS J042348.57-041403.5AB: A Brown Dwarf Binary Straddling the L/T Transition

Burgasser¹,

Reid²,

Leggett³

et al. 2005

ApJ

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We present the discovery of SDSS J042348.57Ϫ041403.5 as a closely separated (0Љ .16) brown dwarf binary, resolved by the Hubble Space Telescope Near-Infrared Camera and Multi-Object Spectrometer. Physical association is deduced from the angular proximity of the components and constraints on their common proper motion. SDSS 0423Ϫ0414AB appears to be composed of two brown dwarfs with spectral types L6‫1ע‬ and T2‫.1ע‬ Hence, this system straddles the transition between L dwarfs and T dwarfs, a unique evolutionary phase of brown dwarfs characterized by substantial shifts in spectral morphology over an apparently narrow effective temperature range. Binarity explains a number of unusual properties of SDSS 0423Ϫ0414, including its overluminosity and high effective temperature compared to other early-type T dwarfs, and possibly its conflicting spectral classifications (L7.5 in the optical, T0 in the near-infrared). The relatively short estimated orbital period of this system (∼15-20 yr) and the presence of Li i absorption in its combined light spectrum make it an ideal target for both resolved spectroscopy and dynamical mass measurements. SDSS 0423Ϫ0414AB joins a growing list of late-L/ early-T dwarf binaries, the high percentage of which (∼50%) may provide a natural explanation for observed peculiarities across the L/T transition.

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“…To put our photometry into context with existing data, we compared F 110W and F 170M magnitudes to J and H photometry, respectively, on the 2MASS and Mauna Kea Observatory (MKO; ; Tokunaga, Simons & Vacca (2002)) systems. MKO data were collated from Leggett et al (2002); Knapp et al (2004); and references therein 12 . Figure 6 compares J-F110W and H-F170M colors to F110W-F170M color for T dwarfs in our sample.…”

Section: T Dwarf Colorsmentioning

confidence: 99%

Hubble Space Telescope NICMOS Observations of T Dwarfs: Brown Dwarf Multiplicity and New Probes of the L/T Transition

Burgasser

Kirkpatrick

Cruz

et al. 2006

ASTROPHYS J SUPPL S

208

271

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We present the results of a Hubble Space Telescope NICMOS imaging survey of 22 T-type field brown dwarfs. Five are resolved as binary systems with angular separations of 0. ′′ 05-0. ′′ 35, and companionship is established on the basis of component F110W-F170M colors (indicative of CH 4 absorption) and low probabilities of background contamination. Prior ground-based observations show 2MASS 1553+1532AB to be a common proper motion binary. The properties of these systems -low multiplicity fraction (11 +7 −3 % resolved, as corrected for sample selection baises), close projected separations (ρ = 1.8-5.0 AU) and near-unity mass ratios -are consistent with previous results for field brown dwarf binaries. Three of the binaries, 2MASS 0518-2828AB, SDSS 0423-0414AB and SDSS 1021-0304AB, have components that span the poorly-understood transition between L dwarfs and T dwarfs. Spectral decomposition analysis of SDSS 1021-0304AB reveals a peculiar flux reversal in this system, with a T5 secondary that is ∼30% brighter at 1.05 and 1.27 µm than the T1 primary. This system, 2MASS 0518-2828AB and SDSS 1534+1615 all demonstrate that the J-band brightening observed between late-type L to mid-type T dwarfs is an intrinsic feature of this spectral transition, albeit less pronounced than previously surmised. We also find that the resolved binary fraction of L7 to T3.5 dwarfs is twice that of other L and T dwarfs, an anomaly that can be explained by a relatively rapid evolution of brown dwarfs through the L/T transition, perhaps driven by dynamic (nonequilibrium) depletion of photospheric condensates.

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Das Weltbild des Mittelalters

Cited by 13 publications

References 1 publication

A deep survey of brown dwarfs in Orion with Gemini

A deep survey of brown dwarfs in Orion with Gemini

SDSS J042348.57-041403.5AB: A Brown Dwarf Binary Straddling the L/T Transition

Hubble Space Telescope NICMOS Observations of T Dwarfs: Brown Dwarf Multiplicity and New Probes of the L/T Transition

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