bluuebunny/crossref_metadata_2025_split huggingface dataset:
A search for brown dwarfs in Collinder 70 and Collinder 121
Authors: Pérez‐Garrido A. , Díaz‐Sánchez A. , Villo I. 
Published: December 2005

AbstractWe present a study of the brown dwarf population in Collinder 70 and 121 open star clusters. Using photometric data from several catalogues we select several candidates in both clusters. We cover a circular area of radius equal to 1 degree around the cluster centers. We found candidates with photometry compatible with theoretical evolutionary models for the age and distance of these clusters. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Observational characteristics of dense cores with deeply embedded young protostars
Authors: Stamatellos D. , Whitworth A. P. , Goodwin S. P. 
Published: December 2005

AbstractClass 0 objects, which are thought to be the youngest protostars, are identified in terms of NIR or radio emission and/or the presence of molecular outflows. We present combined hydrodynamic and radiative transfer simulations of the collapse of a star‐forming molecular core, which suggest two criteria for identifying dense cores with deeply embedded very young protostars that may not be observable in the NIR or radio with current telescopes. We find that cores with protostars are relatively warm (T > 15 K) with their SEDs peaking at wavelengths <170 µm, and they tend to appear circular. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
ULMSF conference summary
Authors: Jameson R. F. 
Published: December 2005

AbstractTen years on from the discovery of the first brown dwarf and the first exoplanet, how well have we progressed in our understanding of these low‐mass objects? In particular how well do we understand their formation? The strong impression from this conference was that the formation of brown dwarfs was just a continuation of the star formation process, no special additional mechanism is indicated. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New brown dwarf companions to dM(e) stars
Authors: Seifahrt A. , Mugrauer M. , Wiese M. , Neuhäuser R. , Guenther E. W. 
Published: December 2005

AbstractWe present new astrometric and spectroscopic data to confirm two new M/L dwarf systems, G124‐62 and LHS5166, and discuss the nature of a third system (LP261‐75). Age and thus mass determinations of the L dwarf companions are discussed based on various activity‐age relationships of the M dwarf primaries. This publication will update the list of widely separated substellar companions to nearby stars. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The IAC online catalog for M‐, L‐ and T‐type dwarfs
Authors: Martín E. L. , Cabrera J. , Cenizo E. 
Published: December 2005

AbstractWe present an online catalog for dwarfs with spectral types M, L and T. The catalog currently contains 893 objects listed in order of right ascension. For most of them the spectra can be downloaded from the catalog in ASCII or FITS formats. The web address is http://www.iac.es/galeria/ege/catalogo spectral/.
NAHUAL: a near‐infrared high‐resolution spectrograph for the GTC optimized for studies of ultracool dwarfs
Authors: Martín E. L. , Guenther E. , Barrado y Navascués D. , Esparza P. , Manescau A. , Laux U. 
Published: December 2005

AbstractWe present the status of an ongoing study for a high‐resolution near‐infrared echelle spectrograph for the 10.4‐m GTC (Gran Telescopio de Canarias) which will soon start operating at the Observatorio del Roque de los Muchachos on the island of La Palma. The main science driver of this instrument, which we have baptized NAHUAL, is to carry out a high precision radial velocity survey of exoplanets around ultracool dwarfs. NAHUAL is being especially designed to achieve the highest possible accuracy for radial velocity measurements. The goal is to reach an accuracy of a few m/s. It is thus required that the instrument is cross‐dispersed and that it covers simultaneously a wide wavelength range. Absorption cells will be placed in front of the slit which will allow a simultaneous self‐reference similar to an iodine‐cell in the optical regime. It is planned to place the instrument at one of the Nasmyth platform of the GTC behind the Adaptive Optics system. Our current design reaches a maximum spectral resolution of λ/Δλ = 50000 with a slit width of 0.175 arcsec, and gives nearly complete spectral coverage from 900 to 2400 nm. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Searching for proto‐brown dwarfs: Extending near IR spectroscopy of protostars below the hydrogen burning limit
Authors: Covey K. R. , Greene T. P. , Doppmann G. W. , Lada C. J. , Wilking B. A. 
Published: December 2005

AbstractRecent observations of nearby star forming regions have offered evidence that young brown dwarfs undergo a period of mass accretion analogous to the T Tauri phase observed in young stars. Brown dwarf analogs to stellar protostars, however, have yet to be definitively observed. These young, accreting objects would shed light on the nature of the dominant brown dwarf formation process, as well as provide ideal laboratories to investigate the dependence of the accretion mechanism on protostellar mass. Recent near infrared surveys have identified candidate proto‐brown dwarfs and characterized low mass protostars in nearby star forming regions. These techniques allow near infrared spectra to diagnose the effective temperature, accretion luminosity, magnetic field strength and rotation velocity of young low mass stars across the stellar/substellar boundary. The lowest mass proto‐brown dwarfs (M < 40 MJup), however, will prove challenging to observe given current near IR observational capabilities. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The lower mass function of young open clusters: clues to (sub)stellar formation
Authors: Moraux E. , Bouvier J. , Clarke C. 
Published: December 2005

AbstractWe report the present day mass functions (PDMFs) of 4 young open clusters over a mass range from 30 Jupiter masses to 3M_ . Three of these clusters have been chosen to have a similar age of ∼100 Myr. Their PDMFs are remarkably similar and are comparable to the field mass function. This suggests little impact of initial conditions (stellar density, metallicity) on the mass distribution and raises some issues concerning the currently debated star and brown dwarf formation theories. The fourth cluster is older (600 Myr) which allow us to investigate the effect of the cluster dynamical evolution on the shape of the mass function. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Studies of the substellar population in the Taurus cloud
Authors: Monin J.‐L. , Dougados C. , Guieu S. 
Published: December 2005

AbstractThe currently known substellar population of the Taurus cloud now approaches three dozen; two third of this population has been published in the literature before 2005, while a remaining 12 were recently found by Guieu et al. (2005a, b). With such a large number of brown dwarfs at hand, a series of statistical studies can be tackled. In this paper, we examine the state of the art of the current studies for brown dwarfs in Taurus and present some general properties of this population. We discuss the number of substellar objects with respect to stars, as well as some preliminary implications for substellar formation models in Taurus. We find that the embryo‐ejection model seems to reproduce both qualitatively and quantitatively the spatial distribution of stars and BDs in Taurus as well as the evolution of the brown dwarfs to stars ratio RSS , and does not appear incompatible with the accretion properties of the Taurus substellar population. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultracool dwarf binaries
Authors: Bouy H. , Martín E. , Brandner W. , Bouvier J. 
Published: December 2005

AbstractWe review here the multiplicity properties of ultracool dwarfs (spectral type later than M6) observed in three different environments and at three different ages: in the field, where the objects are relatively old (1–5 Gyrs) and isolated, in the Pleiades young (∼120 Myr) open cluster, and in the young (∼5 Myr) Upper Scorpius OB association (USco). While the field and Pleiades populations seem to have very similar properties, the preliminary results obtained in USco might show significant differences. If confirmed, it would mean that the phenomena responsible for the “final” properties of ultracool dwarfs multiplicity are still at work at the age of USco, but are already over at the age of the Pleiades. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultra low‐mass star and substellar formation in σ Orionis
Authors: Caballero J. A. 
Published: December 2005

AbstractThe nearby young σ Orionis cluster (∼360 pc, ∼3 Myr) is becoming one of the most important regions for the study of ultra low‐mass star formation and its extension down to the mass regimes of the brown dwarfs and planetarymass objects. Here, I introduce the σ Orionis cluster and present three studies that the JOVIAN group is developing: a pilot programme of near‐infrared adaptive‐optics imaging of stars of the cluster, intermediate‐resolution optical spectroscopy of a large sample of stars of the cluster and a study of the mass function down to the planetary‐mass domain. This paper is a summary of the content of four posters that I presented in the Ultra low‐mass star formation and evolution Workshop, as single author or on behalf of different collaborations. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The distribution of ejected brown dwarfs in clusters
Authors: Goodwin S. P. , Huber D. A. , Moreaux E. , Whitworth A. P. 
Published: December 2005

AbstractWe examine the spatial distribution of brown dwarfs produced by the decay of small‐N stellar systems as expected from the embryo ejection scenario. We model a cluster of several hundred stars grouped into ‘cores’ of a few stars/brown dwarfs. These cores decay, preferentially ejecting their lowest‐mass members. Brown dwarfs are found to have a wider spatial distribution than stars, however once the effects of limited survey areas and unresolved binaries are taken into account it can be difficult to distinguish between clusters with many or no ejections. A large difference between the distributions probably indicates that ejections have occurred, however similar distributions sometimes arise even with ejections. Thus the spatial distribution of brown dwarfs is not necessarily a good discriminator between ejection and non‐ejection scenarios. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Submillimetre observations of low‐mass cloud cores: forming tiny objects in situ
Authors: Greaves J. S. 
Published: December 2005

AbstractThe origin of very low‐mass objects such as brown dwarfs and ‘isolated planets’ is unclear: can they form in‐situ from very low‐mass cloud cores in a scaled‐down version of star formation? Here I discuss methods of detecting and characterising such faint cores using submillimetre‐wavelength observations. Some data are presented for the Ophiuchus clouds that strongly suggest there is little division between stars and ultra low‐mass objects at the earliest evolutionary stages. Some challenging results have emerged (in the context of current theory), including finding cores of only a few Jupiter masses and a core mass function still rising at the mass detection limit: the implications are briefly discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Triggered planet formation in young stellar clusters
Authors: Thies I. , Kroupa P. , Theis C. 
Published: December 2005

AbstractConventional planet formation models via coagulation of planetesimals require timescales in the range of several 10 or even 100 Myr in the outer regions of a protoplanetary disk. But according to observational data, the lifetime of a protoplanetary disk is limited to about 6 Myr. Therefore the existence of Uranus and Neptune poses a problem. Planet formation via gravitational instability may be a solution for this discrepancy. We present a parameter study of the possibility of gravitationally triggered disk instability. Using a restricted N‐body model which allows for a survey of an extended parameter space, we show that a passing dwarf star with a mass between 0.1 and 1 M⊙ can probably induce gravitational instabilities in the pre‐planetary solar disk for prograde passages with minimum separations below 80‐170 AU. Inclined and retrograde encounters lead to similar results but require slightly closer passages. Such encounter distances are quite likely in young moderately massive star clusters. The induced gravitational instabilities may lead to enhanced planetesimal formation in the outer regions of the protoplanetary disk, and could therefore be relevant for the formation of Uranus and Neptune. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The chemical composition of stars with extrasolar planetary systems
Authors: Israelian G. 
Published: December 2005

AbstractSpectroscopic studies of stars with and without planetary systems have concluded that planet hosts are more metal‐rich. This enrichment is also seen in the other chemical elements studied and is likely to be primordial in nature. Interesting trends of different chemical elements begin to appear as the number of extrasolar planets continues to grow. I present our current knowledge concerning the observed abundance trends of chemical elements in planet hosts and their possible implications. In most cases the abundance trends of planet host stars are identical to those of the comparison sample. However, some exceptions (such as Li) have been reported too. No clear correlation was found between orbital parameters of planets and host star metallicity. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Proper motion Pleiades candidate L‐type brown dwarfs
Authors: Bihain G. , Rebolo R. , Béjar V. J. S. , Caballero J. A. , Bailer‐Jones C. A. L. , Mundt R. 
Published: December 2005

AbstractWe present results of an optical and near‐infrared (IR) 1.8 deg2 survey in the Pleiades open cluster to search for substellar objects. From optical I ‐band images from the CFHT and J ‐band images from the 3.5m CAHA Telescope, we identify 18 faint and very red L brown dwarf candidates, with I > 20.9 and I – J > 3.2. The follow‐up observations of nine objects in the H ‐ and K s‐bands confirm that eight belong to the IR sequence of the cluster and the proper motion measurements of seven candidates confirm that they are Pleiades members. A preliminary estimation of the substellar mass spectrum dN/ dM in the form of a power law M c–α provides α = +0.57 ± 0.14. We extrapolate this function to estimate the number of planetary mass objects that could be present in the cluster down to 1 MJup. Sensitive searches combining far red and near‐IR observations may unveal these objects in a near future. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultra‐cool dwarf variability
Authors: Goldman B. 
Published: December 2005

AbstractUltra‐cool dwarf variability studies have matured into a multi‐wavelength, multi‐method probe of ultra‐cool atmospheres. They have the unique potential to address the question of heterogeneity on the ultra‐cool dwarf surface. The constraints on the models that we can gain though time‐sensitive observations are however hampered by the weak signal detected so far, and the limitations of current atmospheric models, otherwise quite successful, to predict dynamical, or even static 2‐D atmosphere characteristics. Here I review the situation of the ultra‐cool dwarf variability studies: possible sources of variability; methods, their limitations and their results; tentative interpretation and prospects. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Brown dwarfs and very low‐mass stars: variability in the Pleiades
Authors: Morales‐Calderón M. , Barrado y Navascués D. , Caballero J. A. , Martín E. L. 
Published: December 2005

AbstractWe present the results of the optical photometric observations of the Pleiades (125 Myr) cluster. The aim of this research is to look for variability, both due to rotation of single stars and the presence of eclipsing binaries. We have used differential photometry and two different methods of statistical analysis of the data.We have found variability in the Pleiades cluster with amplitudes of about 50 mmag and uncertainties of 5 mmag until I=17.9, well within the brown dwarf regime. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Twelve new substellar members in Taurus. Clues for substellar formation models
Authors: Guieu S. , Monin J.‐L. , Dougados C. , Magnier E. , Martín E. L. 
Published: December 2005

AbstractRecent studies of the substellar population in the Taurus cloud have revealed a deficit of brown dwarfs compared to the Trapezium cluster population (Briceño et al. 1998; Luhman 2000; Luhman et al. 2003a; Luhman 2004) However, these works have concentrated on the highest stellar density regions of the Taurus cloud. We have performed a large scale optical survey of this region, covering a total area of ≃ 28 deg2, and encompassing the densest parts of the cloud as well as their surroundings. In this paper, we present optical spectroscopic follow‐up observations of 97 photometrically selected potential new low‐mass Taurus members. We derive spectral types, visual absorption and luminosity class estimates and discuss our criteria to assess Taurus membership. These observations reveal 5 new very low‐mass stars (VLMs) and 12 new Brown Dwarfs (BDs) on the Taurus cloud. We derive a new substellar to stellar ratio in Taurus of ℛss = 0.23 ± 0.05. This revisited ratio appears consistent with the value of 0.26 ± 0.04 previously derived in the Trapezium cluster under similar assumptions. We find indications that the relative numbers of BDs with respect to stars is decreased by a factor 2 in the central regions of the aggregates with respect to the more distributed population. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structure–function correlation of outer membrane protein porin from Paracoccus denitrificans
Authors: Sukumaran S. , Hauser K. , Maier E. , Benz R. , Mäntele W. 
Published: December 2005

AbstractPorins from outer membrane of Gram‐negative bacteria have a highly stable structure. Our previous studies on porin from Paracoccus denitrificans showed that the outer membrane protein porin is extremely stable toward heat, pH, and chemical denaturants. The major question we have addressed in this paper is whether the high stability of porin is a consequence of the β‐barrel structure and whether it is required for its function. To explain this we have analyzed two cases: first, we used porin wild‐type and mutants and compared their structure and function; second, we compared the activity of porin preheated to different temperatures. Structural changes were monitored by infrared spectroscopy. We observed that the structural stability of porin is not equivalent to functional activity as minor alteration in the structure can result in drastic differences in the activity of porins. © 2005 Wiley Periodicals, Inc. Biopolymers 82: 344–348, 2006This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Low versus high molecular weight poly(ethylene glycol)‐induced states of stem bromelain at low pH: Stabilization of molten globule and unfolded states
Authors: Ahmad Basir , Ansari Mairaj A. , Sen Priyankar , Khan Rizwan Hasan 
Published: December 2005

AbstractThe effect of low, medium, and high molecular weight poly(ethylene glycol) (e.g., PEG‐400, ‐6000, and ‐20,000) on the structure of the acid unfolded state of unmodified stem bromelain (SB) obtained at pH 2.0 has been studied by various spectroscopic methods. The conformation of stem bromelain at pH 2.0 exhibits substantial loss of secondary structure and almost complete loss of native tertiary contacts and has been termed the acid unfolded state (AU). Addition of PEG‐400 to AU led to an increase in the mean residue ellipticity (MRE) value at 222 nm, indicating formation of α‐helical structure. On the other hand, PEG‐6000 and 20,000 led to a decrease in the MRE value at 222 nm, indicating unfolding of the AU state. Interestingly, at 70% (w/v) PEG‐400 and 40% (w/v) PEG‐20,000, MRE values at 222 nm almost approach the native state at pH 7.0 and the unfolded state (6 M GnHCl) of stem bromelain, respectively. The probes for tertiary structure showed formation of nonnative tertiary contacts in the presence of 70% (w/v) PEG‐400, while 40% (w/v) PEG‐6000 and 20,000 were found to stabilize the unfolded state of SB. An increase in binding of 1‐anilino 8‐naphthalene sulfonic acid and a decrease in fractional accessibility of tryptophan residues (fa) compared to AU in the presence of 70% PEG‐400 indicate that the PEG‐400–induced state has a significant amount of exposed hydrophobic patches and is more compact than AU. The results imply that the PEG‐400–induced state has characteristics of molten globule, and higher molecular weight PEGs led to the unfolding of the AU state. © 2005 Wiley Periodicals, Inc. Biopolymers 81: 350–359, 2006This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Studies of DNA dumbbells VIII. Melting analysis of DNA dumbbells with dinucleotide repeat stem sequences
Authors: Mandell Kathleen E. , Vallone Peter M. , Owczarzy Richard , Riccelli Peter V. , Benight Albert S. 
Published: December 2005

AbstractMelting curves and circular dichroism spectra were measured for a number of DNA dumbbell and linear molecules containing dinucleotide repeat sequences of different lengths. To study effects of different sequences on the melting and spectroscopic properties, six DNA dumbbells whose stems contain the central sequences (AA)10, (AC)10, (AG)10, (AT)10, (GC)10, and (GG)10 were prepared. These represent the minimal set of 10 possible dinucleotide repeats. To study effects of dinucleotide repeat length, dumbbells with the central sequences (AG)n, n = 5 and 20, were prepared. Control molecules, dumbbells with a random central sequence, (RN)n, n = 5, 10, and 20, were also prepared. The central sequence of each dumbbell was flanked on both sides by the same 12 base pairs and T4 end‐loops. Melting curves were measured by optical absorbance and differential scanning calorimetry in solvents containing 25, 55, 85, and 115 mM Na+. CD spectra were collected from 20 to 45°C and [Na+] from 25 to 115 mM. The spectral database did not reveal any apparent temperature dependence in the pretransition region. Analysis of the melting thermodynamics evaluated as a function of Na+ provided a means for quantitatively estimating the counterion release with melting for the different sequences. Results show a very definite sequence dependence, indicating the salt‐dependent properties of duplex DNA are also sequence dependent. Linear DNA molecules containing the (AG)n and (RN)n, sequences, n = 5, 10, 20, and 30, were also prepared and studied. The linear DNA molecules had the exact sequences of the dumbbell stems. That is, the central repeat sequence in each linear duplex was flanked on both sides by the same 12‐bp sequence. Melting and CD studies were also performed on the linear DNA molecules. Comparison of results obtained for the same sequences in dumbbell and linear molecular environments reveals several interesting features of the interplay between sequence‐dependent structural variability, sequence length, and the unconstrained (linear) or constrained (dumbbell) molecular environments. © 2005 Wiley Periodicals, Inc. Biopolymers 82: 199–221, 2006This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com