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Highlights - Volume 476-3 (December IV 2007)

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HIGHLIGHTS: this week in A&A

Volume 476-3 (December IV 2007)

 


In section 1. Letters

“Superluminal non-ballistic jet swing in the quasar NRAO 150 revealed by mm-VLBI”, by I. Agudo et al., A&A 476, p. L17

The authors used the VLBI in the millimetric range to monitor the emission of a jet from the radio source NRAO 150 on a time base of 10 years. They obtained a spatial resolution of 0.16 milli-arcsec. They surprisingly observed a swing in the jet direction of 11 degrees per year, in the region within 31pc of the AGN. It is the first time that a non-ballistic superluminal motion has been observed, so closely to the AGN. This will allow us to understand the physics of the jet triggering phenomenon better. The jet wobbling could be due to a binary black hole or to the direction change of the jet nozzle. It might be related to the strong magnetic field in the region or could come from an impact with the ambient medium.  

 

In section 10. Planets and planetary systems

“Hubble Space Telescope time-series photometry of the planetary transit of HD189733: no moon, no rings, starspots”, by F. Pont et al. , A&A 476, p. 1347

This is an excellent paper about extracting as much data as possible (concerning planetary transits and star spots) from some high-accuracy, HST stellar light curve observations. The data clearly show that the planetary transit occults starspots. The authors conclude, among other things, that there can be no Earth-size moons or rings around the planet.  

 


In section 1. Letters

“Inhibition of thermohaline mixing by a magnetic field in Ap star descendants: implications for the Galactic evolution of 3He”, by C. Charbonnel and J.P. Zahn, A&A 476, p. L29

Thermohaline mixing has recently been discovered to be able to lead to the distruction of 3He in low-mass red giants, which they would otherwise produce abundantly. In this paper, the authors show that in magnetic stars that may be about 10% in the A star regime, this destruction mechanism is inhibited by the magnetic fields inside these stars. This may help for understanding the surface abundances of many red giant stars and reconciling the chemical evolution of 3He in our Galaxy with the observational constraints.  
In section 6. Interstellar and circumstellar matter

“Carbonaceous dust grains in luminous infrared galaxies. Spitzer/IRS reveals a-C:H as an abundant and ubiquitous ISM component”, by E. Dartois and G.M. Munoz-Caro, A&A 476, p. 1235

This convincing contribution to the "carbon debate" shows that an appreciable fraction of carbon is locked up in the form of hydrogenated amorphous carbon grains in many galaxies.  

 

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Highlights - Volume 476-2 (December III 2007)

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HIGHLIGHTS: this week in A&A

Volume 476-2 (December III 2007)

 


In section 6. Interstellar and circumstellar matter

“Effects of photophoresis on the evolution of transitional circumstellar disks”, by F. Herrmann, A. V. Krivov, A&A 476, p. 829

Photophoresis, one of the lesser known forces in physics, acts together with stellar gravity, radiation pressure, and gas drag in the evolution of solids in transitional circumstellar disks. The authors show in particular that photophoresis may cause a belt of objects to form, but only in a given range of sizes and only around low-luminosity stars. The effects of photophoresis are noticeable for solids in the size range from several micrometers to several centimeters in older transitional disks or even several meters in younger, more gaseous disks. 

 

In section 4. Extragalactic astronomy

“The chemical composition of planetary nebulae and HII regions in NGC 3109”, by M. Peña, G. Stasinska, and M. Richer, A&A 476, p. 745

This is a study of HII region and planetary nebula abundances in the dwarf irregular galaxy NGC 3109. A surprising finding is that the HII region oxygen abundances, while lower than found in the planetary nebulae, are uniform over the galaxy. 

 


In section 6. Interstellar and circumstellar matter

“A spectral line survey of Orion KL from 487-492 and 542-577 GHz with the Odin satellite. I. The observational data”, by A.O.H. Olofsson, C.M. Persson, N. Koning, et al., A&A 476, p. 791

The Orion spectral line survey by Olofsson et al. is an important forerunner of future studies with HERSCHEL. Noteworthy are the tentative detections of ND and SH- (the latter, if confirmed, adding to the small number of interstellar anions).  

 

© Astronomy & Astrophysics 2007

Highlights - Volume 476-1 ( December II 2007)

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HIGHLIGHTS: this week in A&A

Volume 476-1 (December II 2007)

 


In section 4. Extragalactic astronomy

“The contribution of very massive high-redshift SWIRE galaxies to the stellar mass function”, by S. Berta, C.J. Lonsdale, M. Polletta, A. Cimatti, et al., A&A 476, p. 151

It is well known now that star formation activity was much stronger in the past, 10 times higher at z=1 than today, and was possibly peaking at z=2. It has been also observed that most of the star formation today is occurring in small-mass objects, while it occurred in more massive objects at z=2, which is called "downsizing". But the question remains as to when the massive galaxies were assembled. With the help of the mid-IR emission observed with SWIRE on Spitzer, the authors have been able to explore the stellar mass function of galaxies in its high-mass tail. They show that the number of massive galaxies ( M>10**11 Mo) was 10 times lower at z=2-3 than today. Apparently, the high-mass galaxies are assembled progressively according to the hierarchical scenario. 

 

In section 14. Online catalogs and data

“Water maser variability over 20 years in a large sample of star-forming regions: the complete database”, by M. Felli, J. Brand, R. Cesaroni, C. Codella, G. Comoretto, S. Di Franco, F. Massi, L. Moscadelli, R. Nesti, F. Palagi, D. Panella, and R. Valdettaro, A&A 476, p. 373

Felli et al. present 22 GHz water maser emission for a large sample of star-forming regions observed regularly over a 20-year period. The authors present this enormous data set in an easily accessible and useful format that allows maser variability over this long period to be appreciated. 

 


 

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Highlights - Volume 475-3 ( December I 2007)

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HIGHLIGHTS: this week in A&A

Volume 475-3 (December I 2007)

 


In section 10. Planets and planetary systems

“Interferometric imaging of the sulfur-bearing molecules H2S, SO, and CS in comet C/1995 O1 (Hale-Bopp)”, by J. Boissier, D. Bockelée-Morvan, N. Biver, J. Crovisier, D. Despois, B.G. Marsden, and R. Moreno, A&A 475, p. 1131

This article is an interesting presentation of interferometric measurements to refine the orbital solutions and place limits on the dynamical forcing of the comet. The interferometric observations also favor an orbit unaffected by non-gravitational forces, constraining the mass and momentum losses at least during and after perihelion passage.

This is a benchmark study that demonstrates the enormous importance of interferometric observations in the study of time-dependent phenomena in comets and the potential of ALMA to contribute to the study of icy bodies in the solar system.

 

In section 6. Interstellar and circumstellar matter

“Multi-line (sub)millimetre observations of the high-mass proto cluster IRAS 05358+3543”, by S. Leurini, H. Beuther, P. Schilke, F. Wyrowski, Q. Zhang, and K.M. Menten, A&A 475, p. 925

The evolution of massive protostars is thought to involve the presence of a disk around the young accreting star, but identifying such disks has proven difficult. This paper presents evidence of such a disk surrounding a young proto-B star roughly 2 kpc from the sun.

 


 

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Highlights - Volume 475-2 (November IV 2007)

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HIGHLIGHTS: this week in A&A

Volume 475-2 (November IV 2007)

 


In section 7. Structure and stellar evolution

“Hydrodynamic simulations of irradiated secondaries in dwarf novae”, by M. Viallet and J.M. Hameury, A&A 475, p. 597

This is a detailed study of the effects of illumination on a extrasolar planetary atmosphere. The technique is very close to what is now used for modeling planets in the solar system and, among those calculations published so far, probably the closest to the meteorology that is now available.  

 


In section 5. Galactic structure, stellar clusters, and populations

“The Geneva-Copenhagen survey of the solar neighbourhood. II. New uvby calibrations and rediscussion of stellar ages, the G dwarf problem, age-metallicity diagram, and heating mechanisms of the disk”, by J. Holmberg, B. Nordström, and J. Andersen, A&A 475, p. 519

This paper is the second in the series on the Geneva-Copenhagen (GC) survey. This is the definitive test of the statistical uncertainties and biases for the sample presented in Paper I. It explores the sources of biases and statistical uncertainties that affect the global properties, such as the age-metallicity relation and radial metallicity gradients. The estimation of the ages of stars has been reduced by the new calibrations by about 10%, but the overall conclusions remain, making this the definitive sample of dynamics and stellar properties.  
In section 12. Atomic, molecular, and nuclear data

“Electron-impact excitation of Fe II. Collision strengths and effective collision strengths for low-lying fine-structure forbidden transitions”, by C.A. Ramsbottom, C.E. Hudson, P.H. Norrington, and M.P. Scott, A&A 475, p. 765

This paper reports very extensive calculations of effective collision strengths for the electron-impact excitation of Fe II for low-lying forbidden transitions in the lowest 16 fine-structure levels. These calculations provide the most extensive and accurate set of collisional data currently available for Fe II.  

 

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Highlights - Volume 475-1 (November III 2007)

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HIGHLIGHTS: this week in A&A

Volume 475-1 (November III 2007)

 


In section 2. Astrophysical processes

“Radiative transfer and the energy equation in SPH simulations of star formation”, by D. Stamatellos, A.P. Whitworth, T. Bisbas, and S. Goodwin, A&A 475, p. 37

This paper explores new techniques for treating radiative transfer and energy balance in the framework of SPH (smoothed particle hydrodynamics) simulations of protostellar evolution. As an example, the authors follow the evolution of a one solar-mass protostar.  

 

In section 4. Extragalactic astronomy

“VCC 2062: an old tidal dwarf galaxy in the Virgo cluster?”, by P.A. Duc, et al., A&A 475, p. 187

The authors have carried out a multi-wavelength study of the dwarf galaxy VCC 2062 in the Virgo Cluster, which belongs to an HI gas tidal tail linked to the parent galaxy NGC 4694. The high metallicity of the dwarf and the detection of CO emission in it both suggest that it is an old Tidal Dwarf Galaxy (TDG), formed in the merger between two spirals whose remnant is NGC 4694. These new dwarf galaxies, recycled from old material from massive spirals, can be used as a test of dark matter: they should be free of dissipationless CDM, while they could still contain some dark baryons. Detailed kinematical studies are now required to settle this issue.  

 

In section 6. Interstellar and circumstellar matter

“Herbig-Haro flows in B335”, by M. Gålfalk and G. Olofsson, A&A 475, p. 281

This paper reports the discovery of no less than 6 new Herbig-Haro objects in the well-studied outflow from the young protostar in B335. The results suggest the presence of a binary outflow, hence of a proto-binary.  

 


In section 12. Atomic, molecular, and nuclear data

“Energy levels, radiative rates, and excitation rates for transitions in Ni XI”, by K. M. Aggarwal and F. P. Keenan, A&A 475, p. 393

This paper reports radiative and excitation rates for transitions of Ni XI obtained using two independent codes, thus confirming the accuracy and ruling out the possibility of significant errors when determining this type of data. The results of this work will be fundamental to a wide community working not only on astrophysical but also on fusion applications.  

 

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Highlights - Volume 474-3 (November II 2007)

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HIGHLIGHTS: this week in A&A

Volume 474-3 (November II 2007)

 


In section 4. Extragalactic astronomy

“Resolving the complex structure of the dust torus in the active nucleus of the Circinus galaxy”, by K.R.W. Tristram, K. Meisenheimer, W. Jaffe, et al., A&A 474, p. 837

This paper presents high-spatial resolution observations of the nuclear dust distribution in the Circinus galaxy, obtained in the mid-infrared range, with the MIDI interferometric instrument at the VLT. The high enhancement of resolution has allowed the two dust components to be distinguished: a small dense and warm disk of size 0.4 pc, embedded in a 2 pc thick torus. The central disk is perpendicular to the outflow and ionisation cone of the AGN and aligned with the maser accretion disk. The torus is clumpy and filamentary, and it collimates the flow, as expected in the unified model of active nuclei.  

 

In section 10. Planets and planetary systems

“The effect of a planet on the dust distribution in a 3D protoplanetary disk”, by L. Fouchet, S.T. Maddison, J.F. Gonzalez, and J.R. Murray, A&A 474, p. 1037

Using smoothed particle hydrodynamics, the authors investigate the behaviour of dust in protoplanetary disks in the presence of a planet to study the effect of the gap opened in the disk by the planet on subsequent planetesimal growth within the dust layer. They find in particular that gap formation is much more rapid in the dust layer than in the gaseous disk and that a system with a given stellar, disk, and planetary mass will have a very different appearance depending on the grain size.  

 


In section 1. Letters

“AMBER and MIDI interferometric observations of the post-AGB binary IRAS 08544-4431: the circumbinary disc resolved”, by P. Deroo, B. Acke, T. Verhoelst, et al., A&A 474, p. L45

ESO recently published a press release based on these results. It is available at: http://www.eso.org/public/outreach/press-rel/pr-2007/pr-43-07.html  

 

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Highlights - Volume 474-2 (November I 2007)

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HIGHLIGHTS: this week in A&A

Volume 474-2 (November I 2007)

 


In section 9. The Sun

“The electron acceleration at shock waves in the solar corona”, by R. Miteva and G. Mann, A&A 474, p. 617

The solar corona shows transient enhancements of its radio emission through electrons that are accelerated at shocks generated by flares or coronal mass ejections. This paper presents a novel approach to explaining this electron acceleration in three steps, including whistler waves in gyro-resonance with the electrons. Based on this, the "herring-bone" fine structure of solar type II radio bursts can be understood.  

 

In section 5. Galactic structure, stellar clusters, and populations

“The distance to the Orion nebula”, by K.M. Menten, M.J. Reid, J. Forbrich, and A. Brunthaler, A&A 474, p. 515

Recent developments in VLBI (phase referencing) allow accurate distance determinations using the classical parallax technique, resulting in three recent determinations of the distance to the Orion nebula star cluster (ONC). The authors of the paper published in this issue obtained a value of 414 +/- 7 pc from a sample of four stars. This brings Orion ten percent closer than was previously assumed with some consequences for age estimates, but what is impressive point is the accuracy attained by these measurements.  

 


In section 1. Letters

“The X-ray soft excess in classical T Tauri stars”, by M. Güdel and A. Telleschi, A&A 474, p. L25

The authors study the nature of the soft X-ray excess they have discovered in accreting T Tauri stars and show that it is not correlated to the UV excess usually attributed to accretion column emission. It correlates instead with the integrated X-ray luminosity of the stars. This indicates the substantial influence of accretion on the X-ray properties of TTS, although the details of the interaction between accretion column and stellar corona which gives rise to the soft excess, remain uncertain.  

 

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Highlights - Volume 474-1 (October IV 2007)

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HIGHLIGHTS: this week in A&A

Volume 474-1 (October IV 2007)

 


Simulations of solar pores

Radiative magnetohydrodynamic simulations of solar pores”, by R. Cameron, M. Schussler, A. Vögler, and V. Zakharov, A&A 474, p. 261

Solar pores are a kind of small sunspot without a penumbra. This paper describes a first exploratory simulation of such a structure in a 3D MHD simulation accounting for radiative transfer. Therefore this sets a landmark towards the goal of finally understanding a whole sunspot.

 

 

Star-gas decoupling and dwarf galaxy formation

Star-gas decoupling and a non-rotating stellar core in He 2-10. Integral field spectroscopy with FLAMES/ARGUS”, by T. Marquart, K. Fathi, G. Östlin, N. Bergvall, R. Cumming, and P. Amram, A&A 473, p. L9

This is a 2D spectroscopic study of the merger-remnant dwarf galaxy He2-10 with FLAMES/VLT. It shows that the gas and stellar kinematics are decoupled. Although there is evidence of rotation in the gas, the stars are not rotating; they are instead only sustained by velocity dispersions, as in elliptical galaxies. The authors suggest that the object will become a nucleated dwarf elliptical. This object is therefore a prototypical example, highlighting the scenarios of dwarf galaxies formation.

 


 

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Highlights - Volume 473-3 (October III 2007)

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HIGHLIGHTS: this week in A&A

Volume 473-3 (October III 2007)

 


One of the most distant TeV blazars

Discovery of VHE gamma-rays from the distant BL Lacertae 1ES 0347-121”, by F. Aharonian, A.G. Akhperjanian, U. Barres de Almeida, et al., A&A 473, p. L25

This article presents the detection by the HESS collaboration of the TeV blazar 1ES 0347, at energies higher than 250 Gev. It is one of the most distant TeV blazars detected so far. This discovery implies that the universe is more transparent to very-high-energy gamma rays than previously thought and confirms the constraints on the near-infrared extragalactic background light.

 

 

The 6Li/7Li isotopic ratio

Line shift, line asymmetry, and the 6Li/7Li isotopic ratio determination”, by R. Cayrel, M. Steffen, H. Chand, P. Petitjean, M. Spite, F. Spite, H.-G. Ludwig, E. Caffau, and P. Bonifacio, A&A 473, p. L37

Since 6Li is not formed by standard big bang nucleosynthesis, its suspected presence in metal-poor stars has far-reaching consequences. Here, the authors use a high-quality spectrum of HD 74000 (S/N ratio of 600 per pixel and spectral resolution of 120 000) obtained with HARPS at ESO to demonstrate that line asymmetries generated by convective Doppler shifts in the atmosphere of metal-poor stars result in an excess absorption in the red wing of the 7Li absorption feature that mimics the presence of 6Li. A reappraisal of 6Li abundance determinations in halo stars is thus in order.

 


In section 4. Extragalactic astronomy

“The transverse proximity effect in spectral hardness on the line of sight towards HE2347-4342”, by G. Worseck, C. Fechner, L. Wisotzki, and A. Dall'Aglio, A&A 473, p. 805

This is the first evidence of a transverse HeII proximity effect to be found around high redshift quasars.  

 

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Highlights - Volume 473-2 (October II 2007)

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HIGHLIGHTS: this week in A&A

Volume 473-2 (October II 2007)

 


Non-equilibrium ionization in the solar atmosphere

Non-equilibrium hydrogen ionization in 2D simulations of the solar atmosphere”, by J. Leenaarts, M. Carlsson, V. Hansteen, and R.J. Rutten, A&A 473, p. 625

This paper describes a big step forward in 2D chromospheric simulations because it includes not only the non-equilibrium ionization process but also the consequences of the non-equilibrium ionization for the energy balance. So far this has only be possible in 1D simulations. Now one can also study the interaction of different structures accounting for the non-equilibrium ionization effects.

 

 

Dust sedimentation and PAHs in protoplanetary disks

Dust sedimentation in protoplanetary disks with polycyclic aromatic hydrocarbons”, by C.P. Dullemond, Th. Henning, R. Visser, V.C. Geers, E.F. van Dishoeck, and K.M. Pontoppidan, A&A 473, p. 457

The authors investigate how the presence of PAH molecules, when mixed with the larger dust grains, affects the spectral energy distribution of protoplanetary discs when the large grains are allowed to sediment. For low levels of turbulence in the disk, they predict that the PAH emission-to-continuum ratio is enhanced, contrary to what is observed. They speculate that coagulation might be a possible solution to this discrepancy.

 


In section 4. Extragalactic astronomy

“Dust-scattered X-ray halos around two Swift gamma-ray bursts: GRB 061019 and GRB 070129”, by G. Vianello, A. Tiengo, and S. Mereghetti, A&A 473, p. 423

This paper reports the Swift XRT detection of two new X-ray scattering halos during the afterglow phase of gamma-ray burst sources GRB061019 and GRB070129. In both cases, the halos are well resolved in time. The authors found a known Galactic molecular cloud superimposed along the line of sight toward GRB061019 at a distance consistent with the cloud of about 1 kpc. In the future, correlations of high-latitude molecular clouds with GRBs may be useful probes of Galactic molecular environments.  

 

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Highlights - Volume 473-1 (October I 2007)

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HIGHLIGHTS: this week in A&A

Volume 473-1 (October I 2007)

 


Star formation in the outer regions of M 33

Particularly efficient star formation in M 33”, by E. Gardan, J. Braine, K.F. Schuster, N. Brouillet, and A. Sievers, A&A 473, p. 91

CO emission has been mapped at a large radius in the local group spiral galaxy M33 with HERA on the IRAM-30m. The results suggest that molecular gas is ubiquitous, even in the outer parts of spiral galaxies outside of the optical disk. Comparisons with star-formation indicators, such as the Spizer 8 and 24 microns maps, Hα, or Far UV emission, reveal high star-formation efficiency in these outside regions.

 

 

A new 3-D modeling method for reconstructing coronal structures

Three-dimensional reconstruction of the streamer belt and other large-scale structures of the solar corona. I. Method”, by F. Saez, A. Llebaria, P. Lamy, and D. Vibert, A&A 473, p. 265

This paper describes an interesting 3-dimensional model for reproducing observations of coronal structures, such as streamers and CMEs.

 


In section 4. Extragalactic astronomy

“Multicolor observations of the afterglow of the short/hard GRB 050724”, by D. Malesani, S. Covino, P. D'Avanzo, V. D’Elia, et al., A&A 473, p. 77

This paper presents the photometry of the short GRB 050724, beginning about 1/2 day after detection, and the spectroscopy and imagining of its host galaxy (z = 0.26), a relatively low-luminosity, early type system with an old (2.6 Gyr) stellar population. The GRB occurred outside the galactic center (~ 3 kpc). There was no associated supernova, and the light curve is consistent with a binary merging event. The authors propose that the optical emission was related to an early, strong X-ray flare and that the steep optical decline is consistent with low collimation, implying a large energy release comparable to that of long GRBs. The flare properties require a strong Lorentz factor contrast between the colliding shells, and the authors argue that the central engine was active at late times.  

 

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Highlights - Volume 472-3 (September IV 2007)

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HIGHLIGHTS: this week in A&A

Volume 472-3 (September IV 2007)

 


Relationship between G-band bright points and magnetic structures: new observations

Relationships between magnetic foot points and G-band bright structures”, by R. Ishikawa, S. Tsuneta, Y. Kitakoshi, Y. Katsukawa, J. A. Bonet, S. Vargas Dominguez, L.H.M. Rouppe van der Voort, Y. Sakamoto, and T. Ebisuzaki, et al., A&A 472, p. 911

This paper presents superb new observations of the magnetic field’s fine structure and of the intensity in the G-band. It also presents new findings regarding the spatial distribution of G-band bright points with respect to their surrounding “magnetic islands”.

 

 

Migration and long-term orbital evolution of the protoplanets

On the migration of protoplanets embedded in circumbinary disks”, by A. Pierens and R.P. Nelson, A&A 472, p. 993

The authors present the results of hydrodynamical simulations of low-mass protoplanets embedded in circumbinary accretion disks. In all cases, they find that inward migration of the protoplanet is stopped at the edge of the tidally truncated cavity formed by the binary. Migration is halted in a region of long­term stability, suggesting that low-mass circumbinary planets may be common and that gas giant circumbinary planets should be able to form in circumbinary disks.

 


 

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Highlights - Volume 472-2 (September III 2007)

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HIGHLIGHTS: this week in A&A

Volume 472-2 (September III 2007)

 


Large-scale picture of the far-UV sky

SPEAR far UV spectral imaging of highly ionized emission from the North Galactic Pole region”, by B.Y. Welsh, J. Edelstein, E. Korpela, et al., A&A 472, p. 509

This paper presents observations of the emission-line intensities from atomic species at various levels of ionization over a large sector of the sky at high Galactic latitudes. This region is interesting since it includes a portion of the North Polar Spur, which shows up brightly in low-energy X-ray emission.

 

 

Transits of the nearby hot Neptune GJ 436 b

Detection of transits of the nearby hot Neptune GJ 436 b”, by M. Gillon, F. Pont, B.O. Demory, F. Mallmann, M. Mayor, T. Mazeh, D. Queloz, A. Shporer, S. Udry, and C. Vuissoz, A&A 472, p. L13

This paper reports the first measurement of the radius of a hot Neptune.

 


In section 10. Planets and planetary systems

“Planet dispersal in binary systems during transient multiple star phases”, by F. Marzari and M. Barbieri, A&A 472, p. 643

This study addresses a major question regarding the orbital survival of planets formed in binary and multiple star systems. It has important implications for both theories of giant planet formation and observational searches for extrasolar planets.  

 

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Highlights - Volume 472-1 (September II 2007)

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HIGHLIGHTS: this week in A&A

Volume 472-1 (September II 2007)

 


Measurement of the YORP effect on a small near-Earth asteroid

25143 Itokawa: direct detection of the current decelerating spin state due to YORP effect”, by K. Kitazato, M. Abe, M. Ishiguro, and W.-H. Ip, A&A 472, p. L5

The authors have measured the Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect for the small, well-characterized, near-Earth asteroid 25143 Itokawa over a relatively short time period. Using a new and different technique from earlier determinations, they find that the detected deceleration rate of the asteroid is almost consistent with, but slightly smaller than, the theoretically-predicted value.

 

 

New observations of eruptive variable star V1647 Orionis

Optical and infrared properties of V1647 Orionis during the 2003-2006 outburst.I. The reflection nebulas”, by A. Fedele, M.E. van den Ancker, M. G. Petr-Gotzens, N. Ageorges, and P. Rafanelli, A&A 472, p. 199

This paper presents new optical and infrared observations of the eruptive variable star V1647 Orionis and its associated nebula, McNeil's Nebula. The star erupted in 2003 for a period of about 2 years.

 


 

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Highlights - Volume 471-3 (September I 2007)

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HIGHLIGHTS: this week in A&A

Volume 471-3 (September I 2007)

 


Circumbinary molecular rings in Orion

Circumbinary molecular rings around young stars in Orion”, by L.A. Zapata, P.T.P. Ho, L.F. Rodriguez, P. Schilke, and S. Kurtz, A&A 471, p. L59

This paper reports observations of the massive starforming region OMC1S, located behind the Orion nebula, with the Submillimeter Array and the Very Large Array. It offers the first proof that circumbinary rotating rings around two young stars may exist in a region of high-mass star formation.

 

 

Abundance of silicon and iron on the surface of HR 7224

The helium weak silicon star HR 7224. II. Doppler Imaging analysis”, by H. Lehmann, A. Tkachenko, L. Fraga, V. Tsymbal, and D.E. Mkrtichian, A&A 471, p. 919

This paper investigates the abundance distributions of silicon and iron on the surface of HR 7224, using the Doppler imaging technique. The authors show the presence of large silicon and iron spots on the star's surface.

 


In section 1. Letters

“Accurate Spitzer infrared radius measurement for the hot Neptune GJ 436b”, by M. Gillon, B.-O. Demory, T. Barman, X. Bonfils, T. Mazeh, F. Pont, S. Udry, M. Mayor, and D. Queloz, A&A 471, p. L51

In this paper, the authors describe Spitzer infrared photometric observations of the exo-Neptune GJ 436b, which they recently discovered transiting its host star. It is the closest, smallest, and least massive planet known to transit its (M-dwarf) host star.  

 

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Highlights - Volume 471-2 (August IV 2007)

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HIGHLIGHTS: this week in A&A

Volume 471-2 (August IV 2007)

 


VLA observations of the supernova remnant W44

The low-frequency radio emission and spectrum of the extended SNR W44: new VLA observations at 74 and 324 MHz”, by G. Castelletti, G. Dubner, C. Brogan, and N.E. Kassim, A&A 471, p. 515

The interaction of supernova remnants with surrounding molecular clouds is interesting both because of the effects on the surroundings (stimulating star formation, for example) and because of the effects on the remnant itself (particle acceleration, for example). This paper applies low-frequency radio techniques to the study of the well-known supernova remnant W44 and gives evidence that the radio spectral index varies considerably in the region of interaction.

 

 

IR integral-field spectroscopy of SN 1987A

Infrared integral field spectroscopy of SN 1987A”, by K. Kjaer, B. Leibundgut, C. Fransson, P. Gröningsson, J. Spyromilio, and M. Kissler-Patig, A&A 471, p. 595

SN 1987A in the Large Magellanic Cloud was the brightest supernova in the last few centuries and is close enough to study its transition to a supernova remnant. The authors use the SINFONI integral-field spectrograph supported by adaptive optics to obtain a dynamical map of the interaction between the inner circumstellar ring and the supernova shock and to map the cooling in the shocked material.

 


In section 1. Letters

“Low-mass lithium-rich AGB stars in the Galactic bulge: evidence for cool bottom processing?”, by S. Uttenthaler, T. Lebzelter, S. Palmerini, M. Busso, B. Aringer, and M.T. Lederer, A&A 471, p. L41

This paper reports the discovery of two asymptotic giant branch (AGB) stars with solar lithium abundance. The very probable conclusion is that an extra mixing process works below the convective envelopes of these stars. This may lead to a new picture of AGB nucleosynthesis.  

 

© Astronomy & Astrophysics 2007

Highlights - Volume 470-3 (August II 2007)

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HIGHLIGHTS: this week in A&A

Volume 470-3 (August II 2007)

 


Photometric changes in HD 377776

The light variability of the helium strong star HD 37776 as a result of its inhomogeneous elemental surface distribution”, by J. Krticka et al., A&A 470, p. 1089

This work presents a computation of the photometric changes in the spotted early-type star HD37776, starting from a known inhomogeneous distribution of helium and silicon over the stellar surface. These model calculations are able to explain the main features of the photometric curves and support the idea that the main properties of this star can be understood when assuming spots with a peculiar chemical composition.

 

 

The intermediate to high-mass protocluster IRAS 18511+0146

IRAS 18511+0146: a proto Herbig Ae/Be cluster?”, by S. Vig et al. A&A 470, p. 977

This paper presents multi-instrument observations and simulations of the gas and stars surrounding the luminous, young, intermediate to high-mass protocluster IRAS 18511+0146. They find that the central, most obscured part of the protocluster coincides with the compact mm-submm SCUBA source and that it is responsible for most of the luminosity. They identify a number of mid-infrared bright cluster members that appear to be very young stellar sources and also show that IRAS 18511+0146 is probably a precursor to a Herbig type star.

 


In section 1. Letters

“Direct diameter measurement of a star filling its Roche lobe. The semi-detached binary SS Leporis spatially resolved with VINCI/VLTI”, by T. Verhoelst, E. van Aarle, and B. Acke, A&A 470, p. L21

Stellar evolution in close binary systems is strongly influenced by mass transfer from one star to another. That complex process is usually studied in eclipsing binaries through spectroscopy and measurement of the eclipse light curve. The authors adopt an alternative and more direct approach, using optical interferometry to resolve each of the two stars, as well as a circumbinary disk. This method has considerable potential to resolve the ambiguities left by the indirect methods.  

 

© Astronomy & Astrophysics 2007

Highlights - Volume 471-1 (August III 2007)

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HIGHLIGHTS: this week in A&A

Volume 471-1 (August III 2007)

 


Long-term evolution of solar activity

Grand minima and maxima of solar activity: new observational constraints”, I. Usoskin, S. Solanki, and G.A. Kovaltsov, A&A 471, p. 301

This paper shows that the duration of times with high or low sunspot numbers (e.g. the well-known Maunder minimum) is determined by a stochastic or chaotic process. This is very interesting for dynamo modeling, in particular at the level of constraining the mechanism(s) responsible for the occurrence of such minima and maxima (nonlinear modulation, intermittency, etc.).

 

 

Study of a hypercompact HII region

The hyperyoung HII region in G24.78+0.08 A1”, M. T. Beltran, R. Cesaroni, L. Moscadelli, and C. Codella, A&A 471, p. L13

The authors present new, high-quality, VLA continuum observations at 1.3 cm and 7 mm of a hypercompact HII region located at the centre of a massive rotating toroid. This HII region was found to have a ring-shaped structure with an outer radius of 590 AU.
The analysis indicates that the ionized shell is expanding in accordance with the observed kinematics of the water maser spots associated with the HC HII region. According to the model, the HC HII region is extremely young with an expansion age of ~50 yr. This region is then interesting for further observations of the early development of a region of ionized gas.

 


In section 10. Planets and planetary systems

“Surface composition of the largest dwarf planet 136199 Eris (2003 UB313)”, by C. Dumas, O. Hainaut, F. Merlin, M. A. Barucci, C. de Bergh, A. Guilbert, P. Vernazza, and A. Doressoundiram A&A 471, p. 331

The authors have studied the surface composition of the largest TNO, the dwarf planet 136199 Eris, using TNG and ESO-VLT visible and near-infrared reflectance spectra observations. Modeling of the data reveals that the surface of Iris can be explained with two distinct surface compositions, with about half of the surface covered with pure methane ice and the rest of a mixture of methane, nitrogen, water and Tholin ices. The methane on Eris appears to be in its pure form, rather that diluted in a nitrogen matrix as seems to be the case on Pluto.  

 

© Astronomy & Astrophysics 2007

Highlights - Volume 470-2 (August I 2007)

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HIGHLIGHTS: this week in A&A

Volume 470-2 (August I 2007)

 


Flux emergence simulations and complex magnetic fields

Simple emergence structures from complex magnetic fields”, M.J. Murray and A.W. Hood, A&A 470, p. 709

Magnetic flux tubes in the solar interior rise and eventually break through the surface. It is very interesting to understand the relation between the subsurface magnetic field structure and the observable signatures of emerging magnetic flux. Previous models have mostly investigated a simple flux tube emergence, even though the subsurface field structure is much more complex. In this paper, the authors show that the interaction of two flux tubes in the interior leads to a complex subsurface magnetic field. When the complex structure comes close to the surface, it remains quite complex, but the emergence process occurs in a similar manner to what a simpler subsurface field does. This indicates that previous results for flux emergence simulations hold for both simple and complex subsurface field structures.

 

 

The distance to the Pipe nebula

An accurate determination of the distance to the Pipe nebula”, F.O. Alves and G.A.P. Franco, A&A 470, p. 597

This paper presents a new and, so far, the most accurate, determination of the distance to the so-called Pipe nebula, a dark cloud projected against the Galactic bulge. Because of its favourable direction toward a star-rich background, the extinction through this cloud has recently been studied extensively using the JHK multicolour technique. The Pipe nebula is so important for studies related to the initial conditions for star formation (or non-formation) that accurately determining its distance deserves special attention.

 


In section 7. Stellar structure and evolution

“Origin of the early-type R stars: a binary-merger solution to a century-old problem?”, by R. G. Izzard, C. S. Jeffery, and J. Lattanzio A&A 470, p. 661

The early-R stars are core helium burning giants whose surface is enriched in carbon but not in s-process elements. The fact that they are all single stars makes it plausible that these stars are the result of a stellar merger. This paper shows that the expected number of merger events can match the observed number of early-R stars, and thus concludes that stellar merger are in fact responsible for their formation.  

 

© Astronomy & Astrophysics 2007