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Rotation and magnetism of Kepler pulsating solar-like stars Towards asteroseismically calibrated age-rotation relations

Titulo: 
Rotation and magnetism of Kepler pulsating solar-like stars Towards asteroseismically calibrated age-rotation relations
Autores: 
Garcia, RA; Ceillier, T; Salabert, D; Mathur, S; van Saders, JL; Pinsonneault, M; Ballot, J; Beck, PG; Bloemen, S; Campante, TL; Davies, GR; do Nascimento, JD; Mathis, S; Metcalfe, TS; Nielsen, MB; Suarez, JC; Chaplin, WJ; Jimenez, A; Karoff, C
Resumen: 
Kepler ultra-high precision photometry of long and continuous observations provides a unique dataset in which surface rotation and variability can be studied for thousands of stars. Because many of these old field stars also have independently measured asteroseismic ages, measurements of rotation and activity are particularly interesting in the context of age-rotation-activity relations. In particular, age-rotation relations generally lack good calibrators at old ages, a problem that this Kepler sample of old-field stars is uniquely suited to address. We study the surface rotation and photometric magnetic activity of a subset of 540 solar-like stars on the main-sequence and the subgiant branch for which stellar pulsations have been measured. The rotation period was determined by comparing the results from two different analysis methods: i) the projection onto the frequency domain of the time-period analysis, and ii) the autocorrelation function of the light curves. Reliable surface rotation rates were then extracted by comparing the results from two different sets of calibrated data and from the two complementary analyses. General photometric levels of magnetic activity in this sample of stars were also extracted by using a photometric activity index, which takes into account the rotation period of the stars. We report rotation periods for 310 out of 540 targets (excluding known binaries and candidate planet-host stars); our measurements span a range of 1 to 100 days. The photometric magnetic activity levels of these stars were computed, and for 61.5% of the dwarfs, this level is similar to the range, from minimum to maximum, of the solar magnetic activity. We demonstrate that hot dwarfs, cool dwarfs, and subgiants have very different rotation-age relationships, highlighting the importance of separating out distinct populations when interpreting stellar rotation periods. Our sample of cool dwarf stars with age and metallicity data of the highest quality is consistent with gyrochronology relations reported in the literature.
Autor principal: 
Garcia, RA
Autor/es del IAA: 
Suarez, J. C.
DOI: 
10.1051/0004-6361/201423888
Revista: 
ASTRONOMY & ASTROPHYSICS
Fecha de publicación: 
2014/12
Volumen: 
572
Tipo de documento: 
Article
Palabras clave: 
asteroseismology; stars: activity; stars: rotation; stars: solar-type; stars: evolution; stars: oscillations
Número de artículo: 
A34

The Gaia-ESO Survey: the chemical structure of the Galactic discs from the first internal data release

Titulo: 
The Gaia-ESO Survey: the chemical structure of the Galactic discs from the first internal data release
Autores: 
Mikolaitis, S; Hill, V; Recio-Blanco, A; de Laverny, P; Prieto, CA; Kordopatis, G; Tautvaisiene, G; Romano, D; Gilmore, G; Randich, S; Feltzing, S; Micela, G; Vallenari, A; Alfaro, EJ; Bensby, T; Bragaglia, A; Flaccomio, E; Lanzafame, AC; Pancino, E; Smiljanic, R; Bergemann, M; Carraro, G; Costado, MT; Damiani, F; Hourihane, A; Jofre, P; Lardo, C; Magrini, L; Maiorca, E; Morbidelli, L; Sbordone, L; Sousa, SG; Worley, CC; Zaggia, S
Resumen: 
Aims. Until recently, most high-resolution spectroscopic studies of the Galactic thin and thick discs were mostly confined to objects in the solar vicinity. Here we aim at enlarging the volume in which individual chemical abundances are used to characterise the thin and thick discs, using the first internal data release of the Gaia-ESO survey (GES iDR1). Methods. We used the spectra of around 2000 FGK dwarfs and giants from the GES iDR1, obtained at resolutions of up to R similar to 20 000 with the FLAMES/GIRAFFE spectrograph. We derive and discuss the abundances of eight elements (Mg, Al, Si, Ca, Ti, Fe, Cr, Ni, and Y). Results. We show that the trends of these elemental abundances with iron are very similar to those in the solar neighbourhood. We find a natural division between alpha-rich and alpha-poor stars, best seen in the bimodality of the [Mg/M] distributions in bins of metallicity, which we attribute to thick-and thin-disc sequences, respectively. This separation is visible for most alpha-elements and for aluminium. With the possible exception of Al, the observed dispersion around the trends is well described by the expected errors, leaving little room for astrophysical dispersion. Using previously derived distances from the first paper from this series for our sample, we further find that the thick-disc is more extended vertically and is more centrally concentrated towards the inner Galaxy than the thin-disc, which indicates a shorter scale-length. We derive the radial (4 to 12 kpc) and vertical (0 to 3.5 kpc) gradients in metallicity, iron, four alpha-element abundances, and aluminium for the two populations, taking into account the identified correlation between R-GC and vertical bar Z vertical bar. Similarly to other works, a radial metallicity gradient is found in the thin disc. The positive radial individual [alpha/M] gradients found are at variance from the gradients observed in the RAVE survey. The thin disc also hosts a negative vertical metallicity gradient in the solar cylinder, accompanied by positive individual [alpha/M] and [Al/M] gradients. The thick-disc, on the other hand, presents no radial metallicity gradient, a shallower vertical metallicity gradient than the thin-disc, an alpha-elements-to-iron radial gradient in the opposite sense than that of the thin disc, and positive vertical individual [alpha/M] and [Al/M] gradients. We examine several thick-disc formation scenarii in the light of these radial and vertical trends.
Autor principal: 
Mikolaitis, S
Autor/es del IAA: 
Alfaro, E. J.; Costado, M. T.
DOI: 
10.1051/0004-6361/201424093
Revista: 
ASTRONOMY & ASTROPHYSICS
Fecha de publicación: 
2014/12
Volumen: 
572
Tipo de documento: 
Article
Palabras clave: 
Galaxy: disk; Galaxy: stellar content; techniques: spectroscopic
Número de artículo: 
A33

A quiescent galaxy at the position of the long GRB 050219A

Titulo: 
A quiescent galaxy at the position of the long GRB 050219A
Autores: 
Rossi, A; Piranomonte, S; Savaglio, S; Palazzi, E; Michalowski, MJ; Klose, S; Hunt, LK; Amati, L; Elliott, J; Greiner, J; Guidorzi, C; Japelj, J; Kann, DA; Lo Faro, B; Guelbenzu, AN; Schulze, S; Vergani, SD; Arnold, LA; Covino, S; D'Elia, V; Ferrero, P; Filgas, R; Goldoni, P; Yoldas, AK; Le Borgne, D; Pian, E; Schady, P; Stratta, G
Resumen: 
Context. Long-duration gamma-ray bursts (LGRBs) are produced by the collapse of very massive stars. Because of the short life time of their progenitors, LGRBs pinpoint star-forming galaxies. Recent studies demonstrate that LGRBs populate all types of star-forming galaxies from sub-luminous, blue compact dwarfs to luminous infrared galaxies. Aims. We present here a multi-band search for the host galaxy of the long dark GRB 050219A within the enhanced Swift/XRT error circle. We aim to characterise the properties of its host galaxy and compare them with those of other LGRB host galaxies. Methods. We used spectroscopic observations acquired with VLT/X-Shooter to determine the redshift and star-formation rate of the most probable host galaxy identified on the basis of a chance probability criterion. We compared the results with the optical and infrared spectral energy distribution obtained with Swift/UVOT, the seven-channel imager GROND at the 2.2-m telescope on La Silla and the Herschel Space Observatory, supplemented by archival observations obtained with FORS2 at the ESO/VLT, the Spitzer Space Telescope, and the GALEX survey. Results. The most probable host galaxy of the genuine long-duration GRB 050219A is a 3 Gyr-old early-type galaxy at z = 0.211. It is characterised by a ratio of star-formation rate to stellar mass (specific star-formation rate) of similar to 6 x 10(-12) yr(-1) that is unprecedentedly low when compared to all known LGRB host galaxies. Its properties resemble those of post-starburst galaxies. Conclusions. GRB 050219A might be the first known long burst to explode in a quiescent early-type galaxy. This would be further evidence that GRBs can explode in all kinds of galaxies, with the only requirement being an episode of high-mass star formation.
Autor principal: 
Rossi, A
Autor/es del IAA: 
Ferrero, P.
DOI: 
10.1051/0004-6361/201423865
Revista: 
ASTRONOMY & ASTROPHYSICS
Fecha de publicación: 
2014/12
Volumen: 
572
Tipo de documento: 
Article
Palabras clave: 
gamma-ray burst: individual: GRB 050219A
Número de artículo: 
A47

Resolving the stellar components of the massive multiple system Herschel 36 with AMBER/VLTI

Titulo: 
Resolving the stellar components of the massive multiple system Herschel 36 with AMBER/VLTI
Autores: 
Sanchez-Bermudez, J; Alberdi, A; Schodel, R; Hummel, CA; Arias, JI; Barba, RH; Apellaniz, JM; Pott, JU
Resumen: 
Context. Massive stars are extremely important for the evolution of the galaxies; there are large gaps in our understanding of their properties and formation, however, mainly because they evolve rapidly, are rare, and distant. Recent findings suggest that most O-stars belong to multiple systems. It may well be that almost all massive stars are born as triples or higher multiples, but their large distances require very high angular resolution to directly detect the companions at milliarcsecond scales. Aims. Herschel 36 is a young massive system located at 1.3 kpc. It has a combined smallest predicted mass of 45 M-circle dot. Multi-epoch spectroscopic data suggest the existence of at least three gravitationally bound components. Two of them, system Ab, are tightly bound in a spectroscopic binary, and the third one, component Aa, orbits in a wider orbit. Our aim was to image and obtain astrometric and photometric measurements of components Aa and Ab using, for the first time, long-baseline optical interferometry to further constrain its nature. Methods. We observed Herschel 36 with the near-infrared instrument AMBER attached to the ESO VLT Interferometer, which provides an angular resolution of similar to 2 mas. We used the code BSMEM to perform the interferometric image reconstruction. We fitted the interferometric observables using proprietary IDL routines and the code LitPro. Results. We imaged the Aa + Ab components of Herschel 36 in H and K filters. Component Ab is located at a projected distance of 1.81 mas, at a position angle of similar to 222 degrees east of north, the flux ratio between components Aa and Ab is close to one. These findings agree with previous predictions about the properties of Herschel 36. The small measured angular separation indicates that system Ab and Ab may be approaching the periastron of their orbits. These results, only achievable with long-baseline near-infrared interferometry, constitute the first step toward a thorough understanding of this massive triple system.
Autor principal: 
Sanchez-Bermudez, J
Autor/es del IAA: 
Sanchez-Bermudez, J.; Alberdi, A.; Schoedel, R.; Maiz Apellaniz, J.
DOI: 
10.1051/0004-6361/201424901
Revista: 
ASTRONOMY & ASTROPHYSICS
Fecha de publicación: 
2014/12
Volumen: 
572
Tipo de documento: 
Article
Palabras clave: 
instrumentation: high angular resolution; instrumentation: interferometers; binaries: close; stars: massive
Número de artículo: 
L1

The connection between the parsec-scale radio jet and gamma-ray flares in the blazar 1156+295

Titulo: 
The connection between the parsec-scale radio jet and gamma-ray flares in the blazar 1156+295
Autores: 
Ramakrishnan, V; Leon-Tavares, J; Rastorgueva-Foi, EA; Wiik, K; Jorstad, SG; Marscher, AP; Tornikoski, M; Agudo, I; Lahteenmaki, A; Valtaoja, E; Aller, MF; Blinov, DA; Casadio, C; Efimova, NV; Gurwell, MA; Gomez, JL; Hagen-Thorn, VA; Joshi, M; Jarvela, E; Konstantinova, TS; Kopatskaya, EN; Larionov, VM; Larionova, EG; Larionova, LV; Lavonen, N; MacDonald, NR; McHardy, IM; Molina, SN; Morozova, DA; Nieppola, E; Tammi, J; Taylor, BW; Troitsky, IS
Resumen: 
The blazar 1156+295 was active at gamma-ray energies, exhibiting three prominent flares during the year 2010. Here, we present results using the combination of broad-band (X-ray through mm single-dish) monitoring data and radio-band imaging data at 43 GHz on the connection of gamma-ray events to the ejections of superluminal components and other changes in the jet of 1156+295. The kinematics of the jet over the interval 2007.0-2012.5 using 43 GHz Very Long Baseline Array observations reveal the presence of four moving and one stationary component in the inner region of the blazar jet. The propagation of the third and fourth components in the jet corresponds closely in time to the active phase of the source in gamma-rays. We briefly discuss the implications of the structural changes in the jet for the mechanism of gamma-ray production during bright flares. To localize the gamma-ray emission site in the blazar, we performed the correlation analysis between the 43 GHz radio core and the gamma-ray light curve. The time lag obtained from the correlation constrains the gamma-ray emitting region in the parsec-scale jet.
Autor principal: 
Ramakrishnan, V
Autor/es del IAA: 
Agudo, Ivan; Casadio, Carolina; Gomez, Jose L.; Molina, Sol N.
DOI: 
10.1093/mnras/stu1873
Revista: 
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Fecha de publicación: 
2014/12/01
Volumen: 
445
Issue: 
2
Páginas: 
1636-1646
Tipo de documento: 
Article
Palabras clave: 
galaxies: active; galaxies: jets; quasars: individual: 1156+295; gamma-rays: galaxies; radio continuum: galaxies

Fermion pairing and the scalar boson of the 2D conformal anomaly

Titulo: 
Fermion pairing and the scalar boson of the 2D conformal anomaly
Autores: 
Blaschke, DN; Carballo-Rubio, R; Mottola, E
Resumen: 
We analyze the phenomenon of fermion pairing into an effective boson associated with anomalies and the anomalous commutators of currents, bilinear in the fermion fields. In two spacetime dimensions the chiral bosonization of the Schwinger model is determined by the chiral current anomaly of massless Dirac fermions. A similar bosonized description applies to the 2D conformal trace anomaly of the fermion stress-energy tensor. For both the chiral and conformal anomalies, correlation functions involving anomalous currents, j(5) (mu) or T (mu nu) of massless fermions exhibit a massless boson 1/k(2) pole, and the associated spectral functions obey a UV finite sum rule, becoming delta-functions in the massless limit. In both cases the corresponding effective action of the anomaly is non-local, but may be expressed in a local form by the introduction of a new bosonic field, which becomes a bona fide propagating quantum field in its own right. In both cases this is expressed in Fock space by the anomalous Schwinger commutators of currents becoming the canonical commutation relations of the corresponding boson. The boson has a Fock space operator realization as a coherent superposition of massless fermion pairs, which saturates the intermediate state sums in quantum correlation functions of fermion currents. The Casimir energy of fermions on a finite spatial interval [0, L] can also be described as a coherent scalar condensation of pairs, and the one-loop correlation function of any number n of fermion stress-energy tensors [TT . . . T] may be expressed as a combinatoric sum of n!/2 linear tree diagrams of the scalar boson.
Autor principal: 
Blaschke, DN
Autor/es del IAA: 
Carballo-Rubio, Raul
DOI: 
10.1007/JHEP12(2014)153
Revista: 
JOURNAL OF HIGH ENERGY PHYSICS
Fecha de publicación: 
2014/12/23
Issue: 
12
Tipo de documento: 
Article
Palabras clave: 
2D Gravity; Anomalies in Field and String Theories; Field Theories in Lower Dimensions

Ionizing stellar population in the disc of NGC 3310-II. The Wolf-Rayet population

Titulo: 
Ionizing stellar population in the disc of NGC 3310-II. The Wolf-Rayet population
Autores: 
Miralles-Caballero, D; Rosales-Ortega, FF; Diaz, AI; Oti-Floranes, H; Perez-Montero, E; Sanchez, SF
Resumen: 
We use integral field spectroscopy to study in detail the Wolf Rayet (WR) population in NGC 3310, spatially resolving 18 star-forming knots with typical sizes of 200-300 pc in the disc of the galaxy hosting a substantial population of WRs. The detected emission in the so-called blue bump is attributed mainly to late-type nitrogen WRs (WNL), ranging from a few dozens to several hundreds of stars per region. Our estimated WNL/(WNL+0) ratio is comparable to reported empirical relations once the extinction-corrected emission is further corrected by the presence of dust grains inside the nebula that absorb a non-negligible fraction of UV photons. Comparisons of observables with stellar population models show disagreement by factors larger than 2-3. However, if the effects of interacting binaries and/or photon leakage are taken into account, observations and predictions tend to converge. We estimate the binary fraction of the H ii regions hosting WRs to be significant in order to recover the observed X-ray flux, hence proving that the binary channel can be critical when predicting observables. We also explore the connection of the environment with the current hypothesis that WRs can be progenitors to long-duration gamma-ray bursts (GRBs). Galaxy interactions, which can trigger strong episodes of star formation in the central regions, may be a plausible environment where WRs may act as progenitors of GRBs. Finally, even though the chemical abundance is generally homogeneous, we also find weak evidence for rapid N pollution by WR stellar winds at scales of similar to 200 pc.
Autor principal: 
Miralles-Caballero, D
Autor/es del IAA: 
Perez-Montero, E.
DOI: 
10.1093/mnras/stu2002
Revista: 
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Fecha de publicación: 
2014/12/21
Volumen: 
445
Issue: 
4
Páginas: 
3803-3822
Tipo de documento: 
Article
Palabras clave: 
techniques: spectroscopic; stars: Wolf-Rayet; galaxies: individual: NGC 3310; galaxies: ISM; galaxies: starburst; X-rays: galaxies: clusters

The Gaia-ESO Survey: the most metal-poor stars in the Galactic bulge

Titulo: 
The Gaia-ESO Survey: the most metal-poor stars in the Galactic bulge
Autores: 
Howes, LM; Asplund, M; Casey, AR; Keller, SC; Yong, D; Gilmore, G; Lind, K; Worley, C; Bessell, MS; Casagrande, L; Marino, AF; Nataf, DM; Owen, CI; Da Costa, GS; Schmidt, BP; Tisserand, P; Randich, S; Feltzing, S; Vallenari, A; Prieto, CA; Bensby, T; Flaccomio, E; Korn, AJ; Pancino, E; Recio-Blanco, A; Smiljanic, R; Bergemann, M; Costado, MT; Damiani, F; Heiter, U; Hill, V; Hourihane, A; Jofre, P; Lardo, C; de Laverny, P; Magrini, L; Maiorca, E; Masseron, T; Morbidelli, L; Sacco, GG; Minniti, D; Zoccali, M
Resumen: 
We present the first results of the EMBLA survey (Extremely Metal-poor BuLge stars with AAOmega), aimed at finding metal-poor stars in the Milky Way bulge, where the oldest stars should now preferentially reside. EMBLA utilizes SkyMapper photometry to pre-select metal-poor candidates, which are subsequently confirmed using AAOmega spectroscopy. We describe the discovery and analysis of four bulge giants with -2.72 <= [Fe/H] <= -2.48, the lowest metallicity bulge stars studied with high-resolution spectroscopy to date. Using FLAMES/UVES spectra through the Gaia-ESO Survey we have derived abundances of twelve elements. Given the uncertainties, we find a chemical similarity between these bulge stars and halo stars of the same metallicity, although the abundance scatter may be larger, with some of the stars showing unusual [alpha/Fe] ratios.
Autor principal: 
Howes, LM
Autor/es del IAA: 
Costado, M. T.
DOI: 
10.1093/mnras/stu1991
Revista: 
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Fecha de publicación: 
2014/12/21
Volumen: 
445
Issue: 
4
Páginas: 
4241-4246
Tipo de documento: 
Article
Palabras clave: 
stars: abundances; stars: Population II; Galaxy: bulge; Galaxy: evolution

Electromagnetism as an emergent phenomenon: a step-by-step guide

Titulo: 
Electromagnetism as an emergent phenomenon: a step-by-step guide
Autores: 
Barcelo, C; Carballo-Rubio, R; Garay, LJ; Jannes, G
Resumen: 
We give a detailed description of electrodynamics as an emergent theory from condensed-matter-like structures, not only per se but also as a warm-up for the study of the much more complex case of gravity. We concentrate on two scenarios that, although qualitatively different, share some important features with the idea of extracting the basic generic ingredients that give rise to emergent electrodynamics and, more generally, to gauge theories. We start with Maxwell's mechanical model for electrodynamics, where Maxwell's equations appear as dynamical consistency conditions. We next take a superfluid He-3-like system as representative of a broad class of fermionic quantum systems whose low-energy physics reproduces classical electrodynamics (Dirac and Maxwell equations as dynamical low-energy laws). An important lesson that can be derived from both analyses is that the vector potential has a microscopic physical reality and only in the low-energy regime is this physical reality blurred in favor of gauge invariance, which in addition turns out to be secondary to effective Lorentz invariance.
Autor principal: 
Barcelo, C
Autor/es del IAA: 
Barcelo, Carlos; Carballo-Rubio, Raul
DOI: 
10.1088/1367-2630/16/12/123028
Revista: 
NEW JOURNAL OF PHYSICS
Fecha de publicación: 
2014/12/10
Volumen: 
16
Tipo de documento: 
Article
Palabras clave: 
emergent gravity; electrodynamics; quantum gravity; gauge invariance; gravity
Número de artículo: 
123028

Nighttime ozone variability in the high latitude winter mesosphere

Titulo: 
Nighttime ozone variability in the high latitude winter mesosphere
Autores: 
Smith, AK; Lopez-Puertas, M; Funke, B; Garcia-Comas, M; Mlynczak, MG; Holt, LA
Resumen: 
We use satellite observations and a numerical model to investigate polar nighttime ozone at the secondary maximum, around 90-95 km. Observations from the MIPAS and SABER satellite instruments indicate that the highest ozone mixing ratios are seen during the late fall to early winter period in both hemispheres and for all years examined. Simulations using the Whole Atmosphere Community Climate Model (WACCM) find qualitatively the same seasonal evolution. Analysis of WACCM results shows that the high ozone concentration is due in part to the relatively quiet dynamical conditions in early winter. The mean circulation, which brings warmer temperatures and higher concentrations of H, is weaker in early winter than during middle and late winter. H in the late fall to early winter period drops to the lowest levels seen during the year due to lack of a source from photochemistry, weak transport into the region by the mean circulation, and continual loss due to diffusive separation. The low concentration of H leads to higher ozone.
Autor principal: 
Smith, AK
Autor/es del IAA: 
Lopez-Puertas, Manuel; Funke, Bernd; Garcia-Comas, Maya
DOI: 
10.1002/2014JD021987
Revista: 
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Fecha de publicación: 
2014/12/16
Volumen: 
119
Issue: 
23
Páginas: 
13547-13564
Tipo de documento: 
Article

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