Suchergebnisse

The characterization of multiplicity of high-mass stars is of fundamental importance to understand their evolution, the diversity of observed core-collapse supernovae and the formation of gravitational wave progenitor systems. Despite that, until recently, one of the final phases of massive star evolution – the cool supergiant phase – has received comparatively little attention. In this study, we aim to explore the multiplicity among the cool supergiant (CSG) population in the Large and Small Magellanic Clouds (LMC and SMC, respectively). To do this we compile extensive archival radial velocity (RV) measurements for over 1000 CSGs from the LMC and SMC, spanning a baseline of over 40 yr. By statistically correcting the RV measurements of each stellar catalogue to the Gaia DR2 reference frame we are able to effectively compare these diverse observations. We identify 45 CSGs where RV variations cannot be explained through intrinsic variability, and are hence considered binary systems. We obtain a minimum binary fraction of 15±4 per cent for the SMC and of 14±5 per cent for the LMC, restricting our sample to objects with at least 6 and 5 observational epochs, respectively. Combining these results, we determine a minimum binary fraction of 15±3 per cent for CSGs. These results are in good agreement with previous results which apply a correction to account for observational biases. These results add strength to the hypothesis that the binary fraction of CSGs is significantly lower than their main-sequence counterparts. Going forward, we stress the need for long-baseline multi-epoch spectroscopic surveys to cover the full parameter space of CSG binary systems. ; The authors acknowledge support from the Spanish Government Ministerio de Ciencia e Innovación through grants PGC-2018-091 3741-B-C22 and SEV 2015-0548, and from the Canarian Agency for Research, Innovation and Information Society (ACIISI), of the Canary Islands Government, and the European Regional Development Fund (ERDF), under grant with reference ...

We present a new catalogue of cool supergiants in a section of the Perseus arm, most of which had not been previously identified. To generate it, we have used a set of well-defined photometric criteria to select a large number of candidates (637) that were later observed at intermediate resolution in the infrared calcium triplet spectral range, using a long-slit spectrograph. To separate red supergiants from luminous red giants, we used a statistical method, developed in previous works and improved in the present paper. We present a method to assign probabilities of being a red supergiant to a given spectrum and use the properties of a population to generate clean samples, without contamination from lower luminosity stars. We compare our identification with a classification done using classical criteria and discuss their respective efficiencies and contaminations as identification methods. We confirm that our method is as efficient at finding supergiants as the best classical methods, but with a far lower contamination by red giants than any other method. The result is a catalogue with 197 cool supergiants, 191 of which did not appear in previous lists of red supergiants. This is the largest coherent catalogue of cool supergiants in the Galaxy. ; This research is partially supported by the Spanish Government Ministerio de Economía y Competitivad (MINECO/FEDER) under grant AYA2015-68012-C2-2-P.

Aims. We present a spectroscopic analysis of the extremely luminous red star VX Sgr based on high-resolution observations combined with AAVSO light curve data. Given the puzzling characteristics of VX Sgr, we explore three scenarios for its nature: a massive red supergiant (RSG) or red hypergiant (RHG), a Thorne Żytkow object, and an extreme asymptotic giant branch (AGB) star. Methods. Sampling more than one whole cycle of photometric variability, we derive stellar atmospheric parameters by using state-of-the-art PHOENIX atmospheric models. We compare them to optical and near-infrared spectral types. We report on some key features due to neutral elemental atomic species such as Li I, Ca I, and Rb I. Results. We provide new insights into its luminosity, its evolutionary stage, and its pulsation period. Based on all the data, there are two strong reasons to believe that VX Sgr is some sort of extreme AGB star. Firstly, it has Mira-like behaviour during active phases. VX Sgr shows light variation with amplitude that is much larger than any known RSG and clearly larger than all RHGs. In addition, it displays Balmer line emission and, as shown here for the first time, line doubling of its metallic spectrum at maximum light, both characteristics typical of Miras. Secondly, unlike any known RSG or RHG, VX Sgr displays strong Rb I lines. In addition to the photospheric lines that are sometimes seen, it always shows circumstellar components whose expansion velocity is compatible with that of the OH masers in the envelope, demonstrating a continuous enrichment of the outer atmosphere with s-process elements, a behaviour that can only be explained by a third dredge-up during the thermal pulse phase. ; This research is partially supported by the Spanish Government Ministerio de Ciencia e Innovación (MICI) under grants FJCI-2014-23001, AYA2015-68012-C2-2-P, PGC2018-093741-B-C21/C22 (MICI/AEI/FEDER, UE). This work was also supported by Fundação para a Ciência e a Tecnologia (FCT) through the research grants UID/FIS/04434/2019, UIDB/04434/2020 and UIDP/04434/2020. HMT also acknowledges support from the FCT – Fundação para a Ciência e a Tecnologia through national funds (PTDC/FISAST /28953/2017) and by FEDER – Fundo Europeu de Desenvolvimento Regional through COMPETE2020 – Programa Operacional Competitividade e Internacionalização (POCI-01-0145-FEDER-028953). R. D. acknowledges support from the Spanish Government Ministerio de Ciencia e Innovación (MICI) through Grants PGC-2018-091 3741-B-C22 and SEV 2015-0548, and from the Canarian Agency for Research, Innovation and Information Society (ACIISI), of the Canary Islands Government, and the European Regional Development Fund (ERDF), under grant with reference ProID2017010115. EM acknowledges financial support from the Spanish Ministerio de Ciencia e Innovación through fellowship FPU15/01476.

We present an atlas composed of more than 1500 spectra of late-type stars (spectral types from G to M) observed simultaneously in the optical and calcium triplet spectral ranges. These spectra were obtained as part of a survey to search for cool supergiants in the Magellanic Clouds and were taken over four epochs. We provide the spectral and luminosity classification for each spectrum (71% are supergiants, 13% are giants or luminous giants, 4% are carbon or S stars, and the remaining 12% are foreground stars of lesser luminosities). We also provide a detailed guide for the spectral classification of luminous late-type stars, the result of the extensive classification work done for the atlas. Although this guide is based on classical criteria, we have put them together and re-elaborated them for modern CCD-spectra as these criteria were scattered among many different works and mainly conceived for use with photographic plate spectra. The result is a systematic, well-tested process for identifying and classifying luminous late-type stars, illustrated with CCD spectra of standard stars and the classifications of our own catalogue. ; This research is partially supported by the Spanish Government Ministerio de Economía y Competitividad under grant AYA2015-68012-C2-2-P (MINECO/FEDER). The work reported on in this publication has been partially supported by the European Science Foundation (ESF), in the framework of the GREAT Research Networking Programme.

We present a self-consistent study of cool supergiants (CSGs) belonging to the Magellanic clouds. We calculated stellar atmospheric parameters using LTE KURUCZ and MARCS atmospheric models for more than 400 individual targets by fitting a careful selection of weak metallic lines. We explore the existence of a Teff scale and its implications in two different metallicity environments (each Magellanic cloud). Critical and in-depth tests have been performed to assess the reliability of our stellar parameters (i.e. internal error budget, NLTE systematics). In addition, several Monte Carlo tests have been carried out to infer the significance of the Teff scale found. Our findings point towards a unique Teff scale that seems to be independent of the environment. ; This research is partially supported by the Spanish Government Ministerio de Economía y Competitividad under grants FJCI-2014-23001 and AYA2015-68012-C2-2-P (MINECO/FEDER).

The heavily obscured open cluster Berkeley 51 shows characteristics typical of young massive clusters, even though the few previous studies have suggested older ages. We combine optical (UBV) and 2MASS photometry of the cluster field with multi-object and long-slit optical spectroscopy for a large sample of stars. We apply classical photometric analysis techniques to determine the reddening to the cluster, and then derive cluster parameters via isochrone fitting. We find a large population of B-type stars, with a main-sequence turn-off at B3 V, as well as a large number of supergiants with spectral types ranging from F to M. We use intermediate-resolution spectra of the evolved cool stars to derive their stellar parameters and find an essentially solar iron abundance. Under the plausible assumption that our photometry reaches stars still close to the zero-age main sequence, the cluster is located at d ≈ 5.5 kpc and has an age of ∼60 Ma, though a slightly younger and more distant cluster cannot be ruled out. Despite the apparent good fit of isochrones, evolved stars seem to reside in positions of the colour–magnitude diagram far away from the locations where stellar tracks predict helium burning to occur. Of particular interest is the presence of four yellow supergiants, two on the ascending branch and two others close to or inside the instability strip. ; This visit was funded by the Conselleria de Educación, Cultura y Deporte of the Generalitat Valenciana under grant BEST/2014/276. This research is partially supported by the Spanish Government Ministerio de Economía y Competitivad (MINECO/FEDER) under grant AYA2015-68012-C2-2-P. HMT acknowledges support from MINECO under fellowship FJCI-2014-23001. MM acknowledges the support of a research grant funded by the STFC (ST/M001008/1).

Context. It has been suggested that the compact open cluster VdBH 222 is a young massive distant object. Aims. We set out to characterise VdBH 222 using a comprehensive set of multi-wavelength observations. Methods. We obtained multi-band optical (UBVR) and near-infrared (JHKS) photometry of the cluster field, as well as multi-object and long-slit optical spectroscopy for a large sample of stars in the field. We applied classical photometric analysis, as well as more sophisticated methods using the CHORIZOS code, to determine the reddening to the cluster. We then plotted dereddened HR diagrams and determined cluster parameters via isochrone fitting. Results. We have identified a large population of luminous supergiants confirmed as cluster members via radial velocity measurements. We find nine red supergiants (plus one other candidate) and two yellow supergiants. We also identify a large population of OB stars. Ten of them are bright enough to be blue supergiants. The cluster lies behind ≈7.5 mag of extinction for the preferred value of RV = 2.9. Isochrone fitting allows for a narrow range of ages between 12 and 16 Ma. The cluster radial velocity is compatible with distances of ~6 and ~10 kpc. The shorter distance is inconsistent with the age range and Galactic structure. The longer distance implies an age ≈ 12 Ma and a location not far from the position where some Galactic models place the far end of the Galactic bar. Conclusions. VdBH 222 is a young massive cluster with a likely mass >20 000 M⊙. Its population of massive evolved stars is comparable to that of large associations, such as Per OB1. Its location in the inner Galaxy, presumably close to the end of the Galactic bar, adds to the increasing evidence for vigorous star formation in the inner regions of the Milky Way. ; This research is partially supported by the Spanish Ministerio de Ciencia e Innovación (MICINN) under grant AYA2012-39364-C02-02. J.M.A. acknowledges support for this work by the Spanish Government Ministerio de Ciencia e Innovación through grants AYA 2010-17631 and AYA 2010-15081 and by the Junta de Andalucía grant P08-TIC-4075.

Obscuration and confusion conspire to limit our knowledge of the inner Milky Way. Even at moderate distances, the identification of stellar systems becomes compounded by the extremely high density of background sources. Here we provide a very revealing example of these complications by unveiling a large, massive, young cluster in the Sagittarius arm that has escaped detection until now despite containing more than 30 stars brighter than G = 13. By combining Gaia DR2 astrometry, Gaia and 2MASS photometry and optical spectroscopy, we find that the new cluster, which we name Valparaiso 1, located at ∼2.3 kpc, is about 75 Ma old and includes a large complement of evolved stars, among which we highlight the 4 d classical Cepheid CM Sct and an M-type giant that probably represents the first detection of an AGB star in a Galactic young open cluster. Although strong differential reddening renders accurate parameter determination unfeasible with the current dataset, direct comparison to clusters of similar age suggests that Valparaiso 1 was born as one of the most massive clusters in the Solar Neighbourhood, with an initial mass close to 104 M⊙. ; This research is partially supported by the Spanish Government under grants AYA2015-68012-C2-2-P and PGC2018-093741-B-C21 (MICIU/AEI/FEDER, UE). HMT is also supported by FCT - Fundação para a Ciência e a Tecnologia through national funds and by FEDER through COMPETE2020 - Programa Operacional Competitividade e Internacionalização by these grants: UID/FIS/04434/2019, UIDB/04434/2020; UIDP/04434/2020, PTDC/FIS-AST/28953/2017, and POCI-01-0145-FEDER-028953. ANC is supported by the international Gemini Observatory, a program of NSF's NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation, on behalf of the Gemini partnership of Argentina, Brazil, Canada, Chile, the Republic of Korea, and the United States of America. JB and RK are partially funded by ANID ˆa˘A ¸S Millennium Science Initiative Program ˆa˘A ¸S ICN12 009 awarded to the Millennium Institute of Astrophysics MAS.

Context. Galactic starburst clusters play a twin role in astrophysics, serving as laboratories for the study of stellar physics and also delineating the structure and recent star formation history of the Milky Way. Aims. In order to exploit these opportunities we have undertaken a spectroscopic survey of the red supergiant dominated young massive clusters thought to be present at both near and far ends of the Galactic Bar. Methods. Specifically, multi-epoch observations were employed to identify and investigate stellar variability and its potential role in initiating mass loss amongst the cool super-/hypergiant populations of these aggregates. Results. Significant spectroscopic variability suggestive of radial pulsations was found for the yellow supergiant VdBH 222 #505. Follow-up photometric investigations revealed modulation with a period of ~23.325 d; both timescale and pulsational profile are consistent with a Cepheid classification. Conclusions. #505 is one of the longest period Galactic cluster Cepheids identified to date and hence of considerable use in constraining the bright end of the period/luminosity relation at solar metallicities. In conjunction with extant photometry we infer a distance of ~6 kpc for VdBH222 and an age of ~20 Myr. This results in a moderate reduction in both the integrated cluster mass (~2×104M⊙) and the initial masses of the evolved cluster members (~10 M⊙). As such VdBH222 becomes an excellent test-bed for studying the properties of some of the lowest mass stars observed to undergo type-II supernovae. Moreover, the distance is in tension with a location of VdBH 222 at the far end of the Galactic Bar. Instead a birthsite in the near 3 kpc arm is suggested; providing compelling evidence of extensive recent star formation in a region of the inner Milky Way which has hitherto been thought to be devoid of such activity. ; This research is partially supported by the Spanish Ministerio de Economía y Competitividad under grant AYA2012-39364-C02-02, and the European Union.

We aim to identify and characterise binary systems containing red supergiant (RSG) stars in the Small Magellanic Cloud (SMC) using a newly available ultraviolet (UV) point source catalogue obtained using the Ultraviolet Imaging Telescope (UVIT) on board AstroSat. We select a sample of 560 SMC RSGs based on photometric and spectroscopic observations at optical wavelengths and cross-match this with the far-UV point source catalogue using the UVIT F172M filter, finding 88 matches down to mF172M = 20.3 ABmag, which we interpret as hot companions to the RSGs. Stellar parameters (luminosities, effective temperatures and masses) for both components in all 88 binary systems are determined and we find mass distributions in the ranges 6.1 < M/M⊙ < 22.3 for RSGs and 3.7

Context. The Perseus OB1 association, including the h and χ Persei double cluster, is an interesting laboratory for the investigation of massive star evolution as it hosts one of the most populous groupings of blue and red supergiants (Sgs) in the Galaxy at a moderate distance and extinction. Aims. We discuss whether the massive O-type, and blue and red Sg stars located in the Per OB1 region are members of the same population, and examine their binary and runaway status. Methods. We gathered a total of 405 high-resolution spectra for 88 suitable candidates around 4.5 deg from the center of the association, and compiled astrometric information from Gaia DR2 for all of them. This was used to investigate membership and identify runaway stars. By obtaining high-precision radial velocity (RV) estimates for all available spectra, we investigated the RV distribution of the global sample (as well as different subsamples) and identified spectroscopic binaries (SBs). Results. Most of the investigated stars belong to a physically linked population located at d = 2.5 ± 0.4 kpc. We identify 79 confirmed or likely members, and 5 member candidates. No important differences are detected in the distribution of parallaxes when stars in h and χ Persei or the full sample are considered. In contrast, most O-type stars seem to be part of a differentiated population in terms of kinematical properties. In particular, the percentage of runaways among them (45%) is considerable higher than for the more evolved targets (which is lower than ∼5% in all cases). A similar tendency is also found for the percentage of clearly detected SBs, which already decreases from 15% to 10% when the O star and B Sg samples are compared, respectively, and practically vanishes in the cooler Sgs. Concerning this latter result, our study illustrates the importance of taking the effect of the ubiquitous presence of intrinsic variability in the blue-to-red Sg domain into account to avoid the spurious identification of pulsating stars as SBs. Conclusions. All but 4 stars in our working sample (including 10 O giants/Sgs, 36 B Sgs, 9 B giants, 11 A/F Sgs, and 18 red Sgs) can be considered as part of the same (interrelated) population. However, any further attempt to describe the empirical properties of this sample of massive stars in an evolutionary context must take into account that an important fraction of the O stars is or likely has been part of a binary/multiple system. In addition, some of the other more evolved targets may have also been affected by binary evolution. In this line of argument, it is also interesting to note that the percentage of spectroscopic binaries within the evolved population of massive stars in Per OB1 is lower by a factor 4−5 than in the case of dedicated surveys of O-type stars in other environments that include a much younger population of massive stars. ; We acknowledge funding from the Spanish Government Ministerio de Ciencia e Innovación through grants PGC-2018-091 3741-B-C211/C22, SEV 2015-0548, and CEX2019-000920-S and from the Canarian Agency for Research, Innovation and Information Society (ACIISI), of the Canary Islands Government, and the European Regional Development Fund (ERDF), under grant with reference ProID2017010115.

Context. The multiplicity properties of massive stars are one of the important outstanding issues in stellar evolution. Quantifying the binary statistics of all evolutionary phases is essential to paint a complete picture of how and when massive stars interact with their companions, and to determine the consequences of these interactions. Aims. We investigate the multiplicity of an almost complete census of red supergiant stars (RSGs) in NGC 330, a young massive cluster in the Small Magellanic Cloud. Methods. Using a combination of multi-epoch HARPS and MUSE spectroscopy, we estimate radial velocities and assess the kinematic and multiplicity properties of 15 RSGs in NGC 330. Results. Radial velocities are estimated to better than ±100 m s−1 for the HARPS data. The line-of-sight velocity dispersion for the cluster is estimated as σ1D = 3.20 +0.69−0.52 km s−1. When virial equilibrium is assumed, the dynamical mass of the cluster is log (Mdyn/M⊙) = 5.20 ± 0.17, in good agreement with previous upper limits. We detect significant radial velocity variability in our multi-epoch observations and distinguish between variations caused by atmospheric activity and those caused by binarity. The binary fraction of NGC 330 RSGs is estimated by comparisons with simulated observations of systems with a range of input binary fractions. In this way, we account for observational biases and estimate the intrinsic binary fraction for RSGs in NGC 330 as fRSG = 0.3 ± 0.1 for orbital periods in the range 2.3 0.1. Using the distribution of the luminosities of the RSG population, we estimate the age of NGC 330 to be 45 ± 5 Myr and estimate a red straggler fraction of 50%. Conclusions. We estimate the binary fraction of RSGs in NGC 330 and conclude that it appears to be lower than that of main-sequence massive stars, which is expected because interactions between an RSG and a companion are assumed to effectively strip the RSG envelope. ; L. R. P and A. H acknowledge support from grant AYA2015- 68012-C2- 1-P from the Spanish Ministry of Economy and Competitiveness (MINECO). This research is partially supported by the Spanish Government under grants AYA2015-68012-C2-1/2-P and PGC2018-093741-B-C21/2 (MICIU/AEI/FEDER, UE). L. R. P. acknowledges support from the Spanish Government Ministerio de Ciencia, Innovación y Universidades through grants PGC-2018-091 3741-B-C22 and from the Canarian Agency for Research, Innovation and Information Society (ACIISI), of the Canary Islands Government, and the European Regional Development Fund (ERDF), under grant with reference ProID2017010115. Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. We acknowledge support from the FWO-Odysseus program under project G0F8H6N. This project has further received funding from the European Research Council under European Union's Horizon 2020 research programme (grant agreement No 772225 – MULTIPLES).

The X-ray binary population of the Small Magellanic Cloud (SMC) contains a large number of massive X-ray binaries, and the recent survey of the SMC by XMM–Newton has resulted in almost 50 more tentative high-mass X-ray binary (HMXB) candidates. Using probability parameters from Haberl and Sturm together with the optical spectra and timing in this work, we confirm six new massive X-ray binaries in the SMC. We also report two very probable binary periods of 36.4 d in XMM 1859 and of 72.2 d in XMM 2300. These Be X-ray binaries are likely part of the general SMC population, which rarely undergoes an X-ray outburst. ; This paper is based on ESO data from 079.D−0371 and 088.D−0352. The AAT observations have been supported by the OPTICON project (observing proposals 2011A/014 and 2012/A015), which is funded by the European Commission under the Seventh Framework Programme (FP7). VAM acknowledges financial support from the National Research Foundation of South Africa (Grant 93405) and the World Universities Network. RD, AM and IN from the University of Alicante acknowledge support from the Spanish Government Ministerio de Economía y Competitividad under grant AYA2015-68012-C2-2-P (MINECO/FEDER). ESB acknowledges support from a Claude Leon Foundation fellowship and from the Marie Curie Actions of the European Commission (FP7-COFUND). The OGLE project has received funding from the National Science Centre, Poland, grant MAESTRO 2014/14/A/ST9/00121 to AU.

We provide a complete characterization of the astrophysical properties of the σ Ori Aa, Ab, B hierarchical triple system and an improved set of orbital parameters for the highly eccentric σ Ori Aa, Ab spectroscopic binary. We compiled a spectroscopic data set comprising 90 high-resolution spectra covering a total time span of 1963 days. We applied the Lehman-Filhés method for a detailed orbital analysis of the radial velocity curves and performed a combined quantitative spectroscopic analysis of the σ Ori Aa, Ab, B system by means of the stellar atmosphere code FASTWIND. We used our own plus other available information on photometry and distance to the system for measuring the radii, luminosities, and spectroscopic masses of the three components. We also inferred evolutionary masses and stellar ages using the Bayesian code BONNSAI. The orbital analysis of the new radial velocity curves led to a very accurate orbital solution of the σ Ori Aa, Ab pair. We provided indirect arguments indicating that σ Ori B is a fast-rotating early B dwarf. The FASTWIND+BONNSAI analysis showed that the Aa, Ab pair contains the hottest and most massive components of the triple system while σ Ori B is a bit cooler and less massive. The derived stellar ages of the inner pair are intriguingly younger than the one widely accepted for the σ Orionis cluster, at 3 ± 1 Ma. The outcome of this study will be of key importance for a precise determination of the distance to the σ Orionis cluster, the interpretation of the strong X-ray emission detected for σ Ori Aa, Ab, B, and the investigation of the formation and evolution of multiple massive stellar systems and substellar objects. ; Financial support was provided by the Spanish Ministerio de Ciencia e Innovación and Ministerio de Economía y Competitividad under grants AYA2010-17631, AYA2010-15081, AYA2010-21697-C05-04, AYA2011-30147-C03-03, AYA2012-39364-C02-01/02, and Severo Ochoa SEV-2011-0187, and by the Canary Islands Government under grant PID2010119. R.H.B. acknowledges support from FONDECYT Regular project 1140076. J.S.-B. acknowledges support by the JAE-PreDoc program of the Spanish Consejo Superior de Investigaciones Científicas (CSIC). Á.S. acknowledges support by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences.

Aims. We present observations from the Gaia-ESO Survey in the lines of Hα, [N II], [S II], and He I of nebular emission in the central part of the Carina nebula. Methods. We investigate the properties of the two already known kinematic components (approaching and receding), which account for the bulk of emission. Moreover, we investigate the features of the much less known low-intensity high-velocity (absolute RV >50 km s-1) gas emission. Results. We show that gas giving rise to Hα and He I emission is dynamically well correlated with but not identical to gas seen through forbidden-line emission. Gas temperatures are derived from line-width ratios, and densities from [S II] doublet ratios. The spatial variation of N ionization is also studied, and found to differ between the approaching and receding components. The main result is that the bulk of the emission lines in the central part of Carina arise from several distinct shell-like expanding regions, the most evident found around η Car, the Trumpler 14 core, and the star WR25. These "shells" are non-spherical and show distortions probably caused by collisions with other shells or colder, higher-density gas. Some of them are also partially obscured by foreground dust lanes, while very little dust is found in their interior. Preferential directions, parallel to the dark dust lanes, are found in the shell geometries and physical properties, probably related to strong density gradients in the studied region. We also find evidence that the ionizing flux emerging from η Car and the surrounding Homunculus nebula varies with polar angle. The high-velocity components in the wings of Hα are found to arise from expanding dust reflecting the η Car spectrum. ; This work was partly supported by the European Union FP7 programme through ERC grant number 320360 and by the Leverhulme Trust through grant RPG-2012-541.