PN fast winds: Temporal structure and stellar rotation

To diagnose the time-variable structure in the fast winds of central stars of planetary nebulae (CSPN), we present an analysis of P Cygni line profiles in FUSE satellite far-UV spectroscopic data. Archival spectra are retrieved to form time-series datasets for the H-rich CSPN NGC 6826, IC 418, IC 2149, IC 4593 and NGC 6543. Despite limitations due to the fragmented sampling of the time-series, we demonstrate that in all 5 CSPN the UV resonance lines are variable primarily due to the occurrence of blueward migrating discrete absorption components (DACs). Empirical (SEI) line-synthesis modelling is used to determine the range of fluctuations in radial optical depth, which are assigned to the temporal changes in large-scale wind structures. We argue that DACs are common in CSPN winds, and their empirical properties are akin to those of similar structures seen in the absorption troughs of massive OB stars. Constraints on PN central star rotation velocities are derived from Fast-Fourier Transform analysis of photospheric lines for our target stars. Favouring the causal role of co-rotating interaction regions, we explore connections between normalised DAC accelerations and rotation rates of PN central stars and O stars. The comparative properties suggest that the same physical mechanism is acting to generate large-scale structure in the line-driven winds in the two different settings.Comment: Accepted for publication in MNRAS; 10 pages, 5 figure

It is never too early: social participation of early childhood education students from the perspective of families, teachers and students

The aim of this study was to delve into social participation in early childhood education classrooms of centres that include students with ASD, considering social participation as a fundamental element to understand inclusion. To this end, we propose a Convergent Parallel Mixed Methods approach. A quantitative study was carried out with the participation of 85 Early Childhood Education students from centres that include students with ASD. Information was gathered through attitude and social support questionnaires. Six families and eight professionals of these centres participated in the qualitative study. In this case, interviews were conducted. The results show the need to attend to the social participation of all students already in the stage of Early Childhood Education as a fundamental part of what is understood as an inclusive classroom. Similarly, this study identifes both the factors that hinder and facilitate the response of teachers to this aspect in relation to the students, teachers, and familiesThis research was funded by the Spanish Ministry of Economy, Industry, and Competitiveness, grant number EDU 2017-86739-

Production of microbial transglutaminase on media made from sugar cane molasses and glycerol

Transglutaminase is an enzyme that catalyses an acyl transfer reaction between γ-carboxamide groups of glutaminyl residues and lysine residues in proteins. Due to this property, this enzyme is used for enhancing textural properties of protein-rich food. The transglutaminase used as food additive is obtained by microorganisms, mainly by Streptoverticillium ladakanum. On the other hand, sugar cane molasses is a viscous liquid rich in noncrystallized carbohydrates (saccharose, glucose and fructose). In this work, the feasibility of using sugar cane molasses as a carbon source for the production of microbial transglutaminase by Streptoverticillium ladakanum NRRL 3191 has been studied. Carbon sources including sugar cane molasses (60 g of total sugars per L), glycerol (60 g/L) and their mixture in a ratio of 1:1 (30 g/L of each) were evaluated. Time course of microbial growth, transglutaminase activity and carbon source consumption were determined every 24 h during 120 h of fermentations at three agitation speeds (200, 300 or 400 rpm). The results showed that with the increase in agitation speed, the biomass concentration increased up to 8.39 g/L in the medium containing sugar cane molasses alone or the mixture of molasses and glycerol. The highest transglutaminase activity was obtained at 400 rpm in the medium containing a mixture of molasses and glycerol, reaching 0.460 U/mL, while in the medium containing sugar cane molasses alone, the activity was 0.240 U/mL, and using glycerol alone it was 0.250 U/mL. These results show that sugar cane molasses is a suitable medium for transglutaminase production when it is combined with glycerolA grant from FOMIX CONACYT – Gobierno de Tamaulipas (Ref. 2004/1055) to author Portilla-Rivera is gratefully acknowledged. The authors are grateful to Ministerio de Educación y Ciencia (Spain) for the financial support of this work (Project: AGL2006-08250/ALI)S

Near Horizon Limits of Massless BTZ and Their CFT Duals

We consider the massless BTZ black hole and show that it is possible to take its "near horizon" limit in two distinct ways. The first one leads to a null self-dual orbifold of AdS3 and the second to a spacelike singular AdS3/Z_K orbifold in the large K limit, the "pinching orbifold". We show that from the dual 2d CFT viewpoint, the null orbifold corresponds to the p^+=0 sector of the Discrete Light-Cone Quantisation (DLCQ) of the 2d CFT where a chiral sector of the CFT is decoupled, while the pinching orbifold corresponds to taking an infinite mass gap limit in both the right and left sectors of the 2d CFT, essentially leaving us with the states L_0=\bar L_0=c/24 only. In the latter case, one can combine the near horizon limit with sending the 3d Planck length l_P to zero, or equivalently the dual CFT central charge c to infinity. We provide preliminary evidence that in that case some nontrivial dynamics may survive the limit.Comment: 22 pages, no figures, v2: minor improvements, references adde

Detection of frequency spacings in the young O-type binary HD 46149 from CoRoT photometry

Using the CoRoT space based photometry of the O-type binary HD46149, stellar atmospheric effects related to rotation can be separated from pulsations, because they leave distinct signatures in the light curve. This offers the possibility of characterising and exploiting any pulsations seismologically. Combining high-quality space based photometry, multi-wavelength photometry, spectroscopy and constraints imposed by binarity and cluster membership, the detected pulsations in HD46149 are analyzed and compared with those for a grid of stellar evolutionary models in a proof-of-concept approach. We present evidence of solar-like oscillations in a massive O-type star, and show that the observed frequency range and spacings are compatible with theoretical predictions. Thus, we unlock and confirm the strong potential of this seismically unexplored region in the HR diagram.Comment: 11 pages, 12 figures, accepted for publication in A&

Emergent IR dual 2d CFTs in charged AdS5 black holes

We study the possible dynamical emergence of IR conformal invariance describing the low energy excitations of near-extremal R-charged global AdS5 black holes. We find interesting behavior especially when we tune parameters in such a way that the relevant extremal black holes have classically vanishing horizon area, i.e. no classical ground-state entropy, and when we combine the low energy limit with a large N limit of the dual gauge theory. We consider both near-BPS and non-BPS regimes and their near horizon limits, emphasize the differences between the local AdS3 throats emerging in either case, and discuss potential dual IR 2d CFTs for each case. We compare our results with the predictions obtained from the Kerr/CFT correspondence, and obtain a natural quantization for the central charge of the near-BPS emergent IR CFT which we interpret in terms of the open strings stretched between giant gravitons.Comment: 37 page, 3 .eps figure

Projected Rotational Velocities and Stellar Characterization of 350 B Stars in the Nearby Galactic Disk

Projected rotational velocities (vsini) are presented for a sample of 350 early B-type main sequence stars in the nearby Galactic disk. The stars are located within ~1.5 kpc from the Sun, and the great majority within 700 pc. The analysis is based on high-resolution spectra obtained with the MIKE spectrograph on the Magellan Clay 6.5-m telescope at the Las Campanas Observatory in Chile.Spectral types were estimated based on relative intensities of some key line absorption ratios and comparisons to synthetic spectra. Effective temperatures were estimated from the reddening-free Q index, and projected rotational velocities were then determined via interpolation on a published grid that correlates the synthetic full width at half maximum of the He I lines at 4026, 4388 and 4471 A with vsini. As the sample has been selected solely on the basis of spectral types it contains an selection of B stars in the field, in clusters, and in OB associations. The vsini distribution obtained for the entire sample is found to be essentially flat for vsini values between 0-150 km/s, with only a modest peak at low projected rotational velocities. Considering subsamples of stars, there appears to be a gradation in the vsini distribution with the field stars presenting a larger fraction of the slow rotators and the cluster stars distribution showing an excess of stars with vsini between 70 and 130 km/s. Furthermore, for a subsample of potential runaway stars we find that the vsini distribution resembles the distribution seen in denser environments, which could suggest that these runaway stars have been subject to dynamical ejection mechanisms.Comment: 38 pages, 11 figures. Complete sample table. AJ accepte

The VLT-FLAMES Tarantula Survey X: Evidence for a bimodal distribution of rotational velocities for the single early B-type stars

Aims: Projected rotational velocities (\vsini) have been estimated for 334 targets in the VLT-FLAMES Tarantula survey that do not manifest significant radial velocity variations and are not supergiants. They have spectral types from approximately O9.5 to B3. The estimates have been analysed to infer the underlying rotational velocity distribution, which is critical for understanding the evolution of massive stars. Methods: Projected rotational velocities were deduced from the Fourier transforms of spectral lines, with upper limits also being obtained from profile fitting. For the narrower lined stars, metal and non-diffuse helium lines were adopted, and for the broader lined stars, both non-diffuse and diffuse helium lines; the estimates obtained using the different sets of lines are in good agreement. The uncertainty in the mean estimates is typically 4% for most targets. The iterative deconvolution procedure of Lucy has been used to deduce the probability density distribution of the rotational velocities. Results: Projected rotational velocities range up to approximately 450 \kms and show a bi-modal structure. This is also present in the inferred rotational velocity distribution with 25% of the sample having $0\leq$\ve$\leq$100\,\kms and the high velocity component having \ve$\sim 250$\,\kms. There is no evidence from the spatial and radial velocity distributions of the two components that they represent either field and cluster populations or different episodes of star formation. Be-type stars have also been identified. Conclusions: The bi-modal rotational velocity distribution in our sample resembles that found for late-B and early-A type stars. While magnetic braking appears to be a possible mechanism for producing the low-velocity component, we can not rule out alternative explanations.Comment: to be publisged in A&

The VLT-FLAMES Tarantula Survey XVII. Physical and wind properties of massive stars at the top of the main sequence

The evolution and fate of very massive stars (VMS) is tightly connected to their mass-loss properties. Their initial and final masses differ significantly as a result of mass loss. VMS have strong stellar winds and extremely high ionising fluxes, which are thought to be critical sources of both mechanical and radiative feedback in giant Hii regions. However, how VMS mass-loss properties change during stellar evolution is poorly understood. In the framework of the VLT-Flames Tarantula Survey (VFTS), we explore the mass-loss transition region from optically thin O to denser WNh star winds, thereby testing theoretical predictions. To this purpose we select 62 O, Of, Of/WN, and WNh stars, an unprecedented sample of stars with the highest masses and luminosities known. We perform a spectral analysis of optical VFTS as well as near-infrared VLT/SINFONI data using the non-LTE radiative transfer code CMFGEN to obtain stellar and wind parameters. For the first time, we observationally resolve the transition between optically thin O and optically thick WNh star winds. Our results suggest the existence of a kink between both mass-loss regimes, in agreement with recent MC simulations. For the optically thick regime, we confirm the steep dependence on the Eddington factor from previous theoretical and observational studies. The transition occurs on the MS near a luminosity of 10^6.1Lsun, or a mass of 80...90Msun. Above this limit, we find that - even when accounting for moderate wind clumping (with f = 0.1) - wind mass-loss rates are enhanced with respect to standard prescriptions currently adopted in stellar evolution calculations. We also show that this results in substantial helium surface enrichment. Based on our spectroscopic analyses, we are able to provide the most accurate ionising fluxes for VMS known to date, confirming the pivotal role of VMS in ionising and shaping their environments.Comment: Accepted for publication in A&A, 19 pages, 14 figures, 6 tables, (74 pages appendix, 68 figures, 4 tables