Modeling the near-infrared lines of O-type stars

We use a grid of 30 line-blanketed unified stellar photosphere and wind models for O-type stars; computed with the code CMFGEN in order to evaluate its potential in the near-infrared spectral domain. The grid includes dwarfs, giants and supergiants. We analyse the equivalent width behaviour of the 20 strongest lines of hydrogen and helium in spectral windows that can be observed using ground-based instrumentation and compare the results with observations. Our main findings are that: i) HeI/HeII line ratios in the J, H and K bands correlate well with the optical ratio employed in spectral classification, and can therefore be used to determine the spectral type; ii) in supergiant stars the transition from the stellar photosphere to the wind follows a shallower density gradient than the standard approach followed in our models, which can be mimicked by adopting a lower gravity in our prescription of the density stratification. iii) the Brackett gamma line poses a number of peculiar problems which partly might be related to wind clumping, and iv) the Brackett alpha line is an excellent mass-loss indicator. For the first and last item we provide quantitative calibrations.Comment: 14 pages, 7 figures, accepted by A&

Pratiques funéraires du Bronze final IIB au premier âge du Fer en Languedoc occidental et Midi-Pyrénées : approche archéo-anthropologique des nécropoles à incinération

Les populations vers 900-475 avant J.-C. en Languedoc occidental et Midi-Pyrénées, sont essentiellement connues par l'intermédiaire de leurs nécropoles. La crémation des défunts constitue une pratique quasi-exclusive, ce qui limite grandement la caractérisation biologique de ces populations. Nous nous sommes fondée sur un corpus de plus de 2000 tombes secondaires à incinération essentiellement issues de onze nécropoles majeures de la période, qui ont été analysées à travers différents paramètres : modes de dépôt des restes osseux, modalités de recrutement à l'échelle de la nécropole, poids total d'ossements déposés dans la sépulture, indices pondéraux des différentes régions anatomiques et données sur l'aspect des ossements. Les résultats de ce premier niveau d'analyse ont ensuite été replacés dans les contextes chrono-culturels de chaque nécropole. Une évolution chronologique des gestes funéraires notamment en ce qui concerne le mode de dépôt des restes osseux et la quantité d'ossements placés dans la tombe a pu être mise en évidence. Cependant des particularités très locales, parfois à l'échelle d'une seule nécropole et donc vraisemblablement d'une communauté, semblent également se détacher. Un essai d'interprétation de l'évolution de la structuration sociale des populations vivantes et des modalités de recrutement des défunts est aussi proposée. Parallèlement, l'étude anthropologique personnelle de près de 400 amas osseux nous a permis de fonder une réflexion méthodologique sur le traitement des ossements incinérés en dépôt secondaire. Cette démarche a pour objectif d'optimiser la quantité et la qualité des observations, en minimisant le temps imparti à l'analyse.In western Languedoc and in Midi-Pyrénées, information about the inhabitants circa 900-475 B.C. comes mainly from cemetery contexts. The cremation of the deceased consitutes a nearly exclusive practice of the entire time period, which highly distinguishes those populations apart from others. We have based our study on a sample of more than 2000 secondary cremation graves, mostly taken from eleven leading cemeteries of that period. The data were analysed using different parameters : the way the bone remains where deposited, the demographic information at the cemetery scale, the total weight of the skeletal material recovered from each grave, the relative weight of the different anatomical parts of the skeleton, the data on the bones color and other remarks on the preserving conditions. The results of the preliminary analysis have been considered within the temporal context of each cemetery. A chronological evolution of the burial practice, especially regarding the mode of deposition and the bone quantity set in the grave, will be discussed. It also appears that local distinctive features, sometimes only present at the scale of one cemetery, are therefore possibly inherent to only one community. An interpretation of the evolution of the social structure of the living populations and the mortuary behavior of the deceased is also proposed. Simultaneously, the personal anthropological study of bones from nearly 400 samples allowed us to establish a methodological reflection on the treatment of burnt bones in secondary deposits. This was targeted at optimizing the quantity, hence the quality of the observations by minimizing the duration of the analyse

Development of a new microscopic passing maneuver model for two-lane rural roads

Microsimulation is a useful tool to analyze traffic operation. On two-lane highways, the complexity of passing and the interaction with oncoming traffic requires specific models. This study focused on the development of a passing desire, decision and execution model. Results of the observation of 1752 maneuvers on 10 rural roads in Spain were used for this development. The model incorporated the effect of new factors such as available sight distance, delay and remaining travel time until the end of the highway segment. Outputs of the model were compared to observed data: firstly, individual passing maneuvers; secondly, traffic flow, percent followers and number of passing maneuvers in four single passing zones with two different traffic levels. The model was validated in four alternative passing zonesData collection was part of the research project "Desarrollo de modelos de distancias de visibilidad de adelantamiento", funded by the Spanish Ministry of Economy and Competitiveness, with reference number TRA2010-21736. Authors wish to thank Spanish General Directorate of Traffic, Spanish Ministry of Public Works, Valencia Regional Department of Transport and Valencia Province Road Department, for their collaboration in the field study.Llorca Garcia, C.; Moreno Chou, AT.; Lenorzer, A.; Casas, J.; García García, A. (2015). Development of a new microscopic passing maneuver model for two-lane rural roads. Transportation Research Part C: Emerging Technologies. 52:157-172. doi:10.1016/j.trc.2014.06.001S1571725

Non-LTE Line Formation in the Near-IR: Hot Stars

Line-formation calculations in the Rayleigh-Jeans tail of the spectral energy distribution are complicated by an amplification of non-LTE effects. For hot stars this can make quantitative modelling of spectral lines in the near-IR challenging. An introduction to the modelling problems is given and several examples in the context of near-IR line formation for hydrogen and helium are discussed.Comment: 16 pages, 13 figure

An infrared view of (candidate accretion) disks around massive young stars

Near-infrared surveys of high-mass star-forming regions start to shed light onto their stellar content. A particular class of objects found in these regions, the so-called massive Young Stellar Objects (YSOs) are surrounded by dense circumstellar material. Several near- and mid-infrared diagnostic tools are used to infer the physical characteristics and geometry of this circumstellar matter. Near-infrared hydrogen emission lines provide evidence for a disk-wind. The profiles of the first overtone of the CO band-heads, originating in the inner 10 AU from the central star, are well fitted assuming a Keplerian rotating disk. The mid-infrared spectral energy distribution requires the presence of a more extended envelope containing dust at a temperature of about 200 K. CRIRES observations of CO fundamental absorption lines confirm the presence of a cold envelope. We discuss the evolutionary status of these objects

Identification of the ionizing source of NGC 2024

We propose the late-O, early-B star IRS2b as the ionizing source of the Flame Nebula (NGC 2024). It has been clear that such a hot, massive star must be present in this heavily obscured region, and now it has been identified. New near-infrared photometry shows that IRS2b is the most luminous and hottest star in the young star cluster embedded in the center of NGC 2024. The near-infrared observations (5' x 5') cover ~90 % of the HII region detected in radio continuum radiation, making the probability very low that the ionizing star is not present in the field. A K-band spectrum of IRS2b obtained with ISAAC on the Very Large Telescope indicates that the spectral type of IRS2b is in the range O8V - B2V. Additional arguments indicate that its spectral type is likely closer to O8 than to B2. The corresponding amount of ionizing radiation is consistent with published radio continuum and recombination line observations.Comment: 7 pages, 4 figures. Figure 1 included as jpeg. Accepted for publication in Astronomy & Astrophysic

On the central ionizing star of G23.96+0.15 and near-IR spectral classification of O stars

Aims: A near-infrared study of the main ionizing star of the ultracompact HII region G23.96+0.15 (IRAS 18317-0757) is presented, along with a re-evaluation of the distance to this source, and a re-assessment of H- and K-band classification diagnostics for O dwarfs; Methods: We have obtained near-IR VLT/ISAAC imaging and spectroscopy of G23.96+0.15, plus archival imaging from UKIRT/UFTI. A spectroscopic analysis was carried out using a non-LTE model atmosphere code; Results: A quantitative H- and K-band classification scheme for O dwarfs is provided, from which we establish an O7.5V spectral subtype for the central star of G23.96+0.15. We estimate an effective temperature of Teff ~ 38 kK from a spectral analysis; Conclusions: A spectroscopic distance of 2.5 kpc is obtained for G23.96+0.15, substantially lower than the kinematic distance of 4.7 kpc, in common with recent studies of other Milky way HII regions. Such discrepancies would be alleviated if sources are unresolved binaries or clusters.Comment: 5 pages, 3 figures, accepted for Astronomy & Astrophysic