Surface temperature and synthetic spectral energy distributions for rotationally deformed stars

The spectral energy distribution (SED) of a non-spherical star could differ significantly from the SED of a spherical star with the same average temperature and luminosity. Calculation of the SED of a deformed star is often approximated as a composite of several spectra, each produced by a plane parallel model of given effective temperature and gravity. The weighting of these spectra over the stellar surface, and hence the inferred effective temperature and luminosity, will be dependent on the inclination of the rotation axis of the star with respect to the observer, as well as the temperature and gravity distribution on the stellar surface. Here we calculate the surface conditions of rapidly rotating stars with a 2D stellar structure and evolution code and compare the effective temperature distribution to that predicted by von Zeipel's law. We calculate the composite spectrum for a deformed star by interpolating within a grid of intensity spectra of plane parallel model atmospheres and integrating over the surface of the star. Using this method, we find that the deduced variation of effective temperature with inclination can be as much as 3000 K for an early B star, depending on the details of the underlying model.Comment: 38 pages, 9 figures (AAStex preprint format). Accepted for publication in the Ap

A NLTE line blanketed model of a solar type star

We present LTE and NLTE atmospheric models of a star with solar parameters, and study the effect of treating many thousands of Iron group lines out of LTE on the computed atmospheric structure, overall absolute flux distribution, and the moderately high resolution spectrum in the visible and near UV bands. Our NLTE modeling includes the first two or three ionization stages of 20 chemical elements, up to and including much of the Fe-group, and includes about 20000 Fe I and II lines. We investigate separately the effects of treating the light metals and the Fe-group elements in NLTE. Our main conclusions are that 1) NLTE line blanketed models with direct multi-level NLTE for many actual transitions gives qualitatively similar results as the more approximate treatment of Anderson (1989) for both the Fe statistical equilibrium and the atmospheric temperature structure, 2) models with many Fe lines in NLTE have a temperature structure that agrees more closely with LTE semi-empirical models based on center-to-limb variation and a wide variety of spectra lines, whereas LTE models agree more with semi-empirical models based only on an LTE calculation of the Fe I excitation equilibrium, 3) the NLTE effects of Fe-group elements on the model structure and flux distribution are much more important than the NLTE effects of all the light metals combined, and serve to substantially increases the violet and near UV flux level as a result of NLTE Fe over-ionization. These results suggest that there may still be important UV opacity missing from the models.Comment: Accepted for publication in The Astrophysical Journa

On the Absorption of X-rays in the Interstellar Medium

We present an improved model for the absorption of X-rays in the ISM intended for use with data from future X-ray missions with larger effective areas and increased energy resolution such as Chandra and XMM, in the energy range above 100eV. Compared to previous work, our formalism includes recent updates to the photoionization cross section and revised abundances of the interstellar medium, as well as a treatment of interstellar grains and the H2molecule. We review the theoretical and observational motivations behind these updates and provide a subroutine for the X-ray spectral analysis program XSPEC that incorporates our model.Comment: ApJ, in press, for associated software see http://astro.uni-tuebingen.de/nh

The impact of non-LTE effects and granulation inhomogeneities on the derived iron and oxygen abundances in metal-poor halo stars

This paper presents the results of a detailed theoretical investigation of the impact of non-LTE effects and of granulation inhomogeneities on the derived iron and oxygen abundances in the metal-poor halo subgiant HD140283. Our analysis is based on both the `classical' one-dimensional (1D) stellar atmosphere models and on the new generation of three-dimensional (3D) hydrodynamical models. We find that the non-LTE effects on the iron abundance derived from Fe {\sc i} lines are very important, amounting to ${\sim}0.9$ dex and to ${\sim}0.6$ dex in the 3D and 1D cases, respectively. On the other hand, we find that non-LTE and 3D effects have to be taken into account for a reliable determination of the iron abundance from weak Fe {\sc ii} lines, because the significant overexcitation of their upper levels in the granular regions tend to produce emission features. As a result such Fe {\sc ii} lines are weaker than in LTE and the abundance correction amounts to ${\sim}0.4$ dex for the 3D case. We derive also the oxygen-to-iron abundance ratio in the metal-poor star HD140283 by using the O {\sc i} triplet at 7772--5 \AA and the forbidden [O {\sc i}] line at 6300 \AA. Interestingly, when both non-LTE and 3D effects are taken into account there still remains significant discrepancies in the iron abundances derived from Fe {\sc i} and Fe {\sc ii} lines, as well as in the oxygen abundances inferred from the O {\sc i} and [O {\sc i}] lines. We conclude that the metalicity of this type of metal-poor stars could be significantly larger than previously thought, which may have far-reaching implications in stellar astrophysics.Comment: The Astrophysical Journal (in press). (35 pages, 5 figures and 4 tables

Permitted Oxygen Abundances and the Temperature Scale of Metal-Poor Turn-Off Stars

We use high quality VLT/UVES published data of the permitted OI triplet and FeII lines to determine oxygen and iron abundances in unevolved (dwarfs, turn-off, subgiants) metal-poor halo stars. The calculations have been performed both in LTE and NLTE, employing effective temperatures obtained with the new infrared flux method (IRFM) temperature scale by Ramirez & Melendez, and surface gravities from Hipparcos parallaxes and theoretical isochrones. A new list of accurate transition probabilities for FeII lines, tied to the absolute scale defined by laboratory measurements, has been used. We find a plateau in the oxygen-to-iron ratio over more than two orders of magnitude in iron abundance (-3.2 < [Fe/H] < -0.7), with a mean [O/Fe] = 0.5 dex (sigma = 0.1 dex), independent of metallicity, temperature and surface gravity. According to the new IRFM Teff scale, the temperatures of turn-off halo stars strongly depend on metallicity, a result that is in excellent qualitative and quantitative agreement with stellar evolution calculations, which predict that the Teff of the turn-off at [Fe/H] = -3 is about 600-700 K higher than that at [Fe/H] = -1.Comment: In press, Ap

Oxygen in the Very Early Galaxy

Oxygen abundances in a sample of ultra-metal-poor subdwarfs have been derived from measurements of the oxygen triplet at 7771--5 A and OH lines in the near UV performed in high-resolution and high signal-to-noise spectra obtained with WHT/UES, KeckI/HIRES, and VLT/UVES. Our Fe abundances were derived in LTE and then corrected for NLTE effects following Thevenin and Idiart (1999). The new oxygen abundances confirm previous findings for a progressive linear rise in the oxygen-to-iron ratio with a slope -0.33+-0.02 from solar metallicity to [Fe/H] -3. A slightly higher slope would be obtained if the Fe NLTE corrections were not considered. Below [Fe/H]= -2.5 our stars show [O/Fe] ratios as high as ~ 1.17 (G64-12), which can be interpreted as evidence for oxygen overproduction in the very early epoch of the formation of the halo, possibly associated with supernova events with very massive progenitor stars. We show that the arguments against this linear trend given by Fulbright and Kraft (1999), based on the LTE Fe analysis of two metal-poor stars cannot be sustained when an NLTE analysis is performed. Using 1-D models our analysis of three oxygen indicators available for BD +23 3130 gives consistent abundances within 0.16 dex and average [O/Fe] ratio of 0.91.Comment: 45 pages, 11 figures, accepted for publication in The Astrophysical Journa

Defining criteria for disease activity states in systemic juvenile idiopathic arthritis based on the systemic Juvenile Arthritis Disease Activity Score

Objective To develop and validate cutoff values in the systemic Juvenile Arthritis Disease Activity Score 10 (sJADAS10) that distinguish the states of inactive disease (ID), minimal disease activity (MiDA), moderate disease activity (MoDA), and high disease activity (HDA) in children with systemic juvenile idiopathic arthritis (sJIA), based on subjective disease state assessment by the treating pediatric rheumatologist. Methods The cutoffs definition cohort was composed of 400 patients enrolled at 30 pediatric rheumatology centers in 11 countries. Using the subjective physician rating as an external criterion, 6 methods were applied to identify the cutoffs: mapping, calculation of percentiles of cumulative score distribution, Youden index, 90% specificity, maximum agreement, and ROC curve analysis. Sixty percent of the patients were assigned to the definition cohort and 40% to the validation cohort. Cutoff validation was conducted by assessing discriminative ability. Results The sJADAS10 cutoffs that separated ID from MiDA, MiDA from MoDA, and MoDA from HDA were ≤ 2.9, ≤ 10, and > 20.6. The cutoffs discriminated strongly among different levels of pain, between patients with or without morning stiffness, and between patients whose parents judged their disease status as remission or persistent activity/flare or were satisfied or not satisfied with current illness outcome. Conclusion The sJADAS cutoffs revealed good metrologic properties in both definition and validation cohorts, and are therefore suitable for use in clinical trials and routine practice

Are diffuse and limited juvenile systemic sclerosis different in clinical presentation? Clinical characteristics of a juvenile systemic sclerosis cohort

Introduction: Juvenile systemic sclerosis is an orphan disease. Currently, the majority of juvenile systemic sclerosis cohort studies are retrospective in design without standardized assessment. This study was conducted prospectively to investigate the difference in manifestations of limited cutaneous juvenile systemic sclerosis and diffuse cutaneous juvenile systemic sclerosis subtypes. An additional aim was to compare these data to other juvenile systemic sclerosis cohorts and a large adult systemic sclerosis cohort. Methods: Patients fulfilling the Paediatric Rheumatology European Society juvenile systemic sclerosis classification criteria were included. Clinical characteristics and patient-related outcomes were assessed. Results: In all, 88 patients with a mean disease duration of 3.5 years were enrolled, 72.5% with diffuse cutaneous juvenile systemic sclerosis with a mean modified Rodnan Skin score of 18 and 27.5% with limited cutaneous juvenile systemic sclerosis with mean modified Rodnan Skin score of 9. The mean age at the onset of Raynaud’s and first non-Raynaud’s symptoms was similar in both groups, approximately 9 and 10.5 years. Active digital tip ulcerations were present in 29% diffuse cutaneous juvenile systemic sclerosis and none in the limited cutaneous juvenile systemic sclerosis subjects (p = 0.005). Of those with cardiopulmonary testing, 3% of diffuse cutaneous juvenile systemic sclerosis and 23% of limited cutaneous juvenile systemic sclerosis group had cardiac involvement (p = 0.015), and 41% diffuse cutaneous juvenile systemic sclerosis and 22% of the limited cutaneous juvenile systemic sclerosis group had pulmonary involvement (p = 0.009). Physician global disease damage assessment was higher in the diffuse cutaneous juvenile systemic sclerosis group compared to the limited cutaneous juvenile systemic sclerosis group: 35 and 15 (p = 0.021). Discussion: The majority of this international juvenile systemic sclerosis cohort had diffuse cutaneous juvenile systemic sclerosis (72.5%) with more frequent vascular and pulmonary involvement compared to the limited cutaneous group, who had increased cardiac involvement. Our cohort reflects prior findings of published juvenile systemic sclerosis cohorts and emphasizes a difference in the presentation compared to adult-onset systemic sclerosis

Опыт диагностики и лечения болезни Кавасаки в клинике Санкт-Петербургского государственного педиатрического медицинского университета и Д етской городской больнице №1 Санкт-Петербурга

Kawasaki disease (KD) is acute systemic vasculitis of unknown etiology. Approximately 20–25% of untreated patients develop coronary artery changes with a range of severity from asymptomatic coronary artery dilatation to giant coronary artery aneurysms with thrombosis, myocardial infarction, and sudden death. To date there is no official data on the incidence of KD in Russia. In Russia, the disease is not enough known now to a wide circle of physicians and often masks other more common diseases. Since 2010, the detection rate of KD has dramatically increased in Saint-Petersburg.Objective: to analyze the experience in diagnosing and treating KD in two largest hospitals of Saint Petersburg.Patients and methods. The retrospective study included data on 30 children (18 boys, 12 girls) who were hospitalized with a diagnosis of KD in the Saint-Petersburg State Pediatric Medical University Clinic and Children’s Hospital One (Saint Petersburg) between January 2011 and September 2016. Data are represented by median and extreme values. The age of the children was 2.8 (0.2; 4.6) years; of them 5 (16.7%) patients were under the age of 1 year. The children were hospitalized on 5 (1; 14) days of disease onset; KD was diagnosed on 9 (3; 52) day of the disease.Results. Immediately after diagnosis, 27 (90%) children received aspirin. In early stages (before 10 days of the disease), intravenous immunoglobulin (IVIG) therapy was performed in 15 (50%) children, one of them received IVIG before disease day 5 (on day 3), but without effect. On disease days 11-20 (immediately after diagnosis), 10 (33.3%) children were prescribed with IVIG; thereafter fever was abolished in all the patients. Their body temperature became normal on day 11 (6; 23). Ultrasonography revealed coronary artery lesions in 13 (43.3%) patients. Out of the 30 children followed up, one baby who fell ill at the age of 3 months and received IVIG died on day 30 of the disease.Conclusion. Currently, there continues to be a delayed diagnosis of KD. IVIG therapy was effective, especially in cases of timely diagnosis. It is necessary to increase awareness of KD among clinicians and ultrasound diagnosticians.Болезнь Кавасаки (БК) – остро протекающий системный васкулит неизвестной этиологии. Примерно у 20–25% не получивших лечения больных развиваются изменения коронарных артерий различной степени тяжести – от бессимптомной дилатации до гигантских аневризм, тромбоза, инфаркта миокарда и внезапной смерти. До настоящего времени официальных данных о заболеваемости БК в России нет. В нашей стране БК недостаточно известна широкому кругу врачей и часто проходит под маской других более распространенных заболеваний. В Санкт-Петербурге после 2010 г. резко возросла выявляемость БК.Цель исследования – проанализировать опыт диагностики и лечения БК в двух крупных стационарах Санкт-Петербурга.Пациенты и методы. В ретроспективное исследование были включены данные о 30 детях (18 мальчиков, 12 девочек), находившихся на стационарном лечении с диагнозом БК в клинике Санкт-Петербургского государственного педиатрического медицинского университета и Детской городской больнице №1 Санкт-Петербурга с января 2011 г. по сентябрь 2016 г. Данные представлены медианой и крайними значениями. Возраст детей составил 2,8 [0,2; 4,6] года, из них 5 (16,7%) пациентов были в возрасте до 1 года. Дети были госпитализированы на 5-е [1; 14] сутки болезни, диагноз БК установлен на 9-й [3; 52] день болезни.Результаты. Сразу после установления диагноза получили аспирин 27 детей (90%). В ранние сроки (до 10-го дня болезни) терапия внутривенным иммуноглобулином (ВВИГ) проводилась у 15 (50%) пациентов, из них 1 получил ВВИГ ранее 5-го дня болезни (на 3-й день), однако без эффекта. На 11–20-й день болезни (сразу после установления диагноза) ВВИГ назначен 10 (33,3%) детям, после чего лихорадка была купирована у всех пациентов. Температура тела нормализовалась на 11-й [6; 23] день. Поражение коронарных артерий при УЗИ выявлено у 13 (43,3%) пациентов. Из 30 находившихся под наблюдением детей у 1 ребенка, заболевшего в возрасте 3 мес и получившего ВВИГ на 30-й день болезни, зафиксирован летальный исход.Выводы. В настоящее время БК продолжает диагностироваться с опозданием. Терапия ВВИГ была эффективной, особенно в случаях своевременного установления диагноза. Необходимо повышение осведомленности клиницистов и врачей ультразвуковой диагностики о БК