The Origin of B-Type Runaway Stars: Non-LTE Abundances as a Diagnostic

There are two accepted mechanisms to explain the origin of runaway OB-type stars: the Binary Supernova Scenario (BSS), and the Cluster Ejection Scenario (CES). In the former, a supernova explosion within a close binary ejects the secondary star, while in the latter close multi-body interactions in a dense cluster cause one or more of the stars to be ejected from the region at high velocity. Both mechanisms have the potential to affect the surface composition of the runaway star. TLUSTY non-LTE model atmosphere calculations have been used to determine atmospheric parameters and carbon, nitrogen, magnesium and silicon abundances for a sample of B-type runaways. These same analytical tools were used by Hunter et al. (2009) for their analysis of 50 B-type open cluster Galactic stars (i.e. non-runaways). Effective temperatures were deduced using the silicon-ionization balance technique, surface gravities from Balmer line profiles and microturbulent velocities derived using the Si spectrum. The runaways show no obvious abundance anomalies when compared with stars in the open clusters. The runaways do show a spread in composition which almost certainly reflects the Galactic abundance gradient and a range in the birthplaces of the runaways in the Galactic disk. Since the observed Galactic abundance gradients of C, N, Mg and Si are of a similar magnitude, the abundance ratios (e.g., N/Mg) are, as obtained, essentially uniform across the sample

Early-type stars observed in the ESO UVES Paranal Observatory Project - V. Time-variable interstellar absorption

The structure and properties of the diffuse interstellar medium (ISM) on small scales, sub-au to 1 pc, are poorly understood. We compare interstellar absorption-lines, observed towards a selection of O- and B-type stars at two or more epochs, to search for variations over time caused by the transverse motion of each star combined with changes in the structure in the foreground ISM. Two sets of data were used: 83 VLT- UVES spectra with approximately 6 yr between epochs and 21 McDonald observatory 2.7m telescope echelle spectra with 6 - 20 yr between epochs, over a range of scales from 0 - 360 au. The interstellar absorption-lines observed at the two epochs were subtracted and searched for any residuals due to changes in the foreground ISM. Of the 104 sightlines investigated with typically five or more components in Na I D, possible temporal variation was identified in five UVES spectra (six components), in Ca II, Ca I and/or Na I absorption-lines. The variations detected range from 7\% to a factor of 3.6 in column density. No variation was found in any other interstellar species. Most sightlines show no variation, with 3{\sigma} upper limits to changes of the order 0.1 - 0.3 dex in Ca II and Na I. These variations observed imply that fine-scale structure is present in the ISM, but at the resolution available in this study, is not very common at visible wavelengths. A determination of the electron densities and lower limits to the total number density of a sample of the sightlines implies that there is no striking difference between these parameters in sightlines with, and sightlines without, varying components.Comment: 19 pages, 11 figures, accepted for publication in MNRA

Broad Balmer Wings in BA Hyper/Supergiants Distorted by Diffuse Interstellar Bands: Five Examples in the 30 Doradus Region from the VLT-FLAMES Tarantula Survey

Extremely broad emission wings at Hβ and Hα have been found in VLT-FLAMES Tarantula Survey data for five very luminous BA supergiants in or near 30 Doradus in the Large Magellanic Cloud. The profiles of both lines are extremely asymmetrical, which we have found to be caused by very broad diffuse interstellar bands (DIBs) in the longward wing of Hβ and the shortward wing of Hα. These DIBs are well known to interstellar but not to many stellar specialists, so that the asymmetries may be mistaken for intrinsic features. The broad emission wings are generally ascribed to electron scattering, although we note difficulties for that interpretation in some objects. Such profiles are known in some Galactic hyper/supergiants and are also seen in both active and quiescent Luminous Blue Variables (LBVs). No prior or current LBV activity is known in these 30 Dor stars, although a generic relationship to LBVs is not excluded; subject to further observational and theoretical investigation, it is possible that these very luminous supergiants are approaching the LBV stage for the first time. Their locations in the HRD and presumed evolutionary tracks are consistent with that possibility. The available evidence for spectroscopic variations of these objects is reviewed, while recent photometric monitoring does not reveal variability. A search for circumstellar nebulae has been conducted, with an indeterminate result for one of them

Up-Regulation of Annexin-A1 and Lipoxin A4 in Individuals with Ulcerative Colitis May Promote Mucosal Homeostasis

PubMed ID: 22723974This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

β Cephei type variability in the ultraviolet spectrum and radial velocity of PHL 346

International Ultraviolet Explorer low-resolution and optical moderate-resolution spectra are presented for the high galactic latitude β Cephei type star, PHL 346. Variability is identified in both the ultraviolet flux and the radial velocity with periods and phases consistent with those previously deduced from optical photometry. The similarity of both the flux and the radial velocity amplitude to those previously reported for the β Cephei variable, γ Pegasus, is striking and provides evidence for PHL 346 being a young core hydrogen burning star. A distance estimate for PHL 346 of approximately 7 kpc (corresponding to a z-distance of approximately 6 kpc) is obtained by scaling the distance of γ Pegasus obtained from Hipparcos observations.link_to_subscribed_fulltex

mRNA expression of FPR2/ALX in colonic mucosal biopsies from healthy subjects without(Ctrl) or with a prior history (Hx) of UC, or UC patients with active disease (Active) or medically-induced remission (Rem).

<p> Increased expression of FPR2/ALX was detected in biopsies from individuals with UC. Data are expressed as fold change relative to Ctrl (**<i>P</i><.01, n = 5–12).</p

Detection of annexin-A1 NH₂-terminal-intact and -cleaved fragments in biopsies from healthy subjects without(Ctrl) or with a prior history (Hx) of UC, or UC patients with active disease (Active) or medically-induced remission (Rem).

<p>Annexin-1 was overexpressed in colonic mucosal biopsies of patients with UC compared to healthy patients with a prior history of UC (<b>A</b>). Alongside the native 37 kDa fragment, a NH₂-terminal cleaved isoform (33 kDa) could also be visualized, indicating specific degradation in response to externalization from activated cells. Analysis of relative intensity, where annexin-A1 immunoreactivity was normalized against β-actin (<b>B</b>). Data are expressed as mean ± SEM (**<i>P</i><.01, n = 5–11).</p

Figure 3

<p>Expression of Annexin-A1 in colonic mucosal biopsies from healthy subjects without (Ctrl) or with a prior history (Hx) of UC, or UC patients with active disease (Active) or medically-induced remission (Rem) (<b>A</b>). Immunofluorescence detection of Annexin-A1 (red) demonstrates expression is increased in patients with UC, whether active or in medically-induced remission. Integrated pixel intensity revealed ∼3-fold increase in these groups, compared to healthy subjects (<b>B</b>). In biopsies from patients with active UC, Annexin-A1 (blue) staining could be localized to infiltrating PMNs (red; stained with anti-HNE) (<b>C</b>), however in biopsies from patients in medically-induced remission, Annexin-A1 staining (red) closely paralleled tissue infiltration by CD68⁺ macrophages (blue; stained with anti-CD68) (<b>D</b>). Annexin-A1 expression was also detected in crypt epithelial cells in subjects with UC, but not healthy subjects without/with a prior history of UC (<b>E</b>). Data are expressed as mean ± SEM (*<i>P</i><.05, ***<i>P</i><.001, n = 4). Magnification bar = 100 μm.</p

Figure 2

<p>Colonic mucosal lipoxin A₄ levels (<b>A</b>) in biopsies from healthy subjects without (Ctrl) or with a prior history (Hx) of UC, or UC patients with active disease (Active) or medically-induced remission (Rem). Lipoxin A₄ levels were significantly elevated in the samples from patients who were in medically-induced remission compared with healthy subjects and those with a prior history of UC (>4 years disease-free). Quantitative RT-PCR analysis of 5-LO (<b>B</b>), 12-LO (<b>C</b>) and 15-LO (<b>D</b>) expression revealed an increase of 5-LO expression in patients with active disease. This correlated with an increase in the number of 5-LO-positive cells as assessed by immunohistochemistry (<b>E</b>). Data are expressed as fold change relative to Ctrl (*<i>P</i><.05, **<i>P</i><.01 ***<i>P</i><.001, n = 5–20). Magnification bar = 100 μm.</p