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

Obscuration of Supersoft X-ray Sources by Circumbinary Material - A Way to Hide Type Ia Supernova Progenitors?

The progenitors of supernovae (SNe) type Ia are usually assumed to be either a single white dwarf (WD) accreting from a non-degenerate companion (the SD channel) or the result of two merging WDs (DD channel). However, no consensus currently exists as to which progenitor scenario is the correct one, or whether the observed SN Ia rate is produced by a combination of both channels. Unlike a DD progenitor a SD progenitor is expected to emit supersoft X-rays for a prolonged period of time (~1 Myr) as a result of the burning of accreted matter on the surface of the WD. An argument against the SD channel as a significant producer of SNe type Ia has been the lack of observed supersoft X-ray sources (SSS) and the lower-than-expected integrated soft X-ray flux from elliptical galaxies. We wish to determine if it is possible to obscure the supersoft X-ray emission from a nuclear burning white dwarf in an accreting single degenerate binary system. In case of obscured systems we wish to determine their general observational characteristics. We examine the emergent X-ray emission from a canonical SSS system surrounded by a spherically symmetric configuration of material, assuming a black body spectrum with T_BB=50 eV and L=10^38 erg/s. The circumbinary material is assumed to be of solar chemical abundances, and we leave the mechanism behind the mass loss into the circumbinary region unspecified. If steadily accreting, nuclear burning WDs are canonical SSS our analysis suggests that they can be obscured by relatively modest circumbinary mass loss rates. This may explain the discrepancy of SSS compared to the SN Ia rate inferred from observations if the SD progenitor scenario contributes significantly to the SN Ia rate. Recycled emissions from obscured systems may be visible in other wavebands than X-rays. It may also explain the lack of observed SSS in symbiotic binary systems.Comment: 10 pages, 4 figures, accepted A&

Double Beta Decay: Historical Review of 75 Years of Research

Main achievements during 75 years of research on double beta decay have been reviewed. The existing experimental data have been presented and the capabilities of the next-generation detectors have been demonstrated.Comment: 25 pages, typos adde

Severe airway stenosis associated with Crohn's disease: Case report

BACKGROUND: Symptomatic respiratory tract involvement is not common in Crohn's disease. Upper-airway obstruction has been reported before in Crohn's disease and usually responds well to steroid treatment. CASE PRESENTATION: We report a case of a 32-year old patient with Crohn's disease who presented with progressively worsening dyspnea on exertion. Magnetic Resonance Imaging of the chest and bronchoscopy revealed severe tracheal stenosis and marked inflammation of tracheal mucosa. Histopathology of the lesion showed acute and chronic inflammation and extended ulceration of bronchial mucosa, without granulomas. Tracheal stenosis was attributed to Crohn's disease after exclusion of other possible causes and oral and inhaled steroids were administered. Despite steroid treatment, tracheal stenosis persisted and only mild symptomatic improvement was noted after 8 months of therapy. The patient subsequently underwent rigid bronchoscopy with successful dilatation and ablation of the stenosed areas and remission of her symptoms. CONCLUSION: Respiratory involvement in Crohn's disease might be more common than appreciated. Interventional pulmonology techniques should be considered in cases of tracheal stenosis due to Crohn's disease refractory to steroid treatment

Guillain-Barré Syndrome, Influenza Vaccination, and Antecedent Respiratory and Gastrointestinal Infections: A Case-Centered Analysis in the Vaccine Safety Datalink, 2009–2011

Background: Guillain-Barré Syndrome (GBS) can be triggered by gastrointestinal or respiratory infections, including influenza. During the 2009 influenza A (H1N1) pandemic in the United States, monovalent inactivated influenza vaccine (MIV) availability coincided with high rates of wildtype influenza infections. Several prior studies suggested an elevated GBS risk following MIV, but adjustment for antecedent infection was limited. Methods: We identified patients enrolled in health plans participating in the Vaccine Safety Datalink and diagnosed with GBS from July 2009 through June 2011. Medical records of GBS cases with 2009–10 MIV, 2010–11 trivalent inactivated influenza vaccine (TIV), and/or a medically-attended respiratory or gastrointestinal infection in the 1 through 141 days prior to GBS diagnosis were reviewed and classified according to Brighton Collaboration criteria for diagnostic certainty. Using a case-centered design, logistic regression models adjusted for patient-level time-varying sources of confounding, including seasonal vaccinations and infections in GBS cases and population-level controls. Results: Eighteen confirmed GBS cases received vaccination in the 6 weeks preceding onset, among 1.27 million 2009–10 MIV recipients and 2.80 million 2010–11 TIV recipients. Forty-four confirmed GBS cases had infection in the 6 weeks preceding onset, among 3.77 million patients diagnosed with medically-attended infection. The observed-versus-expected odds that 2009–10 MIV/2010–11 TIV was received in the 6 weeks preceding GBS onset was odds ratio = 1.54, 95% confidence interval (CI), 0.59–3.99; risk difference = 0.93 per million doses, 95% CI, −0.71–5.16. The association between GBS and medically-attended infection was: odds ratio = 7.73, 95% CI, 3.60–16.61; risk difference = 11.62 per million infected patients, 95% CI, 4.49–26.94. These findings were consistent in sensitivity analyses using alternative infection definitions and risk intervals for prior vaccination shorter than 6 weeks. Conclusions: After adjusting for antecedent infections, we found no evidence for an elevated GBS risk following 2009–10 MIV/2010–11 TIV influenza vaccines. However, the association between GBS and antecedent infection was strongly elevated

New constraints on protostellar jet collimation from high-density gas UV tracers

The analysis of high-resolution profiles of the semiforbidden UV lines of C III](1908) and Si III](1892) in the spectra of T Tauri stars (TTSs) shows the following : (1) There is C III](1908) and Si III](1892) emission at velocities that are similar to those observed in the optical forbidden lines formed in the TTSs jets. The luminosity of the UV lines is comparable to that of the optical lines. (2) The comparison between the optical and UV light curves indicates that the C III](1908) and Si III](1892) emission of RY Tau is not associated with accretion shocks, but it is produced farther than 2 R-* from the star. (3) The profiles of the UV semiforbidden lines are significantly broader than those of the optical forbidden lines. These profiles cannot be produced in a narrow collimated beam, and they are most likely produced in a bow-shaped shock wave formed at the base of the optical jet, where the hot gas emits in a broad range of projected radial velocities. (4) The atmosphere of RU Lup contributes significantly to the Si III](1892) emission. (5) A puzzling narrow feature is observed close to the C III](1908) line. The feature is blueshifted by -260 km s(-1), which corresponds to the wind terminal velocity measured in the P Cygni profile of the Mg II (UV1) lines. Moreover, constraints are derived on the characteristics of the C III](1908) and Si III](1892) emitting region in RY Tau. It is shown that 4.7 less than or equal to log T-e less than or equal to 5.0 and 10(9) cm(-3) less than or equal to N-e less than or equal to 10(11) cm(-3) provided that the emission is produced in a collisional plasma and that the 1665 Angstrom feature observed in low-dispersion International Ultraviolet Explorer (IUE) spectra is confirmed to be O III](1665) emission produced in the wind. These very high densities are difficult to generate in the shocks produced by the magnetic pinching of centrifugally driven magnetized disk winds. The data also suggest that the shocked layer has a radius of some few stellar radii and it is closer than similar to 38 R-* to the star