Interpretation of the Veiling of the Photospheric Spectrum for T Tauri Stars in Terms of an Accretion Model

The problem on heating the atmospheres of T Tauri stars by radiation from an accretion shock has been solved. The structure and radiation spectrum of the emerging so-called hot spot have been calculated in the LTE approximation. The emission not only in continuum but also in lines has been taken into account for the first time when calculating the spot spectrum. Comparison with observations has shown that the strongest of these lines manifest themselves as narrow components of helium and metal emission lines, while the weaker ones decrease significantly the depth of photospheric absorption lines, although until now, this effect has been thought to be due to the emission continuum alone. The veiling by lines changes the depth of different photospheric lines to a very different degree even within a narrow spectral range. Therefore, the nonmonotonic wavelength dependence of the degree of veiling r found for some CTTS does not suggest a nontrivial spectral energy distribution of the veiling continuum. In general, it makes sense to specify the degree of veiling r only by providing the set of photospheric lines from which this quantity was determined. We show that taking into account the contribution of lines to the veiling of the photospheric spectrum can cause the existing estimates of the accretion rate onto T Tauri stars to decrease by several times, with this being also true for stars with a comparatively weakly veiled spectrum. Neglecting the contribution of lines to the veiling can also lead to appreciable errors in determining the effective temperature, interstellar extinction, radial velocity, and vsin(i)

Observational diagnostics of gas in protoplanetary disks

Protoplanetary disks are composed primarily of gas (99% of the mass). Nevertheless, relatively few observational constraints exist for the gas in disks. In this review, I discuss several observational diagnostics in the UV, optical, near-IR, mid-IR, and (sub)-mm wavelengths that have been employed to study the gas in the disks of young stellar objects. I concentrate in diagnostics that probe the inner 20 AU of the disk, the region where planets are expected to form. I discuss the potential and limitations of each gas tracer and present prospects for future research.Comment: Review written for the proceedings of the conference "Origin and Evolution of Planets 2008", Ascona, Switzerland, June 29 - July 4, 2008. Date manuscript: October 2008. 17 Pages, 6 graphics, 134 reference

Measures of Health-related Quality of Life for Adults with Acute Sinusitis: A Systematic Review

CONTEXT: Symptoms suggestive of acute sinusitis are a common reason for patients to visit primary care providers. Since objective measures of outcome have not been shown to be related to patient reported outcomes, measures of treatment success have focused on symptom relief and improved health-related quality of life (HRQL). Assessing the appropriate role of treatment — for example, antibiotics for patients with acute sinusitis — requires valid, reliable, and responsive measures of outcome. We identified symptom scores and HRQL instruments for adults with sinusitis and assessed their performance characteristics. DATA SOURCES: Articles identified through computer searches of the medline, premedline, and embase databases, the Cochrane Library, and internet documents; inquiries to experts in sinusitis and outcomes assessment; and review of reference lists. STUDY SELECTION: Studies that used HRQL instruments or evaluated the performance characteristics of symptom scores in adults with sinusitis, published in English after 1966. DATA EXTRACTION: Two reviewers independently extracted data on study design, setting, and patient characteristics; instrument length and format; and instrument validity, reliability, responsiveness to change, and interpretability. Study quality was assessed using a 10-point score. DATA SYNTHESIS: Of 1,340 articles in the original search, 29 articles using 16 HRQL instruments and 5 symptoms scores met inclusion and exclusion criteria. The overall quality of these studies was low; only 4 studies scored higher than 4 of 10 points. Four studies included patients with acute sinusitis, but only 2 included exclusively acute sinusitis patients. Three instruments have been shown to meet basic requirements for validity, reliability, and responsiveness: the Chronic Sinusitis Survey, the Rhinosinusitis Outcome Measure-31, and the Sinonasal Outcome Test-16. No instrument has been validated in a primary care setting or for patients with acute sinusitis. CONCLUSIONS: Few validated measures of sinusitis-specific HRQL are available. The 3 instruments shown to be valid, reliable, and responsive have been assessed in patients with chronic sinusitis. No measure has been validated in primary care settings or for patients with acute sinusitis. A lack of valid, responsive outcome measures may limit current treatment recommendations for patients with acute sinusitis