All-Sky spectrally matched UBVRI-ZY and u'g'r'i'z' magnitudes for stars in the Tycho2 catalog

We present fitted UBVRI-ZY and u'g'r'i'z' magnitudes, spectral types and distances for 2.4M stars, derived from synthetic photometry of a library spectrum that best matches the Tycho2 BtVt, NOMAD Rn and 2MASS JHK_{2/S} catalog magnitudes. We present similarly synthesized multi-filter magnitudes, types and distances for 4.8M stars with 2MASS and SDSS photometry to g<16 within the Sloan survey region, for Landolt and Sloan primary standards, and for Sloan Northern (PT) and Southern secondary standards. The synthetic magnitude zeropoints for BtVt, UBVRI, ZvYv, JHK_{2/S}, JHK_{MKO}, Stromgren uvby, Sloan u'g'r'i'z' and ugriz are calibrated on 20 calspec spectrophotometric standards. The UBVRI and ugriz zeropoints have dispersions of 1--3%, for standards covering a range of color from -0.3 < V-I < 4.6; those for other filters are in the range 2--5%. The spectrally matched fits to Tycho2 stars provide estimated 1-sigma errors per star of ~0.2, 0.15, 0.12, 0.10 and 0.08 mags respectively in either UBVRI or u'g'r'i'z'; those for at least 70% of the SDSS survey region to g<16 have estimated 1-sigma errors per star of ~0.2, 0.06, 0.04, 0.04, 0.05 in u'g'r'i'z' or UBVRI. The density of Tycho2 stars, averaging about 60 stars per square degree, provides sufficient stars to enable automatic flux calibrations for most digital images with fields of view of 0.5 degree or more. Using several such standards per field, automatic flux calibration can be achieved to a few percent in any filter, at any airmass, in most workable observing conditions, to facilitate inter-comparison of data from different sites, telescopes and instruments.Comment: 36 pages, 30 figures, 3 printed tables, several electronic tables, accepted PASP Dec 201

Fundamental Properties of O-Type Stars

We present a comprehensive analysis of high-resolution, far-UV HST/STIS, FUSE, and optical spectra of 17 O stars in the SMC. Our analysis is based on NLTE metal line-blanketed model atmospheres calculated with our NLTE code TLUSTY. We systematically explore the sensitivity of various UV and optical lines to different stellar parameters. We have obtained consistent fits of the UV and the optical spectrum to derive the effective temperature, surface gravity, surface composition, and microturbulent velocity of each star. Stellar radii, masses, luminosities and ages then follow. Similarly to more limited recent studies, we derive cooler temperatures than the standard Teff calibration of O stars. We propose a new calibration between the spectral type and effective temperature based on our results from UV metal lines as well as optical hydrogen and helium lines. For stars of the same spectral subtype, we find a general good agreement between Teff determinations obtained with TLUSTY, CMFGEN, and FASTWIND models. We derive ionizing luminosities that are smaller by a factor of 3 compared to luminosities inferred from previous standard calibrations. The chemical composition analysis reveals that the surface of about 3/4 of the program stars is moderately to strongly enriched in nitrogen, while showing the original helium, carbon, and oxygen abundances. Our results support the new stellar evolution models that predict that the surface of fast rotating stars becomes N-rich during the main sequence phase because of rotationally-induced mixing. Most stars exhibit the ``mass discrepancy'' problem. This discrepancy too is a result of fast rotation which lowers the measured effective gravity. Our study thus emphasizes the importance of rotation in our understanding of the properties of massive stars. (abridged)Comment: Submitted to Astrophysical Journal; 69 page

Paraphrases and summaries: A means of clarification or a vehicle for articulating a preferred version of student accounts?

The use of group discussions as a means to facilitate learning from experiences is well documented in adventure education literature. Priest and Naismith (1993) assert that the use of the circular discussion method, where the leader poses questions to the participants, is the most common form of facilitation in adventure education. This paper draws on transcripts of facilitation sessions to argue that the widely advocated practice of leader summaries or paraphrases of student responses in these sessions functions as a potential mechanism to control and sponsor particular knowledge(s). Using transcripts from recorded facilitation sessions the analysis focuses on how the leader paraphrases the students’ responses and how these paraphrases or ‘formulations’ function to modify or exclude particular aspects of the students’ responses. I assert that paraphrasing is not simply a neutral activity that merely functions to clarify a student response, it is a subtle means by which the leader of the session can, often inadvertently or unknowingly, alter the student’s reply with the consequence of favouring particular knowledge(s). Revealing the subtle work that leader paraphrases perform is of importance for educators who claim to provide genuine opportunities for students to learn from their experience

Land resource survey of Rottnest Island - an aid to land use planning

This report provides a description of the landforms, soils and vegetation of Rottnest Island. In addition, it provides a discussion of the relative capability of each of the landforms of the island to sustain various forms of development. The primary objective of this work is to direct development into areas of high capability (low risk of land degradation) in preference to areas of lower capability (higher risk of land degradation). Rottnest Island is located approximately 30 km west of Perth. The proximity of the island to the capital city of Western Australia, its warm Mediterranean climate and the subsequent likelihood of further development, mean that there will be increasing pressure on the natural resources of the island. This report details the nature and inherent stability of those natural resources, and provides a guide for their management.https://researchlibrary.agric.wa.gov.au/bulletins/1062/thumbnail.jp

What makes for prize-winning television?

We investigate the determinants of success in four international television awards festivals between 1994 and 2012. We find that countries with larger markets and greater expenditure on public broadcasting tend to win more awards, but that the degree of concentration in the market for television and rates of penetration of pay-per-view television are unrelated to success. These findings are consistent with general industrial organisation literature on quality and market size, and with media policy literature on public service broadcasting acting as a force for quality. However, we also find that ‘home countries’ enjoy a strong advantage in these festivals, which is not consistent with festival success acting as a pure proxy for television quality

A Candidate Substellar Companion to HR 7329

We present the discovery of a candidate substellar companion from a survey of nearby, young stars with the NICMOS coronagraph on the Hubble Space Telescope. The H ~ 12 mag object was discovered approximately 4" from the young A0V star HR 7329. Using follow-up spectroscopy from STIS, we derive a spectral type between M7V and M8V with an effective temperature of ~ 2600 K. We estimate that the probability of a chance alignment with a foreground dwarf star of this nature is ~ 10^(-8) and therefore suggest the object (HR 7329B) is physically associated with HR 7329 with a projected separation of 200 AU. Current brown dwarf cooling models indicate a mass of less than 50 Jupiter masses for HR 7329B based on age estimates of < 30 Myr for HR7329A.Comment: 8 pages LATEX, 5 ps figures, accepted for Ap

Terminal velocities of luminous, early-type SMC stars

Ultraviolet spectra from the Space Telescope Imaging Spectrograph (STIS) are used to determine terminal velocities for 11 O and B-type giants and supergiants in the Small Magellanic Cloud (SMC) from the Si IV and C IV resonance lines. Using archival data from observations with the Goddard High-Resolution Spectrograph and the International Ultraviolet Explorer telescope, terminal velocities are obtained for a further five B-type supergiants. We discuss the metallicity dependence of stellar terminal velocities, finding no evidence for a significant scaling between Galactic and SMC metallicities for Teff < 30,000 K, consistent with the predictions of radiation driven wind theory for supergiant stars. A comparison of the $v_\infty / v_{esc}$ ratio between the SMC and Galactic samples, while consistent with the above statement, emphasizes that the uncertainties in the distances to galactic O-stars are a serious obstacle to a detailed comparison with theory. For the SMC sample there is considerable scatter in this ratio at a given effective temperature, perhaps indicative of uncertainties in stellar masses.Comment: 28 pages, 8 figures, accepted by ApJ; minor revisions prior to acceptanc

The Heavy Element Enrichment of Lyman alpha Clouds in the Virgo Supercluster

Using high S/N STIS echelle spectra (FWHM=7 km/s) of 3C 273, we constrain the metallicities of two Lya clouds in the vicinity of the Virgo cluster. We detect C II, Si II, and Si III absorption lines in the Lya absorber at z = 0.00530. Previous observations with FUSE have revealed Ly beta - Ly theta lines at this redshift, thereby accurately constraining N(H I). We model the ionization of the gas and derive [C/H] = -1.2^{+0.3}_{-0.2}, [Si/C] = 0.2+/-0.1, and log n_{H} = -2.8+/-0.3. The model implies a small absorber thickness, ~70 pc, and thermal pressure p/k ~ 40 cm^{-3} K. It is most likely that the absorber is pressure confined by an external medium because gravitational confinement would require a very high ratio of dark matter to baryonic matter. Based on Milky Way sight lines in which carbon and silicon abundances have been reliably measured in the same interstellar cloud (including new measurements presented herein), we argue that the overabundance of Si relative to C is not due to dust depletion. Instead, this probably indicates that the gas has been predominately enriched by Type II supernovae. Such enrichment is most plausibly provided by an unbound galactic wind, given the absence of galaxies within a projected distance of 100 kpc and the presence of galaxies capable of driving a wind at larger distances. We also constrain the metallicity and physical conditions of the Virgo absorber at z = 0.00337 based on detections of O VI and H I and an upper limit on C IV. If this absorber is collisionally ionized, the O VI/C IV limit requires T > 10^{5.3} K. For either collisional ionization or photoionization, we find that [O/H] > -2.0 at z = 0.00337.Comment: Final Ap.J. versio