The Angular Diameter and Fundamental Parameters of Sirius A

The Sydney University Stellar Interferometer (SUSI) has been used to make a new determination of the angular diameter of Sirius A. The observations were made at an effective wavelength of 694.1 nm and the new value for the limb-darkened angular diameter is 6.048 +/- 0.040mas (+/-0.66%). This new result is compared with previous measurements and is found to be in excellent agreement with a conventionally calibrated measurement made with the European Southern Observatory's Very Large Telescope Interferometer (VLTI) at 2.176 microns (but not with a second globally calibrated VLTI measurement). A weighted mean of the SUSI and first VLTI results gives the limb-darkened angular diameter of Sirius A as 6.041 +/- 0.017mas (+/-0.28%). Combination with the Hipparcos parallax gives the radius equal to 1.713 +/- 0.009R_sun. The bolometric flux has been determined from published photometry and spectrophotometry and, combined with the angular diameter, yields the emergent flux at the stellar surface equal to (5.32+/- 0.14)x10^8 Wm^-2 and the effective temperature equal to 9845 +/- 64 K. The luminosity is 24.7 +/- 0.7 L_sun.Comment: Accepted for publication in PAS

Determining Parameters of Cool Giant Stars by Modeling Spectrophotometric and Interferometric Observations Using the SAtlas Program

Context: Optical interferometry is a powerful tool for observing the intensity structure and angular diameter of stars. When combined with spectroscopy and/or spectrophotometry, interferometry provides a powerful constraint for model stellar atmospheres. Aims: The purpose of this work is to test the robustness of the spherically symmetric version of the Atlas stellar atmosphere program, SAtlas, using interferometric and spectrophotometric observations. Methods: Cubes (three dimensional grids) of model stellar atmospheres, with dimensions of luminosity, mass, and radius, are computed to fit observations for three evolved giant stars, \psi Phoenicis, \gamma Sagittae, and \alpha Ceti. The best-fit parameters are compared with previous results. Results: The best-fit angular diameters and values of \chi^2 are consistent with predictions using Phoenix and plane-parallel Atlas models. The predicted effective temperatures, using SAtlas, are about 100 to 200 K lower, and the predicted luminosities are also lower due to the differences in effective temperatures. Conclusions: It is shown that the SAtlas program is a robust tool for computing models of extended stellar atmospheres that are consistent with observations. The best-fit parameters are consistent with predictions using Phoenix models, and the fit to the interferometric data for \psi Phe differs slightly, although both agree within the uncertainty of the interferometric observations.Comment: 5 pages, 6 figures, Accepted for publication in A&A as a Research Not

Bringing closure to microlensing mass measurement

Interferometers offer multiple methods for studying microlensing events and determining the properties of the lenses. We investigate the study of microlensing events with optical interferometers, focusing on narrow-angle astrometry, visibility, and closure phase. After introducing the basics of microlensing and interferometry, we derive expressions for the signals in each of these three channels. For various forecasts of the instrumental performance, we discuss which method provides the best means of measuring the lens angular Einstein radius theta_E, a prerequisite for determining the lens mass. If the upcoming generation of large-aperture, AO-corrected long baseline interferometers (e.g. VLTI, Keck, OHANA) perform as well as expected, theta_E may be determined with signal-to-noise greater than 10 for all bright events. We estimate that roughly a dozen events per year will be sufficiciently bright and have long enough durations to allow the measurement of the lens mass and distance from the ground. We also consider the prospects for a VLTI survey of all bright lensing events using a Fisher matrix analysis, and find that even without individual masses, interesting constraints may be placed on the bulge mass function, although large numbers of events would be required.Comment: 23 pages, aastex, submitted to Ap

\gamma^2 Velorum: Orbital Solution and Fundamental Parameter Determination with SUSI

The first complete orbital solution for the double-lined spectroscopic binary system \gamma^2 Velorum, obtained from measurements with the Sydney University Stellar Interferometer (SUSI), is presented. This system contains the closest example of a Wolf-Rayet star and the promise of full characterisation of the basic properties of this exotic high-mass system has subjected it to intense study as an archetype for its class. In combination with the latest radial-velocity results, our orbital solution produces a distance of 336^{+8}_{-7} pc, significantly more distant than the Hipparcos estimation (Schaerer et al. 1997; van der Hucht 1997). The ability to fully specify the orbital parameters has enabled us to significantly reduce uncertainties and our result is consistent with the VLTI observational point (Millour et al. 2006), but not with their derived distance. Our new distance, which is an order of magnitude more precise than prior work, demands critical reassessment of all distance-dependent fundamental parameters of this important system. In particular, membership of the Vela OB2 association has been reestablished, and the age and distance are also in good accord with the population of young stars reported by Pozzo et al. (2000). We determine the O-star primary component parameters to be M_V(O) = -5.63 \pm 0.10 mag, R(O) = 17 \pm 2 R_{\sun} and {\cal M}(O) = 28.5 \pm 1.1 M_{\sun}. These values are consistent with calibrations found in the literature if a luminosity class of II--III is adopted. The parameters of the Wolf-Rayet component are M_v(WR) = -4.33 \pm 0.17 mag and {\cal M}(WR) = 9.0 \pm 0.6 M_{\sun}.Comment: 3 figures, accepted for publication in MNRA

The radius and mass of the subgiant star bet Hyi from interferometry and asteroseismology

We have used the Sydney University Stellar Interferometer (SUSI) to measure the angular diameter of beta Hydri. This star is a nearby G2 subgiant whose mean density was recently measured with high precision using asteroseismology. We determine the radius and effective temperature of the star to be 1.814+/-0.017 R_sun (0.9%) and 5872+/-44 K (0.7%) respectively. By combining this value with the mean density, as estimated from asteroseismology, we make a direct estimate of the stellar mass. We find a value of 1.07+/-0.03 M_sun (2.8%), which agrees with published estimates based on fitting in the H-R diagram, but has much higher precision. These results place valuable constraints on theoretical models of beta Hyi and its oscillation frequencies.Comment: 3 figures, 3 tables, to appear in MNRAS Letter

Indigenous Knowledge System of Fishers on Siganids in Lagonoy

Anchored on the social learning theory, this study aims to infuse indigenous knowledge system in the management of fishery resources that are peculiar to a fishing ground. The study determined the indigenous knowledge of the fishers for the purpose of valuing, preserving and infusing them in managing fishery resources that are peculiar to a locality, which in this phase of the research is focused on siganids (Siganidae) in Lagonoy Gulf, Bicol Region, Philippines where a fishery management initiative exists. Formal knowledge on the species was consolidated and catalogued to serve as references in explicating the indigenous knowledge. The study adopted the qualitative method of research, and made use of key informant interview, focus group discussion and documentary analysis to gather and analyze data.  Fishers were the key informants and formed part of focus group discussions. The researchers who have studied siganids in the area and whose findings formed the basis of resource management strategies in the Lagonoy Gulf were interviewed to explicate the IKs to formal knowledge. The electronic and print media, books, information and communication materials, laws and ordinances were the sources of documents that were analyzed. Indigenous knowledge of fishers on siganids covers diversity, biology and events that indicate the species’ abundance during its spawning season.  Literature on siganids that were reviewed cover the areas of morphology, distribution and stock assessment, habitat, feeding fecundity and maturation, spawning behavior and season, fisheries and socio-economic aspects.  Notable were the locally-generated knowledge from studies that were conducted by a local academic institution, Bicol University Tabaco Campus, which formed the bases of local-government resource management initiatives.  The scientific bases of majority of the indigenous knowledge on siganids were found in the results of studies on siganids in the locality and elsewhere. However, some astronomical and natural events which fishers use to predict production like the date of new moon and production are either spuriously correlated, or limited to certain levels of exploitation.  The results of studies on siganid by the Bicol University Tabaco Campus were published in technical journals but dissemination of the results through printed materials was not sustained. Although siganids are important to fisheries in villages in Lagonoy Gulf, topics on the fish are not included in the text books and are not among the collection of information, communication and educational (IEC) materials of local government units and educational institutions. Siganids in the gulf continue to be overfished, despite several initiatives to manage the resource, which point to the need for effective knowledge management for siganids resource management. Keywords: Indigenous knowledge system, siganids, Lagonoy Gulf, fisheries managemen

Uptake and efficacy of a systematic intensive smoking cessation intervention using motivational interviewing for smokers hospitalised for an acute coronary syndrome: a multicentre before-after study with parallel group comparisons.

To compare the efficacy of a proactive approach with a reactive approach to offer intensive smoking cessation intervention using motivational interviewing (MI). Before-after comparison in 2 academic hospitals with parallel comparisons in 2 control hospitals. Academic hospitals in Switzerland. Smokers hospitalised for an acute coronary syndrome (ACS). In the intervention hospitals during the intervention phase, a resident physician trained in MI systematically offered counselling to all smokers admitted for ACS, followed by 4 telephone counselling sessions over 2 months by a nurse trained in MI. In the observation phase, the in-hospital intervention was offered only to patients whose clinicians requested a smoking cessation intervention. In the control hospitals, no intensive smoking cessation intervention was offered. The primary outcome was 1 week smoking abstinence (point prevalence) at 12 months. Secondary outcomes were the number of smokers who received the in-hospital smoking cessation intervention and the duration of the intervention. In the intervention centres during the intervention phase, 87% of smokers (N=193/225) received a smoking cessation intervention compared to 22% in the observational phase (p<0.001). Median duration of counselling was 50 min. During the intervention phase, 78% received a phone follow-up for a median total duration of 42 min in 4 sessions. Prescription of nicotine replacement therapy at discharge increased from 18% to 58% in the intervention phase (risk ratio (RR): 3.3 (95% CI 2.4 to 4.3; p≤0.001). Smoking cessation at 12-month increased from 43% to 51% comparing the observation and intervention phases (RR=1.20, 95% CI 0.98 to 1.46; p=0.08; 97% with outcome assessment). In the control hospitals, the RR for quitting was 1.02 (95% CI 0.84 to 1.25; p=0.8, 92% with outcome assessment). A proactive strategy offering intensive smoking cessation intervention based on MI to all smokers hospitalised for ACS significantly increases the uptake of smoking cessation counselling and might increase smoking abstinence at 12 months

Pedestrians’ perceptions of automated vehicle movements and light-based eHMIs in real world conditions: A test track study

The development of increasingly automated vehicles (AVs) is likely to lead to new challenges around how they will interact with other road users. In the future, it is envisaged that AVs, manually driven vehicles, and vulnerable road users such as cyclists and pedestrians will need to share the road environment and interact with one another. This paper presents a test track study, funded by the H2020 interACT project, investigating pedestrians’ reactions towards an AV’s movement patterns and external Human Machine Interfaces (eHMIs). Twenty participants, standing on the side of a test-track road and facing an approaching AV, were asked to raise their arm to indicate: (1) when they could perceive the AV’s eHMI, which consisted of either a Full Light Band (FLB) or a Partial Light Band (PLB); (2) when they perceived the deceleration of the AV (with eHMI vs. no eHMI); and (3) when they felt safe to cross the road in front of the approaching AV (with eHMI vs. no eHMI). Statistical analyses revealed no effects of the presence of an eHMI on the pedestrians’ crossing decision or deceleration perception, but significant differences were found regarding the visibility of the FLB and PLB designs. The PLB design could be perceived at further distances than the FLB design. Both eHMI solutions were generally well-received, and participants provided high ratings of perceived safety, and confidence around the AV