The promise of Gaia and how it will influence stellar ages

The Gaia space project, planned for launch in 2011, is one of the ESA cornerstone missions, and will provide astrometric, photometric and spectroscopic data of very high quality for about one billion stars brighter than V=20. This will allow to reach an unprecedented level of information and knowledge on several of the most fundamental astrophysical issues, such as mapping of the Milky Way, stellar physics (classification and parameterization), Galactic kinematics and dynamics, study of the resolved stellar populations in the Local Group, distance scale and age of the Universe, dark matter distribution (potential tracers), reference frame (quasars, astrometry), planet detection, fundamental physics, Solar physics, Solar system science. I will present a description of the instrument and its main characteristics, and discuss a few specific science cases where Gaia data promise to contribute fundamental improvement within the scope of this Symposium.Comment: 10 pages, 2 figures, IAU Symp. 258 on "The Ages of Stars

Discursive Voter Models on the Supercritical Scale-Free Network

The voter model is a classical interacting particle system, modelling how global consensus is formed by local imitation. We analyse the time to consensus for a particular family of voter models when the underlying structure is a scale-free inhomogeneous random graph, in the high edge density regime where this graph features a giant component. In this regime, we verify that the polynomial orders of consensus agree with those of their mean-field approximation in [Moinet et al., 2018]. This "discursive" family of models has a symmetrised interaction to better model discussions, and is indexed by a temperature parameter which, for certain parameters of the power law tail of the network's degree distribution, is seen to produce two distinct phases of consensus speed. Our proofs rely on the well-known duality to coalescing random walks and a control on the mixing time of these walks, using the known fast mixing of the Erd\H{o}s-R\'enyi giant subgraph. Unlike in the subcritical case [Fernley and Ortgiese, 2022] which requires tail exponent of the limiting degree distribution $\tau=1+1/\gamma >3$ as well as low edge density, in the giant component case we also address the "ultrasmall world" power law exponents $\tau \in (2,3]$.Comment: 32 pages, 3 figure

Amplitude Fine-Structure in the Cepheid P-L Relation I: Amplitude Distribution Across the RR Lyrae Instability Strip Mapped Using the Accessibility Restriction Imposed by the Horizontal Branch

The largest amplitude light curves for both RR Lyrae (RRL) variables and classical Cepheids with periods less than 10 days and greater than 20 days occur at the blue edge of the respective instability strips. It is shown that the equation for the decrease in amplitude with penetration into the strip from the blue edge, and hence the amplitude fine structure within the strip, is the same for RRL and the Cepheids despite their metallicity differences. However, the manifestation of this identity is different between the two classes of variables because the sampling of the RRL strip is restricted by the discrete strip positions of the horizontal branch, a restriction that is absent for the Cepheids in stellar aggregates with a variety of ages. To show the similarity of the strip amplitude fine structure for RRL and Cepheids we make a grid of lines of constant amplitude in the HR diagram of the strip using amplitude data for classical Cepheids in the Galaxy, LMC, and SMC. The model implicit in the grid, that also contains lines of constant period, is used to predict the correlations between period, amplitude, and color for the two Oosterhoff RRL groups in globular clusters. The good agreement of the predictions with the observations using the classical Cepheid amplitude fine structure also for the RRL shows one aspect of the unity of the pulsation processes between the two classes of variables.Comment: 24 pages, 3 tables, 5 figures, submitted to The Astrophysical Journa

Proper identification of RR Lyrae Stars brighter than 12.5 mag

RR Lyrae stars are of great importance for investigations of Galactic structure. However, a complete compendium of all RR-Lyraes in the solar neighbourhood with accurate classifications and coordinates does not exist to this day. Here we present a catalogue of 561 local RR-Lyrae stars V_max less equal 12.5 mag according to the magnitudes given in the Combined General Catalogue of Variable Stars (GCVS) and 16 fainter ones. The Tycho2 catalogue contains about 100 RR Lyr stars. However, many objects have inaccurate coordinates in the GCVS, the primary source of variable star information, so that a reliable cross-identification is difficult. We identified RR Lyrae from both catalogues based on an intensive literature search. In dubious cases we carried out photometry of fields to identify the variable. Mennessier and Colome (2002) have published a paper with Tyc2-GCVS identifications, but we found that many of their identifications are wrong. Keywords: astrometry -- Stars: RR Lyrae stars -- Catalogues: Tycho-2 catalogue -- Catalogues: The HST Guide Star Catalogue, Version 1.2 -- Catalogues: Combined General Catalogue of Variable StarsComment: 5 pages with 2 figures; A and A accepted Online-Data are available under http://www.astro.uni-bonn.de/~gmaint

The Meinunger "Nicht Rote" Objects

Four high-latitude slow variable stars have been noted by Meinunger (1972) as "nicht rote" ("not red") objects and thus curious. We have previously reported (Margon & Deutsch 1997) that one of these objects, CC Boo, is in fact a QSO. Here we present observations demonstrating that the remaining three are also highly variable active galactic nuclei. The most interesting object of the four is perhaps S 10765 (= NGP9 F324-0276706), which proves to be a resolved galaxy at z=0.063. Despite the rapid and large reported variability amplitude (~1.6 mag), the spectrum is that of a perfectly normal galaxy, with no emission lines or evident nonthermal continuum. We also present new spectroscopic and photometric observations for AR CVn, suggested by Meinunger to be an RR Lyrae star despite its very faint magnitude (=19.4). The object is indeed one of the most distant RR Lyrae stars known, at a galactocentric distance of ~40 kpc.Comment: Accepted for publication in Publications of the Astronomical Society of the Pacific, Volume 111, January 1999; 14 pages including 4 figures and 1 tabl

Relative age effects in Australian junior rugby union

Each of the four codes of professional football played in Australia (i.e., Rugby Union, Rugby League, Australian Rules Football and Soccer) is faced with the dilemma of identifying and developing talented young athletes into elite senior players. One of the key difficulties faced by talent scouts, coaches and selectors is identifying talented young individuals during adolescence. Individual differences in the timing and tempo of the maturation process, which are most visible during puberty, can have a significant impact on all aspects of sporting performance and resultant judgements of talented players. With junior and youth teams organised according to chronological age-groupings, inequalities related to perceptions of playing ability are likely to emerge between individuals based on when in a calendar year they are born. These inequalities have become known as ‘Relative Age Effects’, with young players born earlier in a selection year gaining advantages over their later-born counterparts. These advantages include more playing time, a perception of possessing more talent and a subsequent increase in the probability of gaining selection in elite representative teams. The purpose of the first part of this investigation was to examine whether a relative age effect was present in a cohort of elite junior rugby union players competing at the annual national U16 championships. Individual birth-date data and playing position was recorded for each participant at the championships over a seven-year period (2004 – 2010). Chi-square statistics were used to examine differences between observed and expected birth date distributions in all players and general playing positions (forwards and backs). Comparison of birth date distributions between players in the 1st (top 8 teams) and 2nd division (bottom 4 teams) was also conducted. Odds ratios (ORs) and 95% confidence intervals (CIs) were also calculated for both quartile and half-year distributions (H1 and H2). For the OR analyses, the relatively youngest members, (i.e. quartile 4 and H2 respectively) of the annual age-groupings were assigned as referent groups. The second part of the investigation examined whether increasing age and skill levels would act as moderators of relative age effects in talented Australian rugby union players. Individual birth-date data was obtained for Australian U20 teams from 2008 to 2011. Birthdate distributions for this group were then compared to distributions from the U16 national championships for the equivalent time period (i.e. 2004 - 2007). Chi-square statistics were again used to examine differences between observed and expected birth date distributions in all players to determine the size of the relative age effect in the U20’s teams and to the compare these results with those from the U16 group. ORs and CIs were also calculated for both quartile and half-year distributions (H1 and H2). For the OR analyses, the relatively youngest members, (i.e. quartile 4 and H2, respectively) of the annual age-groupings were assigned as referent groups. Player retention along the development pathway was also examined, with selection to Australian schoolboys teams observed as the intermediate step from U16 championships to the Australian U20 team. The main finding from the first part of the investigation was the presence of a strong relative age effect within the cohort of elite junior rugby union players. The birth-date distribution was significantly biased towards a higher number of births earlier in the selection year. There was also a significant underrepresentation from players born in the fourth quarter of the year. This study also found that birth date distributions were influenced by age and skill level, but not playing position. A stronger age bias was observed for players from the division one teams competing at the U16 championships, with a larger disparity between players born in the first and last quarters of the selection year than in division two. Playing position did not appear to impact on the birth date distribution. Even though there was a strong overrepresentation of players born in the first half of the year for both forward and backline playing positions, the percentage breakdown for each group were similar. The second part of the investigation showed there was a strong retention of players along the developmental pathway from the U16 age group through to the Australian U20 Junior World Cup team. These findings suggest that increasing age does not appear to act as a moderator of relative age effects in talented Australian rugby union players. In conclusion, the results of this study demonstrated the presence of a strong relative age effect in a group of elite U16 rugby players. This biased birth date distribution also appeared along the developmental pathway until the Australian U20 team. On the basis of these findings, it is recommended that current selection processes require modification to assist with minimising and/or eliminating the various factors that have led to their development in elite junior rugby union teams

Assessing rural sustainable housing development:In Shropshire and Herefordshire

The promotion and inclusion of Sustainable Development has been aprimary consideration for many western economies over the last 35-40years. In the United Kingdom,the Town and Country Planning system has been charged with delivering the spatial elements of sustainable development. The question is,how successful has the planning system been in achieving this?Using rural housing development as an example, this research has focused its investigations using mixed methods of quantitative and qualitative analysis, to provide assessments of how sustainability is pursued by Local Planning Authorities (LPAs). The research covers the period between 2007 and 2017 to enable investigation of LPA decisions over a ten year period. Itinvolved detailed investigation of secondary data from 4,094planning applications across eight case study parishes in two LPA areas, and obtaining primary data from street based surveys and Focus Groups in the same parishes. This research sought to establish if housing targets set in LPA Development Plans are being met, how changes in national planning policy has influenced decision making, the extent to which sustainability considerations have influenced decision making and, to what extent the makingof Neighbourhood Plans has impacted upon decisions relating to rural housing development. The research has concluded that although LPAs have largely adhered to local planning policy, housing targets have only been achieved in the last years of study 2016/17. In the case study parishes the majority of approved and refused planning applications were for single dwellings, with sustainability considerations dominating the reasons quoted in decisions from Planning Officer and Committee reports.The results indicate that some extra levels of community cohesion has taken place where Neighbourhood Plans exist, but insufficient evidence has been found to confirm that Neighbourhood Plans have realised a discernible difference, in other aspects of developmen

A pulsational approach to near infrared and visual magnitudes of RR Lyrae stars

In this paper we present an improved theoretical scenario concerning near infrared and visual magnitudes of RR Lyrae variables, as based on up-to-date pulsating models. On this basis, we revisit the case of the prototype variable RR Lyr, showing that the parallax inferred by this new pulsational approach appears in close agreement with HST absolute parallax. Moreover, available K and V measurements for field and cluster RR Lyrae variables with known reddening and metal content are used to derive a relation connecting the K absolute magnitude to period and metallicity, as well as a new calibration of the M_V-[Fe/H] relation. The comparison between theoretical prescriptions and observations suggests that RR Lyrae stars in the field and in Galactic Globular Clusters should have quite similar evolutionary histories. The comparison between theory and observations also discloses a general agreement that supports the reliability of current pulsational scenario. On the contrary, current empirical absolute magnitudes based on the Baade-Wesselink (BW) method suggest relations with a zero-point that is fainter than predicted by pulsation models, together with a milder metallicity dependence. However, preliminary results based on a new calibration of the BW method provided by Cacciari et al. (2000) for RR Cet and SW And appear in a much better agreement with the pulsational predictions.Comment: 11 pages, 9 postscript figures, accepted for publication on MNRA