The evolving spectrum of the planetary nebula Hen 2-260

We analysed the planetary nebula Hen 2-260 using optical spectroscopy and photometry. We compared our observations with the data from literature to search for evolutionary changes. The nebular line fluxes were modelled with the Cloudy photoionization code to derive the stellar and nebular parameters. The planetary nebula shows a complex structure and possibly a bipolar outflow. The nebula is relatively dense and young. The central star is just starting $\rm O^+$ ionization ($\rm T_{eff} \approx 30,000 \, K$). Comparison of our observations with literature data indicates a 50% increase of the [OIII] 5007 \AA\ line flux between 2001 and 2012. We interpret it as the result of the progression of the ionization of $\rm O^{+}$. The central star evolves to higher temperatures at a rate of $\rm 45 \pm 7\,K\, yr^{-1}$. The heating rate is consistent with a final mass of $\rm 0.626 ^{+0.003}_{-0.005} \, M_{\odot}$ or $\rm 0.645 ^{+0.008}_{-0.008} \, M_{\odot}$ for two different sets of post-AGB evolutionary tracks from literature. The photometric monitoring of Hen 2-260 revealed variations on a timescale of hours or days. The variability may be caused by pulsations of the star. The temperature evolution of the central star can be traced using spectroscopic observations of the surrounding planetary nebula spanning a timescale of roughly a decade. This allows us to precisely determine the stellar mass, since the pace of the temperature evolution depends critically on the core mass. The kinematical age of the nebula is consistent with the age obtained from the evolutionary track. The final mass of the central star is close to the mass distribution peak for central stars of planetary nebulae found in other studies. The object belongs to a group of young central stars of planetary nebulae showing photometric variability.Comment: accepted for publication in A&

Accurate determination of the free-free Gaunt factor. II - relativistic Gaunt factors

When modelling an ionised plasma, all spectral synthesis codes need the thermally averaged free-free Gaunt factor defined over a very wide range of parameter space in order to produce an accurate prediction for the spectrum. Until now no data set exists that would meet these needs completely. We have therefore produced a table of relativistic Gaunt factors over a much wider range of parameter space than has ever been produced before. We present tables of the thermally averaged Gaunt factor covering the range log10(gamma^2) = -6 to 10 and log10(u) = -16 to 13 for all atomic numbers Z = 1 through 36. The data were calculated using the relativistic Bethe-Heitler-Elwert (BHE) approximation and were subsequently merged with accurate non-relativistic results in those parts of the parameter space where the BHE approximation is not valid. These data will be incorporated in the next major release of the spectral synthesis code Cloudy. We also produced tables of the frequency integrated Gaunt factor covering the parameter space log10(gamma^2) = -6 to 10 for all values of Z between 1 and 36. All the data presented in this paper are available online.Comment: 8 pages, 8 figures, 2 table

Young poker faces: Compliance with the legal age limit on multiple gambling products in the Netherlands

Gambling is an activity that can be performed on-premise (slot machines in casinos, bars and restaurants) or off-premise (scratch cards and lottery tickets). Although the addictive potential may depend on the specific gambling product, early onset increases the likelihood for future pathological gambling. To delay the onset of gambling behavior and to reduce gambling-related problems, many countries have introduced age limits that should decrease the availability of gambling products to underage individuals. In this study we evaluated compliance to the legal age limit, making use of a mystery shopping method. We distinguished between (1) off-premise scratch cards (n = 51); (2) off-premise lottery tickets (n = 49); (3) on-premise slot machines in casinos (n = 88); and (4) on-premise slot machines in the catering industry (n = 100), and we focus on the factors, such as characteristics of the establishment, buyer, and vendor, that may account for possible differences. The 288 visits demonstrate that gambling products are highly available and accessible to under-aged customers; young customers are still able to gamble despite the legal regulations. The compliance rates fluctuate and appear to be related to the specific gambling product in question. Furthermore, age verification activities and certain outlet- and buyer characteristics, as well as characteristics associated with the purchase attempt, may influence compliance

Accurate determination of the free-free Gaunt factor; I - non-relativistic Gaunt factors

Modern spectral synthesis codes need the thermally averaged free-free Gaunt factor defined over a very wide range of parameter space in order to produce an accurate prediction for the spectrum emitted by an ionized plasma. Until now no set of data exists that would meet this need in a fully satisfactory way. We have therefore undertaken to produce a table of very accurate non-relativistic Gaunt factors over a much wider range of parameters than has ever been produced before. We first produced a table of non-averaged Gaunt factors, covering the parameter space log10(epsilon_i) = -20 to +10 and log10(w) = -30 to +25. We then continued to produce a table of thermally averaged Gaunt factors covering the parameter space log10(gamma^2) = -6 to +10 and log10(u) = -16 to +13. Finally we produced a table of the frequency integrated Gaunt factor covering the parameter space log10(gamma^2) = -6 to +10. All the data presented in this paper are available online.Comment: 10 pages, 5 tables, 3 figures. Fixed typo in Eq. 1

On the Evolved Nature of CK Vul

Original paper can be found at: http://www.astrosociety.org/pubs/cs/381.html Copyright ASPCK Vul was classified as the oldest observed nova. Recent studies have proven however, that CK Vul cannot be unambiguously classified as any known kind of eruptive variable. We present the optical and radio observations of the remnants of the eruption of CK Vul in the year 1670 in order to discuss possible scenarios for this object. We have measured the proper motion which proves that the nebula is attributed to the star observed during its 1670−1672 brightening. A large bipolar nebula of 70 arcsec is discovered in a deep Hα image. Radio observations reveal a barely resolved source placed in the expansion center of the ejecta

The challenges of urban ageing : making cities age-friendly in Europe

Urban ageing is an emerging domain that deals with the population of older people living in cities. The ageing of society is a positive yet challenging phenomenon, as population ageing and urbanisation are the culmination of successful human development. One could argue whether the city environment is an ideal place for people to grow old and live at an old age compared to rural areas. This viewpoint article explores and describes the challenges that are encountered when making cities age-friendly in Europe. Such challenges include the creation of inclusive neighbourhoods and the implementation of technology for ageing-in-place. Examples from projects in two age-friendly cities in The Netherlands (The Hague) and Poland (Cracow) are shown to illustrate the potential of making cities more tuned to the needs of older people and identify important challenges for the next couple of years. Overall, the global ageing of urban populations calls for more age-friendly approaches to be implemented in our cities. It is a challenge to prepare for these developments in such a way that both current and future generations of older people can benefit from age-friendly strategies

Grain size distributions and photo-electric heating in ionized media

Ever since the pioneering study of Spitzer, it has been widely recognized that grains play an important role in the heating and cooling of photo-ionized environments. A detailed code is necessary to model grains in a photo-ionized medium. In this paper we will use the spectral synthesis code Cloudy for this purpose. The grain model of this code has recently undergone a comprehensive upgrade. Part of this is the newly developed hybrid grain charge model, which will be described in detail. This model allows discrete charge states of very small grains to be modelled accurately while simultaneously avoiding the overhead of fully resolving the charge distribution of large grains, thus making the model both accurate and computationally efficient. A comprehensive comparison with the fully resolved charge state models of Weingartner & Draine (2001) shows that the agreement is very satisfactory for realistic size distributions. The effect of the grain size distribution on the line emission from photo-ionized regions is studied by taking standard models for an H II region and a planetary nebula and adding a dust component to the models with varying grain size distributions. A comparison of the models shows that varying the size distribution has a dramatic effect on the emitted spectrum, and affects the ionization balance as well. These results clearly demonstrate that the grain size distribution is an important parameter in photo-ionization models.Comment: 12 pages, 3 figures, 8 tables, minor typographical corrections wrt v