The age of 47Tuc from self-consistent isochrone fits to colour-magnitude diagrams and the eclipsing member V69

Our aim is to derive a self-consistent age, distance and composition for the globular cluster $47\,$Tucanae ($47\,$Tuc; NGC104). First, we reevaluate the reddening towards the cluster resulting in a nominal $E(B-V)=0.03\pm0.01$ as the best estimate. The $T_{\rm eff}$ of the components of the eclipsing binary member V69 is found to be $5900\pm72$ K from both photometric and spectroscopic evidence. This yields a true distance modulus $(m-M)_0=13.21\pm0.06$(random)$\pm0.03$(systematic) to $47\,$Tuc when combined with existing measurements of V69 radii and luminosity ratio. We then present a new completely self-consistent isochrone fitting method to ground based and $\textit{HST}$ cluster colour-magnitude diagrams and the eclipsing binary member V69. The analysis suggests that the composition of V69, and by extension one of the populations of $47\,$Tuc, is given by [Fe/H]$\sim-0.70$, [O/Fe]$\sim+0.60$, and $Y\sim0.250$ on the solar abundance scale of Asplund, Grevesse & Sauval. However, this depends on the accuracy of the model $T_{\rm eff}$ scale which is 50-75 K cooler than our best estimate but within measurement uncertainties. Our best estimate of the age of $47\,$Tuc is 11.8 Gyr, with firm ($3 \sigma$) lower and upper limits of 10.4 and 13.4 Gyr, respectively, in satisfactory agreement with the age derived from the white dwarf cooling sequence if our determination of the distance modulus is adopted.Comment: 19 pages, 8 figures, accepted for publication in MNRA

Age and helium content of the open cluster NGC 6791 from multiple eclipsing binary members. I. Measurements, methods, and first results

Earlier measurements of the masses and radii of the detached eclipsing binary V20 in the open cluster NGC 6791 were accurate enough to demonstrate that there are significant differences between current stellar models. Here we improve on those results and add measurements of two additional detached eclipsing binaries, the cluster members V18 and V80. The enlarged sample sets much tighter constraints on the properties of stellar models than has hitherto been possible, thereby improving both the accuracy and precision of the cluster age. We employed (i) high-resolution UVES spectroscopy of V18, V20 and V80 to determine their spectroscopic effective temperatures, [Fe/H] values, and spectroscopic orbital elements, and (ii) time-series photometry from the Nordic Optical Telescope to obtain the photometric elements. The masses and radii of the V18 and V20 components are found to high accuracy, with errors on the masses in the range 0.27-0.36% and errors on the radii in the range 0.61-0.92%. V80 is found to be magnetically active, and more observations are needed to determine its parameters accurately. The metallicity of NGC 6791 is measured from disentangled spectra of the binaries and a few single stars to be [Fe/H]= +0.29 \pm 0.03 (random) \pm 0.07 (systematic). The cluster reddening and apparent distance modulus are found to be E(B - V) = 0.160 \pm 0.025 and (m - M)V = 13.51 \pm 0.06 . A first model comparison shows that we can constrain the helium content of the NGC 6791 stars, and thus reach a more accurate age than previously possible. It may be possible to constrain additional parameters, in particular the C, N, and O abundances. This will be investigated in paper II.Comment: Accepted for publication in A&

NGC 6819: testing the asteroseismic mass scale, mass loss, and evidence for products of non-standard evolution

We present an extensive peakbagging effort on Kepler data of $\sim$50 red giant stars in the open star cluster NGC 6819. By employing sophisticated pre-processing of the time series and Markov Chain Monte Carlo techniques we extracted individual frequencies, heights and linewidths for hundreds of oscillation modes. We show that the "average" asteroseismic parameter $\delta\nu_{02}$, derived from these, can be used to distinguish the stellar evolutionary state between the red giant branch (RGB) stars and red clump (RC) stars. Masses and radii are estimated using asteroseismic scaling relations, both empirically corrected to obtain self-consistency as well as agreement with independent measures of distance, and using updated theoretical corrections. Remarkable agreement is found, allowing the evolutionary state of the giants to be determined exclusively from the empirical correction to the scaling relations. We find a mean mass of the RGB stars and RC stars in NGC 6819 to be $1.61\pm0.02\,\textrm{M}_\odot$ and $1.64{\pm}0.02\,\textrm{M}_\odot$, respectively. The difference $\Delta M=-0.03\pm0.01\,\textrm{M}_\odot$ is almost insensitive to systematics, suggesting very little RGB mass loss, if any. Stars that are outliers relative to the ensemble reveal overmassive members that likely evolved via mass-transfer in a blue straggler phase. We suggest that KIC 4937011, a low-mass Li-rich giant, is a cluster member in the RC phase that experienced very high mass-loss during its evolution. Such over- and undermassive stars need to be considered when studying field giants, since the true age of such stars cannot be known and there is currently no way to distinguish them from normal stars.Comment: 21 pages, 11 figure

Training materials for different categories of users

Agricultural and Food Policy, Environmental Economics and Policy, Farm Management, Land Economics/Use, Production Economics, Teaching/Communication/Extension/Profession,

Life cycle assessment of waste prevention

Waste prevention is part of the solution towards circular economy and sustainable consumption. Electronic equipment is known for containing scarce resources and the recycling of these is seen as important. Long lifetime of some electronic products leads to energy consumption during use phase being the most important process for the total impacts from the life cycle. By preventing waste and extending the lifetime of electronics, resources are kept in the loop for a longer period saving the extraction and use of virgin resources. It should be considered if, keeping scarce resources in the loop, will lead to keeping products having low energy efficiency in the loop. A case study was carried out, assessing the environmental impacts from the use and consumption pattern of refrigerators as the electronic product. The study compared two scenarios providing the same functional unit: Cooling of food (5 degrees Celsius) by a 240L refrigerator for 30 years in Denmark during the period 2015-2045. The full lifetime of the refrigerator was assessed including production, use and waste management. The two scenarios assessed were: 1) use of a refrigerator for 10 years and 2) use of a refrigerator with an extended lifetime of 5 years being in total 15 years of use. Both scenarios were assessed for an old refrigerator with a low energy class and a newer refrigerator with a high energy class. Both scenarios were also assessed with substituting the refrigerator in use with one with the same energy class or with one with a more efficient energy class. The assessment showed that the use phase becomes less important, and the production phase becomes the main contributor to the potential environmental impacts when choosing an electronic product with high energy efficiency. Meaning the extraction and production of materials and the assembling of the refrigerator becomes more important when the energy efficiency during use is high. During the life time of electronics the sealing of refrigerators gets worn and the compressor becomes less efficient. Thereby increasing energy consumption is seen for all kinds of electronic devices during the lifetime. It is described in literature that refrigerators tends to have larger energy loss over time than other electronic devices. Therefore the change of energy consumption of scenario 2 was assessed for the two scenarios to have equal potential environmental impacts. For an old refrigerator with low energy efficiency the energy consumption should only increase by ~15% over a period of 30 years consumption time. For the newer refrigerator the change should be ~49% for the two scenarios to have equal environmental impacts. From the assessment it was concluded that it leads to lower potential environmental impacts to replace an old refrigerator with low energy class after 10 years use by a new refrigerator, and again change this to a more energy efficient one after 10 years use (Scenario 1 with substitution to more efficient energy class), than to reuse an old refrigerator with low energy class (Scenario 2 with substitution to same energy class). The study also concludes that it leads to even lower potential environmental impacts to reuse an old refrigerator and replacing it at the end of life with a new one with high energy efficiency, which is also reused to have an extended lifetime (Scenario 2 with substitution to more efficient energy class). The lowest environmental impacts were found by extending the lifetime of refrigerators (Scenario 2) with high energy efficiency. In this way as less energy as possible is used during the use phase, and resources are kept in the loop for as long as possible

The [Y/Mg] clock works for evolved solar metallicity stars

Previously [Y/Mg] has been proven to be an age indicator for solar twins. Here, we investigate if this relation also holds for helium-core-burning stars of solar metallicity. High resolution and high signal-to-noise ratio (S/N) spectroscopic data of stars in the helium-core-burning phase have been obtained with the FIES spectrograph on the NOT 2.56m telescope and the HIRES spectrograph on the Keck I 10 m telescope. They have been analyzed to determine the chemical abundances of four open clusters with close to solar metallicity; NGC 6811, NGC 6819, M67 and NGC 188. The abundances are derived from equivalent widths of spectral lines using ATLAS9 model atmospheres with parameters determined from the excitation and ionization balance of Fe lines. Results from asteroseismology and binary studies were used as priors on the atmospheric parameters, where especially the $\log g$ is determined to much higher precision than what is possible with spectroscopy. It is confirmed that the four open clusters are close to solar metallicity and they follow the [Y/Mg] vs. age trend previously found for solar twins. The [Y/Mg] vs. age clock also works for giant stars in the helium-core burning phase, which vastly increases the possibilities to estimate the age of stars not only in the solar neighborhood, but in large parts of the Galaxy, due to the brighter nature of evolved stars compared to dwarfs.Comment: 5 pages, 3 figures, accepted for publication as a Letter to A&

KIC 8410637: a 408-day period eclipsing binary containing a pulsating red giant

Detached eclipsing binaries (dEBs) are ideal targets for accurate measurement of masses and radii of ther component stars. If at least one of the stars has evolved off the main sequence (MS), the masses and radii give a strict constraint on the age of the stars. Several dEBs containing a bright K giant and a fainter MS star have been discovered by the Kepler satellite. The mass and radius of a red giant (RG) star can also be derived from its asteroseismic signal. The parameters determined in this way depend on stellar models and may contain systematic errors. It is important to validate the asteroseismically determined mass and radius with independent methods. This can be done when stars are members of stellar clusters or members of dEBs. KIC 8410637 consists of an RG and an MS star. The aim is to derive accurate masses and radii for both components and provide the foundation for a strong test of the asteroseismic method and the accuracy of the deduced mass, radius and age. We analyse high-resolution spectra from three different spectrographs. We also calculate a fit to the Kepler light curve and use ground-based photometry to determine the flux ratios between the component stars in the BVRI passbands. We measured the masses and radii of the stars in the dEB, and the classical parameters Teff, log g and [Fe/H] from the spectra and ground-based photometry. The RG component of KIC 8410637 is most likely in the core helium-burning red clump phase of evolution and has an age and composition very similar to the stars in the open cluster NGC 6819. The mass of the RG in KIC 8410637 should therefore be similar to the mass of RGs in NGC 6819, thus lending support to the most up-to-date version of the asteroseismic scaling relations. This is the first direct measurement of both mass and radius for an RG to be compared with values for RGs from asteroseismic scaling relations.Comment: Accepted 20.6.2013 for publication in Astronomy and Astrophysic

The mass and age of the first SONG target: the red giant 46 LMi

Context. The Stellar Observation Network Group (SONG) is an initiative to build a worldwide network of 1m telescopes with high-precision radial-velocity spectrographs. Here we analyse the first radial-velocity time series of a red-giant star measured by the SONG telescope at Tenerife. The asteroseismic results demonstrate a major increase in the achievable precision of the parameters for red-giant stars obtainable from ground-based observations. Reliable tests of the validity of these results are needed, however, before the accuracy of the parameters can be trusted. Aims. We analyse the first SONG time series for the star 46 LMi, which has a precise parallax and an angular diameter measured from interferometry, and therefore a good determination of the stellar radius. We use asteroseismic scaling relations to obtain an accurate mass, and modelling to determine the age. Methods. A 55-day time series of high-resolution, high S/N spectra were obtained with the first SONG telescope. We derive the asteroseismic parameters by analysing the power spectrum. To give a best guess on the large separation of modes in the power spectrum, we have applied a new method which uses the scaling of Kepler red-giant stars to 46 LMi. Results. Several methods have been applied: classical estimates, seismic methods using the observed time series, and model calculations to derive the fundamental parameters of 46 LMi. Parameters determined using the different methods are consistent within the uncertainties. We find the following values for the mass M (scaling), radius R (classical), age (modelling), and surface gravity (combining mass and radius): M = 1.09 ± 0.04 M⊙, R = 7.95 ± 0.11 R⊙ age t = 8.2 ± 1.9 Gy, and log g = 2.674 ± 0.013. Conclusions. The exciting possibilities for ground-based asteroseismology of solar-like oscillations with a fully robotic network have been illustrated with the results obtained from just a single site of the SONG network. The window function is still a severe problem which will be solved when there are more nodes in the network

The M4 Core Project with HST --- I. Overview and First-Epoch

We present an overview of the ongoing Hubble Space Telescope large program GO-12911. The program is focused on the core of M4, the nearest Galactic globular cluster, and the observations are designed to constrain the number of binaries with massive companions (black holes, neutron stars, or white dwarfs) by measuring the ``wobble'' of the luminous (main-sequence) companion around the center of mass of the pair, with an astrometric precision of ~50 micro-arcseconds. The high spatial resolution and stable medium-band PSFs of WFC3/UVIS will make these measurements possible. In this work we describe: (i) the motivation behind this study, (ii) our observing strategy, (iii) the many other investigations enabled by this unique data set, and which of those our team is conducting, and (iv) a preliminary reduction of the first-epoch data-set collected on October 10, 2012.Comment: 25 pages, 14 figures (9 at low resolution), 3 tables. Published in: Astronomische Nachrichten, Volume 334, Issue 10, pages 1062-1085, December 2013. http://onlinelibrary.wiley.com/doi/10.1002/asna.201311911/abstrac