Variable stars in the globular cluster M28 (NGC 6626)

We present a new search for variable stars in the Galactic globular cluster M28 (NGC 6626). The search is based on a series of BVI images obtained with the SMARTS Consortium's 1.3m telescope at Cerro Tololo Inter-American Observatory, Chile. The search was carried out using the ISIS v2.2 image subtraction package. We find a total of 25 variable stars in the field of the cluster, 9 being new discoveries. Of the newly found variables, 1 is an ab-type RR Lyrae star, 6 are c-type RR Lyrae, and 2 are long-period/semi-regular variables. V22, previously classified as a type II Cepheid, appears as a bona-fide RRc in our data. In turn, V20, previously classified as an ab-type RR Lyrae, could not be properly phased with any reasonable period. The properties of the ab-type RR Lyrae stars in M28 appear most consistent with an Oosterhoff-intermediate classification, which is unusual for bona-fide Galactic globulars clusters. However, the cluster's c-type variables do not clearly support such an Oosterhoff type, and a hybrid Oosterhoff I/II system is accordingly another possibility, thus raising the intriguing possibility of multiple populations being present in M28. Coordinates, periods, and light curves in differential fluxes are provided for all the detected variables.Comment: A&A, in pres

Proper motions in the VVV Survey: Results for more than 15 million stars across NGC 6544

Context: In the last six years, the VVV survey mapped 562 sq. deg. across the bulge and southern disk of the Galaxy. However, a detailed study of these regions, which includes $\sim 36$ globular clusters (GCs) and thousands of open clusters is by no means an easy challenge. High differential reddening and severe crowding along the line of sight makes highly hamper to reliably distinguish stars belonging to different populations and/or systems. Aims: The aim of this study is to separate stars that likely belong to the Galactic GC NGC 6544 from its surrounding field by means of proper motion (PM) techniques. Methods: This work was based upon a new astrometric reduction method optimized for images of the VVV survey. Results: Photometry over the six years baseline of the survey allowed us to obtain a mean precision of $\sim0.51$ mas/yr, in each PM coordinate, for stars with Ks < 15 mag. In the area studied here, cluster stars separate very well from field stars, down to the main sequence turnoff and below, allowing us to derive for the first time the absolute PM of NGC 6544. Isochrone fitting on the clean and differential reddening corrected cluster color magnitude diagram yields an age of $\sim$ 11-13 Gyr, and metallicity [Fe/H] = -1.5 dex, in agreement with previous studies restricted to the cluster core. We were able to derive the cluster orbit assuming an axisymmetric model of the Galaxy and conclude that NGC 6544 is likely a halo GC. We have not detected tidal tail signatures associated to the cluster, but a remarkable elongation in the galactic center direction has been found. The precision achieved in the PM determination also allows us to separate bulge stars from foreground disk stars, enabling the kinematical selection of bona fide bulge stars across the whole survey area. Our results show that VVV data is perfectly suitable for this kind of analysis.Comment: 13 pages, 12 figures, accepted in A&

The VVV Survey RR Lyrae Population in the Galactic Center Region

Indexación: Scopus.We gratefully acknowledge the use of data from the ESO Public Survey program ID 179.B-2002 taken with the VISTA telescope, and data products from the Cambridge Astronomical Survey Unit (CASU). Support for the authors is provided by the BASAL Center for Astrophysics and Associated Technologies (CATA) through grant PFB-06, and the Ministry for the Economy, Development, and Tourism, Programa Iniciativa Cientifica Milenio through grant IC120009, awarded to the Millennium Institute of Astrophysics (MAS). D.M. and M.Z. acknowledge support from FONDECYT Regular grants No. 1170121, and 1150345, respectively. P.H. acknowledges financial support from FONDECYT regular grant 1170305. F.G. acknowledge support from CONICYT-PCHA Doctorado Nacional 2017-21171485 and Proyecto Fondecyt Regular 1150345. J.A.-G. acknowledges support by FONDECYT Iniciacion 11150916. D.M. is also grateful for the hospitality of the Vatican Observatory. This research made use of Astropy, a community-developed core Python package for astronomy; Scikit-learn, NumPy, and matplotlib, a Python library for publication-quality graphics; and Aladin Sky Atlas, developed at CDS, Strasbourg Observatory, France, and TOPCAT.Deep near-IR images from the VISTA Variables in the V a L ctea (VVV) Survey were used to search for RR Lyrae stars within 100 arcmin from the Galactic Center. A large sample of 960 RR Lyrae of type ab (RRab) stars were discovered. A catalog is presented featuring the positions, magnitudes, colors, periods, and amplitudes for the sample, in addition to estimated reddenings, distances, and metallicities, and measured individual relative proper motions. We use the reddening-corrected Wesenheit magnitudes, defined as WKs Ks 0.428 J Ks = - ( - ), in order to isolate bona fide RRL belonging to the Galaxy Center, finding that 30 RRab are foreground/background objects. We measure a range of extinctions from AKs 0.19 = to 1.75 mag for the RRab in this region, finding that large extinction is the main cause of the sample incompleteness. The mean period is P =0.5446±0.0025 days, yielding a mean metallicity of [Fe/H] =-1.30±0.01 (ς = 0.33) dex for the RRab sample in the Galactic Center region. The median distance for the sample is D =8.05±0.02 kpc. We measure the RRab surface density using the less reddened region sampled here, finding a density of 1000 RRab/sq deg at a projected Galactocentric distance RG =1.6 deg. Under simple assumptions, this implies a large total mass (M>109Me) for the old and metal-poor population contained inside RG. We also measure accurate relative proper motions, from which we derive tangential velocity dispersions of ςVl =125.0 and ςVb =124.1 km s-1 along the Galactic longitude and latitude coordinates, respectively. The fact that these quantities are similar indicate that the bulk rotation of the RRab population is negligible, and implies that this population is supported by velocity dispersion. In summary, there are two main conclusions of this study. First, the population as a whole is no different from the outer bulge RRab, predominantly a metal-poor component that is shifted with respect to the Oosterhoff type I population defined by the globular clusters in the halo. Second, the RRab sample, as representative of the old and metal-poor stellar population in the region, has high velocity dispersions and zero rotation, suggesting a formation via dissipational collapse. ©2018. The American Astronomical Society. All rights reserved.https://iopscience.iop.org/article/10.3847/1538-4357/aacf9

Extinction ratios in the inner Galaxy as revealed by the VVV survey

Accepted for publication in ApJ Letters, 10 pages, 3 Figures, 2 Tables © 2017 The American Astronomical Society. All rights reserved.Interstellar extinction towards the Galactic Center is large and significantly differential. Its reddening and dimming effects in red clump stars in the Galactic Bulge can be exploited to better constrain the extinction law towards the innermost Galaxy. By virtue of a deep and complete catalog of more than 30 million objets at $|l|\le2.7\deg$ and $|b|\le1.55\deg$ obtained from VVV survey observations, we apply the red clump method to infer the selective-to-total extinction ratios in the $Z$, $Y$, $J$, $H$ and $K_s$ broadband near-infrared filters. The measured values are smaller than previously reported, and are not constant, with mean values, e.g., $A_{K_S}/E(J-K_s)=0.428\pm0.005\pm0.04$ and $A_{K_S}/E(H-K_s)=1.104\pm0.022\pm0.2$. We also obtain a ratio $A_Z$:$A_Y$:$A_J$:$A_H$:$A_{K_S}$ of 7.74:5.38:3.30:1.88:1.0, implying extinction towards the Galactic Center to follow a distribution as a function of wavelength steeper than previously reported, consistent with a power law $A_{\lambda}\propto{\lambda}^{-2.47}$ in the near-infrared.Peer reviewedFinal Accepted Versio

SW @ SPAIN

Executive Summary: This report provides information about the current state of the art in Semantic Web research in Spain. The contents of this report are mainly based on the information that was gathered during the workshop "Ontologías y Web Semántica 2005", which was held in Santiago de Compostela in November 2005, and the contributions that members from most of the research groups working in Semantic-Webrelated areas in Spain have provided. The field of Semantic Web is quite widespread in Spain, with important groups developing methods, techniques and tools to support different areas: Ontological Engineering, semantic extraction and annotation from heterogeneous sources, semantic search engines, personalisation and Semantic Web Services

Molecular control of winter dormancy in establishment in trees

Dormancy is an adaptive mechanism that enables woody plants to survive the freezing temperatures of winter. This complex process is characterized by the cessation of meristem activity, which is accompanied by winter bud set, extensive metabolic remodelling, an acquired high tolerance to cold and, in deciduous trees, by leaf senescence and abscission. The induction of dormancy occurs in response to seasonal environmental signals. In most woody plants, shortening of the photoperiod induces growth cessation, bud set, and some degree of cold acclimation. The subsequent drop in temperature then leads to a greater tolerance to cold and leaf fall. Experimental evidence indicates that the phytochrome system plays an important role as a day length sensor, and it has been recently reported that in poplar (Populus tremula x tremuloides), the photoperiodic control of dormancy induction is driven by a molecular mechanism that shares components with the mechanism of the photoperiodic control of flowering time in Arabidopsis. In contrast, the effects of low temperatures are less well understood. Nonetheless, it has been established that the chestnut (Castanea sativa Mill.) circadian molecular clock is disrupted both during winter and in response to cold, with presumable consequences on the general physiology of the plant. However, there is no direct evidence so far for its role in dormancy regulatio

Milky Way demographics with the VVV survey. IV. PSF photometry from almost one billion stars in the Galactic bulge and adjacent southern disk

Accepted for publication in a forthcoming issue of Astronomy & Astrophysics. Reproduced with permission from Astronomy & Astrophysics. © 2018 ESO.Context. The inner regions of the Galaxy are severely affected by extinction, which limits our capability to study the stellar populations present there. The Vista Variables in the Vía Láctea (VVV) ESO Public Survey has observed this zone at near-infrared wavelengths where reddening is highly diminished. Aims. By exploiting the high resolution and wide field-of-view of the VVV images we aim to produce a deep, homogeneous, and highly complete database of sources that cover the innermost regions of our Galaxy. Methods. To better deal with the high crowding in the surveyed areas, we have used point spread function (PSF)-fitting techniques to obtain a new photometry of the VVV images, in the ZY JHK s near-infrared filters available. Results. Our final catalogs contain close to one billion sources, with precise photometry in up to five near-infrared filters, and they are already being used to provide an unprecedented view of the inner Galactic stellar populations. We make these catalogs publicly available to the community. Our catalogs allow us to build the VVV giga-CMD, a series of color-magnitude diagrams of the inner regions of the Milky Way presented as supplementary videos. We provide a qualitative analysis of some representative CMDs of the inner regions of the Galaxy, and briefly mention some of the studies we have developed with this new dataset so far.Peer reviewe