A. Aparicio - Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain

A. Aparicio
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Name
A. Aparicio
Affiliation
Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain
City
San Cristóbal de La Laguna
Country
Spain

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Astrophysics of Galaxies (29)
 
Solar and Stellar Astrophysics (25)
 
Cosmology and Nongalactic Astrophysics (5)
 
Earth and Planetary Astrophysics (2)
 
Instrumentation and Methods for Astrophysics (2)
 
Physics - Atmospheric and Oceanic Physics (1)
 
Physics - History of Physics (1)
 
Physics - Instrumentation and Detectors (1)
 
High Energy Physics - Experiment (1)

Publications Authored By A. Aparicio

The ongoing surveys of galaxies and those for the next generation of telescopes will demand the execution of high-CPU consuming machine codes for recovering detailed star formation histories (SFHs) and hence age-metallicity relationships (AMRs). We present here an expeditive method which provides quick-look AMRs on the basis of representative ages and metallicities obtained from colour-magnitude diagram (CMD) analyses. We have tested its perfomance by generating synthetic CMDs for a wide variety of galaxy SFHs. Read More

2016Dec
Authors: MicroBooNE Collaboration, R. Acciarri, C. Adams, R. An, A. Aparicio, S. Aponte, J. Asaadi, M. Auger, N. Ayoub, L. Bagby, B. Baller, R. Barger, G. Barr, M. Bass, F. Bay, K. Biery, M. Bishai, A. Blake, V. Bocean, D. Boehnlein, V. D. Bogert, T. Bolton, L. Bugel, C. Callahan, L. Camilleri, D. Caratelli, B. Carls, R. Castillo Fernandez, F. Cavanna, S. Chappa, H. Chen, K. Chen, C. Y. Chi, C. S. Chiu, E. Church, D. Cianci, G. H. Collin, J. M. Conrad, M. Convery, J. Cornele, P. Cowan, J. I. Crespo-Anadon, G. Crutcher, C. Darve, R. Davis, M. Del Tutto, D. Devitt, S. Duffin, S. Dytman, B. Eberly, A. Ereditato, D. Erickson, L. Escudero Sanchez, J. Esquivel, S. Farooq, J. Farrell, D. Featherston, B. T. Fleming, W. Foreman, A. P. Furmanski, V. Genty, M. Geynisman, D. Goeldi, B. Goff, S. Gollapinni, N. Graf, E. Gramellini, J. Green, A. Greene, H. Greenlee, T. Griffin, R. Grosso, R. Guenette, A. Hackenburg, R. Haenni, P. Hamilton, P. Healey, O. Hen, E. Henderson, J. Hewes, C. Hill, K. Hill, L. Himes, J. Ho, G. Horton-Smith, D. Huffman, C. M. Ignarra, C. James, E. James, J. Jan de Vries, W. Jaskierny, C. M. Jen, L. Jiang, B. Johnson, M. Johnson, R. A. Johnson, B. J. P. Jones, J. Joshi, H. Jostlein, D. Kaleko, L. N. Kalousis, G. Karagiorgi, T. Katori, P. Kellogg, W. Ketchum, J. Kilmer, B. King, B. Kirby, M. Kirby, E. Klein, T. Kobilarcik, I. Kreslo, R. Krull, R. Kubinski, G. Lange, F. Lanni, A. Lathrop, A. Laube, W. M. Lee, Y. Li, D. Lissauer, A. Lister, B. R. Littlejohn, S. Lockwitz, D. Lorca, W. C. Louis, G. Lukhanin, M. Luethi, B. Lundberg, X. Luo, G. Mahler, I. Majoros, D. Makowiecki, A. Marchionni, C. Mariani, D. Markley, J. Marshall, D. A. Martinez Caicedo, K. T. McDonald, D. McKee, A. McLean, J. Mead, V. Meddage, T. Miceli, G. B. Mills, W. Miner, J. Moon, M. Mooney, C. D. Moore, Z. Moss, J. Mousseau, R. Murrells, D. Naples, P. Nienaber, B. Norris, N. Norton, J. Nowak, M. OBoyle, T. Olszanowski, O. Palamara, V. Paolone, V. Papavassiliou, S. F. Pate, Z. Pavlovic, R. Pelkey, M. Phipps, S. Pordes, D. Porzio, G. Pulliam, X. Qian, J. L. Raaf, V. Radeka, A. Rafique, R. A Rameika, B. Rebel, R. Rechenmacher, S. Rescia, L. Rochester, C. Rudolf von Rohr, A. Ruga, B. Russell, R. Sanders, W. R. Sands III, M. Sarychev, D. W. Schmitz, A. Schukraft, R. Scott, W. Seligman, M. H. Shaevitz, M. Shoun, J. Sinclair, W. Sippach, T. Smidt, A. Smith, E. L. Snider, M. Soderberg, M. Solano-Gonzalez, S. Soldner-Rembold, S. R. Soleti, J. Sondericker, P. Spentzouris, J. Spitz, J. St. John, T. Strauss, K. Sutton, A. M. Szelc, K. Taheri, N. Tagg, K. Tatum, J. Teng, K. Terao, M. Thomson, C. Thorn, J. Tillman, M. Toups, Y. T. Tsai, S. Tufanli, T. Usher, M. Utes, R. G. Van de Water, C. Vendetta, S. Vergani, E. Voirin, J. Voirin, B. Viren, P. Watkins, M. Weber, T. Wester, J. Weston, D. A. Wickremasinghe, S. Wolbers, T. Wongjirad, K. Woodruff, K. C. Wu, T. Yang, B. Yu, G. P. Zeller, J. Zennamo, C. Zhang, M. Zuckerbrot

This paper describes the design and construction of the MicroBooNE liquid argon time projection chamber and associated systems. MicroBooNE is the first phase of the Short Baseline Neutrino program, located at Fermilab, and will utilize the capabilities of liquid argon detectors to examine a rich assortment of physics topics. In this document details of design specifications, assembly procedures, and acceptance tests are reported. Read More

The Hubble Space Telescope (HST) UV Legacy Survey of Galactic Globular Clusters (GO-13297) has been specifically designed to complement the existing F606W and F814W observations of the Advanced Camera for Surveys (ACS) Globular Cluster Survey (GO-10775) by observing the most accessible 47 of the previous survey's 65 clusters in three WFC3/UVIS filters F275W, F336W, and F438W. The new survey also adds super-solar metallicity open cluster NGC 6791 to increase the metallicity diversity. The combined survey provides a homogeneous 5-band data set that can be used to pursue a broad range of scientific investigations. Read More

We use high-precision photometry of red-giant-branch (RGB) stars in 57 Galactic globular clusters (GCs), mostly from the `Hubble Space Telescope (HST) UV Legacy Survey of Galactic globular clusters', to identify and characterize their multiple stellar populations. For each cluster the pseudo two-color diagram (or `chromosome map') is presented, built with a suitable combination of stellar magnitudes in the F275W, F336W, F438W and F814W filters that maximizes the separation between multiple populations. In the chromosome map of most GCs (Type I clusters), stars separate in two distinct groups that we identify with the first (1G) and the second generation (2G). Read More

We describe a revised collection of the number of sunspot groups from 1610 to the present. This new collection is based on the work of Hoyt and Schatten (Solar Phys. 179, 189, 1998). Read More

Due to their extreme helium abundance, the multiple stellar populations of the globular cluster NGC 2808 have been widely investigated from a photometric, spectroscopic, and kinematic perspective. The most striking feature of the color-magnitude diagram of NGC 2808 is the triple main sequence (MS), with the red MS corresponding to a stellar population with primordial helium, and the middle and the blue MS being enhanced in helium up to Y$\sim$0.32 and $\sim$0. Read More

The solar diameter has been monitored at the Royal Observatory of the Spanish Navy (today the Real Instituto y Observatorio de la Armada: ROA) almost continuously since its creation in 1753 (i.e. during the last quarter of a millennium). Read More

The Initial Star formation and Lifetimes of Andromeda Satellites (ISLAndS) project uses Hubble Space Telescope imaging to study a representative sample of six Andromeda dSph satellite companion galaxies. The main goal of the program is to determine whether the star formation histories (SFHs) of the Andromeda dSph satellites demonstrate significant statistical differences from those of the Milky Way, which may be attributable to the different properties of their local environments. Our observations reach the oldest main sequence turn-offs, allowing a time resolution at the oldest ages of ~ 1 Gyr, which is comparable to the best achievable resolution in the MW satellites. Read More

We present a novel analysis of the internal kinematics of the Fornax dwarf spheroidal galaxy. Our results are based on the largest sample of spectroscopic data for Fornax stars presently available ($> 2500$ stars), for which we have chemical and kinematic information. We introduce new software, Beacon, designed to detect chemo-kinematic patterns among stars of different stellar populations using their metallicity and velocity along the line of sight. Read More

We report the discovery of an optical Einstein Ring in the Sculptor constellation, IAC J010127-334319, in the vicinity of the Sculptor Dwarf Spheroidal Galaxy. It is an almost complete ring ($\sim 300^{\circ}$) with a diameter of $\sim 4.5\, {\rm arcsec}$. Read More

The analysis of the early star formation history (SFH) of nearby galaxies, obtained from their resolved stellar populations is relevant as a test for cosmological models. However, the early time resolution of observationally derived SFHs is limited by several factors. Thus, direct comparison of observationally derived SFHs with those derived from theoretical models of galaxy formation is potentially biased. Read More

The UV-initiative Hubble Space Telescope Treasury survey of Galactic globular clusters provides a new window into the phenomena that shape the morphological features of the horizontal branch (HB). Using this large and homogeneous catalog of UV and blue photometry, we demonstrate that the HB exhibits discontinuities that are remarkably consistent in color (effective temperature). This consistency is apparent even among some of the most massive clusters hosting multiple distinct sub-populations (such as NGC 2808, omega Cen, and NGC 6715), demonstrating that these phenomena are primarily driven by atmospheric physics that is independent of the underlying population properties. Read More

The globular cluster 47 Tuc exhibits a complex sub-giant branch (SGB) with a faint-SGB comprising only about the 10% of the cluster mass and a bright-SGB hosting at least two distinct populations.We present a spectroscopic analysis of 62 SGB stars including 21 faint-SGB stars. We thus provide the first chemical analysis of the intriguing faint-SGB population and compare its abundances with those of the dominant populations. Read More

Based on data aquired in 13 orbits of HST time, we present a detailed evolutionary history of the M31 dSph satellite Andromeda XVI, including its life-time star formation history, the spatial distribution of its stellar populations, and the properties of its variable stars. And XVI is characterized by prolonged star formation activity from the oldest epochs until star formation was quenched ~6 Gyr ago, and, notably, only half of the mass in stars of And XVI was in place 10 Gyr ago. And XVI appears to be a low mass galaxy for which the early quenching by either reionization or starburst feedback seems highly unlikely, and thus, is most likely due to an environmental effect (e. Read More

Open clusters (OCs) are crucial for studying the formation and evolution of the Galactic disc. However, the lack of a large number of OCs analyzed homogeneously hampers the investigations about chemical patterns and the existence of Galactocentric radial and vertical gradients, or an age-metallicity relation. To overcome this, we have designed the Open Cluster Chemical Abundances from Spanish Observatories survey (OCCASO). Read More

Open cluster (OC) stars share the same age and metallicity, and, in general, their age and mass can be estimated with higher precision than for field stars. For this reason, OCs are considered an important laboratory to study the relation between the physical properties of the planets and those of their host stars, and the evolution of planetary systems. We started an observational campaign within the GAPS collaboration to search for and characterize planets in OCs We monitored the Praesepe member Pr0211 to improve the eccentricity of the Hot-Jupiter (HJ) already known to orbit this star and search for additional planets. Read More

We present a comprehensive and detailed study of the stellar populations of the Fornax dwarf spheroidal galaxy. We analyse their spatial distributions along the main body of the galaxy, obtaining their surface density maps, together with their radial density profiles. Results are based on the largest and most complete catalogue of stars in Fornax, with more than $3. Read More

Accurate star formation histories (SFHs) of galaxies are fundamental for understanding the build-up of their stellar content. However, the most accurate SFHs - those obtained from colour-magnitude diagrams (CMDs) of resolved stars reaching the oldest main sequence turnoffs (oMSTO) - are presently limited to a few systems in the Local Group. It is therefore crucial to determine the reliability and range of applicability of SFHs derived from integrated light spectroscopy, as this affects our understanding of unresolved galaxies from low to high redshift. Read More

2015Jul
Affiliations: 1IAC, 2IAC, 3U. Zurich, 4IAC, 5IAC, 6ROE, 7INAF, 8U. Tasmania, 9Raytheon, 10IAC, 11IAC, 12U. Victoria, 13Kapteyn, 14U. Minnesota, 15NRC, Canada, 16U. Washington

We discuss how knowledge of the whole evolutionary history of dwarf galaxies, including details on the early star formation events, can provide insight on the origin of the different dwarf galaxy types. We suggest that these types may be imprinted by the early conditions of formation rather than being only the result of a recent morphological transformation driven by environmental effects. We present precise star formation histories of a sample of Local Group dwarf galaxies, derived from colour-magnitude diagrams reaching the oldest main-sequence turnoffs. Read More

We present a method to identify Ultra Faint Dwarf Galaxy (UFDG) candidates in the halo of the Milky Way using the future Gaia catalogue and we explore its detection limits and completeness. The method is based on the Wavelet Transform and searches for over-densities in the combined space of sky coordinates and proper motions, using kinematics in the search for the first time. We test the method with a Gaia mock catalogue that has the Gaia Universe Model Snapshot (GUMS) as a background, and use a library of around 30 000 UFDGs simulated as Plummer spheres with a single stellar population. Read More

In this paper we combine WFC3/UVIS F275W, F336W, and F438W data from the "UV Legacy Survey of Galactic Globular Clusters: Shedding Light on Their Populations and Formation" (GO-13297) HST Treasury program with F606W, F625W, F658N, and F814W ACS archive data for a multi-wavelength study of the globular cluster NGC 6352. In the color-magnitude and two-color diagrams obtained with appropriate combination of the photometry in the different bands we separate two distinct stellar populations and trace them from the main sequence to the subgiant, red giant, horizontal and asymptotic giant branches. We infer that the two populations differ in He by Delta Y=0. Read More

We present precision radial velocities and stellar population parameters for 77 star clusters in the Local Group galaxy M33. Our GTC and WHT observations sample both young, massive clusters and known/candidate globular clusters, spanning ages ~ 10^6 - 10^10 yr, and metallicities, [M/H] ~-1.7 to solar. Read More

Recent studies have shown that the extended main-sequence turn off (eMSTO) is a common feature of intermediate-age star clusters in the Magellanic Clouds (MCs). The most simple explanation is that these stellar systems harbor multiple generations of stars with an age difference of a few hundred Myrs. However, while an eMSTO has been detected in a large number of clusters with ages between ~1-2 Gyrs, several studies of young clusters in both MCs and in nearby galaxies do not find any evidence for a prolonged star-formation history, i. Read More

We present a high resolution spectroscopic analysis of 62 red giants in the Milky Way globular cluster NGC5286. We have determined abundances of representative light proton-capture, alpha, Fe-peak and neutron-capture element groups, and combined them with photometry of multiple sequences observed along the colour-magnitude diagram. Our principal results are: (i) a broad, bimodal distribution in s-process element abundance ratios, with two main groups, the s-poor and s-rich groups; (ii) substantial star-to-star Fe variations, with the s-rich stars having higher Fe, e. Read More

2014Dec
Affiliations: 1Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain, 2Dept. d'Astronomia i Meteorologia, Institut de Ciéncies del Cosmos, Universitat de Barcelona, 3Dept. d'Astronomia i Meteorologia, Institut de Ciéncies del Cosmos, Universitat de Barcelona, 4Dept. d'Astronomia i Meteorologia, Institut de Ciéncies del Cosmos, Universitat de Barcelona, 5Osservatorio Astronomico di Bologna, Bologna, Italy, 6Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain, 7CNRS/Univ. Bordeaux, LAB, UMR 5804, Floirac, France, 8Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain, 9Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain, 10Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain, 11Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain, 12Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain, 13Laboratoire Lagrange

We present the motivation, design and current status of the Open Cluster Chemical Abundances from Spanish Observatories survey (OCCASO). Using the high resolution spectroscopic facilities available at Spanish observatories, OCCASO will derive chemical abundances in a sample of 20 to 25 open clusters older than 0.5 Gyr. Read More

We present high-precision multi-band photometry for the globular cluster (GC) M2. We combine the analysis of the photometric data obtained from the Hubble Space Telescope UV Legacy Survey of Galactic GCs GO-13297, with chemical abundances by Yong et al.(2014), and compare the photometry with models in order to analyze the multiple stellar sequences we identified in the color-magnitude diagram (CMD). Read More

2014Oct
Affiliations: 1UNIPD, 2ANU, 3INAF-OAPd, 4STScI, 5Univ.Washington, 6ANU, 7UNIPD, 8IAC, 9IAG, 10STScI, 11STScI, 12SFSU, 13UNIPD, 14UNIBO, 15INAF-OABo, 16UNIBO, 17IAC, 18UNIBO, 19IAC, 20UNIPD, 21INAF-OAPd, 22Liverpool John Moores University, 23UFL, 24STScI, 25Univ.Indiana, 26PUC

In this paper we describe a new UV-initiative HST project (GO-13297) that will complement the existing F606W and F814W database of the ACS Globular Cluster (GC) Treasury by imaging most of its clusters through UV/blue WFC3/UVIS filters F275W, F336W and F438W. This "magic trio" of filters has shown an uncanny ability to disentangle and characterize multiple-population (MP) patterns in GCs in a way that is exquisitely sensitive to C, N, and O abundance variations. Combination of these passbands with those in the optical also gives the best leverage for measuring helium enrichment. Read More

We present an analysis of photometric and spectroscopic data of the Carina dSph galaxy, testing a new approach similar to that used to disentangle multiple populations in Galactic globular clusters (GCs). We show that a proper colour combination is able to separate a significant fraction of the red giant branch (RGB) of the two main Carina populations (the old one, \sim 12 Gyr, and the intermediate-age one, 4-8 Gyr). In particular, the c_UBI=(U-B)-(B-I) pseudo-colour allows us to follow the RGB of both populations along a relevant portion of the RGB. Read More

We present a detailed photometric study of the dwarf irregular galaxy NGC 6822 aimed at investigating the properties of its stellar populations and, in particular, the presence of stellar radial gradients. Our goal is to analyse the stellar populations in six fields, which cover the whole bar of this dwarf galaxy. We derived the quantitative star formation history (SFH) of the six fields using the IAC method, involving IAC-pop/MinnIAC codes. Read More

A sunspot catalogue was maintained by the Astronomical Observatory of Valencia University (Spain) from 1920 to 1928. Here we present a machine-readable version of this catalogue (OV catalog or OVc), including a quality control analysis. Sunspot number (total and hemispheric) and sunspot area series are constructed using this catalogue. Read More

The solar program of the Astronomical Observatory of Madrid started in 1876. For ten solar cycles, observations were made in this institution to determine sunspot numbers and areas. The program was completed in 1986. Read More

We produce a comprehensive field star age-metallicity relationship (AMR) from the earliest epoch until ~ 1 Gyr ago for three fields in the Fornax dSph galaxy by using VI photometric data obtained with FORS1 at the VLT. We find that the innermost one does not contains dominant very old stars (age > 12 Gyr), whereas the relatively outer field does not account for representative star field populations younger than ~ 3 Gyr. When focusing on the most prominent stellar populations, we find that the derived AMRs are engraved by the evidence of a outside-in star formation process. Read More

While wide-field surveys of M31 have revealed much substructure at large radii, understanding the nature and origin of this material is not straightforward from morphology alone. Using deep HST/ACS data, we have derived further constraints in the form of quantitative star formation histories (SFHs) for 14 inner halo fields which sample diverse substructures. In agreement with our previous analysis of colour-magnitude diagram morphologies, we find the resultant behaviours can be broadly separated into two categories. Read More

NGC1851 is surrounded by a stellar component that extends more than ten times beyond the tidal radius. Although the nature of this stellar structure is not known, it has been suggested to be a sparse halo of stars or associated with a stellar stream. We analyse the nature of this intriguing stellar component surrounding NGC1851 by investigating its radial velocities and chemical composition, in particular in comparison with those of the central cluster analysed in a homogeneous manner. Read More

We present the first comparison between the lifetime star formation histories (SFHs) of M31 and Milky Way (MW) satellites. Using the Advanced Camera for Surveys aboard the Hubble Space Telescope, we obtained deep optical imaging of Andromeda II (M$_{V} = -$12.0; log(M$_{\star}$/M$_{\odot}$) $\sim$ 6. Read More

Context. The Vista Variables in the V\'ia L\'actea (VVV) ESO Public Survey is a variability survey of the Milky Way bulge and an adjacent section of the disk carried out from 2010 on ESO Visible and Infrared Survey Telescope for Astronomy (VISTA). VVV will eventually deliver a deep near-IR atlas with photometry and positions in five passbands (ZYJHK_S) and a catalogue of 1-10 million variable point sources - mostly unknown - which require classifications. Read More

We present an analysis of the star formation history (SFH) of a field near the half light radius in the Local Group dwarf irregular galaxy IC 1613 based on deep Hubble Space Telescope Advanced Camera for Surveys imaging. Our observations reach the oldest main sequence turn-off, allowing a time resolution at the oldest ages of ~1 Gyr. Our analysis shows that the SFH of the observed field in IC 1613 is consistent with being constant over the entire lifetime of the galaxy. Read More

We present new and accurate optical photometry of the Bulge globular cluster NGC 6528. The images were collected with ACS at HST and together with WFC3 (UVIS, IR) allowed us to measure the proper motion to separate cluster and field stars. We adopted two empirical calibrators and we found that NGC 6528 is coeval with and more metal-rich than 47 Tuc. Read More

A long-term decrease in downward surface solar radiation from the 1950s to the 1980s ("global dimming") followed by a multi-decadal increase up to the present ("brightening") have been detected in many regions worldwide. In addition, some researchers have suggested the existence of an "early brightening" period in the first half of 20th century. However, this latter phenomenon is an open issue due to the opposite results found in literature and the scarcity of solar radiation data during this period. Read More

The horizontal branch (HB) morphology of globular clusters (GCs) is mainly determined by metallicity. However, the fact that GCs with almost the same metallicity exhibit different HB morphologies demonstrates that at least one more parameter is needed to explain the HB morphology. It has been suggested that one of these should be a global parameter that varies from GC to GC, and the other a non-global parameter that varies within the GC. Read More

2013Dec
Affiliations: 1Instituto de Astrofisica de Canarias, Spain, 2Instituto de Astrofisica de Canarias, Spain, 3Instituto de Astrofisica de Canarias, Spain, 4Instituto de Astrofisica de Canarias, Spain, 5Instituto de Astrofisica de Canarias, Spain, 6NRC Herzberg Institute for Astrophysics, Canada, 7Instituto de Astrofisica de Canarias, Spain

We study the evolution of three fields in the outer LMC disk Rgc=3.5-6.2 Kpc. Read More

We present deep and precise multi-band photometry of the Galactic Bulge globular cluster NGC6528. The current dataset includes optical and near-infrared images collected with ACS/WFC, WFC3/UVIS, and WFC3/IR on board the Hubble Space Telescope. The images cover a time interval of almost ten years and we have been able to carry out a proper-motion separation between cluster and field stars. Read More

In this study we compare the photometric data of 34 Milky Way globular clusters, observed within the ACS Treasury Program (PI: Ata Sarajedini) with the corresponding ground-based data, provided by the Photometric Standard Field Catalogs of Stetson (2000, 2005). We focus on the transformation between the HST/ACS F606W to V-band and F814W to I-band only. The goal is to assess the validity of the filter transformation equations by Sirianni et al. Read More

Based on Hubble Space Telescope observations from the Local Cosmology from Isolated Dwarfs project, we present the star formation histories, as a function of galactocentric radius, of four isolated Local Group dwarf galaxies: two dSph galaxies, Cetus and Tucana, and two transition galaxies (dTrs), LGS-3 and Phoenix. The oldest stellar populations of the dSphs and dTrs are, within the uncertainties, coeval ($\sim 13 Gyr$) at all galactocentric radii. We find that there are no significative differences between the four galaxies in the fundamental properties (such as the normalized star formation rate or age-metallicity relation) of their outer regions (radii greater than four exponential scale lengths); at large radii, these galaxies consist exclusively of old ($\geq 10. Read More

We present the Star Formation History (SFH) and the age-metallicity relation (AMR) in three fields of the Fornax dwarf spheroidal galaxy. They sample a region spanning from the centre of the galaxy to beyond one core radius, which allows studying galactocentric gradients. In all the cases, we found stars as old as 12 Gyr, together with intermediate-age and young stellar populations. Read More

We present the results of a new search for variable stars in the Local Group dwarf galaxy Leo A, based on deep photometry from the Advanced Camera for Surveys onboard the Hubble Space Telescope. We detected 166 bona fide variables in our field, of which about 60 percent are new discoveries, and 33 candidate variables. Of the confirmed variables, we found 156 Cepheids, but only 10 RR Lyrae stars despite nearly 100 percent completeness at the magnitude of the horizontal branch. Read More

We present a general overview and the first results of the SUMO project (a SUrvey of Multiple pOpulations in Globular Clusters). The objective of this survey is the study of multiple stellar populations in the largest sample of globular clusters homogeneously analysed to date. To this aim we obtained high signal-to-noise (S/N>50) photometry for main sequence stars with mass down to ~0. Read More

Multi-band Hubble Space Telescope photometry reveals that the main sequence, sub-giant, and the red giant branch of the globular cluster NGC6752 splits into three main components in close analogy with the three distinct segments along its horizontal branch stars. These triple sequences are consistent with three stellar groups: a stellar population with a chemical composition similar to field halo stars (population a), a population (c) with enhanced sodium and nitrogen, depleted carbon and oxygen and enhanced helium abundance (Delta Y ~0.03), and a population (b) with an intermediate (between population a and c) chemical composition and slightly helium enhanced (Delta Y ~0. Read More

The TASTE project is searching for low-mass planets with the Transit Timing Variation (TTV) technique, by gathering high-precision, short-cadence light curves for a selected sample of transiting exoplanets. It has been claimed that the "hot Jupiter" WASP-3b could be perturbed by a second planet. Presenting eleven new light curves (secured at the IAC80 and UDEM telescopes) and re-analyzing thirty-eight archival light curves in a homogeneous way, we show that new data do not confirm the previously claimed TTV signal. Read More

In the last few years many globular clusters (GCs) have revealed complex color-magnitude diagrams, with the presence of multiple main sequences (MSs), broaden or multiple sub-giant branches (SGBs) and MS turn offs, and broad or split red giant branches (RGBs). After a careful correction for differential reddening, high accuracy photometry with the Hubble Space Telescope presented in this paper reveals a broadened or even split SGB in five additional Milky Way GCs: NGC 362, NGC 5286, NGC 6656, NGC 6715, and NGC 7089. In addition, we confirm (with new and archival HST data) the presence of a split SGB in 47Tuc, NGC 1851, and NGC 6388. Read More