A continuous population of variable stars up to about 1.5 mag above the horizontal branch?

Increasing samples of pulsating variable stars populating the classical instability strip from the horizontal branch to a few magnitudes brighter are being found in several Local Group galaxies, irrespective of the galaxy morphological type. We will review the observational scenario focusing in particular on the Anomalous Cepheids and related objects.Comment: 5 pages, 2 figures, invited review in JENAM 2003, "Minisymposium: Asteroseismology and Stellar Evolution", Communications in Asteroseismology, in pres

A hierarchical Bayesian model to infer PL(Z) relations using Gaia parallaxes

Aims. We aim at creating a Bayesian model to infer the coefficients of PL or PLZ relations that propagates uncertainties in the observables in a rigorous and well founded way. Methods. We propose a directed acyclic graph to encode the conditional probabilities of the inference model that will allow us to infer probability distributions for the PL and PL(Z) relations. We evaluate the model with several semi-synthetic data sets and apply it to a sample of 200 fundamental mode and first overtone mode RR Lyrae stars for which Gaia DR1 parallaxes and literature Ks-band mean magnitudes are available. We define and test several hyperprior probabilities to verify their adequacy and check the sensitivity of the solution with respect to the prior choice. Results. The main conclusion of this work is the absolute necessity of incorporating the existing correlations between the observed variables (periods, metallicities and parallaxes) in the form of model priors in order to avoid systematically biased results, especially in the case of non-negligible uncertainties in the parallaxes. The tests with the semi-synthetic data based on the data set used in Gaia Collaboration et al. (2017) reveal the significant impact that the existing correlations between parallax, metallicity and periods have on the inferred parameters. The relation coefficients obtained here have been superseded by those presented in Muraveva et al. (2018a), that incorporates the findings of this work and the more recent Gaia DR2 measurements.Comment: 14 pages, 12 figures. Submitted to A&

Five colour photometry of the RRd star V372 Ser

The first UBV(RI)_C time series photometry of the RRd star V372 Ser is presented to determine some parameters of the star. In April, May 2007 2812 U, B, V, R_C, I_C frames were obtained at Konkoly and Teide Observatories, 1508 V observations were collected from the literature. Fourier fitted light curves have been derived in all bands. The non-linearly coupled frequencies f_0=(2.121840+/-.000001) c/day, f_1=(2.851188+/-.000001) c/d, i.e. periods P_0=0.4712891+/-.0000002 days, P_1=0.3507310+/-.0000001 d, P_1/P_0=0.7441950, amplitudes A_0(V)=0.15399 mag, A_1(V)=0.20591 mag, and phases have been found. A_1/A_0=1.319+/-.008 has been found from averaging the amplitude ratio in the different bands i.e. the first overtone is the dominant pulsation mode. From the V observations upper limits are given for secular change of the Fourier parameters. The period ratio and period put V372 Ser among the RRd stars of the globular clusters M3 and IC 4499, mass, luminosity, and metallicity estimates are given.Comment: accepted by Astronomy and Astrophysics (5 pages, 3 figures, 4 tables

The Spectra of Main Sequence Stars in Galactic Globular Clusters II. CH and CN Bands in M71

Spectra with a high signal-to-noise ratio of 79 stars which are just below the main sequence turnoff of M71 are presented. They yield indices for the strength of the G band of CH and the ultraviolet CN band at 3885 \AA. These indices are each to first order bimodal and they are anti-correlated. There are approximately equal numbers of CN weak/CH strong and CN strong/CH weak main sequence stars in M71. It is not yet clear whether these star-to-star variations arise from primordial variations or from mixing within a fraction of individual stars as they evolve.Comment: Accepted for publication in the AJ to appear back to back with paper I. 14 pages with 5 figure

The VISTA near-infrared YJKs public survey of the Magellanic Clouds System (VMC)

The VISTA public survey project VMC targets the Large Magellanic Cloud, the Small Magellanic Cloud, the Bridge and two fields in the Stream. The VMC survey is a uniform and homogeneous survey in the Y, J and Ks near-infrared filters. The main goals are the determination of the star formation history and the three-dimensional structure of the Magellanic system. The survey is therefore designed to reach stars as faint as the oldest main sequence turn-off point and to constrain the mean magnitude of pulsating variable stars such as RR Lyrae and Cepheids. We provide a brief overview of the survey strategy and first science results. Further details are given in Cioni et al. (2011)

A novel technique to close large perforation of sinus membrane

Maxillary sinus floor elevation is generally accepted as a regenerative procedure to facilitate dental implants placement in the posterior atrophic maxilla. Although the sinus lift procedure is relatively safe, some potential problems could be occur. The most prevalent intraoperative complication is perforation of sinus membrane, which can lead to graft infection and early failure. The Aim of this work. Is to present a new technique to repair large perforation of sinus membrane. This case report. Is focused on a 10 mm perforation of sinus membrane occurred during preparation of the sinus window. The obliteration of the perforation was obtained by means of suturing sinus membrane with a resorbable material to the bone directly lateral to the osteotomy site. Sinus augmentation procedure could complete and the insertion of a graft was permitted

Multi-Epoch HST Observations of IZw18: Characterization of Variable Stars at Ultra-Low Metallicities

Variable stars have been identified for the first time in the very metal-poor Blue Compact dwarf galaxy IZw18, using deep multi-band (F606W, F814W)time-series photometry obtained with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST). We detected 34 candidate variable stars in the galaxy. We classify three of them as Classical Cepheids, with periods of 8.71, 125.0 and 130.3 days, respectively, and other two as long period variables with periodicities longer than a hundred days. These are the lowest metallicity Classical Cepheids known so far, thus providing the opportunity to explore and fit models of stellar pulsation fo Classical Cepheids at previously inaccessible metallicities. The period distribution of the confirmed Cepheids is markedly different from what is seen in other nearby galaxies, which is likely related to the star bursting nature of IZw18. By applying to the 8.71 days Cepheid theoretical Wesenheit (V,I) relations based on new pulsation models of Classical Cepheids specifically computed for the extremely low metallicity of this galaxy (Z=0.0004, Y=0.24), we estimate the distance modulus of IZw18 to be mu_0= 31.4pm0.2 D=19.0^{+1.8}_{-1.7}Mpc) for canonical models of Classical Cepheids, and of 31.2pm0.2 mag (D=17.4^{+1.6}_{-1.6}Mpc) using over luminous models. The theoretical modeling of the star's light curves provides mu_0=31.4pm0.1 mag, D=19.0^{+0.9}_{-0.9} Mpc, in good agreement with the results from the theoretical Wesenheit relations. These pulsation distances bracket the distance of 18.2pm1.5Mpc inferred by Aloisi et al. (2007) using the galaxy's Red Giant Branch Tip.Comment: 13 Pages, 6 Figures, accepted, Ap