Examinando por Autor "Olivares, F"

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    New spectroscopic binary companions of giant stars and updated metallicity distribution for binary systems
    (EDP SCIENCES, 2016-09) Bluhm, P; Jones, MI; Vanzi, L; Soto, MG; Voss, J; Wittenmyer, RA; Drass, H; Jenkins, JS; Olivares, F; Mennickent, RE; Vuckovic, M; Rojo, P; Melo, CHF
    We report the discovery of 24 spectroscopic binary companions to giant stars. We fully constrain the orbital solution for 6 of these systems. We cannot unambiguously derive the orbital elements for the remaining stars because the phase coverage is incomplete. Of these stars, 6 present radial velocity trends that are compatible with long-period brown dwarf companions. The orbital solutions of the 24 binary systems indicate that these giant binary systems have a wide range in orbital periods, eccentricities, and companion masses. For the binaries with restricted orbital solutions, we find a range of orbital periods of between similar to 97-1600 days and eccentricities of between similar to 0.1-0.4. In addition, we studied the metallicity distribution of single and binary giant stars. We computed the metallicity of a total of 395 evolved stars, 59 of wich are in binary systems. We find a flat distribution for these binary stars and therefore conclude that stellar binary systems, and potentially brown dwarfs, have a different formation mechanism than planets. This result is confirmed by recent works showing that extrasolar planets orbiting giants are more frequent around metal-rich stars. Finally, we investigate the eccentricity as a function of the orbital period. We analyzed a total of 130 spectroscopic binaries, including those presented here and systems from the literature. We find that most of the binary stars with periods. 30 days have circular orbits, while at longer orbital periods we observe a wide spread in their eccentricities.
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    Pan-STARRS and PESSTO search for an optical counterpart to the LIGO gravitational-wave source GW150914
    (OXFORD UNIV PRESS, 2016-11) Smartt, SJ; Chambers, KC; Smith, KW; Huber, ME; Young, DR; Cappellaro, E; Wright, DE; Coughlin, M; Schultz, ASB; Denneau, L; Flewelling, H; Heinze, A; Magnier, EA; Primak, N; Rest, A; Sherstyuk, A; Stalder, B; Stubbs, CW; Tonry, J; Waters, C; Willman, M; Anderson, JP; Baltay, C; Botticella, MT; Campbell, H; Dennefeld, M; Chen, TW; Della Valle, M; Elias-Rosa, N; Fraser, M; Inserra, C; Kankare, E; Kotak, R; Kupfer, T; Harmanen, J; Galbany, L; Gal-Yam, A; Le Guillou, L; Lyman, JD; Maguire, K; Mitra, A; Nicholl, M; Olivares, F; Rabinowitz, D; Razza, A; Sollerman, J; Smith, M; Terreran, G; Valenti, S; Gibson, B; Goggia, T
    We searched for an optical counterpart to the first gravitational-wave source discovered by LIGO (GW150914), using a combination of the Pan-STARRS1 wide-field telescope and the Public ESO Spectroscopic Survey of Transient Objects (PESSTO) spectroscopic follow-up programme. As the final LIGO sky maps changed during analysis, the total probability of the source being spatially coincident with our fields was finally only 4.2 per cent. Therefore, we discuss our results primarily as a demonstration of the survey capability of Pan-STARRS and spectroscopic capability of PESSTO. We mapped out 442 deg2 of the northern sky region of the initial map. We discovered 56 astrophysical transients over a period of 41 d from the discovery of the source. Of these, 19 were spectroscopically classified and a further 13 have host galaxy redshifts. All transients appear to be fairly normal supernovae (SNe) and AGN variability and none is obviously linked with GW150914. We illustrate the sensitivity of our survey by defining parametrized light curves with time-scales of 4, 20 and 40 d and use the sensitivity of the Pan-STARRS1 images to set limits on the luminosities of possible sources. The Pan-STARRS1 images reach limiting magnitudes of iP1 = 19.2, 20.0 and 20.8, respectively, for the three time-scales. For long time-scale parametrized light curves (with full width half-maximum ≃40 d), we set upper limits of Mi≤−17.2−0.9+1.4 Mi≤−17.2+1.4−0.9 if the distance to GW150914 is DL = 400 ± 200 Mpc. The number of Type Ia SN we find in the survey is similar to that expected from the cosmic SN rate, indicating a reasonably complete efficiency in recovering SN like transients out to DL = 400 ± 200 Mpc.
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    THE HIGH CADENCE TRANSIENT SURVEY (HITS). I. SURVEY DESIGN AND SUPERNOVA SHOCK BREAKOUT CONSTRAINTS
    (Universidad Andrés Bello, 2016-12) Forster, F; Maureira, JC; San Martin, J; Hamuy, M; Martinez, J; Huijse, P; Cabrera, G; Galbany, L; de Jaeger, T; Gonzalez-Gaitan, S; Anderson, JP; Kunkarayakti, H; Pignata, G; Bufano, F; Littin, J; Olivares, F; Medina, G; Smith, RC; Vivas, AK; Estevez, PA; Munoz, R; Vera, E
    We present the first results of the High Cadence Transient Survey (HiTS), a survey for which the objective is to detect and follow-up optical transients with characteristic timescales from hours to days, especially the earliest hours of supernova (SN) explosions. HiTS uses the Dark Energy Camera and a custom pipeline for image subtraction, candidate filtering and candidate visualization, which runs in real-time to be able to react rapidly to the new transients. We discuss the survey design, the technical challenges associated with the real-time analysis of these large volumes of data and our first results. In our 2013, 2014, and 2015 campaigns, we detected more than 120 young SN candidates, but we did not find a clear signature from the short-lived SN shock breakouts (SBOs) originating after the core collapse of red supergiant stars, which was the initial science aim of this survey. Using the empirical distribution of limiting magnitudes from our observational campaigns, we measured the expected recovery fraction of randomly injected SN light curves, which included SBO optical peaks produced with models from Tominaga et al. (2011) and Nakar & Sari (2010). From this analysis, we cannot rule out the models from Tominaga et al. (2011) under any reasonable distributions of progenitor masses, but we can marginally rule out the brighter and longer-lived SBO models from Nakar & Sari (2010) under our best-guess distribution of progenitor masses. Finally, we highlight the implications of this work for future massive data sets produced by astronomical observatories, such as LSST.