Examinando por Autor "Elias-Rosa, N"

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    Low-luminosity Type II supernovae - III. SN 2018hwm, a faint event with an unusually long plateau
    (Oxford University Press, 2021-02-01) Reguitti, A; Pumo, M. L; Mazzali, P. A; Pastorello, A; Pignata, G; Elias-Rosa, N; Prentice, S. J; Reynolds, T; Benetti, S; Rodrìguez, O; Mattila, S; Kuncarayakti, H
    In this work, we present photometric and spectroscopic data of the low-luminosity (LL) Type IIP supernova (SN) 2018hwm. The object shows a faint (Mr = -15 mag) and very long (∼130 d) plateau, followed by a 2.7 mag drop in the r band to the radioactive tail. The first spectrum shows a blue continuum with narrow Balmer lines, while during the plateau the spectra show numerous metal lines, all with strong and narrow P-Cygni profiles. The expansion velocities are low, in the 1000-1400 km s-1 range. The nebular spectrum, dominated by H α in emission, reveals weak emission from [O i] and [Ca ii] doublets. The absolute light curve and spectra at different phases are similar to those of LL SNe IIP. We estimate that 0.002 M of 56Ni mass were ejected, through hydrodynamical simulations. The best fit of the model to the observed data is found for an extremely low explosion energy of 0.055 foe, a progenitor radius of 215 R, and a final progenitor mass of 9-10 M. Finally, we performed a modelling of the nebular spectrum, to establish the amount of oxygen and calcium ejected. We found a low M(16O)$\approx 0.02\, \mathrm{ M}_{\odot }$, but a high M(40Ca) of 0.3 M. The inferred low explosion energy, the low ejected 56Ni mass, and the progenitor parameters, along with peculiar features observed in the nebular spectrum, are consistent with both an electron-capture SN explosion of a superasymptotic giant branch star and with a low-energy, Ni-poor iron core-collapse SN from a 10-12 M red supergiant.
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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.