Examinando por Autor "Gall, C."

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    SN 2017dio: A Type-Ic Supernova Exploding in a Hydrogen-rich Circumstellar Medium
    (Institute of Physics Publishing, 2018-02) Kuncarayakti, H.; Maeda, K.; Ashall, C.J.; Prentice, S.J.; Mattila, S.; Kankare, E.; Fransson, C.; Lundqvist, P.; Pastorello, A.; Leloudas, G.; Anderson, J.P.; Benetti, S.; Bersten, M.C.; Cappellaro, E.; Cartier, R.; Denneau, L.; Della Valle, M.; Elias-Rosa, N.; Folatelli, G.; Fraser, M.; Galbany, L.; Gall, C.; Gal-Yam, A.; Gutiérrez, C.P.; Hamanowicz, A.; Heinze, A.; Inserra, C.; Kangas, T.; Mazzali, P.; Melandri, A.; Pignata, G.; Rest, A.; Reynolds, T.; Roy, R.; Smartt, S.J.; Smith, K.W.; Sollerman, J.; Somero, A.; Stalder, B.; Stritzinger, M.; Taddia, F.; Tomasella, L.; Tonry, J.; Weiland, H.; Young, D.R.
    SN 2017dio shows both spectral characteristics of a type-Ic supernova (SN) and signs of a hydrogen-rich circumstellar medium (CSM). Prominent, narrow emission lines of H and He are superposed on the continuum. Subsequent evolution revealed that the SN ejecta are interacting with the CSM. The initial SN Ic identification was confirmed by removing the CSM interaction component from the spectrum and comparing with known SNe Ic and, reversely, adding a CSM interaction component to the spectra of known SNe Ic and comparing them to SN 2017dio. Excellent agreement was obtained with both procedures, reinforcing the SN Ic classification. The light curve constrains the pre-interaction SN Ic peak absolute magnitude to be around Mg = -17.6 mag. No evidence of significant extinction is found, ruling out a brighter luminosity required by an SN Ia classification. These pieces of evidence support the view that SN 2017dio is an SN Ic, and therefore the first firm case of an SN Ic with signatures of hydrogen-rich CSM in the early spectrum. The CSM is unlikely to have been shaped by steady-state stellar winds. The mass loss of the progenitor star must have been intense, M ∼ 0.02 ϵ Hα/0.01)-1(vwind/500 km s-1) (vshock 10,000 kms-1)-3Me yr-1, peaking at a few decades before the SN. Such a high mass-loss rate might have been experienced by the progenitor through eruptions or binary stripping.
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    The Early Detection and Follow-up of the Highly Obscured Type II Supernova 2016ija/DLT16am
    (Institute of Physics Publishing, 2018-01) Tartaglia, L.; Sand, D.J.; Valenti, S.; Wyatt, S.; Anderson, J.P.; Arcavi, I.; Ashall, C.; Botticella, M.T.; Cartier, R.; Chen, T.-W.; Cikota, A.; Coulter, D.; Valle, M.D.; Foley, R.J.; Gal-Yam, A.; Galbany, L.; Gall, C.; Haislip, J.B.; Harmanen, J.; Hosseinzadeh, G.; Howell, D.A.; Hsiao, E.Y.; Inserra, C.; Jha, S.W.; Kankare, E.; Kilpatrick, C.D.; Kouprianov, V.V.; Kuncarayakti, H.; Maccarone, T.J.; Maguire, K.; Mattila, S.; Mazzali, P.A.; McCully, C.; Melandri, A.; Morrell, N.; Phillips, M.M.; Pignata, G.; Piro, A.L.; Prentice, S.; Reichart, D.E.; Rojas-Bravo, C.; Smartt, S.J.; Smith, K.W.; Sollerman, J.; Stritzinger, M.D.; Sullivan, M.; Taddia, F.; Young, D.R.
    We present our analysis of the Type II supernova DLT16am (SN 2016ija). The object was discovered during theongoing D < 40 Mpc (DLT40) one-day cadence supernova search at r ∼ 20.1 mag in the edge-on nearby(D = 20.0 ± 4.0 Mpc) galaxy NGC 1532. The subsequent prompt and high-cadenced spectroscopic andphotometric follow-up revealed a highly extinguished transient, with E(B - V) = 1.95 ±0.15 mag, consistentwith a standard extinction law with RV=3.1 and a bright (MV = -18.48 ±0.77 mag) absolute peak magnitude. Acomparison of the photometric features with those of large samples of SNe II reveals a fast rise for the derivedluminosity and a relatively short plateau phase, with a slope of S50V = 0.84 ±0.04 mag 50 days, consistent withthe photometric properties typical of those of fast-declining SNe II. Despite the large uncertainties on the distance andthe extinction in the direction of DLT16am, the measured photospheric expansion velocity and the derived absoluteV-band magnitude at ~50 days after the explosion match the existing luminosity-velocity relation for SNe II.
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    Two transitional type Ia supernovae located in the Fornax cluster member NGC 1404: SN 2007on and SN 2011iv
    (EDP Sciences, 2018-03) Gall, C.; Stritzinger, M.D.; Ashall, C.; Baron, E.; Burns, C.R.; Hoeflich, P.; Hsiao, E.Y.; Mazzali, P.A.; Phillips, M.M.; Filippenko, A.V.; Anderson, J.P.; Benetti, S.; Brown, P.J.; Campillay, A.; Challis, P.; Contreras, C.; Elias De La Rosa, N.; Folatelli, G.; Foley, R.J.; Fraser, M.; Holmbo, S.; Marion, G.H.; Morrell, N.; Pan, Y.-C.; Pignata, G.; Suntzeff, N.B.; Taddia, F.; Robledo, S.T.; Valenti, S.
    We present an analysis of ultraviolet (UV) to near-infrared observations of the fast-declining Type Ia supernovae (SNe Ia) 2007on and 2011iv, hosted by the Fornax cluster member NGC 1404. The B-band light curves of SN 2007on and SN 2011iv are characterised by Δm 15 (B) decline-rate values of 1.96 mag and 1.77 mag, respectively. Although they have similar decline rates, their peak B- and H-band magnitudes differ by ~ 0.60 mag and ~0.35 mag, respectively. After correcting for the luminosity vs. decline rate and the luminosity vs. colour relations, the peak B-band and H-band light curves provide distances that differ by ~ 14% and ~ 9%, respectively. These findings serve as a cautionary tale for the use of transitional SNe Ia located in early-type hosts in the quest to measure cosmological parameters. Interestingly, even though SN 2011iv is brighter and bluer at early times, by three weeks past maximum and extending over several months, its B - V colour is 0.12 mag redder than that of SN 2007on. To reconcile this unusual behaviour, we turn to guidance from a suite of spherical one-dimensional Chandrasekhar-mass delayed-detonation explosion models. In this context, 56 Ni production depends on both the so-called transition density and the central density of the progenitor white dwarf. To first order, the transition density drives the luminosity-width relation, while the central density is an important second-order parameter. Within this context, the differences in the B - V colour evolution along the Lira regime suggest that the progenitor of SN 2011iv had a higher central density than SN 2007on. © ESO 2018.