Examinando por Autor "Angus, C.R."

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    A kilonova as the electromagnetic counterpart to a gravitational-wave source
    (Nature Publishing Group, 2017-11) Smartt, S.J.; Chen, T.-W.; Jerkstrand, A.; Coughlin, M.; Kankare, E.; Sim, S.A.; Fraser, M.; Inserra, C.; Maguire, K.; Chambers, K.C.; Huber, M.E.; Krühler, T.; Leloudas, G.; Magee, M.; Shingles, L.J.; Smith, K.W.; Young, D.R.; Tonry, J.; Kotak, R.; Gal-Yam, A.; Lyman, J.D.; Homan, D.S.; Agliozzo, C.; Anderson, J.P.; Angus, C.R.; Ashall, C.; Barbarino, C.; Bauer, F.E.; Berton, M.; Botticella, M.T.; Bulla, M.; Bulger, J.; Cannizzaro, G.; Cano, Z.; Cartier, R.; Cikota, A.; Clark, P.; De Cia, A.; Della Valle, M.; Denneau, L.; Dennefeld, M.; Dessart, L.; Dimitriadis, G.; Elias-Rosa, N.; Firth, R.E.; Flewelling, H.; Flörs, A.; Franckowiak, A.; Frohmaier, C.; Galbany, L.; González-Gaitán, S.; Greiner, J.; Gromadzki, M.; Nicuesa Guelbenzu, A.; Gutiérrez, C.P.; Hamanowicz, A.; Hanlon, L.; Harmanen, J.; Heintz, K.E.; Heinze, A.; Hernandez, M.-S.; Hodgkin, S.T.; Hook, I.M.; Izzo, L.; James, P.A.; Jonker, P.G.; Kerzendorf, W.E.; Klose, S.; Kostrzewa-Rutkowska, Z.; Kowalski, M.; Kromer, M.; Kuncarayakti, H.; Lawrence, A.; Lowe, T.B.; Magnier, E.A.; Manulis, I.; Martin-Carrillo, A.; Mattila, S.; McBrien, O.; Müller, A.; Nordin, J.; O'Neill, D.; Onori, F.; Palmerio, J.T.; Pastorello, A.; Patat, F.; Pignata, G.; Pumo, M.L.; Prentice, S.J.; Rau, A.; Razza, A.; Rest, A.; Reynolds, T.; Roy, R.; Ruiter, A.J.; Rybicki, K.A.; Salmon, L.; Schady, P.; Schultz, A.S.B.; Schweyer, T.; Seitenzahl, I.R.; Smith, M.; Sollerman, J.; Stalder, B.; Stubbs, C.W.; Sullivan, M.; Szegedi, H.; Taddia, F.; Taubenberger, S.; Terreran, G.; Van Soelen, B.; Vos, J.; Wainscoat, R.J.; Waters, C.; Weiland, H.; Willman, M.; Wiseman, P.; Wright, D.E.; Walton, N.A.; Wyrzykowski, L.; Yaron, O.
    Gravitational waves were discovered with the detection of binary black-hole mergers1 and they should also be detectable from lowermass neutron-star mergers. These are predicted to eject material rich in heavy radioactive isotopes that can power an electromagnetic signal. This signal is luminous at optical and infrared wavelengths and is called a kilonova2-5. The gravitational-wave source GW170817 arose from a binary neutron-star merger in the nearby Universe with a relatively well confined sky position and distance estimate6. Here we report observations and physical modelling of a rapidly fading electromagnetic transient in the galaxy NGC 4993, which is spatially coincident with GW170817 and with a weak, short γ-ray burst7,8. The transient has physical parameters that broadly match the theoretical predictions of blue kilonovae from neutron-star mergers. The emitted electromagnetic radiation can be explained with an ejected mass of 0.04 ± 0.01 solar masses, with an opacity of less than 0.5 square centimetres per gram, at a velocity of 0.2 ± 0.1 times light speed. The power source is constrained to have a power-law slope of -1.2 ± 0.3, consistent with radioactive powering from r-process nuclides. (The r-process is a series of neutron capture reactions that synthesise many of the elements heavier than iron.) We identify line features in the spectra that are consistent with light r-process elements (atomic masses of 90-140). As it fades, the transient rapidly becomes red, and a higher-opacity, lanthanide-rich ejecta component may contribute to the emission. This indicates that neutron-star mergers produce gravitational waves and radioactively powered kilonovae, and are a nucleosynthetic source of the r-process elements. © 2017 Macmillan Publishers Limited, part of Springer Nature.
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    SN 2020kyg and the rates of faint Iax supernovae from ATLAS
    (Oxford University Press, 2022-04-01) Srivastav, Shubham; Smartt, S.J.; Huber, M.E.; Chambers, K.C.; Angus, C.R.; Chen, T.-W.; Callan, F.P.; Gillanders, J.H.; McBrien, O.R.; Sim, S.A.; Fulton, M.; Hjorth, J.; Smith, K.W.; Young, D.R.; Auchettl, K.; Anderson, J.P.; Pignata, G.; De Boer, T.J.L.; Lin, C.-C.; Magnier, E.A.
    We present multiwavelength follow-up observations of the ATLAS discovered faint Iax supernova SN 2020kyg that peaked at an absolute magnitude of Mg ≈-14.9 ± 0.2, making it another member of the faint Iax supernova population. The bolometric light curve requires only ≈7 × 10-3 M· of radioactive 56Ni, with an ejected mass of Mej ∼0.4 M· and a low kinetic energy of E ≈ 0.05 ± 0.02 × 1051 erg. We construct a homogeneous volume-limited sample of 902 transients observed by ATLAS within 100 Mpc during a 3.5 yr span. Using this sample, we constrain the rates of faint Iax (Mr ≳-16) events within 60 Mpc at 12+14-8 per cent of the SN Ia rate. The overall Iax rate, at 15+17-9 per cent of the Ia rate, is dominated by the low-luminosity events, with luminous SNe Iax (Mr ≲-17.5) like 2002cx and 2005hk, accounting for only 0.9+1.1-0.5 per cent of the Ia rate (a 2σ upper limit of approximately 3 per cent). We favour the hybrid CONe WD + He star progenitor channel involving a failed deflagration of a near Chandrasekhar mass white dwarf, expected to leave a bound remnant and a surviving secondary companion, as a candidate explanation for faint Iax explosions. This scenario requires short delay times, consistent with the observed environments of SNe Iax. Furthermore, binary population synthesis calculations have suggested rates of 1-18 per cent of the SN Ia rate for this channel, consistent with our rate estimates. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.