Examinando por Autor "Harmanen, J."
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Ítem 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.Ítem Investigating the properties of stripped-envelope supernovae; what are the implications for their progenitors?(Monthly Notices of the Royal Astronomical Society, 2019-02-15) Prentice, S. J.; Ashall, C.; James, P. A.; Short, L.; Mazzali, P. A.; Bersier, D.; Crowther, P. A.; Barbarino, C.; Chen, T.-W.; Copperwheat, C. M.; Darnley, M. J.; Denneau, L.; Elias-Rosa, N.; Fraser, M.; Galbany, L.; Gal-Yam, A.; Harmanen, J.; Howell, D. A.; Hosseinzadeh, G.; Inserra, C.; Kankare, E.; Karamehmetoglu, E.; Lamb, G. P.; Limongi, M.; Maguire, K.; McCully, C.; Olivares E., F.; Piascik, A. S.; Pignata, G.; Reichart, D. E.; Rest, A.; Reynolds, T.; Rodríguez, O.; Saario, J. L. O.; Schulze, S.; Smartt, S. J.; Smith, K. W.; Sollerman, J.; Stalder, B.; Sullivan, M.; Taddia, F.; Valenti, S.; Vergani, S. D.; Williams, S. C.; Young, D. R.We present observations and analysis of 18 stripped-envelope supernovae observed during 2013–2018. This sample consists of five H/He-rich SNe, six H-poor/He-rich SNe, three narrow lined SNe Ic, and four broad lined SNe Ic. The peak luminosity and characteristic time-scales of the bolometric light curves are calculated, and the light curves modelled to derive 56Ni and ejecta masses (MNi and Mej). Additionally, the temperature evolution and spectral line velocity curves of each SN are examined. Analysis of the [O I] line in the nebular phase of eight SNe suggests their progenitors had initial masses <20 M . The bolometric light curve properties are examined in combination with those of other SE events from the literature. The resulting data set gives the Mej distribution for 80 SE–SNe, the largest such sample in the literature to date, and shows that SNe Ib have the lowest median Mej, followed by narrow-lined SNe Ic, H/He-rich SNe, broad-lined SNe Ic, and finally gamma-ray burst SNe. SNe Ic-6/7 show the largest spread of Mej ranging from ∼1.2–11 M , considerably greater than any other subtype. For all SE–SNe = 2.8 ± 1.5 M which further strengthens the evidence that SE–SNe arise from low-mass progenitors which are typically <5 M at the time of explosion, again suggesting MZAMS <25 M . The low and lack of clear bimodality in the distribution implies <30 M progenitors and that envelope stripping via binary interaction is the dominant evolutionary pathway of these SNe.Ítem SN 2016gsd: An unusually luminous and linear Type II supernova with high velocities(Oxford University Press, 2020-04) Reynolds, T.M.; Fraser, M.; Mattila, S.; Ergon, M.; Dessart, L.; Lundqvist, P.; Dong, S.; Elias-Rosa, N.; Galbany, L.; Gutierrez, C.P.; Kangas, T.; Kankare, E.; Kotak, R.; Kuncarayakti, H.; Pastorello, A.; Rodriguez, O.; Smartt, S.J.; Stritzinger, M.; Tomasella, L.; Chen, P.; Harmanen, J.; Hosseinzadeh, G.; Howell, D.A.; Inserra, C.; Nicholl, M.; Nielsen, M.; Smith, K.; Somero, A.; Tronsgaard, R.; Young, D.R.We present observations of the unusually luminous Type II supernova (SN) 2016gsd. With a peak absolute magnitude of V = -19.95 ± 0.08, this object is one of the brightest Type II SNe, and lies in the gap of magnitudes between the majority of Type II SNe and the superluminous SNe. Its light curve shows little evidence of the expected drop from the optically thick phase to the radioactively powered tail. The velocities derived from the absorption in H α are also unusually high with the blue edge tracing the fastest moving gas initially at 20 000 km s-1, and then declining approximately linearly to 15 000 km s-1 over ∼100 d. The dwarf host galaxy of the SN indicates a low-metallicity progenitor which may also contribute to the weakness of the metal lines in its spectra. We examine SN 2016gsd with reference to similarly luminous, linear Type II SNe such as SNe 1979C and 1998S, and discuss the interpretation of its observational characteristics. We compare the observations with a model produced by the jekyll code and find that a massive star with a depleted and inflated hydrogen envelope struggles to reproduce the high luminosity and extreme linearity of SN 2016gsd. Instead, we suggest that the influence of interaction between the SN ejecta and circumstellar material can explain the majority of the observed properties of the SN. The high velocities and strong H α absorption present throughout the evolution of the SN may imply a circumstellar medium configured in an asymmetric geometry. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.Ítem Supernova 2013fc in a circumnuclear ring of a luminous infrared galaxy: The big brother of SN 1998S(OXFORD UNIV PRESS, 2016-02) Kangas, T.; Mattila, S.; Kankare, E.; Lundqvist, P.; Väisänen, P.; Childress, M.; Pignata, G.; McCully, C.; Valenti, S.; Vinkó, J.; Pastorello, A.; Elias-Rosa, N.; Fraser, M.; Gal-Yam, A.; Kotak, R.; Kotilainen, J. K.; Smartt, S. J.; Galbany, L.; Harmanen, J.; Howell, D. A.; Inserra, C.; Marion, G. H.; Quimby, R. M.; Silverman, J. M.; Szalai, T.; Wheeler, J. C.; Ashall, C.; Benetti, S.; Romero-Cañizales, C.; Smith, K. W.; Sullivan, M.; Takáts, K.; Young, D. R.We present photometric and spectroscopic observations of SN 2013fc, a bright type II supernova (SN) in a circumnuclear star-forming ring in the luminous infrared galaxy ESO 154-G010, observed as part of the Public ESO Spectroscopic Survey of Transient Objects. SN 2013fc is both photometrically and spectroscopically similar to the well-studied type IIn SN 1998S and to the bright type II-L SN 1979C. It exhibits an initial linear decline, followed by a short plateau phase and a tail phase with a decline too fast for Co-56 decay with full. gamma-ray trapping. Initially, the spectrum was blue and featureless. Later on, a strong broad (similar to 8000 km s(-1)) H alpha emission profile became prominent. We apply a STARLIGHT stellar population model fit to the SN location (observed when the SN had faded) to estimate a high extinction of A(V) = 2.9 +/- 0.2 mag and an age of 10(+ 3) (- 2) Myr for the underlying cluster. We compare the SN to SNe 1998S and 1979C and discuss its possible progenitor star considering the similarities to these events. With a peak brightness of B = - 20.46 +/- 0.21 mag, SN 2013fc is 0.9 mag brighter than SN 1998S and of comparable brightness to SN 1979C. We suggest that SN 2013fc was consistent with a massive red supergiant (RSG) progenitor. Recent mass loss probably due to a strong RSG wind created the circumstellar matter illuminated through its interaction with the SN ejecta. We also observe a near- infrared excess, possibly due to newly condensed dust.Ítem 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.Ítem Unraveling the Infrared Transient VVV-WIT-06: The Case for the Origin as a Classical Nova(Institute of Physics Publishing, 2018-11) Banerjee, D.P.K.; Hsiao, E.Y.; Diamond, T.; Galbany, L.; Morrell, N.; Minniti, D.; Kuncarayakti, H.; Mattila, S.; Harmanen, J.The enigmatic near-infrared transient VVV-WIT-06 underwent a large-amplitude eruption of unclear origin in 2013 July. Based on its light curve properties and late-time post-outburst spectra, various possibilities have been proposed in the literature for the origin of the object, namely a Type I supernova, a classical nova (CN), or a violent stellar merger event. We show that, of these possibilities, an origin in a CN outburst convincingly explains the observed properties of VVV-WIT-06. We estimate that the absolute K-band magnitude of the nova at maximum was M k = -8.2 ±0.5, its distance d = 13.35 ±2.18 kpc, and the extinction A v = 15.0 ±0.55 mag. © 2018. The American Astronomical Society. All rights reserved.