Examinando por Autor "Terreran, G."
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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 Forbidden hugs in pandemic times: III. Observations of the luminous red nova AT 2021biy in the nearby galaxy NGC 4631(EDP Sciences, 2022-11-01) Cai, Y.-Z.; Pastorello, A.; Fraser, M.; Wang, X.-F.; Filippenko, A.V.; Reguitti, A.; Patra, K.C.; Goranskij, V.P.; Barsukova, E.A.; Brink, T.G.; Elias-Rosa, N.; Stevance, H.F.; Zheng, W.; Yang, Y.; Atapin, K.E.; Benetti, S.; De Boer, T.J.L.; Bose, S.; Burke, J.; Byrne, R.; Cappellaro, E.; Chambers, K.C.; Chen, W.-L.; Emami, N.; Gao, H.; Hiramatsu, D.; Howell, D.A.; Huber, M.E.; Kankare, E.; Kelly, P.L.; Kotak, R.; Kravtsov, T.; Lander, V. Yu.; Li, Z.-T.; Lin, C.-C.; Lundqvist, P.; Magnier, E.A.; Malygin, E.A.; Maslennikova, N.A.; Matilainen, K.; Mazzali, P.A.; Mccully, C.; Mo, J.; Moran, S.; Newsome, M.; Oparin, D.V.; Padilla Gonzalez, E.; Reynolds, T.M.; Shatsky, N.I.; Smartt, S.J.; Smith, K.W.; Stritzinger, M.D.; Tatarnikov, A.M.; Terreran, G.; Uklein, R.I.; Valerin, G.; Vallely, P.J.; Vozyakova, O.V.; Wainscoat, R.; Yan, S.-Y.; Zhang, J.-J.; Zhang, T.-M.; Zheltoukhov, S.G.; Dastidar, R.; Fulton, M.; Galbany, L.; Gangopadhyay, A.; Ge, H.-W.; Gutiérrez, C.P.; Lin, H.; Misra, K.; Ou, Z.-W.; Salmaso, I.; Tartaglia, L.; Xiao, L.; Zhang, X.-H.We present an observational study of the luminous red nova (LRN) AT 2021biy in the nearby galaxy NGC 4631. The field of the object was routinely imaged during the pre-eruptive stage by synoptic surveys, but the transient was detected only at a few epochs from ∼231 days before maximum brightness. The LRN outburst was monitored with unprecedented cadence both photometrically and spectroscopically. AT 2021biy shows a short-duration blue peak, with a bolometric luminosity of ∼1.6×1041 erg s-1, followed by the longest plateau among LRNe to date, with a duration of 210 days. A late-time hump in the light curve was also observed, possibly produced by a shell-shell collision. AT 2021biy exhibits the typical spectral evolution of LRNe. Early-time spectra are characterised by a blue continuum and prominent H emission lines. Then, the continuum becomes redder, resembling that of a K-type star with a forest of metal absorption lines during the plateau phase. Finally, late-time spectra show a very red continuum (TBB ≈ 2050 K) with molecular features (e.g., TiO) resembling those of M-type stars. Spectropolarimetric analysis indicates that AT 2021biy has local dust properties similar to those of V838 Mon in the Milky Way Galaxy. Inspection of archival Hubble Space Telescope data taken on 2003 August 3 reveals a ∼20 M⊗ progenitor candidate with log (L/L⊗) = 5.0 dex and Teff 5900 K at solar metallicity. The above luminosity and colour match those of a luminous yellow supergiant. Most likely, this source is a close binary, with a 17-24 M⊗ primary component. © Y.-Z. Cai et al. 2022.Ítem Intermediate-luminosity red transients: Spectrophotometric properties and connection to electron-capture supernova explosions(EDP Sciences, 2021-10-01) Cai, Y.-Z.; Pastorello, A.; Fraser, M.; Botticella, M. T.; Elias-Rosa, N.; Wang, L.-Z.; Kotak, R.; Benetti, S.; Cappellaro, E.; Turatto, M.; Reguitti, A.; Mattila, S.; Smartt, S. J.; Ashall, C.; Benitez, S.; Chen, T.-W.; Harutyunyan, A.; Kankare, E.; Lundqvist, P.; Mazzali, P. A.; Morales-Garoffolo, A.; Ochner, P.; Pignata, G.; Prentice, S. J.; Reynolds, T. M.; Shu, X.-W.; Stritzinger, M. D.; Tartaglia, L.; Terreran, G.; Tomasella, L.; Valenti, S.; Valerin, G.; Wang, G.-J.; Wang, X.-F.; Borsato, L.; Callis, E.; Cannizzaro, G.; Chen, S.; Congiu, E.; Ergon, M.; Galbany, L.; Gal-Yam, A.; Gao, X.; Gromadzki, M.; Holmbo, S.; Huang, F.; Inserra, C.; Itagaki, K.; Kostrzewa-Rutkowska, Z.; Maguire, K.; Margheim, S.; Moran, S.; Onori, F.; Sagués Carracedo, A.; Smith, K. W.; Sollerman, J.; Somero, A.; Wang, B.; Young, D. R.We present the spectroscopic and photometric study of five intermediate-luminosity red transients (ILRTs), namely AT 2010dn, AT 2012jc, AT 2013la, AT 2013lb, and AT 2018aes. They share common observational properties and belong to a family of objects similar to the prototypical ILRT SN 2008S. These events have a rise time that is less than 15 days and absolute peak magnitudes of between-11.5 and-14.5 mag. Their pseudo-bolometric light curves peak in the range 0.5-9.0 × 1040 erg s-1 and their total radiated energies are on the order of (0.3-3) × 1047 erg. After maximum brightness, the light curves show a monotonic decline or a plateau, resembling those of faint supernovae IIL or IIP, respectively. At late phases, the light curves flatten, roughly following the slope of the 56Co decay. If the late-time power source is indeed radioactive decay, these transients produce 56Ni masses on the order of 10-4 to 10-3 M⊙. The spectral energy distribution of our ILRT sample, extending from the optical to the mid-infrared (MIR) domain, reveals a clear IR excess soon after explosion and non-negligible MIR emission at very late phases. The spectra show prominent H lines in emission with a typical velocity of a few hundred km s-1, along with Ca II features. In particular, the [Ca II] λ7291,7324 doublet is visible at all times, which is a characteristic feature for this family of transients. The identified progenitor of SN 2008S, which is luminous in archival Spitzer MIR images, suggests an intermediate-mass precursor star embedded in a dusty cocoon. We propose the explosion of a super-asymptotic giant branch star forming an electron-capture supernova as a plausible explanation for these events.Ítem PESSTO: Survey description and products from the first data release by the Public ESO Spectroscopic Survey of Transient Objects(EDP Sciences, 2015-07) Smartt, S.J.; Valenti, S.; Fraser, M.; Inserra, C.; Young, D.R.; Sullivan, M.; Pastorello, A.; Benetti, S.; Gal-Yam, A.; Knapic, C.; Molinaro, M.; Smareglia, R.; Smith, K.W.; Taubenberger, S.; Yaron, O.; Anderson, J.P.; Ashall, C.; Balland, C.; Baltay, C.; Barbarino, C.; Bauer, F.E.; Baumont, S.; Bersier, D.; Blagorodnova, N.; Bongard, S.; Botticella, M.T.; Bufano, F.; Bulla, M.; Cappellaro, E.; Campbell, H.; Cellier-Holzem, F.; Chen, T.-W.; Childress, M.J.; Clocchiatti, A.; Contreras, C.; Dall'Ora, M.; Danziger, J.; De Jaeger, T.; De Cia, A.; Della Valle, M.; Dennefeld, M.; Elias-Rosa, N.; Elman, N.; Feindt, U.; Fleury, M.; Gall, E.; Gonzalez-Gaitan, S.; Galbany, L.; Morales Garoffolo, A.; Greggio, L.; Guillou, L.L.; Hachinger, S.; Hadjiyska, E.; Hage, P.E.; Hillebrandt, W.; Hodgkin, S.; Hsiao, E.Y.; James, P.A.; Jerkstrand, A.; Kangas, T.; Kankare, E.; Kotak, R.; Kromer, M.; Kuncarayakti, H.; Leloudas, G.; Lundqvist, P.; Lyman, J.D.; Hook, I.M.; Maguire, K.; Manulis, I.; Margheim, S.J.; Mattila, S.; Maund, J.R.; Mazzali, P.A.; McCrum, M.; McKinnon, R.; Moreno-Raya, M.E.; Nicholl, M.; Nugent, P.; Pain, R.; Pignata, G.; Phillips, M.M.; Polshaw, J.; Pumo, M.; Rabinowitz, D.; Reilly, E.; Romero-Cañizales, C.; Scalzo, R.; Schmidt, B.; Schulze, S.; Sim, S.; Sollerman, J.; Taddia, F.; Tartaglia, L.; Terreran, G.; Tomasella, L.; Turatto, M.; Walker, E.; Walton, N.A.; Wyrzykowski, L.; Yuan, F.; Zampieri, L.Context. The Public European Southern Observatory Spectroscopic Survey of Transient Objects (PESSTO) began as a public spectroscopic survey in April 2012. PESSTO classifies transients from publicly available sources and wide-field surveys, and selects science targets for detailed spectroscopic and photometric follow-up. PESSTO runs for nine months of the year, January - April and August - December inclusive, and typically has allocations of 10 nights per month. Aims. We describe the data reduction strategy and data products that are publicly available through the ESO archive as the Spectroscopic Survey data release 1 (SSDR1). Methods. PESSTO uses the New Technology Telescope with the instruments EFOSC2 and SOFI to provide optical and NIR spectroscopy and imaging. We target supernovae and optical transients brighter than 20.5m for classification. Science targets are selected for follow-up based on the PESSTO science goal of extending knowledge of the extremes of the supernova population. We use standard EFOSC2 set-ups providing spectra with resolutions of 13-18 Å between 3345-9995 Å. A subset of the brighter science targets are selected for SOFI spectroscopy with the blue and red grisms (0.935-2.53 μm and resolutions 23-33 Å) and imaging with broadband JHKs filters. Results. This first data release (SSDR1) contains flux calibrated spectra from the first year (April 2012-2013). A total of 221 confirmed supernovae were classified, and we released calibrated optical spectra and classifications publicly within 24 h of the data being taken (via WISeREP). The data in SSDR1 replace those released spectra. They have more reliable and quantifiable flux calibrations, correction for telluric absorption, and are made available in standard ESO Phase 3 formats. We estimate the absolute accuracy of the flux calibrations for EFOSC2 across the whole survey in SSDR1 to be typically ∼15%, although a number of spectra will have less reliable absolute flux calibration because of weather and slit losses. Acquisition images for each spectrum are available which, in principle, can allow the user to refine the absolute flux calibration. The standard NIR reduction process does not produce high accuracy absolute spectrophotometry but synthetic photometry with accompanying JHKs imaging can improve this. Whenever possible, reduced SOFI images are provided to allow this. Conclusions. Future data releases will focus on improving the automated flux calibration of the data products. The rapid turnaround between discovery and classification and access to reliable pipeline processed data products has allowed early science papers in the first few months of the survey. © ESO, 2015.Ítem SN 2020acat: an energetic fast rising Type IIb supernova(Oxford University Press, 2022-07-01) Medler, K.; Mazzali, P.A.; Teffs, J.; Ashall, C.; Anderson, J.P.; Arcavi, I.; Benetti, S.; Bostroem, K.A.; Burke, J.; Cai, Y.-Z.; Charalampopoulos, P.; Elias Rosa, N.; Ergon, M.; Galbany, L.; Gromadzki, M.; Hiramatsu, D.; Howell, D.A.; Inserra, C.; Lundqvist, P.; McCully, C.; Müller Bravo, T.; Newsome, M.; Nicholl, M.; Gonzalez, E. Padilla; Paraskeva, E.; Pastorello, A.; Pellegrino, C.; Pessi, P.J.; Reguitti, A.; Reynolds, T.M.; Roy, R.; Terreran, G.; Tomasella, L.; Young, D.R.The ultraviolet (UV) and near-infrared (NIR) photometric and optical spectroscopic observations of SN 2020acat covering ∼250 d after explosion are presented here. Using the fast rising photometric observations, spanning from the UV to NIR wavelengths, a pseudo-bolometric light curve was constructed and compared to several other well-observed Type IIb supernovae (SNe IIb). SN 2020acat displayed a very short rise time reaching a peak luminosity of Log10(L) = 42.49 ± 0.17 erg s-1 in only ∼14.6 ± 0.3 d. From modelling of the pseudo-bolometric light curve, we estimated a total mass of 56Ni synthesized by SN 2020acat of MNi = 0.13 ± 0.03 M⊙, with an ejecta mass of Mej = 2.3 ± 0.4 M⊙ and a kinetic energy of Ek = 1.2 ± 0.3 × 1051 erg. The optical spectra of SN 2020acat display hydrogen signatures well into the transitional period (≳ 100 d), between the photospheric and the nebular phases. The spectra also display a strong feature around 4900 Å that cannot be solely accounted for by the presence of the Fe ii 5018 line. We suggest that the Fe ii feature was augmented by He i 5016 and possibly by the presence of N ii 5005. From both photometric and spectroscopic analysis, we inferred that the progenitor of SN 2020acat was an intermediate-mass compact star with an MZAMS of 15-20 M⊙. © 2022 The Author(s).Ítem SNe 2013K and 2013am: Observed and physical properties of two slow, normal Type IIP events(Oxford University Press, 2018-04) Tomasella, L.; Cappellaro, E.; Pumo, M.L.; Jerkstrand, A.; Benetti, S.; Elias-Rosa, N.; Fraser, M.; Inserra, C.; Pastorello, A.; Turatto, M.; Anderson, J.P.; Galbany, L.; Gutiérrez, C.P.; Kankare, E.; Pignata, G.; Terreran, G.; Valenti, S.; Barbarino, C.; Bauer, F.E.; Botticella, M.T.; Chen, T.-W.; Gal-Yam, A.; Harutyunyan, A.; Howell, D.A.; Maguire, K.; Garoffolo, A.M.; Ochner, P.; Smartt, S.J.; Schulze, S.; Young, D.R.; Zampieri, L.We present 1 yr of optical and near-infrared photometry and spectroscopy of the Type IIP SNe 2013K and 2013am. Both objects are affected by significant extinction, due to their location in dusty regions of their respective host galaxies, ESO 009-10 and NGC 3623 (M65). From the photospheric to nebular phases, these objects display spectra congruent with those of underluminous Type IIP SNe (i.e. the archetypal SNe 1997D or 2005cs), showing low photospheric velocities (~2 × 10 3 km s -1 at 50 d) together with features arising from Ba II that are particularly prominent in faint SNe IIP. The peak V-band magnitudes of SN 2013K (-15.6mag) and SN 2013am (-16.2mag) are fainter than standard-luminosity Type IIP SNe. The ejected nickel masses are 0.012 ± 0.010 and 0.015 ± 0.006 M ⊙ for SN 2013K and SN 2013am, respectively. The physical properties of the progenitors at the time of explosion are derived through hydrodynamical modelling. Fitting the bolometric curves, the expansion velocity and the temperature evolution, we infer total ejected masses of 12 and 11.5 M ⊙ , pre- SN radii of~460 and~360 R ⊙ , and explosion energies of 0.34 foe and 0.40 foe for SN 2013K and SN 2013am. Late time spectra are used to estimate the progenitormasses from the strength of nebular emission lines, which turn out to be consistent with red supergiant progenitors of ~15 M ⊙ . For both SNe, a low-energy explosion of a moderate-mass red supergiant star is therefore the favoured scenario. © 2017 The Authors.Ítem SNhunt151: An explosive event inside a dense cocoon(Oxford University Press, 2018-04) Elias-Rosa, N.; Benetti, S.; Cappellaro, E.; Pastorello, A.; Terreran, G.; Morales-Garoffolo, A.; Howerton, S.C.; Valenti, S.; Kankare, E.; Drake, A.J.; Djorgovski, S.G.; Tomasella, L.; Tartaglia, L.; Kangas, T.; Ochner, P.; Filippenko, A.V.; Ciabattari, F.; Geier, S.; Howell, D.A.; Isern, J.; Leonini, S.; Pignata, G.; Turatto, M.SNhunt151 was initially classified as a supernova (SN) impostor (nonterminal outburst of a massive star). It exhibited a slow increase in luminosity, lasting about 450 d, followed by a major brightening that reaches M V ≈ -18 mag. No source is detected to M V ≳ -13 mag in archival images at the position of SNhunt151 before the slow rise. Low-to-mid-resolution optical spectra obtained during the pronounced brightening show very little evolution, being dominated at all times by multicomponent Balmer emission lines, a signature of interaction between the material ejected in the new outburst and the pre-existing circumstellar medium. We also analysed mid-infrared images from the Spitzer Space Telescope, detecting a source at the transient position in 2014 and 2015. Overall, SNhunt151 is spectroscopically a Type IIn SN, somewhat similar to SN 2009ip. However, there are also some differences, such as a slow pre-discovery rise, a relatively broad light-curve peak showing a longer rise time (~50 d), and a slower decline, along with a negligible change in the temperature around the peak (T ≤ 10 4 K). We suggest that SNhunt151 is the result of an outburst, or an SN explosion, within a dense circumstellar nebula, similar to those embedding some luminous blue variables like η Carinae and originating from past mass-loss events. © 2017 The Author(s).Ítem Type II supernovae in low-luminosity host galaxies(Oxford University Press, 2018-09) Gutiérrez, C.P.; Anderson, J.P.; Sullivan, M.; Dessart, L.; González-Gaitan, S.; Galbany, L.; Dimitriadis, G.; Arcavi, I.; Bufano, F.; Chen, T.-W.; Dennefeld, M.; Gromadzki, M.; Haislip, J.B.; Hosseinzadeh, G.; Howell, D.A.; Inserra, C.; Kankare, E.; Leloudas, G.; Maguire, K.; McCully, C.; Morrell, N.; Olivares, E.F.; Pignata, G.; Reichart, D.E.; Reynolds, T.; Smartt, S.J.; Sollerman, J.; Taddia, F.; Takáts, K.; Terreran, G.; Valenti, S.; Young, D.R.We present an analysis of a new sample of type II core-collapse supernovae (SNe II) occurring within low-luminosity galaxies, comparing these with a sample of events in brighter hosts. Our analysis is performed comparing SN II spectral and photometric parameters and estimating the influence of metallicity (inferred from host luminosity differences) on SN II transient properties. We measure the SN absolute magnitude at maximum, the light-curve plateau duration, the optically thick duration, and the plateau decline rate in the V band, together with expansion velocities and pseudo-equivalent-widths (pEWs) of several absorption lines in the SN spectra. For the SN host galaxies, we estimate the absolute magnitude and the stellar mass, a proxy for the metallicity of the host galaxy. SNe II exploding in low-luminosity galaxies display weaker pEWs of Fe II λ5018, confirming the theoretical prediction that metal lines in SN II spectra should correlate with metallicity.We also find that SNe II in low-luminosity hosts have generally slower declining light curves and display weaker absorption lines. We find no relationship between the plateau duration or the expansion velocities with SN environment, suggesting that the hydrogen envelope mass and the explosion energy are not correlated with the metallicity of the host galaxy. This result supports recent predictions that mass-loss for red supergiants is independent of metallicity. © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.