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Linking supernovae to their progenitors is a powerful method for furthering our understanding of the physical origin of their observed differences, while at the same time testing stellar evolution theory. In this second study of a series of three papers where we characterise SNe II to understand their diversity, we derive progenitor properties (initial and ejecta masses, and radius), explosion energy, $^{56}$Ni mass, and its degree of mixing within the ejecta for a large sample of SNe II. This dataset was obtained by the Carnegie Supernova Project-I and is characterised by a high cadence of their optical and NIR light curves and optical spectra that were homogeneously observed and processed. A large grid of hydrodynamical models and a fitting procedure based on MCMC methods were used to fit the bolometric light curve and the evolution of the photospheric velocity of 53 SNe II. We infer ejecta masses between 7.9 and 14.8 $M_{\odot}$, explosion energies between 0.15 and 1.40 foe, and $^{56}$Ni masses between 0.006 and 0.069 $M_{\odot}$. We define a subset of 24~SNe (the `gold sample') with well-sampled bolometric light curves and expansion velocities for which we consider the results more robust. Most SNe~II in the gold sample ($\sim$88%) are found with ejecta masses in the range of $\sim$8-10 $M_{\odot}$, coming from low zero-age main-sequence masses (9-12 $M_{\odot}$). The modelling of the initial-mass distribution of the gold sample gives an upper mass limit of 21.3$^{+3.8}_{-0.4}$ $M_{\odot}$ and a much steeper distribution than that for a Salpeter massive-star IMF. This IMF incompatibility is due to the large number of low-mass progenitors found -- when assuming standard stellar evolution. This may imply that high-mass progenitors lose more mass during their lives than predicted. However, a deeper analysis of all stellar evolution assumptions is required to test this hypothesis., Comment: Accepted for publication in Astronomy & Astrophysics

KM, MRM, and SJP are supported by H2020 ERC grant no. 758638. LG acknowledges financial support from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 839090, and from the Spanish Ministry of Science, Innovation and Universities (MICIU) under the 2019 Ramon y Cajal programme RYC2019-027683. TMB ´ was funded by the CONICYT PFCHA / DOCTORADOBECAS CHILE/2017-72180113. MG is supported by the EU Horizon 2020 research and innovation programme under grant agreement no. 101004719. SGG acknowledges support by FCT under Project CRISP PTDC/FIS-AST-31546/2017. MN is supported by a Royal Astronomical Society Research Fellowship and H2020 ERC grant no. 948381. T-WC acknowledges the EU Funding under Marie Skłodowska-Curie grant H2020-MSCA-IF-2018-842471. The LT is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, as part of ePESSTO+ (the advanced Public ESO Spectroscopic Survey for Transient Objects Survey). ePESSTO+ observations were obtained under ESO programme ID 1103.D-0328 (PI: Inserra). The WHT is operated on the island of La Palma by the Isaac Newton Group of Telescopes in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrof´ısica de Canarias. SJP thanks GPL for many insightful discussions at the bar over the last few years., The division between stripped-envelope supernovae (SE-SNe) and superluminous supernovae (SLSNe) is not well-defined in either photometric or spectroscopic space. While a sharp luminosity threshold has been suggested, there remains an increasing number of transitional objects that reach this threshold without the spectroscopic signatures common to SLSNe. In this work, we present data and analysis on four SNe transitional between SE-SNe and SLSNe; the He-poor SNe 2019dwa and 2019cri, and the He-rich SNe 2019hge and 2019unb. Each object displays long-lived and variable photometric evolution with luminosities around the SLSN threshold of Mr < -19.8 mag. Spectroscopically however, these objects are similar to SE-SNe, with line velocities lower than either SE-SNe and SLSNe, and thus represent an interesting case of rare transitional events., H2020 ERC grant no. 758638, European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 839090, Spanish Ministry of Science, Innovation and Universities (MICIU) under the 2019 Ramon y Cajal programme RYC2019-027683, CONICYT PFCHA / DOCTORADOBECAS CHILE/2017-72180113, EU Horizon 2020 research and innovation programme under grant agreement no. 101004719, FCT under Project CRISP PTDC/FIS-AST-31546/2017, Royal Astronomical Society Research Fellowship, H2020 ERC grant no. 948381, UK Science and Technology Facilities Council, ESO programme ID 1103.D-0328 (PI: Inserra)

Type II supernovae (SNe II) show great photometric and spectroscopic diversity which is attributed to the varied physical characteristics of their progenitor and explosion properties. In this study, the third of a series of papers where we analyse a large sample of SNe II observed by the Carnegie Supernova Project-I, we present correlations between their observed and physical properties. Our analysis shows that explosion energy is the physical property that correlates with the highest number of parameters. We recover previously suggested relationships between the hydrogen-rich envelope mass and the plateau duration, and find that more luminous SNe II with higher expansion velocities, faster declining light curves, and higher 56Ni masses are consistent with higher energy explosions. In addition, faster declining SNe II (usually called SNe IIL) are also compatible with more concentrated 56Ni in the inner regions of the ejecta. Positive trends are found between the initial mass, explosion energy, and 56Ni mass. While the explosion energy spans the full range explored with our models, the initial mass generally arises from a relatively narrow range. Observable properties were measured from our grid of bolometric LC and photospheric velocity models to determine the effect of each physical parameter on the observed SN II diversity. We argue that explosion energy is the physical parameter causing the greatest impact on SN II diversity, that is, assuming the non-rotating solar-metallicity single-star evolution as in the models used in this study. The inclusion of pre-SN models assuming higher mass loss produces a significant increase in the strength of some correlations, particularly those between the progenitor hydrogen-rich envelope mass and the plateau and optically thick phase durations. These differences clearly show the impact of having different treatments of stellar evolution, implying that changes in the assumption of standard single-star evolution are necessary for a complete understanding of SN II diversity., The work of the Carnegie Supernova Project was supported by the National Science Foundation under grants AST-0306969, AST-0607438, AST-1008343, AST-1613426, AST-1613472, and AST-1613455. L.M. acknowledges support from a CONICET fellowship. L.M. and M.O. acknowledge support from UNRN PI2018 40B885 grant. M.H. acknowledges support from the Hagler Institute of Advanced Study at Texas A&M University. S.G.G. acknowledges support by FCT under Project CRISP PTDC/FIS-AST-31546/2017 and Project No. UIDB/00099/2020. M.S. is supported by grants from the VILLUM FONDEN (grant number 28021) and the Independent Research Fund Denmark (IRFD; 8021-00170B). F.F. acknowledges support from the National Agency for Research and Development (ANID) grants: BASAL Center of Mathematical Modelling AFB-170001, Ministry of Economy, Development, and Tourism’s Millennium Science Initiative through grant IC12009, awarded to the Millennium Institute of Astrophysics, and FONDECYT Regular #1200710. L.G. acknowledges financial support from the Spanish Ministry of Science, Innovation and Universities (MICIU) under the 2019 Ramón y Cajal program RYC2019-027683 and from the Spanish MICIU project PID2020-115253GA-I00. P.H. acknowledges the support by National Science Foundation (NSF) grant AST-1715133.

We present the first results of the High cadence Transient Survey (HiTS), a survey whose objective is to detect and follow up optical transients with characteristic timescales from hours to days, especially the earliest hours of supernova (SN) explosions. HiTS uses the Dark Energy Camera (DECam) and a custom made pipeline for image subtraction, candidate filtering and candidate visualization, which runs in real-time to be able to react rapidly to the new transients. We discuss the survey design, the technical challenges associated with the real-time analysis of these large volumes of data and our first results. In our 2013, 2014 and 2015 campaigns we have detected more than 120 young SN candidates, but we did not find a clear signature from the short-lived SN shock breakouts (SBOs) originating after the core collapse of red supergiant stars, which was the initial science aim of this survey. Using the empirical distribution of limiting-magnitudes from our observational campaigns we measured the expected recovery fraction of randomly injected SN light curves which included SBO optical peaks produced with models from Tominaga et al. (2011) and Nakar & Sari (2010). From this analysis we cannot rule out the models from Tominaga et al. (2011) under any reasonable distributions of progenitor masses, but we can marginally rule out the brighter and longer-lived SBO models from Nakar & Sari (2010) under our best-guess distribution of progenitor masses. Finally, we highlight the implications of this work for future massive datasets produced by astronomical observatories such as LSST., 30 pages, 14 figures, accepted for publication in ApJ

Type II supernovae (SNe II) originate from the explosion of hydrogen-rich supergiant massive stars. Their first electromagnetic signature is the shock breakout (SBO), a short-lived phenomenon that can last for hours to days depending on the density at shock emergence. We present 26 rising optical light curves of SN II candidates discovered shortly after explosion by the High Cadence Transient Survey and derive physical parameters based on hydrodynamical models using a Bayesian approach. We observe a steep rise of a few days in 24 out of 26 SN II candidates, indicating the systematic detection of SBOs in a dense circumstellar matter consistent with a mass loss rate of Ṁ> 10M yr or a dense atmosphere. This implies that the characteristic hour-timescale signature of stellar envelope SBOs may be rare in nature and could be delayed into longer-lived circumstellar material SBOs in most SNe II. © 2018, Nature Publishing Group. All rights reserved., We thank L. Dessart, K. Maeda, Ph. Podsiadlowski and K. Pichara for useful discussions. F.F. and T.J.M. thank the Yukawa Institute for Theoretical Physics at Kyoto University, where part of this work was initiated during the YITP-T-16-05 on 'Transient Universe in the Big Survey Era: Understanding the Nature of Astrophysical Explosive Phenomena'. T.J.M. is supported by the Grants-in-Aid for Scientific Research of the Japan Society for the Promotion of Science (16H07413 and 17H02864). The Powered@NLHPC research was partially supported by the supercomputing infrastructure of the NLHPC (ECM-02). Numerical computations were partially carried out on PC cluster at the Center for Computational Astrophysics, National Astronomical Observatory of Japan. We acknowledge support from Conicyt through the infrastructure Quimal project (number 140003). F.F., J.S.M., E.V. and S.G.-G. acknowledge support from Conicyt Basal fund AFB170001. F.F., G.C.-V., A.C., P.A.E., M.H., P. Huijse, H.K., J.M., G.M., F.O.E., G.P., A.R. and I.R. acknowledge support from the Ministry of Economy, Development and Tourism's Millennium Science Initiative through grant IC120009, awarded to The Millennium Institute of Astrophysics. S.-C.Y. was supported by the Korea Astronomy and Space Science Institute under the research and development programme (project number 3348-20160002) supervised by the Ministry of Science, ICT and Future Planning and Monash Centre for Astrophysics via the distinguished visitor programme. E.Y.H. and C.A. acknowledge the support provided by the National Science Foundation under grant number AST-1613472 and the Florida Space Grant Consortium. F.F., J.M., G.M. and A.R. acknowledge support from Conicyt through Fondecyt project number 11130228. J.C.M., G.C-V., P.A.E.,P. Huijse, H.K., G.P. and F.O.E. acknowledge support from Conicyt through Fondecyt project numbers 11170657, 3160747, 1171678, 3150460, 3140563, 1140352 and 11170953, respectively. G.M. and I.R. acknowledge support from CONICYT-PCHA/Magister Nacional/2016-22162353 and 201622162464, respectively. G.G. is supported by the Deutsche Forschungsgemeinschaft, grant number GR 1717/5. S.G.-G. acknowledges support from Comite Mixto ESO Chile project ORP 48/16. F.F., J.C.M., P. Huijse, G.C.-V. and P.A.E. acknowledge support from Conicyt through the Programme of International Cooperation project DPI20140090. L.G. was supported in part by the US National Science Foundation under grant AST-1311862. A.G.-Y. is supported by the EU via ERC grant number 725161, the Quantum Universe I-Core programme, the ISF, the BSF Transformative programme and a Kimmel award. M.F. is supported by the Royal Society-Science Foundation Ireland University Research Fellowship (reference 15/RS-URF/3304). S.B. acknowledges funding from project RSCF 18-12-00522. This study was based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 292.D-5042(A) and 094.D-0358(A). This work is partly based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile as part of the PESSTO ESO programmes 188.D-3003, 191.D-0935 and 197.D-1075. It is partly based on observations obtained with the Gran Telescopio Canarias telescope. This project used data obtained with DECam, which was constructed by the Dark Energy Survey (DES) collaboration. r Funding for the DES projects was provided by the US Department of Energy, US National Science Foundation, Ministry of Science and Education of Spain, Science and Technology Facilities Council of the United Kingdom, Higher Education Funding Council for England, National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, Kavli Institute of Cosmological Physics at the University of Chicago, Center for Cosmology and AstroParticle Physics at The Ohio State University, Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundacao Carlos Chagas Filho de Amparo, Financiadora de Estudos e Projetos, Fundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Cientifico e Tecnologico, Ministerio da Ciencia, Tecnologia e Inovacao, Deutsche Forschungsgemeinschaft and Collaborating Institutions in the DES. The Collaborating Institutions are Argonne National Laboratory, the University of California at Santa Cruz, University of Cambridge, Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas-Madrid, University of Chicago, University College London, DES-Brazil Consortium, University of Edinburgh, Eidgenossische Technische Hochschule Zurich, Fermi National Accelerator Laboratory, University of Illinois at Urbana-Champaign, Institut de Ciencies de l'Espai, Institut de Fisica d'Altes Energies, Lawrence Berkeley National Laboratory, Ludwig-Maximilians Universitat Munchen and the associated Excellence Cluster Universe, University of Michigan, National Optical Astronomy Observatory, University of Nottingham, Ohio State University, University of Pennsylvania, University of Portsmouth, SLAC National Accelerator Laboratory, Stanford University, University of Sussex and Texas A&M University.