| 1. |
- Aamodt, K., et al.
(author)
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Alignment of the ALICE Inner Tracking System with cosmic-ray tracks
- 2010
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In: Journal of Instrumentation. - 1748-0221. ; 5
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Conference paper (peer-reviewed)abstract
- ALICE (A Large Ion Collider Experiment) is the LHC (Large Hadron Collider) experiment devoted to investigating the strongly interacting matter created in nucleus-nucleus collisions at the LHC energies. The ALICE ITS, Inner Tracking System, consists of six cylindrical layers of silicon detectors with three different technologies; in the outward direction: two layers of pixel detectors, two layers each of drift, and strip detectors. The number of parameters to be determined in the spatial alignment of the 2198 sensor modules of the ITS is about 13,000. The target alignment precision is well below 10 mu m in some cases (pixels). The sources of alignment information include survey measurements, and the reconstructed tracks from cosmic rays and from proton-proton collisions. The main track-based alignment method uses the Millepede global approach. An iterative local method was developed and used as well. We present the results obtained for the ITS alignment using about 10(5) charged tracks from cosmic rays that have been collected during summer 2008, with the ALICE solenoidal magnet switched off.
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| 2. |
- Aamodt, K., et al.
(author)
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First proton-proton collisions at the LHC as observed with the ALICE detector: measurement of the charged-particle pseudorapidity density at root s=900 GeV
- 2010
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 65:1-2, s. 111-125
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Journal article (peer-reviewed)abstract
- On 23rd November 2009, during the early commissioning of the CERN Large Hadron Collider (LHC), two counter-rotating proton bunches were circulated for the first time concurrently in the machine, at the LHC injection energy of 450 GeV per beam. Although the proton intensity was very low, with only one pilot bunch per beam, and no systematic attempt was made to optimize the collision optics, all LHC experiments reported a number of collision candidates. In the ALICE experiment, the collision region was centred very well in both the longitudinal and transverse directions and 284 events were recorded in coincidence with the two passing proton bunches. The events were immediately reconstructed and analyzed both online and offline. We have used these events to measure the pseudorapidity density of charged primary particles in the central region. In the range vertical bar eta vertical bar < 0.5, we obtain dN(ch)/d eta = 3.10 +/- 0.13(stat.) +/- 0.22(syst.) for all inelastic interactions, and dN(ch)/d eta = 3.51 +/- 0.15(stat.) +/- 0.25(syst.) for nonsingle diffractive interactions. These results are consistent with previous measurements in proton-antiproton interactions at the same centre-of-mass energy at the CERN Sp<(p)over bar>S collider. They also illustrate the excellent functioning and rapid progress of the LHC accelerator, and of both the hardware and software of the ALICE experiment, in this early start-up phase.
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| 3. |
- Aamodt, K., et al.
(author)
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Production of pions, kaons and protons in pp collisions at root s=900 GeV with ALICE at the LHC
- 2011
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In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 71:6
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Journal article (peer-reviewed)abstract
- The production of pi(+), pi(-), K+, K-, p, and (p) over bar at mid-rapidity has been measured in proton-proton collisions at root s = 900 GeV with the ALICE detector. Particle identification is performed using the specific energy loss in the inner tracking silicon detector and the time projection chamber. In addition, time-of-flight information is used to identify hadrons at higher momenta. Finally, the distinctive kink topology of the weak decay of charged kaons is used for an alternative measurement of the kaon transverse momentum (p(t)) spectra. Since these various particle identification tools give the best separation capabilities over different momentum ranges, the results are combined to extract spectra from p(t) = 100 MeV/c to 2.5 GeV/c. The measured spectra are further compared with QCD-inspired models which yield a poor description. The total yields and the mean pt are compared with previous measurements, and the trends as a function of collision energy are discussed.
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| 4. |
- Aamodt, K., et al.
(author)
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The ALICE experiment at the CERN LHC
- 2008
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In: Journal of Instrumentation. - 1748-0221. ; 3:S08002
-
Research review (peer-reviewed)abstract
- ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries, Its overall dimensions are 16 x 16 x 26 m(3) with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008.
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| 5. |
- Aamodt, K., et al.
(author)
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Midrapidity Antiproton-to-Proton Ratio in pp Collisons root s=0.9 and 7 TeV Measured by the ALICE Experiment
- 2010
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In: Physical Review Letters. - 1079-7114. ; 105:7
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Journal article (peer-reviewed)abstract
- The ratio of the yields of antiprotons to protons in pp collisions has been measured by the ALICE experiment at root s = 0.9 and 7 TeV during the initial running periods of the Large Hadron Collider. The measurement covers the transverse momentum interval 0.45 < p(t) < 1.05 GeV/c and rapidity vertical bar y vertical bar < 0.5. The ratio is measured to be R-vertical bar y vertical bar<0.5 = 0.957 +/- 0.006(stat) +/- 0.0014(syst) at 0.9 Tev and R-vertical bar y vertical bar<0.5 = 0.991 +/- 0.005 +/- 0.014(syst) at 7 TeV and it is independent of both rapidity and transverse momentum. The results are consistent with the conventional model of baryon-number transport and set stringent limits on any additional contributions to baryon-number transfer over very large rapidity intervals in pp collisions.
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| 6. |
- Aamodt, K., et al.
(author)
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Transverse momentum spectra of charged particles in proton-proton collisions at root s=900 GeV with ALICE at the LHC
- 2010
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In: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 693:2, s. 53-68
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Journal article (peer-reviewed)abstract
- The inclusive charged particle transverse momentum distribution is measured in proton-proton collisions at root s = 900 GeV at the LHC using the ALICE detector. The measurement is performed in the central pseudorapidity region (vertical bar eta vertical bar < 0.8) over the transverse momentum range 0.15 < p(T) < 10 GeV/c. The correlation between transverse momentum and particle multiplicity is also studied. Results are presented for inelastic (INEL) and non-single-diffractive (NSD) events. The average transverse momentum for vertical bar eta vertical bar < 0.8 is < p(T)>(INEL) = 0.483 +/- 0.001 (stat.) +/- 0.007 (syst.) GeV/c and < p(T)>(NSD) = 0.489 +/- 0.001 (stat.) +/- 0.007 (syst.) GeV/c, respectively. The data exhibit a slightly larger < p(T)> than measurements in wider pseudorapidity intervals. The results are compared to simulations with the Monte Carlo event generators PYTHIA and PHOJET. (C) 2010 Published by Elsevier B.V.
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| 7. |
- Aamodt, K., et al.
(author)
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Two-pion Bose-Einstein correlations in pp collisions at root s=900 GeV
- 2010
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In: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 82:5
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Journal article (peer-reviewed)abstract
- We report on the measurement of two-pion correlation functions from pp collisions at root s = 900 GeV performed by the ALICE experiment at the Large Hadron Collider. Our analysis shows an increase of the Hanbury Brown-Twiss radius with increasing event multiplicity, in line with other measurements done in particle- and nuclear collisions. Conversely, the strong decrease of the radius with increasing transverse momentum, as observed at the Relativistic Heavy Ion Collider and at Tevatron, is not manifest in our data.
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| 8. |
- Aamodt, K., et al.
(author)
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Charged-particle multiplicity measurement in proton-proton collisions at root s=0.9 and 2.36 TeV with ALICE at LHC
- 2010
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 68:1-2, s. 89-108
-
Journal article (peer-reviewed)abstract
- Charged-particle production was studied in proton-proton collisions collected at the LHC with the ALICE detector at centre-of-mass energies 0.9 TeV and 2.36 TeV in the pseudorapidity range vertical bar eta vertical bar < 1.4. In the central region (vertical bar eta vertical bar < 0.5), at 0.9 TeV, we measure charged-particle pseudo-rapidity density dN(ch)/d eta = 3.02 +/- 0.01(stat.)(-0.05)(+0.08)(syst.) for inelastic interactions, and dN(ch)/d eta = 3.58 +/- 0.01 (stat.)(-0.12)(+0.12)(syst.) for non-single-diffractive interactions. At 2.36 TeV, we find dN(ch)/d eta = 3.77 +/- 0.01(stat.)(-0.12)(+0.25)(syst.) for inelastic, and dN(ch)/d eta = 4.43 +/- 0.01(stat.)(-0.12)(+0.17)(syst.) for non-single-diffractive collisions. The relative increase in charged-particle multiplicity from the lower to higher energy is 24.7% +/- 0.5%(stat.)(-2.8)(+5.7)%(syst.) for inelastic and 23.7% +/- 0.5%(stat.)(-1.1)(+4.6)%(syst.) for non-single-diffractive interactions. This increase is consistent with that reported by the CMS collaboration for non-single-diffractive events and larger than that found by a number of commonly used models. The multiplicity distribution was measured in different pseudorapidity intervals and studied in terms of KNO variables at both energies. The results are compared to proton-antiproton data and to model predictions.
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| 9. |
- Aamodt, K., et al.
(author)
-
Charged-particle multiplicity measurement in proton-proton collisions at root s=7 TeV with ALICE at LHC
- 2010
-
In: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 68:3-4, s. 345-354
-
Journal article (peer-reviewed)abstract
- The pseudorapidity density and multiplicity distribution of charged particles produced in proton-proton collisions at the LHC, at a centre-of-mass energy root s = 7 TeV, were measured in the central pseudorapidity region vertical bar eta vertical bar < 1. Comparisons are made with previous measurements at root s = 0.9 TeV and 2.36 TeV. At root s = 7 TeV, for events with at least one charged particle in |eta vertical bar| < 1, we obtain dN(ch)/d eta = 6.01 +/- 0.01(stat.)(-0.12)(+0.20) (syst.). This corresponds to an increase of 57.6%+/-0.4%(stat.)(-1.8%)(+3.6) (syst.) relative to collisions at 0.9 TeV, significantly higher than calculations from commonly used models. The multiplicity distribution at 7 TeV is described fairly well by the negative binomial distribution.
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| 10. |
- Buchanan, E. M., et al.
(author)
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The Psychological Science Accelerator's COVID-19 rapid-response dataset
- 2023
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In: Scientific Data. - : Springer Science and Business Media LLC. - 2052-4463. ; 10:1
-
Journal article (peer-reviewed)abstract
- In response to the COVID-19 pandemic, the Psychological Science Accelerator coordinated three large-scale psychological studies to examine the effects of loss-gain framing, cognitive reappraisals, and autonomy framing manipulations on behavioral intentions and affective measures. The data collected (April to October 2020) included specific measures for each experimental study, a general questionnaire examining health prevention behaviors and COVID-19 experience, geographical and cultural context characterization, and demographic information for each participant. Each participant started the study with the same general questions and then was randomized to complete either one longer experiment or two shorter experiments. Data were provided by 73,223 participants with varying completion rates. Participants completed the survey from 111 geopolitical regions in 44 unique languages/dialects. The anonymized dataset described here is provided in both raw and processed formats to facilitate re-use and further analyses. The dataset offers secondary analytic opportunities to explore coping, framing, and self-determination across a diverse, global sample obtained at the onset of the COVID-19 pandemic, which can be merged with other time-sampled or geographic data.
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| 11. |
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| 12. |
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| 13. |
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| 14. |
- Naehrlich, L., et al.
(author)
-
Incidence of SARS-CoV-2 in people with cystic fibrosis in Europe between February and June 2020
- 2021
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In: Journal of Cystic Fibrosis. - : Elsevier BV. - 1569-1993. ; 20:4, s. 566-577
-
Journal article (peer-reviewed)abstract
- Background: Viral infections can cause significant morbidity in cystic fibrosis (CF). The current Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic could therefore have a serious impact on the health of people with CF (pwCF). Methods: We used the 38-country European Cystic Fibrosis Society Patient Registry (ECFSPR) to collect case data about pwCF and SARS-CoV-2 infection. Results: Up to 30 June 2020, 16 countries reported 130 SARS-CoV-2 cases in people with CF, yielding an incidence of 2.70/10 0 0 pwCF. Incidence was higher in lung-transplanted patients (n = 23) versus non transplanted patients (n = 107) (8.43 versus 2.36 cases/10 0 0). Incidence was higher in pwCF versus the age-matched general population in the age groups < 15, 15-24, and 25-49 years (p < 0.001), with similar trends for pwCF with and without lung transplant. Compared to the general population, pwCF (regardless of transplantation status) had significantly higher rates of admission to hospital for all age groups with available data, and higher rates of intensive care, although not statistically significant. Most pwCF recovered (96.2%), however 5 died, of whom 3 were lung transplant recipients. The case fatality rate for pwCF (3.85%, 95% CI: 1.26-8.75) was non-significantly lower than that of the general population (7.46%; p = 0.133). Conclusions: SARS-CoV-2 infection can result in severe illness and death for pwCF, even for younger patients and especially for lung transplant recipients. PwCF should continue to shield from infection and should be prioritized for vaccination. (c) 2021 The Authors. Published by Elsevier B.V. on behalf of European Cystic Fibrosis Society. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )
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| 15. |
- Jung, A, et al.
(author)
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Factors for severe outcomes following SARS-CoV-2 infection in people with cystic fibrosis in Europe
- 2021
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In: ERJ open research. - : European Respiratory Society (ERS). - 2312-0541. ; 7:4
-
Journal article (peer-reviewed)abstract
- Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in people with cystic fibrosis (pwCF) can lead to severe outcomes.MethodsIn this observational study, the European Cystic Fibrosis Society Patient Registry collected data on pwCF and SARS-CoV-2 infection to estimate incidence, describe clinical presentation and investigate factors associated with severe outcomes using multivariable analysis.ResultsUp to December 31, 2020, 26 countries reported information on 828 pwCF and SARS-CoV-2 infection. Incidence was 17.2 per 1000 pwCF (95% CI: 16.0–18.4). Median age was 24 years, 48.4% were male and 9.4% had lung transplants. SARS-CoV-2 incidence was higher in lung-transplanted (28.6; 95% CI: 22.7–35.5) versus non-lung-transplanted pwCF (16.6; 95% CI: 15.4–17.8) (p≤0.001).SARS-CoV-2 infection caused symptomatic illness in 75.7%. Factors associated with symptomatic SARS-CoV-2 infection were age >40 years, at least one F508del mutation and pancreatic insufficiency.Overall, 23.7% of pwCF were admitted to hospital, 2.5% of those to intensive care, and regretfully 11 (1.4%) died. Hospitalisation, oxygen therapy, intensive care, respiratory support and death were 2- to 6-fold more frequent in lung-transplanted versus non-lung-transplanted pwCF.Factors associated with hospitalisation and oxygen therapy were lung transplantation, cystic fibrosis-related diabetes (CFRD), moderate or severe lung disease and azithromycin use (often considered a surrogate marker for Pseudomonas aeruginosa infection and poorer lung function).ConclusionSARS-CoV-2 infection yielded high morbidity and hospitalisation in pwCF. PwCF with forced expiratory volume in 1 s <70% predicted, CFRD and those with lung transplants are at particular risk of more severe outcomes.
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| 16. |
- Pastorello, A., et al.
(author)
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ESC and KAIT observations of the transitional type Ia SN 2004eo
- 2007
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 377:4, s. 1531-1552
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Journal article (peer-reviewed)abstract
- We present optical and infrared observations of the unusual Type Ia supernova (SN) 2004eo. The light curves and spectra closely resemble those of the prototypical SN 1992A, and the luminosity at maximum (M-B = -19.08) is close to the average for a Type Ia supernova (SN Ia). However, the ejected Ni-56 mass derived by modelling the bolometric light curve (about 0.45M(circle dot)) lies near the lower limit of the Ni-56 mass distribution observed in normal SNe Ia. Accordingly, SN 2004eo shows a relatively rapid post-maximum decline in the light curve [Delta m(15)(B)(true) = 1.46], small expansion velocities in the ejecta and a depth ratio Si II lambda 5972/ Si II lambda 6355 similar to that of SN 1992A. The physical properties of SN 2004eo cause it to fall very close to the boundary between the faint, low-velocity gradient and high-velocity gradient subgroups proposed by Benetti et al. Similar behaviour is seen in a few other SNe Ia. Thus, there may in fact exist a few SNe Ia with intermediate physical properties.
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| 17. |
- Spiro, S., et al.
(author)
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Low luminosity Type II supernovae - II. Pointing towards moderate mass precursors
- 2014
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 439:3, s. 2873-2892
-
Journal article (peer-reviewed)abstract
- We present new data for five underluminous Type II-plateau supernovae (SNe IIP), namely SN 1999gn, SN 2002gd, SN 2003Z, SN 2004eg and SN 2006ov. This new sample of low-luminosity SNe IIP (LL SNe IIP) is analysed together with similar objects studied in the past. All of them show a flat light-curve plateau lasting about 100 d, an underluminous late-time exponential tail, intrinsic colours that are unusually red, and spectra showing prominent and narrow P Cygni lines. A velocity of the ejected material below 10(3) km s(-1) is inferred from measurements at the end of the plateau. The Ni-56 masses ejected in the explosion are very small (< 10(-2) M-circle dot). We investigate the correlations among Ni-56 mass, expansion velocity of the ejecta and absolute magnitude in the middle of the plateau, confirming the main findings of Hamuy, according to which events showing brighter plateau and larger expansion velocities are expected to produce more Ni-56. We propose that these faint objects represent the LL tail of a continuous distribution in parameters space of SNe IIP. The physical properties of the progenitors at the explosion are estimated through the hydrodynamical modelling of the observables for two representative events of this class, namely SN 2005cs and SN 2008in. We find that the majority of LL SNe IIP, and quite possibly all, originate in the core collapse of intermediate-mass stars, in the mass range 10-15 M-circle dot.
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| 18. |
- Carr, S.B., et al.
(author)
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Factors associated with clinical progression to severe COVID-19 in people with cystic fibrosis: A global observational study
- 2022
-
In: Journal of Cystic Fibrosis. - : Elsevier BV. - 1569-1993. ; 21:4, s. E221-E231
-
Journal article (peer-reviewed)abstract
- Background: This international study aimed to characterise the impact of acute SARS-CoV-2 infection in people with cystic fibrosis and investigate factors associated with severe outcomes. Methods Data from 22 countries prior to 13th December 2020 and the introduction of vaccines were included. It was de-identified and included patient demographics, clinical characteristics, treatments, outcomes and sequalae following SARS-CoV-2 infection. Multivariable logistic regression was used to investigate factors associated with clinical progression to severe COVID-19, using the primary outcome of hospitalisation with supplemental oxygen. Results: SARS-CoV-2 was reported in 1555 people with CF, 1452 were included in the analysis. One third were aged <18 years, and 9.4% were solid-organ transplant recipients. 74.5% were symptomatic and 22% were admitted to hospital. In the non-transplanted cohort, 39.5% of patients with ppFEV1<40% were hospitalised with oxygen verses 3.2% with ppFEV >70%: a 17-fold increase in odds. Worse outcomes were independently associated with older age, non-white race, underweight body mass index, and CF-related diabetes. Prescription of highly effective CFTR modulator therapies was associated with a significantly reduced odds of being hospitalised with oxygen (AOR 0.43 95%CI 0.31-0.60 p<0.001). Transplanted patients were hospitalised with supplemental oxygen therapy (21.9%) more often than non-transplanted (8.8%) and was independently associated with the primary outcome (Adjusted OR 2.45 95%CI 1.27-4.71 p=0.007). Conclusions: This is the first study to show that there is a protective effect from the use of CFTR modulator therapy and that people with CF from an ethnic minority are at more risk of severe infection with SARS-CoV-2. © 2022
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| 19. |
- Pastorello, A., et al.
(author)
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A giant outburst two years before the core-collapse of a massive star
- 2007
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 447:7146, s. 829-832
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Journal article (peer-reviewed)abstract
- The death of massive stars produces a variety of supernovae, which are linked to the structure of the exploding stars(1,2). The detection of several precursor stars of type II supernovae has been reported ( see, for example, ref. 3), but we do not yet have direct information on the progenitors of the hydrogen-deficient type Ib and Ic supernovae. Here we report that the peculiar type Ib supernova SN 2006jc is spatially coincident with a bright optical transient(4) that occurred in 2004. Spectroscopic and photometric monitoring of the supernova leads us to suggest that the progenitor was a carbon-oxygen Wolf - Rayet star embedded within a helium-rich circumstellar medium. There are different possible explanations for this pre-explosion transient. It appears similar to the giant outbursts of luminous blue variable stars (LBVs) of 60 - 100 solar masses(5), but the progenitor of SN 2006jc was helium- and hydrogen-deficient ( unlike LBVs). An LBV-like outburst of a Wolf - Rayet star could be invoked, but this would be the first observational evidence of such a phenomenon. Alternatively, a massive binary system composed of an LBV that erupted in 2004, and a Wolf - Rayet star exploding as SN 2006jc, could explain the observations.
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| 20. |
- Pastorello, A., et al.
(author)
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SN 2009E : a faint clone of SN 1987A
- 2012
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 537
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Journal article (peer-reviewed)abstract
- Context. 1987A-like events form a rare sub-group of hydrogen-rich core-collapse supernovae that are thought to originate from the explosion of blue supergiant stars. Although SN 1987A is the best known supernova, very few objects of this group have been discovered and, hence, studied. Aims. In this paper we investigate the properties of SN 2009E, which exploded in a relatively nearby spiral galaxy (NGC 4141) and that is probably the faintest 1987A-like supernova discovered so far. We also attempt to characterize this subgroup of core-collapse supernovae with the help of the literature and present new data for a few additional objects. Methods. The lack of early-time observations from professional telescopes is compensated by frequent follow-up observations performed by a number of amateur astronomers. This allows us to reconstruct a well-sampled light curve for SN 2009E. Spectroscopic observations which started about 2 months after the supernova explosion, highlight significant differences between SN 2009E and the prototypical SN 1987A. Modelling the data of SN 2009E allows us to constrain the explosion parameters and the properties of the progenitor star, and compare the inferred estimates with those available for the similar SNe 1987A and 1998A. Results. The light curve of SN 2009E is less luminous than that of SN 1987A and the other members of this class, and the maximum light curve peak is reached at a slightly later epoch than in SN 1987A. Late-time photometric observations suggest that SN 2009E ejected about 0.04 M-circle dot of Ni-56, which is the smallest Ni-56 mass in our sample of 1987A-like events. Modelling the observations with a radiation hydrodynamics code, we infer for SN 2009E a kinetic plus thermal energy of about 0.6 foe, an initial radius of similar to 7x10(12) cm and an ejected mass of similar to 19 M-circle dot. The photospheric spectra show a number of narrow (v approximate to 1800 km s(-1)) metal lines, with unusually strong Ba II lines. The nebular spectrum displays narrow emission lines of H, Na I, [Ca II] and [O I], with the [O I] feature being relatively strong compared to the [Ca II] doublet. The overall spectroscopic evolution is reminiscent of that of the faint Ni-56-poor type II-plateau supernovae. This suggests that SN 2009E belongs to the low-luminosity, low Ni-56 mass, low-energy tail in the distribution of the 1987A-like objects in the same manner as SN 1997D and similar events represent the faint tail in the distribution of physical properties for normal type II-plateau supernovae.
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| 21. |
- Young, D. R., et al.
(author)
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Two type Ic supernovae in low-metallicity, dwarf galaxies : diversity of explosions
- 2010
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 512, s. 70-
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Journal article (peer-reviewed)abstract
- Aims: The aim of this paper is to discuss the nature of two type Ic supernovae SN 2007bg and SN 2007bi and their host galaxies. Both supernovae were discovered in wide-field, non-targeted surveys and are found to be associated with sub-luminous blue dwarf galaxies identified in SDSS images. Methods: We present BVRI photometry and optical spectroscopy of SN 2007bg and SN 2007bi and their host galaxies. Their lightcurves and spectra are compared to those of other type Ic SNe and analysis of these data provides estimates of the energetics, total ejected masses and synthesised mass of 56Ni. Detection of the host galaxy emission lines allows for metallicity measurements. Results: Neither SNe 2007bg nor 2007bi were found in association with an observed GRB, but from estimates of the metallicities of their host-galaxies they are found to inhabit similar low-metallicity environments as GRB associated supernovae. The radio-bright SN 2007bg is hosted by an extremely sub-luminous galaxy of magnitude MB = -12.4 ± 0.6 mag and an estimated oxygen abundance of 12+log(O/H) = 8.18 ± 0.17 (on the Pettini & Pagel 2004 scale). The early lightcurve evolution of SN 2007bg matches the fast-pace decline of SN 1994I giving it one of the fastest post-maximum decline rates of all broad-lined type Ic supernovae known to date and, when combined with its high expansion velocities, a high kinetic energy to ejected mass ratio (EK/Mej~2.7). We also show that SN 2007bi is possibly the most luminous type Ic known, reaching a peak magnitude of MR ~ -21.3 mag and displays a remarkably slow decline, following the radioactive decay rate of 56Co to 56Fe throughout the course of its observed lifetime. SN 2007bi also displays an extreme longevity in its spectral evolution and is still not fully nebular at approximately one year post-maximum brightness. From a simple model of the bolometric light curve of SN 2007bi we estimate a total ejected 56Ni mass of MNi = 3.5-4.5 M_ȯ, the largest 56Ni mass measured in the ejecta of a supernova to date. There are two models that could explain the high luminosity and large ejected 56Ni mass. One is a pair-instability supernova (PISN) which has been predicted to occur for massive stars at low metallicities. We measure the host galaxy metallicity of SN 2007bi to be 12+log(O/H) = 8.15 ± 0.15 (on the McGaugh 1991 scale) which is somewhat high to be consistent with the PISN model. An alternative is the core-collapse of a C+O star of 20-40 Mȯ which is the core of a star of originally 50-100 Mȯ.
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| 22. |
- Harutyunyan, A. H., et al.
(author)
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ESC supernova spectroscopy of non-ESC targets
- 2008
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 488:1, s. 383-399
-
Research review (peer-reviewed)abstract
- Aims. We present the spectra of 36 supernovae (SNe) of various types, obtained by the European Supernova Collaboration. Because of the spectral classification and the phase determination at their discovery the SNe did not warrant further study, and the spectra we present are the only ones available for the respective objects. In this paper we present and discuss this material using a new software for the automated classification of SNe spectra. Methods. As a validation of the software, we verify the classification and phase estimate reported for these objects in their discovery/classification circulars. For the comparison, the software uses the library of template spectra of Padova-Asiago Supernova Archive (ASA). Results. For each spectrum of our sample we present a brief, individual discussion, highlighting the main characteristics and possible peculiarities. The comparison with ASA spectra confirms the previous classification of all objects and refines the age estimates. For our software, we determine numerical limits of ""safe"" spectral classification and the uncertainties of the phase determination.
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| 23. |
- Pastorello, A., et al.
(author)
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INTERACTING SUPERNOVAE AND SUPERNOVA IMPOSTORS : SN 2009ip, IS THIS THE END?
- 2013
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In: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 767:1, s. 1-
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Journal article (peer-reviewed)abstract
- We report the results of a three-year-long dedicated monitoring campaign of a restless luminous blue variable (LBV) in NGC 7259. The object, named SN 2009ip, was observed photometrically and spectroscopically in the optical and near-infrared domains. We monitored a number of erupting episodes in the past few years, and increased the density of our observations during eruptive episodes. In this paper, we present the full historical data set from 2009 to 2012 with multi-wavelength dense coverage of the two high-luminosity events between 2012 August and September. We construct bolometric light curves and measure the total luminosities of these eruptive or explosive events. We label them the 2012a event (lasting similar to 50 days) with a peak of 3x10(41) erg s(-1), and the 2012b event (14 day rise time, still ongoing) with a peak of 8 x 1042 erg s(-1). The latter event reached an absolute R-band magnitude of about -18, comparable to that of a core-collapse supernova (SN). Our historical monitoring has detected high-velocity spectral features (similar to 13,000 km s(-1)) in 2011 September, one year before the current SN-like event. This implies that the detection of such high-velocity outflows cannot, conclusively, point to a core-collapse SN origin. We suggest that the initial peak in the 2012a event was unlikely to be due to a faint core-collapse SN. We propose that the high intrinsic luminosity of the latest peak, the variability history of SN 2009ip, and the detection of broad spectral lines indicative of high-velocity ejecta are consistent with a pulsational pair-instability event, and that the star may have survived the last outburst. The question of the survival of the LBV progenitor star and its future fate remain open issues, only to be answered with future monitoring of this historically unique explosion.
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| 24. |
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| 25. |
- Taubenberger, S., et al.
(author)
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High luminosity, slow ejecta and persistent carbon lines : SN 2009dc challenges thermonuclear explosion scenarios
- 2011
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 412:4, s. 2735-2762
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Research review (peer-reviewed)abstract
- Extended optical and near-IR observations reveal that SN 2009dc shares a number of similarities with normal Type Ia supernovae (SNe Ia), but is clearly overluminous, with a (pseudo-bolometric) peak luminosity of log (L) = 43.47 (erg s-1). Its light curves decline slowly over half a year after maximum light [delta m(15)(B)(true) = 0.71], and the early-time near-IR light curves show secondary maxima, although the minima between the first and the second peaks are not very pronounced. The bluer bands exhibit an enhanced fading after similar to 200 d, which might be caused by dust formation or an unexpectedly early IR catastrophe. The spectra of SN 2009dc are dominated by intermediate-mass elements and unburned material at early times, and by iron-group elements at late phases. Strong C ii lines are present until similar to 2 weeks past maximum, which is unprecedented in thermonuclear SNe. The ejecta velocities are significantly lower than in normal and even subluminous SNe Ia. No signatures of interaction with a circumstellar medium (CSM) are found in the spectra. Assuming that the light curves are powered by radioactive decay, analytic modelling suggests that SN 2009dc produced similar to 1.8 M(circle dot) of 56Ni assuming the smallest possible rise time of 22 d. Together with a derived total ejecta mass of similar to 2.8 M(circle dot), this confirms that SN 2009dc is a member of the class of possible super-Chandrasekhar-mass SNe Ia similar to SNe 2003fg, 2006gz and 2007if. A study of the hosts of SN 2009dc and other superluminous SNe Ia reveals a tendency of these SNe to explode in low-mass galaxies. A low metallicity of the progenitor may therefore be an important prerequisite for producing superluminous SNe Ia. We discuss a number of possible explosion scenarios, ranging from super-Chandrasekhar-mass white-dwarf progenitors over dynamical white-dwarf mergers and Type I SNe to a core-collapse origin of the explosion. None of the models seems capable of explaining all properties of SN 2009dc, so that the true nature of this SN and its peers remains nebulous.
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