| 1. |
- Barbarino, C., et al.
(author)
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SN 2012ec : mass of the progenitor from PESSTO follow-up of the photospheric phase
- 2015
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 448:3, s. 2312-2331
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Journal article (peer-reviewed)abstract
- We present the results of a photometric and spectroscopic monitoring campaign of SN 2012ec, which exploded in the spiral galaxy NGC 1084, during the photospheric phase. The photometric light curve exhibits a plateau with luminosity L = 0.9 x 10(42) erg s(-1) and duration similar to 90 d, which is somewhat shorter than standard Type II-P supernovae (SNe). We estimate the nickel mass M(Ni-56) = 0.040 +/- 0.015 M-circle dot from the luminosity at the beginning of the radioactive tail of the light curve. The explosion parameters of SN 2012ec were estimated from the comparison of the bolometric light curve and the observed temperature and velocity evolution of the ejecta with predictions from hydrodynamical models. We derived an envelope mass of 12.6 M-circle dot, an initial progenitor radius of 1.6 x 10(13) cm and an explosion energy of 1.2 foe. These estimates agree with an independent study of the progenitor star identified in pre-explosion images, for which an initial mass of M = 14-22 M-circle dot was determined. We have applied the same analysis to two other Type II-P SNe (SNe 2012aw and 2012A), and carried out a comparison with the properties of SN 2012ec derived in this paper. We find a reasonable agreement between the masses of the progenitors obtained from pre-explosion images and masses derived from hydrodynamical models. We estimate the distance to SN 2012ec with the standardized candle method (SCM) and compare it with other estimates based on other primary and secondary indicators. SNe 2012A, 2012aw and 2012ec all follow the standard relations for the SCM for the use of Type II-P SNe as distance indicators.
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| 2. |
- Childress, M. J., et al.
(author)
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Measuring nickel masses in Type Ia supernovae using cobalt emission in nebular phase spectra
- 2015
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 454:4, s. 3816-3842
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Journal article (peer-reviewed)abstract
- The light curves of Type Ia supernovae (SNe Ia) are powered by the radioactive decay of Ni-56 to Co-56 at early times, and the decay of Co-56 to Fe-56 from similar to 60 d after explosion. We examine the evolution of the [Co III] lambda 5893 emission complex during the nebular phase for SNe Ia with multiple nebular spectra and show that the line flux follows the square of the mass of Co-56 as a function of time. This result indicates both efficient local energy deposition from positrons produced in Co-56 decay and long-term stability of the ionization state of the nebula. We compile SN Ia nebular spectra from the literature and present 21 new late-phase spectra of 7 SNe Ia, including SN 2014J. From these we measure the flux in the [Co III] lambda 5893 line and remove its well-behaved time dependence to infer the initial mass of Ni-56 (M-Ni, produced in the explosion. We then examine Ni-56 yields for different SN Ia ejected masses (M-ej-calculated using the relation between light-curve width and ejected mass) and find that the Ni-56 masses of SNe Ia fall into two regimes: for narrow light curves (low stretch s similar to 0.7-0.9), M-Ni is clustered near MN, 0.4 Me and shows a shallow increase as Mei increases from similar to 1 to 1.4 M-circle dot; at high stretch, M-ej clusters at the Chandrasekhar mass (1.4 M-circle dot) while M-Ni, spans a broad range from 0.6 to 1.2 M-circle dot. This could constitute evidence for two distinct SN Ia explosion mechanisms.
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| 3. |
- Gutiérrez, C. P., et al.
(author)
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SN 2017ivv : two years of evolution of a transitional Type II supernova
- 2020
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 499:1, s. 974-992
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Journal article (peer-reviewed)abstract
- We present the photometric and spectroscopic evolution of the Type II supernova (SN II) SN 2017ivv (also known as ASASSN-17qp). Located in an extremely faint galaxy (M-r =-10.3 mag), SN 2017ivv shows an unprecedented evolution during the 2 yr of observations. At early times, the light curve shows a fast rise (similar to 6-8 d) to a peak of M-g(max) = -17.84 mag, followed by a very rapid decline of 7.94 +/- 0.48 mag per 100 d in the V band. The extensive photometric coverage at late phases shows that the radioactive tail has two slopes, one steeper than that expected from the decay of Co-56 (between 100 and 350 d), and another slower (after 450 d), probably produced by an additional energy source. From the bolometric light curve, we estimated that the amount of ejected 5(6)Ni is similar to 0.059 +/- 0.003M(circle dot). The nebular spectra of SN 2017ivv show a remarkable transformation that allows the evolution to be split into three phases: (1) H alpha strong phase (<200 d); (2) H alpha weak phase (between 200 and 350 d); and (3) H alpha broad phase (>500 d). We find that the nebular analysis favours a binary progenitor and an asymmetric explosion. Finally, comparing the nebular spectra of SN 2017ivv to models suggests a progenitor with a zero-age main-sequence mass of 15-17M(circle dot).
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| 4. |
- Gutiérrez, C. P., et al.
(author)
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Type II supernovae in low-luminosity host galaxies
- 2018
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 479:3, s. 3232-3253
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Journal article (peer-reviewed)abstract
- 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 lambda 5018, 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.
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| 5. |
- Kangas, T., et al.
(author)
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Supernova 2013fc in a circumnuclear ring of a luminous infrared galaxy : the big brother of SN 1998S
- 2016
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 456:1, s. 323-346
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Journal article (peer-reviewed)abstract
- 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.
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| 6. |
- Maguire, K., et al.
(author)
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A statistical analysis of circumstellar material in Type Ia supernovae
- 2013
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 436:1, s. 222-240
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Journal article (peer-reviewed)abstract
- A key tracer of the elusive progenitor systems of Type Ia supernovae (SNe Ia) is the detection of narrow blueshifted time-varying Na I D absorption lines, interpreted as evidence of circumstellar material surrounding the progenitor system. The origin of this material is controversial, but the simplest explanation is that it results from previous mass-loss in a system containing a white dwarf and a non-degenerate companion star. We present new single-epoch intermediate-resolution spectra of 17 low-redshift SNe Ia taken with XShooter on the European Southern Observatory Very Large Telescope. Combining this sample with events from the literature, we confirm an excess (similar to 20 per cent) of SNe Ia displaying blueshifted narrow Na I D absorption features compared to redshifted Na I D features. The host galaxies of SNe Ia displaying blueshifted absorption profiles are skewed towards later-type galaxies, compared to SNe Ia that show no Na I D absorption and SNe Ia displaying blueshifted narrow Na I D absorption features have broader light curves. The strength of the Na I D absorption is stronger in SNe Ia displaying blueshifted Na I D absorption features than those without blueshifted features, and the strength of the blueshifted Na I D is correlated with the B - V colour of the SN at maximum light. This strongly suggests the absorbing material is local to the SN. In the context of the progenitor systems of SNe Ia, we discuss the significance of these findings and other recent observational evidence on the nature of SN Ia progenitors. We present a summary that suggests that there are at least two distinct populations of normal, cosmologically useful SNe Ia.
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| 7. |
- Nicholl, M., et al.
(author)
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On the diversity of superluminous supernovae : ejected mass as the dominant factor
- 2015
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 452:4, s. 3869-3893
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Journal article (peer-reviewed)abstract
- We assemble a sample of 24 hydrogen-poor superluminous supernovae (SLSNe). Parameterizing the light-curve shape through rise and decline time-scales shows that the two are highly correlated. Magnetar-powered models can reproduce the correlation, with the diversity in rise and decline rates driven by the diffusion time-scale. Circumstellar interaction models can exhibit a similar rise-decline relation, but only for a narrow range of densities, which may be problematic for these models. We find that SLSNe are approximately 3.5 mag brighter and have light curves three times broader than SNe Ibc, but that the intrinsic shapes are similar. There are a number of SLSNe with particularly broad light curves, possibly indicating two progenitor channels, but statistical tests do not cleanly separate two populations. The general spectral evolution is also presented. Velocities measured from Fe II are similar for SLSNe and SNe Ibc, suggesting that diffusion time differences are dominated by mass or opacity. Flat velocity evolution in most SLSNe suggests a dense shell of ejecta. If opacities in SLSNe are similar to other SNe Ibc, the average ejected mass is higher by a factor 2-3. Assuming. = 0.1 cm(2) g(-1), we estimate a mean (median) SLSN ejecta mass of 10 M-circle dot (6 M-circle dot), with a range of 3-30 M-circle dot. Doubling the assumed opacity brings the masses closer to normal SNe Ibc, but with a high-mass tail. The most probable mechanism for generating SLSNe seems to be the core collapse of a very massive hydrogen-poor star, forming a millisecond magnetar.
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| 8. |
- Nicholl, M., et al.
(author)
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Superluminous supernovae from PESSTO
- 2014
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 444:3, s. 2096-2113
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Journal article (peer-reviewed)abstract
- We present optical spectra and light curves for three hydrogen-poor superluminous supernovae followed by the Public ESO Spectroscopic Survey of Transient Objects (PESSTO). Time series spectroscopy from a fewdays aftermaximum light to 100 d later shows them to be fairly typical of this class, with spectra dominated by Ca II, MgII, FeII, and Si II, which evolve slowly over most of the post-peak photospheric phase. We determine bolometric light curves and apply simple fitting tools, based on the diffusion of energy input by magnetar spin-down, Ni-56 decay, and collision of the ejecta with an opaque circumstellar shell. We investigate how the heterogeneous light curves of our sample (combined with others from the literature) can help to constrain the possible mechanisms behind these events. We have followed these events to beyond 100-200 d after peak, to disentangle host galaxy light from fading supernova flux and to differentiate between the models, which predict diverse behaviour at this phase. Models powered by radioactivity require unrealistic parameters to reproduce the observed light curves, as found by previous studies. Both magnetar heating and circumstellar interaction still appear to be viable candidates. A large diversity is emerging in observed tail-phase luminosities, with magnetar models failing in some cases to predict the rapid drop in flux. This would suggest either that magnetars are not responsible, or that the X-ray flux from the magnetar wind is not fully trapped. The light curve of one object shows a distinct rebrightening at around 100 d after maximum light. We argue that this could result either from multiple shells of circumstellar material, or from a magnetar ionization front breaking out of the ejecta.
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| 9. |
- Prentice, S. J., et al.
(author)
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Investigating the properties of stripped-envelope supernovae; what are the implications for their progenitors?
- 2019
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 485:2, s. 1559-1578
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Journal article (peer-reviewed)abstract
- We present observations and analysis of 18 stripped-envelope supernovae observed during 2013-2018. This sample consists of five H/He-rich SNe, sixH-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 Ni-56 and ejecta masses (M-Ni and M-cj). 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-circle dot. The bolometric light curve properties are examined in combination with those of other SE events from the literature. The resulting data set gives the M-ej distribution for 80 SE-SNe, the largest such sample in the literature to date, and shows that SNe Ib have the lowest median M-ej, 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 M-ej ranging from similar to 1.2-11 M-circle dot, considerably greater than any other subtype. For all SE-SNe = 2.8 +/- 1.5 M-circle dot which further strengthens the evidence that SE-SNe arise from low-mass progenitors which are typically <5 M-circle dot at the time of explosion, again suggesting M-ZAMS < 25 M-circle dot. The low and lack of clear bimodality in the distribution implies < 30 M-circle dot progenitors and that envelope stripping via binary interaction is the dominant evolutionary pathway of these SNe.
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| 10. |
- Scalzo, R. A., et al.
(author)
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Early ultraviolet emission in the Type Ia supernova LSQ12gdj : No evidence for ongoing shock interaction
- 2014
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In: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 445:1, s. 30-48
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Journal article (peer-reviewed)abstract
- We present photospheric-phase observations of LSQ12gdj, a slowly declining, UV-bright Type Ia supernova. Classified well before maximum light, LSQ12gdj has extinction-corrected absolute magnitude M-B = -19.8, and pre-maximum spectroscopic evolution similar to SN 1991T and the super-Chandrasekhar-mass SN 2007if. We use ultraviolet photometry from Swift, ground-based optical photometry, and corrections from a near-infrared photometric template to construct the bolometric (1600-23 800 angstrom) light curve out to 45 d past B-band maximum light. We estimate that LSQ12gdj produced 0.96 +/- 0.07 M-circle dot of Ni-56, with an ejected mass near or slightly above the Chandrasekhar mass. As much as 27 per cent of the flux at the earliest observed phases, and 17 per cent at maximum light, is emitted bluewards of 3300 angstrom. The absence of excess luminosity at late times, the cutoff of the spectral energy distribution bluewards of 3000 angstrom and the absence of narrow line emission and strong Na I D absorption all argue against a significant contribution from ongoing shock interaction. However, similar to 10 per cent of LSQ12gdj's luminosity near maximum light could be produced by the release of trapped radiation, including kinetic energy thermalized during a brief interaction with a compact, hydrogen-poor envelope (radius < 10(13) cm) shortly after explosion; such an envelope arises generically in double-degenerate merger scenarios.
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