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SN 2015as: A low luminosity Type IIb supernova without an early light curve peak
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We present results of the photometric (from 3 to 509 days past explosion) and spectroscopic (up to 230 days past explosion) monitoring campaign of the He-rich Type IIb supernova (SN) 2015as. The {\it (B-V)} colour evolution of SN 2015as closely resemble those of SN 2008ax, suggesting that SN 2015as belongs to the SN IIb subgroup that does not show the early, short-duration photometric peak. The light curve of SN 2015as reaches the $B$-band maximum about 22 days after the explosion, at an absolute magnitude of -16.82 $\pm$ 0.18 mag. At $\sim$ 75 days after the explosion, its spectrum transitions from that of a SN II to a SN Ib. P~Cygni features due to He I lines appear at around 30 days after explosion, indicating that the progenitor of SN 2015as was partially stripped. For SN~2015as, we estimate a $^{56}$Ni mass of $\sim$ 0.08 M$_{\odot}$ and ejecta mass of 1.1--2.2 M$_{\odot}$, which are similar to the values inferred for SN 2008ax. The quasi bolometric analytical light curve modelling suggests that the progenitor of SN 2015as has a modest mass ($\sim$ 0.1 M$_{\odot}$), a nearly-compact ($\sim$ 0.05$\times$10$^{13}$ cm) H envelope on top of a dense, compact ($\sim$ 2$\times$10$^{11}$ cm) and a more massive ($\sim$ 1.2 M$_{\odot}$) He core. The analysis of the nebular phase spectra indicates that $\sim$ 0.44 M$_{\odot}$ of O is ejected in the explosion. The intensity ratio of the [Ca II]/[O I] nebular lines favours either a main sequence progenitor mass of $\sim$ 15 M$_{\odot}$ or a Wolf Rayet star of 20 M$_{\odot}$.
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... Type IIb SNe are shown by colored hollow rhombus connected by colored solid lines and the other type II SNe are shown by colored solid lines. 2024), SN 2015as ∼ 5.2 × 10 42 erg s −1(Gangopadhyay 2018). And the L peak of SN 2019tua is similar to SN 2020cpg ∼ 6.03 × 10 42 erg s −1(Medler et al. 2021;Teffs et al. 2022). ...
... And the L peak of SN 2019tua is similar to SN 2020cpg ∼ 6.03 × 10 42 erg s −1(Medler et al. 2021;Teffs et al. 2022). We also plotted the LCs from the referenceMedler et al. 2022;Teffs et al. 2022;Gangopadhyay 2018) as shown inFigure 8, with the The bolometric LC of SN 2019tua reproduced by the 56 Ni model. The total luminosity Linp,Ni is represented by the solid blue line. ...
We present photometric and spectroscopic observations and analysis of the type IIb supernova (SN) SN 2019tua, which exhibits multiple bumps in its declining light curves between 40 and 65 days after discovery. SN 2019tua shows a time to peak of about 25 days similar to other type IIb SNe. Our observations indicate a decrease in its brightness of about 1 magnitude in the 60 days after the peak. At about days 50, and 60, its multiband light curves exhibit bumpy behavior. The complex luminosity evolution of SN 2019tua could not be well modeled with a single currently popular energy source model, e.g., radioactive decay of $^{56}$Ni, magnetar, interaction between the ejecta and a circumstellar shell. Even though the magnetar model has a smaller \( \chi^2 / \text{dof} \) value, the complex changes in SN 2019tua's brightness suggest that more than one physical process might be involved. We propose a hybrid CSM interaction plus $^{56}$Ni model to explain the bolometric light curve (LC) of SN 2019tua. The fitting results show that the ejecta mass $M_{\rm ej} \approx 2.4~M_\odot$, the total CSM mass $M_{\rm CSM} \approx 1.0~M_\odot$, and the $^{56}$Ni mass $M_{\rm Ni} \approx 0.4~M_\odot$. The total kinetic energy of the ejecta is $E_k\approx 0.5 \times 10^{51}\rm~erg$. Pre-existing multiple shells suggest that the progenitor of SN 2019tua experienced mass ejections within approximately $\sim6 - 44$ years prior to the explosion.
We present optical, near-infrared, and radio observations of supernova (SN) SN IIb 2022crv. We show that it retained a very thin H envelope and transitioned from an SN IIb to an SN Ib; prominent H α seen in the pre-maximum phase diminishes toward the post-maximum phase, while He i lines show increasing strength. SYNAPPS modeling of the early spectra of SN 2022crv suggests that the absorption feature at 6200 Å is explained by a substantial contribution of H α together with Si ii , as is also supported by the velocity evolution of H α . The light-curve evolution is consistent with the canonical stripped-envelope SN subclass but among the slowest. The light curve lacks the initial cooling phase and shows a bright main peak (peak M V = −17.82 ± 0.17 mag), mostly driven by radioactive decay of ⁵⁶ Ni. The light-curve analysis suggests a thin outer H envelope ( M env ∼ 0.05 M ⊙ ) and a compact progenitor ( R env ∼ 3 R ⊙ ). An interaction-powered synchrotron self-absorption model can reproduce the radio light curves with a mean shock velocity of 0.1 c . The mass-loss rate is estimated to be in the range of (1.9−2.8) × 10 ⁻⁵ M ⊙ yr ⁻¹ for an assumed wind velocity of 1000 km s ⁻¹ , which is on the high end in comparison with other compact SNe IIb/Ib. SN 2022crv fills a previously unoccupied parameter space of a very compact progenitor, representing a beautiful continuity between the compact and extended progenitor scenario of SNe IIb/Ib.
We present a systematic analysis of 191 stripped-envelope supernovae (SE SNe), aimed at computing their ⁵⁶ Ni masses from the luminosity in their radioactive tails ( M Ni tail ) and/or in their maximum light, and the mean ⁵⁶ Ni and iron yields of SE SNe and core-collapse SNe. Our sample consists of SNe IIb, Ib, and Ic from the literature and from the Zwicky Transient Facility Bright Transient Survey. To calculate luminosities from optical photometry, we compute bolometric corrections using 49 SE SNe with optical and near-IR photometry, and develop corrections to account for the unobserved UV and IR flux. We find that the equation of Khatami & Kasen for radioactive ⁵⁶ Ni-powered transients with a single free parameter does not fit the observed peak time–luminosity relation of SE SNe. Instead, we find a correlation between M Ni tail , peak time, peak luminosity, and decline rate, which allows for measuring individual ⁵⁶ Ni masses to a precision of 14%. Applying this method to the whole sample, we find, for SNe IIb, Ib, and Ic, mean ⁵⁶ Ni masses of 0.066 ± 0.006, 0.082 ± 0.009, and 0.132 ± 0.011 M ⊙ , respectively. After accounting for their relative rates, for SE SNe as a whole, we compute mean ⁵⁶ Ni and iron yields of 0.090 ± 0.005 and 0.097 ± 0.007 M ⊙ , respectively. Combining these results with the recent Type II SN mean ⁵⁶ Ni mass derived by Rodríguez et al., core-collapse SNe, as a whole, have mean ⁵⁶ Ni and iron yields of 0.055 ± 0.006 and 0.058 ± 0.007 M ⊙ , respectively. We also find that radioactive ⁵⁶ Ni-powered models typically underestimate the peak luminosity of SE SNe by 60%–70%, suggesting the presence of an additional power source contributing to the luminosity at peak.
This paper studies about the 130-cm Devasthal Fast Optical Telescope (DFOT) at Devasthal, India that has been in operation for more than 10 years and is the main workhorse for the photometric observations for a wide range of scientific programs carried out at ARIES, Nainital. Having a [Formula: see text] pixel imager mounted on the prime focus of the telescope, DFOT provides a field of view of about [Formula: see text] arcmin ² in the sky. Another frame transfer CCD imager of [Formula: see text] pixel size enables monitoring transient sources with millisecond temporal resolution. DFOT is equipped with a filter assembly having eight filters, an auto-guider, an All Sky Camera, and GPS-enabled weather monitoring system to support the observations in the most optimum way. The telescope is capable of producing sub-milimag photometric stability which has allowed us to detect many small-scale photometric variations.
We present a systematic analysis of 191 stripped-envelope supernovae (SE SNe), aimed to compute their $^{56}$Ni masses from the luminosity in their radioactive tails ($M_\mathrm{Ni}^\mathrm{tail}$) and/or in their maximum light, and the mean $^{56}$Ni and iron yields of SE SNe and core-collapse SNe. Our sample consists of SNe of types IIb, Ib, and Ic from the literature and from the Zwicky Transient Facility Bright Transient Survey. We use color curves to infer host galaxy reddenings and the representative $R_V$ value for each SN type. To calculate luminosities from optical photometry, we compute bolometric corrections using 49 SE SNe with optical and near-IR photometry. We find that the equation of Khatami & Kasen relating peak time and luminosity is not a reliable estimator of the $^{56}$Ni masses of SE SNe. Instead, we find a correlation between $M_\mathrm{Ni}^\mathrm{tail}$, peak time, peak luminosity, and decline rate, which allows measuring individual $^{56}$Ni masses to a precision of 14%. Applying this method to the whole sample, we find, for SNe IIb, Ib, and Ic, mean $^{56}$Ni masses of $0.066\pm0.006$, $0.082\pm0.009$, and $0.132\pm0.011$ M$_{\odot}$, respectively. After accounting for their relative rates, for SE SNe as a whole we compute mean $^{56}$Ni and iron yields of $0.090\pm0.005$ and $0.097\pm0.006$ M$_{\odot}$, respectively. Combining these results with the recent Type II SN mean $^{56}$Ni mass derived by Rodr\'iguez et al., core-collapse SNe, as a whole, have mean $^{56}$Ni and iron yields of $0.055\pm0.006$ and $0.058\pm0.007$ M$_{\odot}$, respectively. We highlight that the Arnett model, Arnett's rule, and hydrodynamical models typically overestimate the $^{56}$Ni masses of SE SNe by 75, 90 and 65%, respectively.
We report results of optical imaging and low-resolution spectroscopic monitoring of supernova (SN) 2017iro that occurred in the nearby (∼31 Mpc) galaxy NGC 5480. The He i λ 5876 feature present in the earliest spectrum (−7 days) classified it as a Type Ib SN. The follow-up observations span from −7 to +266 days with respect to the B -band maximum. With a peak absolute magnitude in V band M V = −17.76 ± 0.15 mag and bolometric luminosity log 10 L = 42.39 ± 0.09 erg s ⁻¹ , SN 2017iro is a moderately luminous Type Ib SN. The overall light-curve evolution of SN 2017iro is similar to that of SN 2012au and SN 2009jf during the early (up to ∼100 days) and late phases (>150 days), respectively. The line velocities of both Fe ii λ 5169 and He i λ 5876 are ∼9000 km s ⁻¹ near the peak. The analysis of the nebular phase spectrum (∼+209 days) indicates an oxygen mass of ∼0.35 M ⊙ . The smaller [O i ]/[Ca ii ] flux ratio of ∼1 favors a progenitor with a zero-age main-sequence mass in the range ∼13–15 M ⊙ , most likely in a binary system, similar to the case of iPTF13bvn. The explosion parameters are estimated by applying different analytical models to the quasi-bolometric light curve of SN 2017iro. ⁵⁶ Ni mass synthesized in the explosion has a range of ∼0.05–0.10 M ⊙ , ejecta mass ∼1.4–4.3 M ⊙ , and kinetic energy ∼(0.8–1.9) × 10 ⁵¹ erg.
We report results of optical imaging and low-resolution spectroscopic monitoring of supernova (SN) 2017iro that occurred in the nearby ($\sim$\,31 Mpc) galaxy NGC 5480. The \ion{He}{1} 5876 \AA\, feature present in the earliest spectrum (--\,7 d) classified it as a Type Ib SN. The follow-up observations span from --\,7 to +\,266 d with respect to the $B$-band maximum. With a peak absolute magnitude in $V$-band, ($M_{V}$)\,=\,$-17.76\pm0.15$ mag and bolometric luminosity (log$_{10}$\,L)\,=\,42.39\,$\pm$\, 0.09 erg s$^{-1}$, SN 2017iro is a moderately luminous Type Ib SN. The overall light curve evolution of SN 2017iro is similar to SN 2012au and SN 2009jf during the early (up to $\sim$100 d) and late phases ($>$150 d), respectively. The line velocities of both \ion{Fe}{2} 5169 \AA\, and \ion{He}{1} 5876 \AA\, are $\sim$\,9000 km s$^{-1}$ near the peak. The analysis of the nebular phase spectrum ($\sim$\,+209 d) indicates an oxygen mass of $\sim$\,0.35 M$_{\odot}$. The smaller [\ion{O}{1}]/[\ion{Ca}{2}] flux ratio of $\sim$\,1 favours a progenitor with a zero-age main-sequence mass in the range $\sim$\,13--15 M$_{\odot}$, most likely in a binary system, similar to the case of iPTF13bvn. The explosion parameters are estimated by applying different analytical models to the quasi-bolometric light curve of SN 2017iro. $^{56}$Ni mass synthesized in the explosion has a range of $\sim$\,0.05\,--\,0.10 M$_{\odot}$, the ejecta mass $\sim$1.4\,--\,4.3 M$_{\odot}$ and the kinetic energy $\sim$\,0.8\,--\,1.9\,$\times$ 10$^{51}$ erg.
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 (Mr = −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 (∼6−8 d) to a peak of ${\it M}^{\rm max}_{g}= -17.84$ 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 56Co (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 56Ni is ∼0.059 ± 0.003 M⊙. The nebular spectra of SN 2017ivv show a remarkable transformation that allows the evolution to be split into three phases: (1) Hα strong phase (<200 d); (2) Hα weak phase (between 200 and 350 d); and (3) Hα 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 15–17 M⊙.
We present an extensive (∼1200 d) photometric and spectroscopic monitoring of the Type IIn supernova (SN) 2012ab. After a rapid initial rise leading to a bright maximum (MR = −19.39 mag), the light curves show a plateau lasting about 2 months followed by a steep decline up to about 100 d. Only in the U band, the decline is constant in the same interval. At later phases, the light curves remain flatter than the 56Co decline, suggesting the increasing contribution of the interaction between SN ejecta with circumstellar material (CSM). Although heavily contaminated by emission lines of the host galaxy, the early spectral sequence (until 32 d) shows persistent narrow emissions, indicative of slow unshocked CSM, and the emergence of broad Balmer lines of hydrogen with P-Cygni profiles over a blue continuum, arising from a fast expanding SN ejecta. From about 2 months to ∼1200 d, the P-Cygni profiles are overcome by intermediate width emissions [full width at half-maximum (FWHM) ∼6000 km s−1], produced in the shocked region due to interaction. On the red wing, a red bump appears after 76 d, likely a signature of the onset of interaction of the receding ejecta with the CSM. The presence of fast material both approaching and then receding is suggestive that we are observing the SN along the axis of a jet-like ejection in a cavity devoid of or uninterrupted by CSM in the innermost regions.
Type IIb supernovae (SNe IIb) present a unique opportunity for investigating the evolutionary channels and mechanisms governing the evolution of stripped-envelope SN progenitors due to a variety of observational constraints. Comparison of these constraints with the full distribution of theoretical properties not only helps determine the prevalence of observed properties in nature, but can also reveal currently unobserved populations. In this follow-up paper, we use the large grid of models presented in Sravan et al. to derive distributions of single and binary SNe IIb progenitor properties and compare them to constraints from three independent observational probes: multiband SN light curves, direct progenitor detections, and X-ray/radio observations. Consistent with previous work, we find that while current observations exclude single stars as SN IIb progenitors, SN IIb progenitors in binaries can account for them. We also find that the distributions indicate the existence of an unobserved dominant population of binary SNe IIb at low metallicity that arise due to mass transfer initiated on the Hertzsprung Gap. In particular, our models indicate the existence of a group of highly stripped (envelope mass ∼0.1–0.2 M ☉ ) progenitors that are compact (<50 R ☉ ) and blue ( T eff ≲ 10 ⁵ K) with ∼10 4.5 –10 5.5 L ☉ and low-density circumstellar mediums. As discussed in Sravan et al., this group is necessary to account for SN IIb fractions and likely exist regardless of metallicity. The detection of the unobserved populations indicated by our models would support weak stellar winds and inefficient mass transfer in SN IIb progenitors.
Optical and near-infrared photometry and optical spectroscopy are reported for SN 2003bg, starting a few days after explosion and extending for a period of more than 300 days. Our early-time spectra reveal the presence of broad, high-velocity Balmer lines. The nebular-phase spectra, on the other hand, show a remarkable resemblance to those of Type Ib/c supernovae, without clear evidence for hydrogen. Near maximum brightness SN 2003bg displayed a bolometric luminosity comparable to that of other Type I hypernovae unrelated to gamma-ray bursts, implying a rather normal amount of 56Ni production (0.1-0.2 M ☉) compared with other such objects. The bolometric light curve of SN 2003bg, on the other hand, is remarkably broad, thus suggesting a relatively large progenitor mass at the moment of explosion. These observations, together with the large value of the kinetic energy of expansion established in the accompanying paper, suggest that SN 2003bg can be regarded as a Type IIb hypernova.
We present astrometric, photometric and spectroscopic observations of supernova 1993J in M8 1, obtained with the Isaac Newton
Group telescopes and the Carlsberg Automatic Meridian Circle. The spectral data set includes the first spectrum ever taken
of SN1993J. The early spectra also yield an estimate of the total visual extinction, $A_\nu$. This is combined with the photometric data to produce a bolometric light curve. Implications of the latter and of the spectral
development are also discussed. The spectral evolution includes an infrared excess, which appeared after day 50 and may be
indicative of an IR echo. The unchanging nature of blueshifted oxygen lines in the spectra argues for asymmetry in the distribution
of the line-emitting region.
We present late-time Hubble Space Telescope ultraviolet (UV) and optical observations of the site of SN 2011dh in the galaxy M51, ∼1164 days post-explosion. At the
supernova (SN) location, we observe a point source that is visible at all wavelengths, which is significantly fainter than
the spectral energy distribution (SED) of the yellow supergiant progenitor observed prior to explosion. The previously reported
photometry of the progenitor is, therefore, completely unaffected by any sources that may persist at the SN location after
explosion. In comparison with the previously reported late-time photometric evolution of SN 2011dh, we find that the light
curve has plateaued at all wavelengths. The SED of the late-time source is clearly inconsistent with an SED of stellar origin.
Although the SED is bright at UV wavelengths, there is no strong evidence that the late-time luminosity originates solely
from a stellar source corresponding to the binary companion, although a partial contribution to the observed UV flux from
a companion star cannot be ruled out.
We present optical and near-infrared observations of the type IIb supernova (SN) 2011fu from a few days to ∼300 d after explosion.
The SN presents a double-peaked light curve (LC) similar to that of SN 1993J, although more luminous and with a longer cooling
phase after the primary peak. The spectral evolution is also similar to SN 1993J's, with hydrogen dominating the spectra to
∼40 d, then helium gaining strength, and nebular emission lines appearing from ∼60 d post-explosion. The velocities derived
from the P-Cygni absorptions are overall similar to those of other type IIb SNe. We have found a strong similarity between
the oxygen and magnesium line profiles at late times, which suggests that these lines are forming at the same location within
the ejecta. The hydrodynamical modelling of the pseudo-bolometric LC and the observed photospheric velocities suggest that
SN 2011fu was the explosion of an extended star (R∼ 450 R⊙), in which 1.3 × 1051 erg of kinetic energy were released and 0.15 M⊙ of 56Ni were synthesized. In addition, a better reproduction of the observed early pseudo-bolometric LC is achieved if a more massive
H-rich envelope than for other type IIb SNe is considered (0.3 M⊙). The hydrodynamical modelling of the LC and the comparison of our late-time spectra with nebular spectral models for type
IIb SNe, point to a progenitor for SN 2011fu with a Zero Age Main Sequence (ZAMS) mass of 13–18 M⊙.
Hubble Space Telescope observations of the site of the supernova (SN) 2008ax
obtained in 2011 and 2013 reveal that the possible progenitor object detected
in pre-explosion images was in fact multiple. Four point sources are resolved
in the new, higher-resolution images. We identify one of the sources with the
fading SN. The other three objects are consistent with single supergiant stars.
We conclude that their light contaminated the previously identified progenitor
candidate. After subtraction of these stars, the progenitor appears to be
significantly fainter and bluer than previously measured. Post-explosion
photometry at the SN location indicates that the progenitor object has
disappeared. If single, the progenitor is compatible with a supergiant star of
B to mid-A spectral type, while a Wolf-Rayet (WR) star would be too luminous in
the ultraviolet to account for the observations. Moreover, our hydrodynamical
modelling shows the pre-explosion mass was $4-5$ $M_\odot$ and the radius was
$30-50$ $R_\odot$, which is incompatible with a WR progenitor. We present a
possible interacting binary progenitor computed with our evolutionary models
that reproduces all the observational evidence. A companion star as luminous as
an O9-B0 main-sequence star may have remained after the explosion.
Super-luminous supernovae (SLSNe) are tremendously luminous explosions whose power sources and progenitors are highly debated. Broad-lined SNe Ic (SNe Ic-bl) are the only type of SNe that are connected with long duration gamma ray bursts (GRBs). Studying the spectral similarity and difference between the populations of hydrogen-poor SLSNe (SLSNe I) and of hydrogen-poor stripped-envelope core-collapse SNe, in particular SNe Ic and SNe Ic-bl, can provide crucial observations to test predictions of theories based on various power source models and progenitor models. In this paper, we collected all of the published optical spectra of 32 SLSNe I, 21 SNe Ic-bl, as well as 17 SNe Ic, quantified their spectral features, constructed average spectra, and compared them in a systematic way using new tools we have developed recently. We find that SLSNe I and SNe Ic-bl have comparable average spectral features and average absorption velocities at all phases, which are $\sim1$0,000 \kms~broader and $\sim8$,000 \kms~higher than those in SNe Ic at specifically 15 days after the date of maximum light, respectively. We find that the presence of a narrow `w' feature around 4300 \AA, in addition to a blue continuum, at early phases is likely to be an indicator for SLSNe I spectra, as suggested in earlier works. Moreover, we find that such high absorption and width velocities may be hard to explain by the interaction model, and none of 13 SLSNe I with measured absorption velocities spanning over 10 days has a convincing flat velocity-evolution, which is inconsistent with the magnetar model in one dimension. Lastly, we find that SN 2011kl, the first SN that is connected with an ultra-long GRB, is broadly consistent with the mean spectrum of SLSNe I, but does not resemble the SNe Ic-bl that have accompanied long-duration GRBs when considering the spectral continuum.
We re-examine the classifications of supernovae (SNe) presented in the Lick Observatory Supernova Search (LOSS) volume-limited sample with a focus on the stripped-envelope SNe. The LOSS volumetric sample, presented by Leaman et al. (2011) and Li et al. (2011b), was calibrated to provide meaningful measurements of SN rates in the local universe; the results presented therein continue to be used for comparisons to theoretical and modeling efforts. Many of the objects from the LOSS sample were originally classified based upon only a small subset of the data now available, and recent studies have both updated some subtype distinctions and improved our ability to perform robust classifications, especially for stripped-envelope SNe. We re-examine the spectroscopic classifications of all events in the LOSS volumetric sample (180 SNe and SN impostors) and update them if necessary. We discuss the populations of rare objects in our sample including broad-lined Type Ic SNe, Ca-rich SNe, SN 1987A-like events (we identify SN 2005io as SN 1987A-like here for the first time), and peculiar subtypes. The relative fractions of Type Ia SNe, Type II SNe, and stripped-envelope SNe in the local universe are not affected, but those of some subtypes are. Most significantly, after discussing the often unclear boundary between SNe Ib and Ic, we find a higher SN Ib fraction and a lower SN Ic fraction than calculated by Li et al. (2011b): SNe Ib occur in the local universe 1.5 $\pm$ 0.7 times more often than do SNe Ic.
Here we revisit line identifications of type I supernovae (SNe I) and highlight trace amounts of unburned hydrogen as an important free parameter for the composition of the progenitor. Most one-dimensional stripped-envelope models of supernovae indicate that observed features near 6000-6400 Å in type I spectra are due to more than Si ii λ6355. However, while an interpretation of conspicuous Si ii λ6355 can approximate 6150 Å absorption features for all SNe Ia during the first month of free expansion, similar identifications applied to 6250 Å features of SNe Ib and Ic have not been as successful. When the corresponding synthetic spectra are compared with high-quality timeseries observations, the computed spectra are frequently too blue in wavelength. Some improvement can be achieved with Fe ii lines that contribute redward of 6150 Å; however, the computed spectra either remain too blue or the spectrum only reaches a fair agreement when the rise-time to peak brightness of the model conflicts with observations by a factor of two. This degree of disagreement brings into question the proposed explosion scenario. Similarly, a detection of strong Si ii λ6355 in the spectra of broadlined Ic and super-luminous events of type I/R is less convincing despite numerous model spectra used to show otherwise. Alternatively, we suggest 6000-6400 Å features are possibly influenced by either trace amounts of hydrogen or blueshifted absorption and emission in Hα, the latter being an effect which is frequently observed in the spectra of hydrogen-rich, SNe II. © 2016. The American Astronomical Society. All rights reserved.
We present an improved version of a light curve model, which is able to estimate the physical properties of different types of core-collapse supernovae having double-peaked light curves, in a quick and efficient way. The model is based on a two-component configuration consisting of a dense, inner region and an extended, low-mass envelope. Using this configuration, we estimate the initial parameters of the progenitor via fitting the shape of the quasi-bolometric light curves of 10 SNe, including Type IIP and IIb events, with model light curves. In each case we compare the fitting results with available hydrodynamic calculations, and also match the derived expansion velocities with the observed ones. Furthermore, we also compare our calculations with hydrodynamic models derived by the SNEC code, and examine the uncertainties of the estimated physical parameters caused by the assumption of constant opacity and the inaccurate knowledge of the moment of explosion.
The optical and optical/near-infrared pseudobolometric light curves of 84 stripped-envelope supernovae (SNe) are constructed
using a consistent method and a standard cosmology. The light curves are analysed to derive temporal characteristics and peak
luminosity Lp, enabling the construction of a luminosity function. Subsequently, the mass of 56Ni synthesised in the explosion, along with the ratio of ejecta mass to ejecta kinetic energy, are found. Analysis shows that
host-galaxy extinction is an important factor in accurately determining luminosity values as it is significantly greater than
Galactic extinction in most cases. It is found that broad-lined SNe Ic (SNe Ic-BL) and gamma-ray burst SNe are the most luminous
subtypes with a combined median Lp, in erg s−1, of log(Lp) = 42.99 compared to 42.51 for SNe Ic, 42.50 for SNe Ib, and 42.36 for SNe IIb. It is also found that SNe Ic-BL synthesise
approximately twice the amount of 56Ni compared with SNe Ic, Ib, and IIb, with median MNi = 0.34, 0.16, 0.14, and 0.11 M⊙, respectively. SNe Ic-BL, and to a lesser extent SNe Ic, typically rise from Lp/2 to Lp more quickly than SNe Ib/IIb; consequently, their light curves are not as broad.