Models for the spectra and the light curve, in the photospheric as well as in the late nebular phase, are used to infer the properties of the very radio-bright, broad-lined type IIb Supernova 2003bg. Consistent fits to the light curve and the spectral evolution are obtained with an explosion that ejected ~ 4 M_sun of material with a kinetic energy of ~ 5 10^51 erg. A thin layer of hydrogen, comprising ~ 0.05 M_sun, is inferred to be present in the ejecta at the highest velocities (v >~ 9000 km/s), while a thicker helium layer, comprising ~ 1.25 M_sun, was ejected at velocities between 6500 and 9000 km/s. At lower velocities, heavier elements are present, including ~ 0.2 M_sun of 56Ni that shape the light curve and the late-time nebular spectra. These values suggest that the progenitor star had a mass of ~ 20-25 M_sun (comparable to, but maybe somewhat smaller than that of the progenitor of the XRF/SN 2008D). The rather broad-lined early spectra are the result of the presence of a small amount of material (~ 0.03 M_sun) at velocities > 0.1 c, which carries ~ 10 % of the explosion kinetic energy. No clear signatures of a highly aspherical explosion are detected.
We present the early-phase spectra and the light curves of the broad-lined supernova (SN) 2016coi from $t=7$ to $67$ days after the estimated explosion date. This SN was initially reported as a broad-lined Type SN Ic (SN Ic-BL). However, we found that spectra up to $t=12$ days exhibited the He~{\sc i} $λ$5876, $λ$6678, and $λ$7065 absorption lines. We show that the smoothed and blueshifted spectra of normal SNe Ib are remarkably similar to the observed spectrum of SN 2016coi. The line velocities of SN 2016coi were similar to those of SNe Ic-BL and significantly faster than those of SNe Ib. Ana…
The diffuse interstellar bands (DIBs) are absorption features observed in optical and near-infrared spectra that are thought to be associated with carbon-rich polyatomic molecules in interstellar gas. However, because the central wavelengths of these bands do not correspond with electronic transitions of any known atomic or molecular species, their nature has remained uncertain since their discovery almost a century ago. Here we report on unusually strong DIBs in optical spectra of the broad-lined Type Ic supernova SN 2012ap that exhibit changes in equivalent width over short (~30 days) timesc…
We present the spectroscopic discovery of a broad-lined Type Ic supernova (SN 2010bh) associated with the nearby long-duration gamma-ray burst (GRB) 100316D. At z = 0.0593, this is the third-nearest GRB-SN. Nightly optical spectra obtained with the Magellan telescopes during the first week after explosion reveal the gradual emergence of very broad spectral features superposed on a blue continuum. The supernova features are typical of broad-lined SNe Ic and are generally consistent with previous supernovae associated with low-redshift GRBs. However, the inferred velocities of SN 2010bh at 21 da…
We present the first systematic investigation of spectral properties of 17 Type Ic Supernovae (SNe Ic), 10 broad-lined SNe Ic (SNe Ic-bl) without observed Gamma-Ray Bursts (GRBs) and 11 SNe Ic-bl with GRBs (SN-GRBs) as a function of time in order to probe their explosion conditions and progenitors. We analyze a total of 407 spectra, which were drawn from published spectra of individual SNe as well as from the densely time-sampled spectra data of Modjaz et al. (2014). In order to quantify the diversity of the SN spectra as a function of SN subtype, we construct average spectra of SNe Ic, SNe Ic…
Many young, massive stars are found in close binaries. Using population synthesis simulations we predict the likelihood of a companion star being present when these massive stars end their lives as core-collapse supernovae (SNe). We focus on stripped-envelope SNe, whose progenitors have lost their outer hydrogen and possibly helium layers before explosion. We use these results to interpret new Hubble Space Telescope observations of the site of the broad-lined Type Ic SN 2002ap, 14 years post-explosion. For a subsolar metallicity consistent with SN 2002ap, we expect a main-sequence companion pr…
We simulate the evolution of binary systems with a massive primary star of 15Mo where we introduce an enhanced mass loss due to jets that the secondary star might launch, and find that in many cases the enhanced mass loss brings the binary system to experience the grazing envelope evolution (GEE) and form a progenitor of Type IIb supernova (SN IIb). The jets, the Roche lobe overflow (RLOF), and a final stellar wind remove most of the hydrogen-rich envelope, leaving a blue-compact SN IIb progenitor. In many cases without this jet-driven mass loss the system enters a common envelope evolution (C…
Type IIb supernovae (SNe) are important candidates to understand mechanisms that drive the stripping of stripped-envelope (SE) supernova (SN) progenitors. While binary interactions and their high incidence are generally cited to favor them as Type IIb SN progenitors, this idea has not been tested using models covering a broad parameter space. In this paper, we use non-rotating single- and binary-star models at solar and low metallicities spanning a wide parameter space in primary mass, mass ratio, orbital period, and mass transfer efficiencies. We find that our single- and binary-star models c…
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 available. Comparison of these constraints with the full distribution of theoretical properties not only help ascertain 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. 2019 to derive distributions of single and binary SNe IIb progenitor …
Long duration gamma-ray bursts are a rare subclass of stripped-envelope core-collapse supernovae that launch collimated relativistic outflows (jets). All gamma-ray-burst-associated supernovae are spectroscopically of Type Ic with broad lines, but the fraction of broad-lined Type Ic supernovae harboring low-luminosity gamma-ray-burst remains largely unconstrained. Some supernovae should be accompanied by off-axis $γ$-ray burst jets that remain invisible initially, but then emerge as strong radio sources (as the jets decelerate). However, this critical prediction of the jet model for gamma-ray b…
I propose a scenario where the majority of the progenitors of type IIb supernovae (SNe IIb) lose most of their hydrogen-rich envelope during a grazing envelope evolution (GEE). In the GEE the orbital radius of the binary system is about equal to the radius of the giant star, and the more compact companion accretes mass through an accretion disk. The accretion disk is assumed to launch two opposite jets that efficiently remove gas from the envelope along the orbit of the companion. The efficient envelope removal by jets prevents the binary system from entering a common envelope evolution, at le…
Core-collapse supernovae showing little or no hydrogen (denoted by Type IIb and Ib, respectively) are the explosions of massive stars that have lost some or most of their outer envelopes. How they lose their mass is unclear, but it likely involves binary interaction. So far, seven progenitors of such supernovae have been identified in pre-explosion imaging (five for Type IIb events and two for Type Ib events). Here, we evolve detailed binary stellar evolution models in order to better understand the nature of these progenitors. We find that the amount of hydrogen left in the envelope at the ti…
Unusually high velocities (< ~0.1c) and correspondingly high kinetic energies have been observed in a subset of Type Ic supernovae (so-called "broad-lined Ic" supernovae; SNe Ic-BL), prompting a search for a central engine model capable of generating such energetic explosions. A clue to the explosion mechanism may lie in the fact that all supernovae that accompany long-duration gamma-ray bursts belong to the SN Ic-BL class. Using a combination of two-dimensional relativistic hydrodynamics and radiation transport calculations, we demonstrate that the central engine responsible for long gamma-ra…
In this work, photometric and spectroscopic analyses of a very low-luminosity Type IIb supernova (SN) 2016iyc have been performed. SN 2016iyc lies near the faint end among the distribution of similar supernovae (SNe). Given lower ejecta mass ($M_{\rm ej}$) and low nickel mass ($M_{\rm Ni}$) from the literature, combined with SN 2016iyc lying near the faint end, one-dimensional stellar evolution models of 9 - 14 M$_{\odot}$ zero-age main-sequence (ZAMS) stars as the possible progenitors of SN 2016iyc have been performed using the publicly available code MESA. Moreover, synthetic explosions of t…
We simulate the evolution of eccentric binary systems in the frame of the grazing envelope evolution (GEE) channel for the formation of Type IIb supernovae (SNe IIb), and find that extra mass removal by jets increases the parameter space for the formation of SNe IIb in this channel. To explore the role of eccentricity and the extra mass removal by jets we use the stellar evolutionary code MESA binary. The initial primary and secondary masses are M1i=15Mo and M2i=2.5Mo. We examine initial semi-major axes of 600-1000Ro, and eccentricities of e=0-0.9. Both Roche lobe overflow (RLOF) and mass remo…
We present ZTF18aaqjovh (SN 2018bvw), a high-velocity ("broad-lined") stripped-envelope (Type Ic) supernova (Ic-BL SN) discovered in the Zwicky Transient Facility one-day cadence survey. ZTF18aaqjovh shares a number of features in common with engine-driven explosions: the photospheric velocity and the shape of the optical light curve are very similar to that of the Type Ic-BL SN 1998bw, which was associated with a low-luminosity gamma-ray burst (LLGRB) and had relativistic ejecta. However, the radio luminosity of ZTF18aaqjovh is almost two orders of magnitude fainter than that of SN 1998bw at …
In this paper, we fit the spectral energy distributions (SEDs) of iPTF 16asu that has so far been classified as a luminous rapidly evolving broad-lined Ic supernova (SN Ic-BL), and re-construct its post-peak bolometric light curve. We find that the luminosity of the post-peak bolometric light curve of iPTF 16asu is about 3 times that of the pseudo-bolometric light curve derived in the literature, and the extrapolated peak luminosity exceeds $\sim 10^{44}$ erg s$^{-1}$, which is higher than the threshold of superluminous SNe (SLSNe). We then use the $^{56}$Ni model and the magnetar plus $^{56}$…
Type IIb supernovae are believed to originate from core-collapse progenitors having kept only a very thin hydrogen envelope. We aim to explore how some physical factors, such as rotation, metallicity, overshooting, and the initial orbital period in binaries, significantly affect the Roche lobe overflow and the formation of type IIb supernovae. It is found that binaries are the main channel that capable of producing type typeIIb supernovae progenitors in the mass range for initial masses below 20 $M_{\odot}$. The formation of type IIb supernova progenitors is extremely sensitive to the initial …
We present a detection in pre-explosion Hubble Space Telescope (HST) imaging of a point source consistent with being the progenitor star of the Type IIb supernova (SN IIb) 2016gkg. Post-explosion imaging from the Keck Adaptive Optics system was used to perform relative astrometry between the Keck and HST imaging. We identify a single point source in the HST images coincident with the SN position to 0.89-sigma. The HST photometry is consistent with the progenitor star being an A0Ia star with T=9500 K and log (L/Lsun)=5.15. We find that the SN 2016gkg progenitor star appears more consistent with…
SN 2017ein is a narrow-lined Type Ic SN that was found to share a location with a point-like source in the face on spiral galaxy NGC 3938 in pre-supernova images, making SN 2017ein the first credible detection of a Type Ic progenitor. Results in the literature suggest this point-like source is likely a massive progenitor of 60-80 M$_{\odot}$, depending on if the source is a binary, a single star, or a compact cluster. Using new photometric and spectral data collected for 200 days, including several nebular spectra, we generate a consistent model covering the photospheric and nebular phase usin…
Broad-lined type Ic supernovae (SNe Ic-BL) are peculiar stellar explosions that distinguish themselves from ordinary SNe. Some SNe Ic-BL are associated with long-duration (\gtrsim 2 s) gamma-ray bursts (GRBs). Black holes and magnetars are two types of compact objects that are hypothesized to be central engines of GRBs. In spite of decades of investigations, no direct evidence for the formation of black holes or magnetars has been found for GRBs so far. Here we report the finding that the early peak (t \lesssim 50 days) and late-time (t \gtrsim 300 days) slow decay displayed in the light curve…
SN 2018ivc is an unusual type II supernova (SN II). It is a variant of SNe IIL, which might represent a transitional case between SNe IIP with a massive H-rich envelope, and IIb with only a small amount of the H-rich envelope. However, SN 2018ivc shows an optical light curve evolution more complicated than canonical SNe IIL. In this paper, we present the results of prompt follow-up observations of SN 2018ivc with the Atacama Large Millimeter/submillimeter Array (ALMA). Its synchrotron emission is similar to that of SN IIb 1993J, suggesting that it is intrinsically an SN IIb-like explosion of a…
We report the late-time evolution of Type IIb Supernova (SN IIb) 2013df. SN 2013df showed a dramatic change in its spectral features at ~1 year after the explosion. Early on it showed typical characteristics shared by SNe IIb/Ib/Ic dominated by metal emission lines, while later on it was dominated by broad and flat-topped Halpha and He I emissions. The late-time spectra are strikingly similar to SN IIb 1993J, which is the only previous example clearly showing the same transition. This late-time evolution is fully explained by a change in the energy input from the $^{56}$Co decay to the interac…
The classic example of a Type IIb supernova is SN 1993J, which had a cool extended progenitor surrounded by a dense wind. There is evidence for another category of Type IIb supernova which has a more compact progenitor with a lower density, probably fast, wind. Distinguishing features of the compact category are: weak optical emission from the shock heated envelope at early times; nonexistent or very weak H emission in the late nebular phase; rapidly evolving radio emission; rapid expansion of the radio shell; and expected nonthermal as opposed to thermal X-ray emission. Type IIb supernovae th…
We present results based on a well sampled optical ($UBVRI$) and ultraviolet ({\it Swift}/UVOT) imaging, and low-resolution optical spectroscopic follow-up observations of the nearby Type Ic supernova (SN) ASASSN-16fp (SN 2016coi). The SN was monitored during the photospheric phase ($-10$ to $+$33 days with respect to the $B$-band maximum light). The rise to maximum light and early post-maximum decline of the light curves are slow. The peak absolute magnitude ($M_{V}$ = $-17.7\pm0.2$ mag) of ASASSN-16fp is comparable with broad-lined Ic SN 2002ap, SN 2012ap and transitional Ic SN 2004aw but co…
Type II supernovae (SNe II) show strong hydrogen features in their spectra throughout their whole evolution while type IIb supernovae (SNe IIb) spectra evolve from dominant hydrogen lines at early times to increasingly strong helium features later on. However, it is currently unclear whether the progenitors of these supernova (SN) types form a continuum in pre-SN hydrogen mass or whether they are physically distinct. SN light-curve morphology directly relates to progenitor and explosion properties such as the amount of hydrogen in the envelope, the pre-SN radius, the explosion energy and the s…
We explore properties of Type Ib and IIb SN progenitors that are produced by stable mass transfer in binary systems, using a new grid of stellar evolution models from an initial primary mass in the range of 10 - 18 $\mathrm{M_\odot}$ at solar and Large Magellanic Cloud metallicities. We find that blue and yellow supergiant SN IIb progenitors (e.g., of SN 2008ax, SN 2011dh, SN 2016gkg) have a hydrogen envelope mass less than about 0.15 $\mathrm{M_\odot}$, mostly resulting from early Case B mass transfer with relatively low initial masses and/or low metallicity. Red supergiant (RSG) SN IIb proge…
We present optical photometry and spectroscopy of the broad-lined Type Ic supernova (SNIc-BL) PTF10qts, which was discovered as part of the Palomar Transient Factory. The supernova was located in a dwarf galaxy of magnitude $r=21.1$ at a redshift $z=0.0907$. We find that the $R$-band light curve is a poor proxy for bolometric data and use photometric and spectroscopic data to construct and constrain the bolometric light curve. The derived bolometric magnitude at maximum light is $M_{\rm bol} = -18.51\pm0.2$ mag, comparable to that of SN 1998bw ($M_{\rm bol} = -18.7$ mag) which was associated w…
MASTER OT J033744.97+723159.0/SN 2017gpn was discovered in the error-box of LIGO/Virgo G299232 gravitational wave alert. The spectrum of SN 2017gpn is consistent with a Type IIb supernova. In this work we present the photometry of 20 epochs of observations performed with CCD-photometer on the Zeiss-1000 telescope. The light curves in B and Rc filters were obtained. The multicolour light curves were also modelled numerically using the one-dimensional radiation hydro-dynamical code STELLA.
It is well-known that ordinary supernovae (SNe) are powered by 56Ni cascade decay. Broad-lined type Ic SNe (SNe Ic-BL) are a subclass of SNe that are not all exclusively powered by 56Ni decay. It was suggested that some SNe Ic-BL are powered by magnetar spin-down. iPTF16asu is a peculiar broad-lined type Ic supernova discovered by the intermediate Palomar Transient Factory. With a rest-frame rise time of only 4 days, iPTF16asu challenges the existing popular models, for example, the radioactive heating (56Ni-only) and the magnetar+56Ni models. Here we show that this rapid rise could be attribu…
Core-collapse stripped-envelope supernova (SN) explosions reflect the diversity of physical parameters and evolutionary paths of their massive star progenitors. We have observed the type Ic SN iPTF15dld (z = 0.047), reported by the Palomar Transient Factory. Spectra were taken starting 20 rest-frame days after maximum luminosity and are affected by a young stellar population background. Broad spectral absorption lines associated with the SN are detected over the continuum, similar to those measured for broad-lined, highly energetic SNe Ic. The light curve and maximum luminosity are instead mor…
We present extensive radio monitoring of a type IIb supernova (SN IIb), SN 2016gkg during $t \sim$ 8$-$1429 days post explosion at frequencies $ν\sim$ 0.33$-$25 GHz. The detailed radio light curves and spectra are broadly consistent with self-absorbed synchrotron emission due to the interaction of the SN shock with the circumstellar medium. The model underpredicts the flux densities at $t \sim$ 299 days post-explosion by a factor of 2, possibly indicating a density enhancement in the CSM due to a non-uniform mass-loss from the progenitor. Assuming a wind velocity $v_{\rm w} \sim$ 200 km s$^{-1…
The shape of the light curve peak of radioactive--powered core--collapse "stripped--envelope" supernovae constrains the ejecta mass, nickel mass, and kinetic energy by the brightness and diffusion time for a given opacity and observed expansion velocity. Late--time light curves give constraints on the ejecta mass and energy, given the gamma--ray opacity. Previous work has shown that the principal light curve peaks for SN~IIb with small amounts of hydrogen and for hydrogen/helium--deficient SN~Ib/c are often rather similar near maximum light, suggesting similar ejecta masses and kinetic energie…
In this work we present the photometric and spectroscopic observations of Type IIb Supernova 2017gpn. This supernova was discovered in the error-box of LIGO/Virgo G299232 gravitational-wave event. We obtained the light curves in B and R passbands and modelled them numerically using the one-dimensional radiation hydrocode STELLA. The best-fit model has the following parameters: the pre-SN star mass and the radius are 3.5 Msun and 50 Rsun, respectively; the explosion energy is Eexp = 1.2 * 10^51 erg; the mass of radioactive nickel is M56Ni =0.11 Msun, which is totally mixed through the ejecta, t…
We present optical and near infrared observations of the type IIb supernova (SN) 2011fu from a few days to $\sim300$ 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 $\sim40$ d, then helium gaining strength, and nebular emission lines appearing from $\sim60$ d post-explosion. The velocities derived from the P-Cygni absorptions are overall similar to those of other type IIb SNe…
We present Hubble Space Telescope (HST) observations of the type IIb supernova (SN) 2016gkg at 652, 1698, and 1795 days with the Advanced Camera for Surveys (ACS) and Wide Field Camera 3 (WFC3). Comparing to pre-explosion imaging from 2001 obtained with the Wide Field Planetary Camera 2, we demonstrate that SN 2016gkg is now fainter than its candidate counterpart in the latest WFC3 imaging, implying that the counterpart has disappeared and confirming that it was the SN progenitor star. We show the latest light curve and Keck spectra of SN 2016gkg, which implies that SN 2016gkg is declining mor…
Broad-lined type Ic supernovae (SNe Ic-BL) are a subclass of rare core collapse SNe whose energy source is debated in the literature. Recently a series of investigations on SNe Ic-BL with the magnetar (plus 56Ni) model were carried out. Evidence for magnetar formation was found for the well-observed SNe Ic-BL 1998bw and 2002ap. In this paper we systematically study a large sample of SNe Ic-BL not associated with gamma-ray bursts. We use photospheric velocity data determined in a homogeneous way. We find that the magnetar+56Ni model provides a good description of the light curves and velocity e…
Type IIb Supernova (SN) 2011dh, with conclusive detection of an unprecedented Yellow Supergiant (YSG) progenitor, provides an excellent opportunity to deepen our understanding on the massive star evolution in the final centuries toward the SN explosion. In this paper, we report on detection and analyses of thermal X-ray emission from SN IIb 2011dh at ~500 days after the explosion on Chandra archival data, providing a solidly derived mass loss rate of an YSG progenitor for the first time. We find that the circumstellar media (CSM) should be dense, more than that expected from a Wolf-Rayet (WR) …
We present observations of supernova (SN) 2017ens, discovered by the ATLAS survey and identified as a hot blue object through the GREAT program. The redshift z=0.1086 implies a peak brightness of M_g=-21.1 mag, placing the object within the regime of superluminous supernovae. We observe a dramatic spectral evolution, from initially being blue and featureless, to later developing features similar to those of the broadlined Type Ic SN 1998bw, and finally showing ~2000 km s^-1 wide H-alpha and H-beta emission. Relatively narrow Balmer emission (reminiscent of a SN IIn) is present at all times. We…
The nature of the peculiar `Ca-rich' SN 2019ehk in the nearby galaxy M100 remains unclear. Its origin has been debated as either a stripped core-collapse supernova or a thermonuclear helium detonation event. Here, we present very late-time photometry of the transient obtained with the Keck I telescope at $\approx280$ days from peak light. Using the photometry to perform accurate flux calibration of a contemporaneous nebular phase spectrum, we measure an [O I] luminosity of $(0.19-1.08)\times10^{38}$ erg s$^{-1}$ and [Ca II] luminosity of $(2.7-15.6)\times10^{38}$ erg s$^{-1}$ over the range of…
The progenitor stars of several Type IIb supernovae (SNe) show indications for extended hydrogen envelopes. These envelopes might be the outcome of luminous energetic pre-explosion events, so-called precursor eruptions. We use the Palomar Transient Factory (PTF) pre-explosion observations of a sample of 27 nearby Type IIb SNe to look for such precursors during the final years prior to the SN explosion. No precursors are found when combining the observations in 15-day bins, and we calculate the absolute-magnitude-dependent upper limit on the precursor rate. At the 90% confidence level, Type IIb…
Type Ic supernovae (SNe Ic) are a sub-class of core-collapse supernovae that exhibit no helium or hydrogen lines in their spectra. Their progenitors are thought to be bare carbon-oxygen cores formed during the evolution of massive stars that are stripped of their hydrogen and helium envelopes sometime before collapse. SNe Ic present a range of luminosities and spectral properties, from luminous GRB-SNe with broad-lined spectra to less luminous events with narrow-line spectra. Modelling SNe\,Ic reveals a wide range of both kinetic energies, ejecta masses, and $^{56}\text{Ni}$ masses. To explore…
Few published ultraviolet (UV) spectra exist for stripped-envelope supernovae, and none to date for broad-lined Type Ic supernovae (SN Ic-bl). These objects have extremely high ejecta velocities and are the only supernova type directly linked to gamma-ray bursts (GRBs). Here we present two epochs of HST/STIS spectra of the SN Ic-bl 2014ad, the first UV spectra for this class. We supplement this with 26 new epochs of ground-based optical spectra, augmenting a rich spectral time series. The UV spectra do not show strong features and are consistent with broadened versions of other SN Ic spectra o…
From stellar evolution simulations (using MESA) we conclude that the fatal common envelope evolution (CEE) channel for the formation of Type IIb core collapse supernova (SN IIb) progenitors can indeed account for some SNe IIb. In the fatal CEE channel for SNe IIb a low mass main sequence secondary star inspirals inside the giant envelope of the massive primary star and removes most of the giant envelope before it merges with the giant core. The key ingredient of the scenario studied here is that the tidally destroyed secondary star forms a new giant envelope. The mass-loss process in a wind du…
We perform binary stellar evolutionary calculations following the simultaneous evolution of both stars in the system to study a potential progenitor system for the Type IIb supernova 2011dh. Pre-explosion photometry as well as light-curve modeling have provided constraints on the physical properties of the progenitor system. Here we present a close binary system that is compatible with such constraints. The system is formed by stars of solar composition with 16 Msun + 10 Msun on a circular orbit with an initial period of 125 days. The primary star ends its evolution as a yellow supergiant with…
We investigate line formation processes in Type IIb supernovae (SNe) from 100 to 500 days post-explosion using spectral synthesis calculations. The modeling identifies the nuclear burning layers and physical mechanisms that produce the major emission lines, and the diagnostic potential of these. We compare the model calculations with data on the three best observed Type IIb SNe to-date - SN 1993J, SN 2008ax, and SN 2011dh. Oxygen nucleosynthesis depends sensitively on the main-sequence mass of the star and modeling of the [O I] 6300, 6364 lines constrains the progenitors of these three SNe to …
A subset of type Ic supernovae (SNe Ic), broad-lined SNe Ic (SNe Ic-bl), show unusually high kinetic energies ($\sim 10^{52}$ erg) which cannot be explained by the energy supplied by neutrinos alone. Many SNe Ic-bl have been observed in coincidence with long gamma-ray bursts (GRBs) which suggests a connection between SNe and GRBs. A small fraction of core-collapse supernovae (CCSNe) form a rapidly-rotating and strongly-magnetized protoneutron star (PNS), a proto-magnetar. Jets from such magnetars can provide the high kinetic energies observed in SNe Ic-bl and also provide the connection to GRB…
We present 1-D non-Local-Thermodynamic-Equilibrium time-dependent radiative-transfer simulations for a large grid of supernovae (SNe) IIb/Ib/Ic that result from the terminal explosion of the mass donor in a close-binary system. Our sample covers ejecta masses $M_{\rm e}$ of 1.7$-$5.2M$_\odot$, kinetic energies $E_{\rm kin}$ of 0.6$-$5.0$\times$10$^{51}$erg, and $^{56}$Ni masses of 0.05$-$0.30M$_\odot$. We find a strong correlation between the $^{56}$Ni mass and the photometric properties at maximum, and between the rise time to bolometric maximum and the post-maximum decline rate. We confirm t…
We present 1-D non-Local-Thermodynamic-Equilibrium time-dependent radiative-transfer simulations for supernovae (SNe) of type IIb, Ib, and Ic that result from the terminal explosion of the mass donor in a close-binary system. Here, we select three ejecta with a total kinetic energy of ~1.2e51erg, but characterised by different ejecta masses (2-5Msun), composition, and chemical mixing. The type IIb/Ib models correspond to the progenitors that have retained their He-rich shell at the time of explosion. The type Ic model arises from a progenitor that has lost its helium shell, but retains 0.32Msu…
Broad-lined type Ic supernovae (SNe Ic-BL) are of great importance because their association with long-duration gamma-ray bursts (LGRBs) holds the key to deciphering the central engine of LGRBs, which refrains from being unveiled despite decades of investigation. Among the two popularly hypothesized types of central engine, i.e., black holes and strongly magnetized neutron stars (magnetars), there is mounting evidence that the central engine of GRB-associated SNe (GRB-SNe) is rapidly rotating magnetars. Theoretical analysis also suggests that magnetars could be the central engine of SNe Ic-BL.…
Here we present previously unpublished optical spectra of supernova (SN) 2001ig, a Type IIb SN, from about a week after explosion until nearly one year later. The earliest spectrum consists of only a few broad absorption features, but soon more common Type II SN features including hydrogen P-Cygni profiles and helium absorption become apparent. At later times, as the H features fade and the He I absorption becomes more prominent, we observe the SN to transition from a Type II to a Type Ib. Finally, observations after 250 days past explosion show a nebular-phase SN spectrum with one of the larg…
We use the new NLTE lightcurve and spectral synthesis code JEKYLL to evolve a macroscopically mixed ejecta model of a type IIb Supernova (SN) originating from a star with an initial mass of 12 solar masses through the photospheric and nebular phase. We compare to SN 2011dh, and find that both the spectra and the lightcurves are well reproduced. Our work further strengthens the evidence that this SN originated from a star with an initial mass of about 12 solar masses that had lost all but tiny (<0.1 solar masses) fraction of its hydrogen envelope. We also investigate the effects of the macrosco…
Optical observations of the type IIb SN 2013df from a few days to about 250 days after explosion are presented. These observations are complemented with UV photometry taken by \textit{SWIFT} up to 60 days post-explosion. The double-peak optical light curve is similar to those of SNe 1993J and 2011fu although with different decline and rise rates. From the modelling of the bolometric light curve, we have estimated that the total mass of synthesised $^{56}$Ni in the explosion is $\sim0.1$ M$_{\odot}$, while the ejecta mass is $0.8-1.4$ M$_{\odot}$ and the explosion energy $0.4-1.2 \times 10^{51}…
We present optical observations of the Type I superluminous supernova (SLSN-I) SN2017dwh at $z\!\approx\!0.13$, which reached $M_{i}\!\approx\!-21$ mag at peak. Spectra taken a few days after peak show an unusual and strong absorption line centered near 3200Å that we identify with Co II, suggesting a high fraction of synthesized $^{56}$Ni in the ejecta. By $\sim\!1$ month after peak, SN2017dwh became much redder than other SLSNe-I, instead strongly resembling broad-lined Type Ic supernovae (Ic-BL SNe) with clear suppression of the flux redward of $\sim\!5000$ Å, providing further evidence for …
We present optical and near-infrared observations of the rapidly evolving supernova (SN) 2017czd that shows hydrogen features. The optical light curves exhibit a short plateau phase ($\sim 13$ days in the $R$-band) followed by a rapid decline by $4.5$ mag in $\sim 20 \mathrm{days}$ after the plateau. The decline rate is larger than those of any standard SNe, and close to those of rapidly evolving transients. The peak absolute magnitude is $-16.8$ mag in the $V$-band, which is within the observed range for SNe IIP and rapidly evolving transients. The spectra of SN 2017czd clearly show the hydro…
We present HST/WFC3 ultraviolet imaging in the F275W and F336W bands of the Type IIb SN 2001ig at an age of more than 14 years. A clear point source is detected at the site of the explosion having $m_{\rm F275W}=25.39 \pm 0.10$ and $m_{\rm F336W}=25.88 \pm 0.13$ mag. Despite weak constraints on both the distance to the host galaxy NGC 7424 and the line-of-sight reddening to the supernova, this source matches the characteristics of an early B-type main sequence star having $19,000 < T_{\rm eff} < 22,000$ K and $\log (L_{\rm bol}/L_{\odot})=3.92 \pm 0.14$. A BPASS v2.1 binary evolution model, wi…
We compare the diversity of spectral line velocities in a large sample of type IIb supernovae (SNe IIb) with the expected asphericity in the explosion, as measured from the light echoes of Cassiopeia A (Cas A), which was a historical galactic SN IIb. We revisit the results of Rest et al. (2011a), who used light echoes to observe Cas A from multiple lines of sight and hence determine its asphericity, as seen in the velocity of three spectral lines (He I $λ$5876, H$α$ and the Ca II NIR triplet). We confirm and improve on this measurement by reproducing the effect of the light echoes in the spect…
We present ultraviolet, optical, and near-infrared observations of SN 2012ap, a broad-lined Type Ic supernova in the galaxy NGC 1729 that produced a relativistic and rapidly decelerating outflow without a gamma-ray burst signature. Photometry and spectroscopy follow the flux evolution from -13 to +272 days past the B-band maximum of -17.4 +/- 0.5 mag. The spectra are dominated by Fe II, O I, and Ca II absorption lines at ejecta velocities of 20,000 km/s that change slowly over time. Other spectral absorption lines are consistent with contributions from photospheric He I, and hydrogen may also …
