Type Ic Superluminous Supernovae Research Articles

Related Progenitor Models for Long-duration Gamma-Ray Bursts and Type Ic Superluminous Supernovae

Abstract We model the late evolution and mass loss history of rapidly rotating Wolf–Rayet stars in the mass range 5 M ⊙…100 M ⊙). We find that quasi-chemically homogeneously evolving single stars computed with enhanced mixing retain very little or no helium and are compatible with Type Ic supernovae. The more efficient removal of core angular momentum and the expected smaller compact object mass in our lower-mass models lead to core spins in the range suggested for magnetar-driven superluminous supernovae. Our higher-mass models retain larger specific core angular momenta, expected for long-duration gamma-ray bursts in the collapsar scenario. Due to the absence of a significant He envelope, the rapidly increasing neutrino emission after core helium exhaustion leads to an accelerated contraction of the whole star, inducing a strong spin-up and centrifugally driven mass loss at rates of up to in the last years to decades before core collapse. Because the angular momentum transport in our lower-mass models enhances the envelope spin-up, they show the largest relative amounts of centrifugally enforced mass loss, i.e., up to 25% of the expected ejecta mass. Our most massive models evolve into the pulsational pair-instability regime. We would thus expect signatures of interaction with a C/O-rich circumstellar medium for Type Ic superluminous supernovae with ejecta masses below ∼10 M ⊙ as well as for the most massive engine-driven explosions with ejecta masses above ∼30 M ⊙. Signs of such interaction should be observable at early epochs of the supernova explosion; they may be related to bumps observed in the light curves of superluminous supernovae, or to the massive circumstellar CO-shell proposed for Type Ic superluminous supernova Gaia16apd.

Toward an inner connection of SNe Ic, SLSNe Ic, XRF connected SNe, SNe Ic-BL, and GRB connected SNe

AbstractType Ic supernovae can be classified as normal supernovae Ic, type Ic super-luminous supernovae, X-ray flash-connected supernovae, broad-line supernovae Ic, and gamma-ray burst-connected supernovae. Here we suggest an inner connection for all kinds of supernovae Ic which is based on whether a pair of jets are successfully launched: a normal supernovae Ic is a normal core collapsar without jets launched; a gamma-ray burst-associated supernovae Ic is a core collapsar with relativistic jets launched and successfully breaking out the envelope of the progenitor; an X-ray flash-associated supernovae Ic is a core collapsar with jets launched but can only develop a relativistic shock breakout; a broad-line supernovae Ic is an off-axis gamma-ray burst or an X-ray flash-associated supernova; and a type Ic super-luminous supernovae is close to the X-ray flash-connected supernovae Ic, but the shock breakout is not relativistic and most of the jet energy is deposited into the supernova component. Based on the luminosity-distance diagram, we derived the luminosity function of all different types of supernovae Ic as a whole. We also show that the normal supernovae Ic and gamma-ray burst-connected supernovae Ic have similar accumulative distributions.

Gaia16apd – a link between fast and slowly declining type I superluminous supernovae

We present ultraviolet, optical and infrared photometry and optical spectroscopy of the type Ic superluminous supernova (SLSN) Gaia16apd (= SN 2016eay), covering its evolution from 26 d before the $g$-band peak to 234.1 d after the peak. Gaia16apd was followed as a part of the NOT Unbiased Transient Survey (NUTS). It is one of the closest SLSNe known ($z = 0.102\pm0.001$), with detailed optical and ultraviolet (UV) observations covering the peak. Gaia16apd is a spectroscopically typical type Ic SLSN, exhibiting the characteristic blue early spectra with O II absorption, and reaches a peak $M_{g} = -21.8 \pm 0.1$ mag. However, photometrically it exhibits an evolution intermediate between the fast- and slowly-declining type Ic SLSNe, with an early evolution closer to the fast-declining events. Together with LSQ12dlf, another SLSN with similar properties, it demonstrates a possible continuum between fast- and slowly-declining events. It is unusually UV-bright even for a SLSN, reaching a non-$K$-corrected $M_{uvm2} \simeq -23.3$ mag, the only other type Ic SLSN with similar UV brightness being SN 2010gx. Assuming that Gaia16apd was powered by magnetar spin-down, we derive a period of $P = 1.9\pm0.2$ ms and a magnetic field of $B = 1.9\pm0.2 \times 10^{14}$ G for the magnetar. The estimated ejecta mass is between 8 and 16 $\mathrm{M}_{\odot}$ and the kinetic energy between 1.3 and $2.5 \times 10^{52}$ erg, depending on opacity and assuming that the entire ejecta is swept up into a thin shell. Despite the early photometric differences, the spectra at late times are similar to slowly-declining type Ic SLSNe, implying that the two subclasses originate from similar progenitors.

Properties of Magnetars Mimicking 56Ni-Powered Light Curves in Type IC Superluminous Supernovae

Abstract Many Type Ic superluminous supernovae have light-curve decline rates after their luminosity peak, which are close to the nuclear decay rate of , consistent with the interpretation that they are powered by and possibly pair-instability supernovae. However, their rise times are typically shorter than those expected from pair-instability supernovae, and Type Ic superluminous supernovae are often suggested to be powered by magnetar spin-down. If magnetar spin-down is actually a major mechanism to power Type Ic superluminous supernovae, it should be able to produce decline rates similar to the decay rate rather easily. In this study, we investigate the conditions for magnetars under which their spin-down energy input can behave like the nuclear decay energy input. We find that an initial magnetic field strength within a certain range is sufficient to keep the magnetar energy deposition within a factor of a few of the decay energy for several hundreds of days. Magnetar spin-down needs to be by almost pure dipole radiation with the braking index close to three to mimic in a wide parameter range. Not only late-phase -decay-like light curves, but also rise time and peak luminosity of most -powered light curves can be reproduced by magnetars. Bolometric light curves for more than 700 days are required to distinguish the two energy sources solely by them. We expect that more slowly declining superluminous supernovae with short rise times should be found if they are mainly powered by magnetar spin-down.

LONG-DURATION SUPERLUMINOUS SUPERNOVAE AT LATE TIMES

ABSTRACT Nebular-phase observations and spectral models of Type Ic superluminous supernovae (SLSNe) are presented. LSQ14an and SN 2015bn both display late-time spectra similar to galaxy-subtracted spectra of SN 2007bi, and the class shows strong similarity with broad-lined SNe Ic such as SN 1998bw. Near-infrared observations of SN 2015bn show a strong Ca ii triplet, O i 9263, O i 1.13 μm, and Mg i 1.50 μm, but no distinct He, Si, or S emission. The high Ca ii NIR/[Ca ii] 7291, 7323 ratio of ∼2 indicates a high electron density of cm−3. Spectral models of oxygen-zone emission are investigated to put constraints on the emitting region. Models require M ⊙ to produce enough [O i] 6300, 6364 luminosity, irrespective of the powering situation and the density. The high oxygen-zone mass, supported by high estimated magnesium masses, points to explosions of massive CO cores, requiring . Collisions of pair-instability pulsations do not provide enough mass to account for the emission. [O ii] and [O iii] lines emerge naturally in many models, which strengthens the identification of broad [O ii] 7320, 7330, [O iii] 4363, and [O iii] 4959, 5007 in some spectra. A small filling factor for the O/Mg zone is needed to produce enough luminosity in Mg i] 4571, Mg i 1.504 μm, and O i recombination lines, which shows that the ejecta is clumped. We review the constraints from the nebular spectral modeling in the context of the various scenarios proposed for SLSNe.

Revealing the binary origin of Type Ic superluminous supernovae through nebular hydrogen emission

We propose that nebular H-alpha emission as detected in the Type Ic superluminous supernova iPTF13ehe stems from matter which is stripped from a companion star when the supernova ejecta collide with it. The temporal evolution, the line broadening, and the overall blueshift of the emission are consistent with this interpretation. We scale the nebular H-alpha luminosity predicted for Type Ia supernovae in single-degenerate systems to derive the stripped mass required to explain the H-alpha luminosity of iPTF13ehe. We find a stripped mass of 0.1 - 0.9 solar masses, assuming that the supernova luminosity is powered by radioactivity or magnetar spin down. Because a central heating source is required to excite the H-alpha emission, an interaction-powered model is not favored for iPTF13ehe if the H-alpha emission is from stripped matter. We derive a companion mass of more than 20 solar masses and a binary separation of less than about 20 companion radii based on the stripping efficiency during the collision, indicating that the supernova progenitor and the companion formed a massive close binary system. If Type Ic superluminous supernovae generally occur in massive close binary systems, the early brightening observed previously in several Type Ic superluminous supernovae may also be due to the collision with a close companion. Observations of nebular hydrogen emission in future Type Ic superluminous supernovae will enable us to test this interpretation.

A UNIFIED ENERGY-RESERVOIR MODEL CONTAINING CONTRIBUTIONS FROM ${}^{56}\mathrm{Ni}$ AND NEUTRON STARS AND ITS IMPLICATION FOR LUMINOUS TYPE Ic SUPERNOVAE

Most type-Ic core-collapse supernovae (CCSNe) produce $^{56}$Ni and neutron stars (NSs) or black holes (BHs). The dipole radiation of nascent NSs has usually been neglected in explaining supernovae (SNe) with peak absolute magnitude $M_{\rm peak}$ in any band are $\gtrsim -19.5$~mag, while the $^{56}$Ni can be neglected in fitting most type-Ic superluminous supernovae (SLSNe Ic) whose $M_{\rm peak}$ in any band are $\lesssim -21$~mag, since the luminosity from a magnetar (highly magnetized NS) can outshine that from a moderate amount of $^{56}$Ni. For luminous SNe Ic with $-21 \lesssim M_{\rm peak}\lesssim -19.5$~mag, however, both contributions from $^{56}$Ni and NSs cannot be neglected without serious modeling, since they are not SLSNe and the $^{56}$Ni mass could be up to $\sim 0.5 M_{\odot}$. In this paper we propose a unified model that contain contributions from both $^{56}$Ni and a nascent NS. We select three luminous SNe Ic-BL, SN~2010ay, SN~2006nx, and SN~14475, and show that, if these SNe are powered by $^{56}$Ni, the ratio of $M_{\rm Ni}$ to $M_{\rm ej}$ are unrealistic. Alternatively, we invoke the magnetar model and the hybrid ($^{56}$Ni + NS) model and find that they can fit the observations, indicating that our models are valid and necessary for luminous SNe Ic. Owing to the lack of late-time photometric data, we cannot break the parameter degeneracy and thus distinguish among the model parameters, but we can expect that future multi-epoch observations of luminous SNe can provide stringent constraints on $^{56}$Ni yields and the parameters of putative magnetars.

TESTING COSMOLOGICAL MODELS WITH TYPE Ic SUPER LUMINOUS SUPERNOVAE

The use of type Ic Super Luminous Supernovae (SLSN Ic) to examine the cosmological expansion introduces a new standard ruler with which to test theoretical models. The sample suitable for this kind of work now includes 11 SLSNe Ic, which have thus far been used solely in tests involving $\Lambda$CDM. In this paper, we broaden the base of support for this new, important cosmic probe by using these observations to carry out a one-on-one comparison between the $R_{\rm h}=ct$ and $\Lambda$CDM cosmologies. We individually optimize the parameters in each cosmological model by minimizing the $\chi^{2}$ statistic. We also carry out Monte Carlo simulations based on these current SLSN Ic measurements to estimate how large the sample would have to be in order to rule out either model at a $\sim 99.7\%$ confidence level. The currently available sample indicates a likelihood of $\sim$$70-80\%$ that the $R_{\rm h}=ct$ Universe is the correct cosmology versus $\sim$$20-30\%$ for the standard model. These results are suggestive, though not yet compelling, given the current limited number of SLSNe Ic. We find that if the real cosmology is $\Lambda$CDM, a sample of $\sim$$240$ SLSNe Ic would be sufficient to rule out $R_{\rm h}=ct$ at this level of confidence, while $\sim$$480$ SLSNe Ic would be required to rule out $\Lambda$CDM if the real Universe is instead $R_{\rm h}=ct$. This difference in required sample size reflects the greater number of free parameters available to fit the data with $\Lambda$CDM. If such SLSNe Ic are commonly detected in the future, they could be a powerful tool for constraining the dark-energy equation of state in $\Lambda$CDM, and differentiating between this model and the $R_{\rm h}=ct$ Universe.

Selecting superluminous supernovae in faint galaxies from the first year of the Pan-STARRS1 Medium Deep Survey

The Pan-STARRS1 (PS1) survey has obtained imaging in 5 bands (grizy_P1) over 10 Medium Deep Survey (MDS) fields covering a total of 70 square degrees. This paper describes the search for apparently hostless supernovae (SNe) within the first year of PS1 MDS data with an aim of discovering new superluminous supernovae (SLSNe). A total of 249 hostless transients were discovered down to a limiting magnitude of M_AB ~ 23.5, of which 76 were classified as Type Ia SNe. There were 57 SNe with complete light curves that are likely core-collapse SNe (CCSNe) or SLSNe and 12 of these have had spectra taken. Of these 12 hostless, non-Type Ia SNe, 7 were SLSNe of Type Ic at redshifts between 0.5-1.4. This illustrates that the discovery rate of Type Ic SLSNe can be maximised by concentrating on hostless transients and removing normal SNe Ia. We present data for two new possible SLSNe; PS1-10pm (z = 1.206) and PS1-10ahf (z = 1.1), and estimate the rate of SLSNe-Ic to be between 3^{+3}_{-2} * 10^{-5} and 8^{+2}_{-1} * 10^{-5} of the CCSNe rate within 0.3 <= z <= 1.4 by applying a Monte-Carlo technique. The rate of slowly evolving, SN2007bi-like explosions is estimated as a factor of 10 lower than this range.

SUPERLUMINOUS SUPERNOVAE AS STANDARDIZABLE CANDLES AND HIGH-REDSHIFT DISTANCE PROBES

We investigate the use of type Ic Super Luminous Supernovae as standardizable candles and distance indicators. Their appeal as cosmological probes stems from their remarkable peak luminosities, hot blackbody temperatures and bright restframe ultraviolet emission. We present a sample of sixteen published SLSN, from redshifts 0.1 to 1.2 and calculate accurate K-corrections to determine uniform magnitudes in two synthetic rest-frame filters with central wavelengths at 400nm and 520nm. At 400nm, we find a low scatter in their uncorrected, raw mean magnitudes with M(400)=-21.70 for the full sample of sixteen objects. We investigate the correlation between their decline rates and peak magnitude and find that the brighter events appear to decline more slowly. We define a $\Delta M(30)$ decay relation. This correlates peak magnitude and decline over 30 days and can reduce the scatter to 0.25. We further show that M(400) appears to have a strong colour dependence. Using this colour rate decay relation, a low scatter of between 0.19 and 0.26 can be found depending on sample selection. However we caution that only eight to ten objects currently have enough data to test this colour rate decline relation. We conclude that SLSN Ic are promising distance indicators at high redshift in regimes beyond those possible with SNe Ia. Although the empirical relationships are encouraging, the unknown progenitor systems and how they may evolve with redshift are of some concern. The two major measurement uncertainties are the limited numbers of low redshift objects to test these relationships and internal dust extinction in the host galaxies.