Luminous Supernova Research Articles

Origin of post-maximum bump in luminous Type Ic supernova 2019stc

ABSTRACT We address the issue of the post-maximum bump observed in the light curve of some superluminous supernovae. We rule out the popular mechanism of a circumstellar interaction suggested for the bump explanation. Instead, we propose that the post-maximum bump is caused by the magnetar dipole field enhancement several months after the explosion. The modelling of SN 2019stc light curve based on the thin shell approximation implies that at the age of ∼90 d, the initial dipole magnetic field should be amplified by a factor of 2.8 to account for the post-maximum bump. The specific mechanism for the field amplification of the newborn magnetar on the time-scale of several months has yet to be identified.

A Sample of Massive Black Holes in Dwarf Galaxies Detected via [Fe x] Coronal Line Emission: Active Galactic Nuclei and/or Tidal Disruption Events

Abstract The massive black hole (BH) population in dwarf galaxies (M BH ≲ 105 M ⊙) can provide strong constraints on the origin of BH seeds. However, traditional optical searches for active galactic nuclei (AGNs) only reliably detect high-accretion, relatively high-mass BHs in dwarf galaxies with low amounts of star formation, leaving a large portion of the overall BH population in dwarf galaxies relatively unexplored. Here, we present a sample of 81 dwarf galaxies (M ⋆ ≤ 3 × 109 M ⊙) with detectable [Fe x]λ6374 coronal line emission indicative of accretion onto massive BHs, only two of which were previously identified as optical AGNs. We analyze optical spectroscopy from the Sloan Digital Sky Survey and find [Fe x]λ6374 luminosities in the range L [Fe x] ≈ 1036–1039 erg s−1, with a median value of 1.6 × 1038 erg s−1. The [Fe x] λ6374 luminosities are generally much too high to be produced by stellar sources, including luminous Type IIn supernovae (SNe). Moreover, based on known SNe rates, we expect at most eight Type IIn SNe in our sample. That said, the [Fe x]λ6374 luminosities are consistent with accretion onto massive BHs from AGNs or tidal disruption events (TDEs). We find additional indicators of BH accretion in some cases using other emission line diagnostics, optical variability, and X-ray and radio emission (or some combination of these). However, many of the galaxies in our sample only have evidence for a massive BH based on their [Fe x]λ6374 luminosities. This work highlights the power of coronal line emission to find BHs in dwarf galaxies missed by other selection techniques and to probe the BH population in bluer, lower-mass dwarf galaxies.

Faintest of Them All: ZTF 21aaoryiz/SN 2021fcg—Discovery of an Extremely Low Luminosity Type Iax Supernova

Abstract We present the discovery of ZTF 21aaoryiz/SN 2021fcg—an extremely low luminosity Type Iax supernova. SN 2021fcg was discovered by the Zwicky Transient Facility in the star-forming galaxy IC0512 at a distance of ≈27 Mpc. It reached a peak absolute magnitude of M r = −12.66 ± 0.20 mag, making it the least luminous thermonuclear supernova discovered to date. The E(B − V) contribution from the underlying host galaxy is unconstrained. However, even if it were as large as 0.5 mag, the peak absolute magnitude would be M r = −13.78 ± 0.20 mag—still consistent with being the lowest-luminosity SN. Optical spectra of SN 2021fcg taken at 37 and 65 days post-maximum show strong [Ca ii], Ca ii, and Na i D emission and several weak [Fe ii] emission lines. The [Ca ii] emission in the two spectra has extremely low velocities of ≈1300 and 1000 km s−1, respectively. The spectra very closely resemble those of the very low luminosity Type Iax supernovae SN 2008 ha, SN 2010ae, and SN 2019gsc taken at similar phases. The peak bolometric luminosity of SN 2021fcg is ≈ 2.5 − 0.3 + 1.5 × 10 40 erg s−1, which is a factor of 3 lower than that for SN 2008 ha. The bolometric lightcurve of SN 2021fcg is consistent with a very low ejected nickel mass (M Ni ≈ 0.8 − 0.5 + 0.4 × 10 − 3 M ⊙). The low luminosity and nickel mass of SN 2021fcg pose a challenge to the picture that low-luminosity SNe Iax originate from deflagrations of near-M ch hybrid carbon–oxygen–neon white dwarfs. Instead, the merger of a carbon–oxygen and oxygen–neon white dwarf is a promising model to explain SN 2021fcg.

SN 2008iy circumstellar interaction: bright and lesser light effects

ABSTRACT Optical photometry and spectra of the luminous type IIn supernova SN 2008iy are analysed in detail with implications for cosmic ray acceleration and the radio emission. The light curve and expansion velocities indicate ejecta with the kinetic energy of 3 × 1051 erg to collide with the ∼10 M⊙ circumstellar envelope. The luminous H α is explained as originated primarily from circumstellar clouds interacting with the forward shock. For the first time the fluorescent O i 8446 Å emission is used to demonstrate that the cloud fragmentation cascade spans a scale range >2.3 dex. The narrow circumstellar H α permitted us to estimate the acceleration efficiency of cosmic rays. The found value is close to the efficiency inferred in the same way for other two SNe IIn, SN 1997eg and SN 2002ic. The efficiency of cosmic ray acceleration is utilized to reproduce the radio flux from SN 2008iy for the amplified magnetic field consistent with the saturated turbulent magnetic field in the diffusive shock acceleration mechanism.

ASASSN-14ms: The Most Energetic Known Explosion of a Type Ibn Supernova and Its Physical Origin

Abstract ASASSN-14ms may represent the most luminous Type Ibn supernova (SN Ibn) ever detected, with an absolute U-band magnitude brighter than −22.0 mag and a total bolometric luminosity >1.0 × 1044 erg s−1 near maximum light. The early-time spectra of this SN are characterized by a blue continuum on which are superimposed narrow P Cygni profile lines of He i, suggesting the presence of slowly moving (∼1000 km s−1), He-rich circumstellar material (CSM). At 1–2 months after maximum brightness, the He i line profiles become only slightly broader, with blueshifted velocities of 2000–3000 km s−1, consistent with the CSM shell being continuously accelerated by the SN light and ejecta. Like most SNe Ibn, the light curves of ASASSN-14ms show rapid post-peak evolution, dropping by ∼7 mag in the V band over three months. Such a rapid post-peak decline and high luminosity can be explained by interaction between SN ejecta and helium-rich CSM of 0.9 M ⊙ at a distance of ∼1015 cm. The CSM around ASASSN-14ms is estimated to originate from a pre-explosion event with a mass-loss rate of 6.7 M ⊙ yr−1 (assuming a velocity of ∼1000 km s−1), which is consistent with abundant He-rich material violently ejected during the late Wolf–Rayet (WN9-11 or Opfe) stage. After examining the light curves for a sample of SNe Ibn, we find that the more luminous ones tend to have slower post-peak decline rates, reflecting that the observed differences may arise primarily from discrepancies in the CSM distribution around the massive progenitors.

Supernova Luminosity Powered by Magnetar–Disk System

Abstract Magnetars are one of the potential power sources for some energetic supernova explosions such as type I superluminous supernovae (SLSNe I) and broad-lined type Ic supernovae (SNe Ic-BL). In order to explore the possible link between these two subclasses of supernovae (SNe), we study the effect of fallback accretion disk on magnetar evolution and magnetar-powered SNe. In this scenario, the interaction between a magnetar and a fallback accretion disk would accelerate the spin of the magnetar in the accretion regime but could result in substantial spin-down of the magnetars in the propeller regime. Thus, the initial rotation of the magnetar plays a less significant role in the spin evolution. Such a magnetar–disk interaction scenario can explain well the light curves of both SNe Ic-BL and SLSNe I, for which the observed differences are sensitive to the initial magnetic field of the magnetar and the fallback mass and timescale for the disk. Compared to the magnetars powering the SNe Ic-BL, those accounting for more luminous SNe usually maintain faster rotation and have relatively lower effective magnetic fields around peak time. In addition, the association between SLSNe I and long gamma-ray bursts, if observed in the future, could be explained in the context of a magnetar–disk system.

The Luminous and Double-peaked Type Ic Supernova 2019stc: Evidence for Multiple Energy Sources

Abstract We present optical photometry and spectroscopy of SN 2019stc (=ZTF19acbonaa), an unusual Type Ic supernova (SN Ic) at a redshift of z = 0.117. SN 2019stc exhibits a broad double-peaked light curve, with the first peak having an absolute magnitude of M r = −20.0 mag, and the second peak, about 80 rest-frame days later, M r = −19.2 mag. The total radiated energy is large, E rad ≈ 2.5 × 1050 erg. Despite its large luminosity, approaching those of Type I superluminous supernovae (SLSNe), SN 2019stc exhibits a typical SN Ic spectrum, bridging the gap between SLSNe and SNe Ic. The spectra indicate the presence of Fe-peak elements, but modeling of the first light-curve peak with radioactive heating alone leads to an unusually high nickel mass fraction of f Ni ≈ 0.31 (M Ni ≈ 3.2 M ⊙). Instead, if we model the first peak with a combined magnetar spin-down and radioactive heating model we find a better match with M ej ≈ 4 M ⊙, a magnetar spin period of P spin ≈ 7.2 ms, and magnetic field of B ≈ 1014 G, and f Ni ≲ 0.2 (consistent with SNe Ic). The prominent second peak cannot be naturally accommodated with radioactive heating or magnetar spin-down, but instead can be explained as circumstellar interaction with ≈0.7 M ⊙ of hydrogen-free material located ≈400 au from the progenitor. Accounting for the ejecta mass, circumstellar shell mass, and remnant neutron star mass, we infer a CO core mass prior to explosion of ≈6.5 M ⊙. The host galaxy has a metallicity of ≈0.26 Z ⊙, low for SNe Ic but consistent with SLSNe. Overall, we find that SN 2019stc is a transition object between normal SNe Ic and SLSNe.

AT2020caa: A Type Ia Supernova with a Prior Outburst or a Statistical Fluke?

Abstract We recently discovered an extragalactic transient, AT2020caa, from the Zwicky Transient Facility alert stream using the community broker ANTARES. This transient apparently exhibited two outbursts within one year (between 2020 and 2021). Based on a decade-long historical light curve of the candidate host galaxy, we rule out activity from the galaxy nucleus to explain these outbursts. The measured peak magnitudes (assuming the known spectroscopic redshift of the candidate host galaxy) put AT2020caa in the realm of thermonuclear supernovae (SNe) or luminous core-collapse SNe. A handful of the latter are known to show prior outbursts (POs), thought to be linked to mass loss in massive stars. Using Gemini/GMOS, we obtained a spectrum of the current outburst that shows it to be a Type Ia supernova. We examine the nature of AT2020caa’s PO seen a year earlier and conclude that it is likely a separate SN within the same galaxy.

Constraints on the Rate of Supernovae Lasting for More Than a Year from Subaru/Hyper Suprime-Cam

Abstract Some supernovae, such as pair-instability supernovae, are predicted to have a duration of more than a year in the observer frame. To constrain the rates of supernovae lasting for more than a year, we conducted a long-term deep transient survey using Hyper Suprime-Cam (HSC) on the 8.2 m Subaru telescope. HSC is a wide-field (a 1.75 deg2 field-of-view) camera and it can efficiently conduct transient surveys. We observed the same 1.75 deg2 field repeatedly using the g-, r-, i-, and z-band filters with the typical depth of 26 mag for four seasons (from late 2016 to early 2020). Using these data, we searched for transients lasting for more than a year. Two supernovae were detected in two continuous seasons, one supernova was detected in three continuous seasons, but no transients lasted for all four seasons searched. The discovery rate of supernovae lasting for more than a year with the typical limiting magnitudes of 26 mag is constrained to be . All the long-lasting supernovae we found are likely Type IIn supernovae and our results indicate that about 40% of Type IIn supernovae have long-lasting light curves. No plausible pair-instability supernova candidates lasting for more than a year are discovered. By comparing the survey results and survey simulations, we constrain the luminous pair-instability supernova rate up to z ≃ 3 is of the order of 100 Gpc−3 yr−1 at most, which is 0.01–0.1% of the core-collapse supernova rate.

Luminous supernovae associated with ultra-long gamma-ray bursts from hydrogen-free progenitors extended by pulsational pair-instability

We show that the luminous supernovae associated with ultra-long gamma-ray bursts can be related to the slow cooling from the explosions of hydrogen-free progenitors that are extended by pulsational pair-instability. We have recently shown that some rapidly-rotating hydrogen-free gamma-ray burst progenitors that experience pulsational pair-instability can keep an extended structure caused by pulsational pair-instability until the core collapse. These types of progenitors have large radii exceeding 10 R⊙ and they sometimes reach beyond 1000 R⊙ at the time of the core collapse. They are, therefore, promising progenitors of ultra-long gamma-ray bursts. Here, we perform light-curve modeling of the explosions of one extended hydrogen-free progenitor with a radius of 1962 R⊙. The progenitor mass is 50 M⊙ and 5 M⊙ exists in the extended envelope. We use the one-dimensional radiation hydrodynamics code STELLA in which the explosions are initiated artificially by setting given explosion energy and 56Ni mass. Thanks to the large progenitor radius, the ejecta experience slow cooling after the shock breakout and they become rapidly evolving (≲10 days), luminous (≳1043 erg s−1) supernovae in the optical even without energy input from the 56Ni nuclear decay when the explosion energy is more than 1052 erg. The 56Ni decay energy input can affect the light curves after the optical light-curve peak and make the light-curve decay slowly when the 56Ni mass is around 1 M⊙. They also have a fast photospheric velocity above 10 000 km s−1 and a hot photospheric temperature above 10 000 K at around the peak luminosity. We find that the rapid rise and luminous peak found in the optical light curve of SN 2011kl, which is associated with the ultra-long gamma-ray burst GRB 111209A, can be explained as the cooling phase of the extended progenitor. The subsequent slow light-curve decline can be related to the 56Ni decay energy input. The ultra-long gamma-ray burst progenitors we proposed recently can explain both the ultra-long gamma-ray burst duration and the accompanying supernova properties. When the gamma-ray burst jet is off-axis or choked, the luminous supernovae could be observed as fast blue optical transients without accompanying gamma-ray bursts.

Four (Super)luminous Supernovae from the First Months of the ZTF Survey

Abstract We present photometry and spectroscopy of four hydrogen-poor luminous supernovae discovered during the 2-month long science commissioning and early operations of the Zwicky Transient Facility (ZTF) survey. Three of these objects, SN 2018bym (ZTF18aapgrxo), SN 2018avk (ZTF18aaisyyp), and SN 2018bgv (ZTF18aavrmcg), resemble typical SLSN-I spectroscopically, while SN 2018don (ZTF18aajqcue) may be an object similar to SN 2007bi experiencing considerable host galaxy reddening, or an intrinsically long-lived, luminous, and red SN Ic. We analyze the light curves, spectra, and host galaxy properties of these four objects and put them in context of the population of SLSN-I. SN 2018bgv stands out as the fastest-rising SLSN-I observed to date, with a rest-frame g-band rise time of just 10 days from explosion to peak—if it is powered by magnetar spin-down, the implied ejecta mass is only ≃1 M ⊙. SN 2018don also displays unusual properties—in addition to its red colors and comparatively massive host galaxy, the light curve undergoes some of the strongest light-curve undulations postpeak seen in an SLSN-I, which we speculate may be due to interaction with circumstellar material. We discuss the promises and challenges of finding SLSNe in large-scale surveys like ZTF given the observed diversity in the population.

On the Energy Sources of the Most Luminous Supernova ASASSN-15lh

Abstract In this paper, we investigate the energy-source models for the most luminous supernova ASASSN-15lh. We revisit the ejecta–circumstellar medium (CSM) interaction (CSI) model and the CSI plus magnetar spin-down with full gamma-ray/X-ray trapping, which were adopted by Chatzopoulos et al., and find that the two models cannot fit the bolometric light curve (LC) of ASASSN-15lh. Therefore, we consider a CSI plus magnetar model with the gamma-ray/X-ray leakage effect to eliminate the late-time excess of the theoretical LC. We find that this revised model can reproduce the bolometric LC of ASASSN-15lh. Moreover, we construct a new hybrid model (i.e., the CSI plus fallback model), and find that it can also reproduce the bolometric LC of ASASSN-15lh. Assuming that the conversion efficiency (η) of fallback accretion to an outflow is typically ∼10−3, we derive that the total mass accreted is ∼3.9 M ⊙. The inferred CSM mass in the two models is rather large, indicating that the progenitor could have experienced an eruption of hydrogen-poor materials followed by an energetic core-collapse explosion leaving behind a magnetar or a black hole.

GRB 111209A/SN 2011kl: Collapse of a Supramassive Magnetar with r-mode Oscillation and Fallback Accretion onto a Newborn Black Hole

Abstract Ultra-long-duration gamma-ray burst GRB 111209A was found to be associated with a very luminous supernovae (SNe) SN 2011kl. The physics of GRB 111209A/SN 2011kl has been extensively studied in the literature, but such research has not yet settled down. By investigating in detail the characteristics of the X-ray light curve of GRB 111209A, coupled with the temporal and spectral features observed in SN 2011kl, we argue that a short-lived supramassive magnetar could be responsible for the initial shallow X-ray emission. Then the electromagnetic extraction of spin energy from a black hole (BH) results in the steeply declining X-ray flux when the magnetar collapses into a BH. A fraction of the envelope materials falls back and activates the accretion onto the newborn BH, which produces the X-ray rebrightening bump at late times. During this process, a centrifugally driven baryon-rich quasi-isotropic Blandford & Payne outflow from the revived accretion disk deposits its kinetic energy on the SN ejecta, which powers luminous SN 2011kl. Finally, we place a limitation on the magnetar’s physical parameters based on the observations.

Looks can be deceiving

Context. White dwarfs (WDs) are important and abundant tools to study the structure and evolution of the Galactic environment. However, the multiplicity of WD progenitors is generally neglected. Specifically, a merger in a binary system can lead to a single WD, which could result in wrongly inferred quantities if only single stellar evolution (SSE) is considered. These mergers are linked to transients such as luminous red novae and Type Ia supernovae. Aims. We investigate the impact of binary evolution (BE) upon observable single WDs, and compare their properties to WDs formed through SSE. We assess the evolutionary channels and the age and mass distributions of the resulting single WDs. Methods. We employed SeBa to model the evolution of single star and binary populations. We synthesised the observable single WD population within 100 pc, including cooling and observational selection effects. Additionally, we constructed models with different evolution and primordial population properties to study the effects on the properties of the resulting single WDs. Results. White dwarfs from binary mergers make up about 10−30% of all observable single WDs and 30−50% of massive WDs. On average, individual WDs take 3.1−5 times longer to form through BE than SE, and so appear ∼1 Gyr younger than they are if BE is ignored. In all models, the effect of mergers on the age distribution is clearly noticeable. The median age typically increases by 85−430 Myr and 200−390 Myr for massive WDs. Although abundant, we do not find evidence that WDs from mergers significantly alter the shape of the WD mass distribution. Conclusions. Assuming SSE for inferring properties of single WDs gives rise to intrinsic errors as single WDs can also be formed following a binary merger. Strategies for mitigating the effect of mergers on the WD age distributions are discussed.

The Energy Sources of Double-peaked Superluminous Supernova PS1-12cil and Luminous Supernova SN 2012aa

Abstract In this paper, we present the study of the energy reservoir powering the light curves (LCs) of PS1-12cil and SN 2012aa, which are superluminous and luminous supernovae (SNe), respectively. The multiband and bolometric LCs of these two SNe show unusual secondary bumps after the main peaks. The two-peaked LCs cannot be explained by any simple energy-source models (e.g., the 56Ni cascade decay model, the magnetar spindown model, or the ejecta-circumstellar medium interaction model). Therefore, we employ the 56Ni plus ejecta-circumstellar medium (CSM) interaction (CSI) model, the magnetar plus CSI model, and the double CSI model to fit their bolometric LCs, and find that both these two SNe can be explained by the double CSI model and the magnetar plus CSI model. Based on the modeling, we calculate the the time when the shells were expelled by the progenitors: provided that they were powered by double ejecta-shell CSI, the inner and outer shells might be expelled ∼0.2–3.6 and ∼2–25 yr before the explosions of the SNe, respectively; the shells were expelled ∼2–20 yr before the explosions of the SNe if they were powered by magnetars plus CSI.

SN 2017gmr: An Energetic Type II-P Supernova with Asymmetries

We present high-cadence ultraviolet (UV), optical, and near-infrared (NIR) data on the luminous Type II-P supernova SN 2017gmr from hours after discovery through the first 180 days. SN 2017gmr does not show signs of narrow, high-ionization emission lines in the early optical spectra, yet the optical lightcurve evolution suggests that an extra energy source from circumstellar medium (CSM) interaction must be present for at least 2 days after explosion. Modeling of the early lightcurve indicates a ~500R$_{\odot}$ progenitor radius, consistent with a rather compact red supergiant, and late-time luminosities indicate up to 0.130 $\pm$ 0.026 M$_{\odot}$ of $^{56}$Ni are present, if the lightcurve is solely powered by radioactive decay, although the $^{56}$Ni mass may be lower if CSM interaction contributes to the post-plateau luminosity. Prominent multi-peaked emission lines of H$\alpha$ and [O I] emerge after day 154, as a result of either an asymmetric explosion or asymmetries in the CSM. The lack of narrow lines within the first two days of explosion in the likely presence of CSM interaction may be an example of close, dense, asymmetric CSM that is quickly enveloped by the spherical supernova ejecta.

The Most Luminous Supernovae

Over a decade ago, a group of supernova explosions with peak luminosities far exceeding (often by >100 times) those of normal events has been identified. These superluminous supernovae (SLSNe) have been a focus of intensive study. I review the accumulated observations and discuss the implications for the physics of these extreme explosions. ▪ SLSNe can be classified into hydrogen-poor (SLSNe-I) and hydrogen-rich (SLSNe-II) events. ▪ Combining photometric and spectroscopic analysis of samples of nearby SLSNe-I and lower-luminosity events, a threshold of [Formula: see text] mag at peak appears to separate SLSNe-I from the normal population. ▪ SLSN-I light curves can be quite complex, presenting both early bumps and late postpeak undulations. ▪ SLSNe-I spectroscopically evolve from an early hot photospheric phase with a blue continuum and weak absorption lines, through a cool photospheric phase resembling spectra of SNe Ic, and into the late nebular phase. ▪ SLSNe-II are not nearly as well studied, lacking information based on large-sample studies. Proposed models for the SLSN power source are challenged to explain all the observations. SLSNe arise from massive progenitors, with some events associated with very massive stars ([Formula: see text] M[Formula: see text]). Host galaxies of SLSNe in the nearby Universe tend to have low mass and subsolar metallicity. SLSNe are rare, with rates <100 times lower than ordinary supernovae. SLSN cosmology and their use as beacons to study the high-redshift Universe offer exciting prospects.

Modeling the Light Curves of the Luminous Type Ic Supernova 2007D

SN~2007D is a nearby (redshift $z = 0.023146$), luminous Type Ic supernova (SN) having a narrow light curve (LC) and high peak luminosity. Previous research based on the assumption that it was powered by the $^{56}$Ni cascade decay suggested that the inferred $^{56}$Ni mass and the ejecta mass are $\sim 1.5$M$_{\odot}$ and $\sim 3.5$M$_{\odot}$, respectively. In this paper, we employ some multiband LC models to model the $R$-band LC and the color ($V-R$) evolution of SN~2007D to investigate the possible energy sources powering them. We find that the pure $^{56}$Ni model is disfavored; the multiband LCs of SN~2007D can be reproduced by a magnetar whose initial rotational period $P_{0}$ and magnetic field strength $B_p$ are $7.28_{-0.21}^{+0.21}$ (or $9.00_{-0.42}^{+0.32}$) ms and $3.10_{-0.35}^{+0.36}\times 10^{14}$ (or $2.81_{-0.44}^{+0.43}\times 10^{14}$) G, respectively. By comparing the spectrum of SN~2007D with that of some superluminous SNe (SLSNe), we find that it might be a luminous SN like several luminous ``gap-filler" optical transients that bridge ordinary and SLSNe, rather than a genuine SLSN.

The Type II-plateau Supernova 2017eaw in NGC 6946 and Its Red Supergiant Progenitor

Abstract We present extensive optical photometric and spectroscopic observations, from 4 to 482 days after explosion, of the Type II-plateau (II-P) supernova (SN) 2017eaw in NGC 6946. SN 2017eaw is a normal SN II-P intermediate in properties between, for example, SN 1999em and SN 2012aw and the more luminous SN 2004et, also in NGC 6946. We have determined that the extinction to SN 2017eaw is primarily due to the Galactic foreground and that the SN site metallicity is likely subsolar. We have also independently confirmed a tip-of-the-red-giant-branch (TRGB) distance to NGC 6946 of 7.73 ± 0.78 Mpc. The distances to the SN that we have also estimated via both the standardized candle method and expanding photosphere method corroborate the TRGB distance. We confirm the SN progenitor identity in pre-explosion archival Hubble Space Telescope (HST) and Spitzer Space Telescope images, via imaging of the SN through our HST Target of Opportunity program. Detailed modeling of the progenitor’s spectral energy distribution indicates that the star was a dusty, luminous red supergiant consistent with an initial mass of ∼15 M ⊙.

A Six-year Image-subtraction Light Curve of SN 2010jl

SN 2010jl was a luminous Type IIn supernova (SN), detected in radio, optical, X-ray and hard X-rays. Here we report on its six-year R- and g-band light curves obtained using the Palomar Transient Factory. The light curve was generated using a pipeline based on the proper image-subtraction method and we discuss the algorithm performances. As noted before, the R-band light curve, up to about 300 days after maximum light is well described by a power-law decline with a power-law index of α ≈ −0.5. Between day 300 and day 2300 after maximum light, it is consistent with a power-law decline, with a power-law index of about α ≈ −3.4. The longevity of the light curve suggests that the massive circumstellar material around the progenitor was ejected on timescales of at least tens of years prior to the progenitor explosion.