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![Comparison with hydrogen-free PPI models
a–c, The inferred properties of SN 2017egm are shown against four hydrogen-free PPI models of W07⁴² (orange squares), W17⁴³ (blue stars), M19⁴⁵ (purple triangles) and R20⁴⁶ (green circles), in the diagrams of PPI-driven mass loss versus pre-pulsation helium-core mass (a), delay time between the PPI onset and core-collapse explosion versus pre-pulsation helium-core mass (b) and delay time versus PPI-driven mass loss (c). The narrow grey shading shows the total mass range (within 1σ uncertainty) of four CSM shells inferred from light-curve modelling of SN 2017egm. Assuming velocities of vw = 500 km s⁻¹, vw = 1,000 km s⁻¹ and vw = 3,000 km s⁻¹, the inferred delay times between core collapse and the eruption related to the outermost shell (Tw) are shown with grey dashed lines. The yellow lines represent the steady mass ejections with mass-loss rates of Ṁ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{M}$$\end{document} = 10⁻³ M⊙ yr⁻¹, 0.1 M⊙ yr⁻¹ and 10 M⊙ yr⁻¹.](publication/370442003/figure/fig5/AS:11431281175635401@1689821914877/Comparison-with-hydrogen-free-PPI-models-a-c-The-inferred-properties-of-SN2017egm-are.png)
Comparison with hydrogen-free PPI models a–c, The inferred properties of SN 2017egm are shown against four hydrogen-free PPI models of W07⁴² (orange squares), W17⁴³ (blue stars), M19⁴⁵ (purple triangles) and R20⁴⁶ (green circles), in the diagrams of PPI-driven mass loss versus pre-pulsation helium-core mass (a), delay time between the PPI onset and core-collapse explosion versus pre-pulsation helium-core mass (b) and delay time versus PPI-driven mass loss (c). The narrow grey shading shows the total mass range (within 1σ uncertainty) of four CSM shells inferred from light-curve modelling of SN 2017egm. Assuming velocities of vw = 500 km s⁻¹, vw = 1,000 km s⁻¹ and vw = 3,000 km s⁻¹, the inferred delay times between core collapse and the eruption related to the outermost shell (Tw) are shown with grey dashed lines. The yellow lines represent the steady mass ejections with mass-loss rates of Ṁ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{M}$$\end{document} = 10⁻³ M⊙ yr⁻¹, 0.1 M⊙ yr⁻¹ and 10 M⊙ yr⁻¹.
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![The nebular-phase [O i]/([Ca ii] + [O ii]) ratios of SLSNe-I and other...](publication/370442003/figure/fig4/AS:11431281175588306@1689821914708/The-nebular-phase-Oi-Caii-Oii-ratios-of-SLSNe-I-and-other-types-of_Q320.jpg)
Superluminous supernovae are among the most energetic stellar explosions in the Universe, but their energy sources remain an open question. Here we present long-term observations of one of the closest examples of the hydrogen-poor superluminous supernovae subclass SLSNe-I, supernova SN 2017egm, revealing the most complicated known luminosity evolut...
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We present detailed optical photometry and spectroscopy of the Type IIn supernova (SN) 2021qqp. Its unusual light curve is marked by a long gradual brightening (i.e., precursor) for about 300 days, a rapid increase in brightness for about 60 days, and then a sharp increase of about 1.6 mag in only a few days to a first peak of $M_r\approx -19.5$ ma...
Citations
... For the PPI scenario, the derived CSM mass is comparable with the values derived from the literature (see, e.g., Table 2 of Liu et al. 2018; Extended Data Table 1 of Lin et al. 2023) using this scenario. The fact that the CSM of SN 2017dio is hydrogen-rich suggests that the metallicity (Z) of the progenitor of SN 2017dio might be lower than those of the progenitors of Type I SNe (e.g., SN 2017egm) whose progenitors are assumed to experience PPI, since it retained a moderate amount of hydrogen envelope prior to the PPI. ...
We study the energy sources, the physical properties of the ejecta and the circumstellar medium (CSM), and the mass-loss history of the progenitor of SN 2017dio, which is a broad-lined Ic (Ic-BL) supernova (SN) having unusual light curves (LCs) and signatures of hydrogen-rich CSM in its early spectrum. We find that the temperature of SN 2017dio began to increase linearly about 20 days after the explosion. We use the ⁵⁶ Ni plus the ejecta–CSM interaction model to fit the LCs of SN 2017dio, finding that the masses of the ejecta, the ⁵⁶ Ni, and the CSM are ∼12.41 M ⊙ , ∼0.17 M ⊙ , and ∼5.82 M ⊙ , respectively. The early-time photosphere velocity and the kinetic energy of the SN are, respectively, ∼1.89 × 10 ⁴ km s ⁻¹ and ∼2.66 × 10 ⁵² erg, which are comparable to those of SNe Ic-BL and hypernovae (HNe), respectively. We suggest that the CSM of SN 2017dio might be from a luminous blue variable–like outburst or pulsational pair instability ∼1.2−11.4 yr prior to the SN explosion or binary mass transfer. Moreover, we find that its ejecta mass is larger than those of many SNe Ic-BL and that its ⁵⁶ Ni mass ( M Ni ) is approximately equal to the mean (or median) value of M Ni of SNe Ic-BL in the literature but lower than M Ni of prototype HNe (e.g., SN 1998bw and SN 2003dh).
... The post-peak bump observed in SN 2019tua reminds the post-peak bump behavior seen in some of type IIn SNe, such as SN 2005la , SN 2006jd ), SN 2009ip (Margutti et al. 2014Martin et al. 2015), and iPTF13z (Nyholm et al. 2017). These bumpy behaviors are typically attributed to interactions between SN ejecta and CSM Andrews et al. 2019;Lin et al. 2023). Due to the brightness variation of SN 2019tua around 50 days post-explosion, We will explain these two bumps during the 40-50 and 50-65 days period post-explosion through model fitting in the Section 4. Figure 3 illustrates the spectral evolution of SN 2019tua from the rising phase (t = 3.1 days) to the peaking phase that 3.3 days after the peaking day (t = 29.5 days ). ...
... Here we present a multiple CSI model to explain the complicated light curve of SN 2020tua. Such CSI model have been successfully applied to some SLSNe with bumpy features Lin et al. 2023). Considering the non-negligible contribution of the decay of 56 Ni/Co, a comprehensive model should include both CSI and radioactive decay. ...
... The expanding photosphere model is used for centrally located energy sources that heat the SN ejecta as it expands, whereas the fixed photosphere model is typically employed in CSI scenarios where the almost stationary CSM relative to the ejecta is heated. Thus the semianalytic CSI plus 56 Ni model can be written as Lin et al. 2023) 3 : ...
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.
... Waxman 2017 ; Metzger, Margalit & Sironi 2019 ;Margalit, Metzger & Sironi 2020 ), superluminous supernova (e.g. Woosley, Blinnikov & Heger 2007 ;Benetti et al. 2014 ;Moriya, Sorokina & Che v alier 2018 ;Khatami & Kasen 2023 ;Lin et al. 2023 ), magnetar giant flares (e.g. Granot et al. 2006 ;Fermi-LAT Collaboration 2021 ), etc. ...
... Here at moderate values of a u ∼ 2, the RS is still stronger than the FS while the o v erall efficienc y is ∼ 10 per cent . We note that this efficiency reduction comes in addition to the already tiny estimated efficiency in this model resulting from: (i) the efficiency of converting shock heated plasma to maser radiation, (ii) the efficiency loss due to the requirement that the optical depth for induced Compton close to the peak of the observed spectrum should not be too large, (iii) the efficiency loss due to the requirement that the bursts could reproduce the high observed level of temporal and spectral variability, and (iv) the efficiency suppression in magnetar models due to the fact that escaping outflow should be moving along open field lines (Metzger, Margalit & Sironi 2019 ;Beniamini & Kumar 2020, 2023. ...
Emission in many astrophysical transients originates from a shocked fluid. A central engine typically produces an outflow with varying speeds, leading to internal collisions within the outflow at finite distances from the source. Each such collision produces a pair of forward and reverse shocks with the two shocked regions separated by a contact discontinuity (CD). As a useful approximation, we consider the head-on collision between two cold and uniform shells (a slower leading shell and a faster trailing shell) of finite radial width, and study the dynamics of shock propagation in planar geometry. We find significant differences between the forward and reverse shocks, in terms of their strength, internal energy production efficiency, and the time it takes for the shocks to sweep through the respective shells. We consider the subsequent propagation of rarefaction waves in the shocked regions and explore the cases where these waves can catch up with the shock fronts and thereby limit the internal energy dissipation. We demonstrate the importance of energy transfer from the trailing to leading shell through pdV work across the CD. We outline the parameter space regions relevant for models of different transients,e.g. Gamma-ray burst (GRB) internal shock model, fast radio burst (FRB) blastwave model, Giant flare due to magnetars, and superluminous supernovae (SLSN) ejecta. We find that the reverse shock likely dominates the internal energy production for many astrophysical transients.
... After solar conjunction, points are unfilled to represent sparse photometry and large uncertainties. (Nicholl et al. 2016c(Nicholl et al. ,b,a, 2013Lunnan et al. 2016;Lin et al. 2023;Bose et al. 2018;Nicholl et al. 2017aNicholl et al. , 2014Gutiérrez et al. 2022) By looking at Figure 5, it is apparent that the temperature evolution is not consistent with other SLSNe, as it appears to increase over the first ∼100 days. This is in stark contrast with most other events, which tend to show a decreasing temperature (Chen et al. 2023a). ...
... Post-maximum bumps in the light curve could also indicate interaction with PPI shells. The long term light curve of SN2017egm shows multiple late time bumps as well as varying levels of decline ( Figure 5) (Lin et al. 2023;Zhu et al. 2023). Lin et al. (2023) reproduce the evolution of this event using four distinct shells of CSM produced by PPI ejections from a star with a 48-51 M ⊙ He core. ...
... The long term light curve of SN2017egm shows multiple late time bumps as well as varying levels of decline ( Figure 5) (Lin et al. 2023;Zhu et al. 2023). Lin et al. (2023) reproduce the evolution of this event using four distinct shells of CSM produced by PPI ejections from a star with a 48-51 M ⊙ He core. This is similar to the proposed He-core mass of SN2019szu and so we might expect to see similar features between the two events. ...
We present a detailed study on SN2019szu, a Type I superluminous supernova at z = 0.213, that displayed unique photometric and spectroscopic properties. Pan-STARRS and ZTF forced photometry shows a pre-explosion plateau lasting ∼ 40 days. Unlike other SLSNe that show decreasing photospheric temperatures with time, the optical colours show an apparent temperature increase from ∼15000 K to ∼20000 K over the first 70 days, likely caused by an additional pseudo-continuum in the spectrum. Remarkably, the spectrum displays a forbidden emission line (likely attributed to λλ7320,7330) visible 16 days before maximum light, inconsistent with an apparently compact photosphere. This identification is further strengthened by the appearances of [O III] λλ4959, 5007, and [O III] λ4363 seen in the spectrum. Comparing with nebular spectral models, we find that the oxygen line fluxes and ratios can be reproduced with ∼0.25 M⊙ of oxygen rich material with a density of $\sim 10^{-15}\, \rm {g\, cm}^{-3}$. The low density suggests a circumstellar origin, but the early onset of the emission lines requires that this material was ejected within the final months before the terminal explosion, consistent with the timing of the precursor plateau. Interaction with denser material closer to the explosion likely produced the pseudo-continuum bluewards of ∼5500 Å. We suggest that this event is one of the best candidates to date for a pulsational pair-instability ejection, with early pulses providing the low density material needed for the formation of the forbidden emission line, and collisions between the final shells of ejected material producing the pre-explosion plateau.
... However, the magnetar model does not naturally predict the bumps often seen in SLSNe-I LCs both before and after maximum (see e.g. Nicholl et al. 2016a;Smith et al. 2016;Vreeswijk et al. 2017;Nicholl et al. 2017;Lunnan et al. 2020;Fiore et al. 2021;Gutiérrez et al. 2022;Chen et al. 2023a,b;West et al. 2023;Lin et al. 2023, but see Moriya et al. 2022) but is able to account for the huge variety of LC evolutionary timescales shown by SLSNe I (Inserra et al. 2013;Chatzopoulos et al. 2013;Nicholl et al. 2014Nicholl et al. , 2015aNicholl et al. , 2017. ...
SN 2019neq was a very fast evolving superluminous supernova. At a redshift z = 0.1059, its peak absolute magnitude was −21.5 ± 0.2 mag in g band. In this work, we present data and analysis from an extensive spectrophotometric follow-up campaign using multiple observational facilities. Thanks to a nebular spectrum of SN 2019neq, we investigated some of the properties of the host galaxy at the location of SN 2019neq and found that its metallicity and specific star formation rate are in a good agreement with those usually measured for SLSNe-I hosts. We then discuss the plausibility of the magnetar and the circumstellar interaction scenarios to explain the observed light curves, and interpret a nebular spectrum of SN 2019neq using published SUMO radiative-transfer models. The results of our analysis suggest that the spindown radiation of a millisecond magnetar with a magnetic field B ≃ 6 × 1014 G could boost the luminosity of SN 2019neq.
... SN 2017egm is a nearby SLSN-I with undulated LCs that has attracted a lot of attention. Its main peak displays a typical inverted triangle shape (e.g.,Bose et al. 2018;Tsvetkov et al. 2022;Zhu et al. 2023), which is challenging to explain using the magnetar model.Lin et al. (2023) has analyzed the overall LC evolution of SN2017egm and found that its complex LC can be well modeled by successive CSM interactions. In combination with these discussions and our baseline fitting, we excluded this source from our sample.3. LIGHT CURVES FITTING ...
Recent observations indicate that hydrogen-poor superluminous supernovae often display bumpy declining light curves. However, the cause of these undulations remains unclear. In this paper, we have improved the magnetar model, which includes flare activities. We present a systematic analysis of a well-observed SLSNe-I sample with bumpy light curves in the late-phase. These SLSNe-I were identified from multiple transient surveys, such as the Pan-STARRS1 Medium Deep Survey (PS1 MDS) and the Zwicky Transient Facility (ZTF). Our study provides a set of magnetar-powered model light curve fits for five SLSNe-I, which accurately reproduce observed light curves using reasonable physical parameters. By extracting essential characteristics of both explosions and central engines, these fits provide valuable insights into investigating their potential association with gamma ray burst engines. We found that the SLSN flares tend to be the dim and long extension of the GRB flares in the peak luminosity versus peak time plane. Conducting large-scale, high cadence surveys in the near future could enhance our comprehension of both SLSN undulation properties and their potential relationship with GRBs by modeling their light curve characteristics.
... magnetar) activities, CSM interaction, or combination of both (e.g. Gomez et al. 2021;Hosseinzadeh et al. 2022;Moriya et al. 2022;Chen et al. 2023;Lin et al. 2023). ...
We report on our study of SN 2022xxf during the first four months of its evolution. The light curves (LCs) display two humps at similar maximum brightness separated by 75d, unprecedented for a broad-lined Type Ic supernova (SN IcBL). SN~2022xxf is the most nearby SN IcBL to date (in NGC~3705, $z = 0.0037$, 20 Mpc). Optical and NIR photometry and spectroscopy are used to identify the energy source powering the LC. Nearly 50 epochs of high S/N-ratio spectroscopy were obtained within 130d, comprising an unparalleled dataset for a SN IcBL, and one of the best-sampled SN datasets to date. The global spectral appearance and evolution of SN~2022xxf points to typical SN Ic/IcBL, with broad features (up to $\sim14000$ km~s$^{-1}$) and a gradual transition from the photospheric to the nebular phase. However, narrow emission lines (corresponding to $\sim1000-2500$ km~s$^{-1}$) are present from the time of the second rise, suggesting slower-moving circumstellar material (CSM). These lines are subtle, but some are readily noticeable at late times such as in Mg~I $\lambda$5170 and [O~I] $\lambda$5577. Unusually, the near-infrared spectra show narrow line peaks, especially among features formed by ions of O and Mg. We infer the presence of CSM that is free of H and He. We propose that the radiative energy from the ejecta-CSM interaction is a plausible explanation for the second LC hump. This interaction scenario is supported by the color evolution, which progresses to the blue as the light curve evolves along the second hump, and the slow second rise and subsequent rapid LC drop. SN~2022xxf may be related to an emerging number of CSM-interacting SNe Ic, which show slow, peculiar LCs, blue colors, and subtle CSM interaction lines. The progenitor stars of these SNe likely experienced an episode of mass loss shortly prior to explosion consisting of H/He-free material.
Tsinghua University-Ma Huateng Telescopes for Survey (TMTS) aims to detect fast-evolving transients in the Universe, which has led to the discovery of thousands of short-period variables and eclipsing binaries since 2020. In this paper, we present the observed properties of 125 flare stars identified by TMTS within the first two years, with an attempt to constrain their eruption physics. As expected, most of these flares were recorded in late-type red stars with GBP − GRP >2.0 mag; however, the flares associated with bluer stars tend to be on average more energetic and have broader profiles. The peak flux (Fpeak) of the flare is found to depend strongly on the equivalent duration (ED) of the energy release, i.e. Fpeak∝ED0.72 ± 0.04, which is consistent with results derived from the Kepler and Evryscope samples. This relation is likely to be related to the magnetic loop emission, while, for the more popular non-thermal electron heating model, a specific time evolution may be required to generate this relation. We notice that flares produced by hotter stars have a flatter Fpeak - ED relation compared to that from cooler stars. This is related to the statistical discrepancy in light-curve shape of flare events with different colours. In spectra from LAMOST, we find that flare stars have apparently stronger H α emission than inactive stars, especially at the low-temperature end, suggesting that chromospheric activity plays an important role in producing flares. On the other hand, the subclass with frequent flares is found to show H α emission of similar strength in its spectra to that recorded with only a single flare but similar effective temperature, implying that chromospheric activity may not be the only trigger for eruptions.
Current observations of binary black-hole (BBH) merger events show support for a feature in the primary BH-mass distribution at ∼ 35 M⊙, previously interpreted as a signature of pulsational pair-instability (PPISN) supernovae. Such supernovae are expected to map a wide range of pre-supernova carbon-oxygen (CO) core masses to a narrow range of BH masses, producing a peak in the BH mass distribution. However, recent numerical simulations place the mass location of this peak above 50 M⊙. Motivated by uncertainties in the progenitor’s evolution and explosion mechanism, we explore how modifying the distribution of BH masses resulting from PPISN affects the populations of gravitational-wave (GW) and electromagnetic (EM) transients. To this end, we simulate populations of isolated BBH systems and combine them with cosmic star-formation rates. Our results are the first cosmological BBH-merger predictions made using the binary_c rapid population synthesis framework. We find that our fiducial model does not match the observed GW peak. We can only explain the 35 M⊙ peak with PPISNe by shifting the expected CO core-mass range for PPISN downwards by ∼15 M⊙. Apart from being in tension with state-of-the art stellar models, we also find that this is likely in tension with the observed rate of hydrogen-less super-luminous supernovae. Conversely, shifting the mass range upward, based on recent stellar models, leads to a predicted third peak in the BH mass function at ∼64 M⊙. Thus we conclude that the ∼35 M⊙ feature is unlikely to be related to PPISN.
