We perform one-dimensional radiation-hydrodynamic simulations of energetic supernova ejecta colliding with a massive circumstellar medium (CSM) aiming at explaining SN 2016aps, likely the brightest supernova observed to date. SN 2016aps was a superluminous Type-IIn SN, which released as much as $\gtrsim 5\times 10^{51}$ erg of thermal radiation. Our results suggest that the multi-band light curve of SN 2016aps is well explained by the collision of a $30\ M_\odot$ SN ejecta with the explosion energy of $10^{52}$ erg and a $\simeq 8\ M_\odot$ wind-like CSM with the outer radius of $10^{16}$ cm, i.e., a hypernova explosion embedded in a massive CSM. This finding indicates that very massive stars with initial masses larger than $40\ M_\odot$, which supposedly produce highly energetic SNe, occasionally eject their hydrogen-rich envelopes shortly before the core-collapse. We suggest that the pulsational pair-instability SNe may provide a natural explanation for the massive CSM and the energetic explosion. We also provide the relations between the peak luminosity, the radiated energy, and the rise time for interacting SNe with the kinetic energy of $10^{52}$ erg, which can be used for interpreting SN 2016aps-like objects in future surveys.
The recent study of SN 2013fs flash spectrum suggests enormous for SN IIP explosion energy, far beyond possibilities of the neutrino mechanism. The issue of the explosion energy of SN 2013fs is revisited making use of effects of the early supernova interaction with the dense circumstellar shell. The velocity of the cold dense shell between reverse and forward shocks is inferred from the analysis of the broad \heii\,4686\,Å on day 2.4. This velocity alongside with other observables provide us with an alternative energy estimate of $\sim1.8\times10^{51}$\,erg for the preferred mass of $\sim10$\m…
Motivated by a recent discovery of Supernova 2010gx and numerical results of Fryer et al.(2010), we simulate light curves for several type I supernova models, enshrouded by dense circumstellar shells, or "super-wind", rich in carbon and oxygen and having no hydrogen. We demonstrate that the most luminous events like SN2010gx can be explained by those models at moderate explosion energies (2-3) foe if the total mass of SN ejecta and a shell is (3-5) Msun and the radius of the shell is ~10^{16} cm.
We present extensive radio observations of the nearby Type Ibc supernovae 2004cc, 2004dk, and 2004gq spanning 8-1900 days after explosion. Using a dynamical model developed for synchrotron emission from a slightly decelerated shockwave, we estimate the velocity and energy of the fastest ejecta and the density profile of the circumstellar medium. The shockwaves of all three supernovae are characterized by non-relativistic velocities of v ~ (0.1-25)c and associated energies of E ~ (2-10) * 1e47 erg, in line with the expectations for a typical homologous explosion. Smooth circumstellar density pr…
We investigate circumstellar and explosion properties of Type Ibn supernovae (SNe) by analyzing their bolometric light curves. Bolometric light curves of Type Ibn SNe generally have a large contrast between peak luminosity and late-phase luminosity, which is much larger than those of 56Ni-powered SNe. Thus, most of them are likely powered by the interaction between SN ejecta and dense circumstellar media. In addition, Type Ibn SNe decline much faster than Type IIn SNe, and this indicates that the interaction in Type Ibn SNe ceases earlier than in Type IIn SNe. Thus, we argue that Type Ibn SN p…
Recent supernova searches revealed a number of fast-evolving luminous transients. We perform radiation hydrodynamic simulations of light curves of several models of supernova from super--asymptotic giant branch (super-AGB, SAGB) stars with low mass envelopes ($M_{\rm env}$ $\sim$ $0.05-1.25$ $M_{\odot}$). The differences in the light curves found among the models are used to link the observed events to the most appropriate models. In particular, we propose that KSN 2015K is an electron-capture supernova. We assume "optically" thick CSM around SAGB and the circumstellar interaction powers the p…
Recent modeling of hydrogen-rich Type II supernova (SN II) light curves suggests the presence of dense circumstellar material (CSM) surrounding the exploding progenitor stars. This has important implications for the activity and structure of massive stars near the end of their lives. Since previous work focused on just a few events, here we expand to a larger sample of twenty well-observed SNe II. For each event we are able to constrain the progenitor zero-age main-sequence (ZAMS) mass, explosion energy, and the mass and radial extent of dense CSM. We then study the distribution of each of the…
Usual supernova remnants have either ionizing plasma or plasma in collisional ionization equilibrium, i.e., the ionization temperature is lower than or equal to the electron temperature. However, the existence of recombining supernova remnants, i.e., supernova remnants with the ionization temperature higher than the electron temperature, is recently confirmed. One suggested way to have recombining plasma in a supernova remnant is to have a dense circumstellar medium at the time of the supernova explosion. If the circumstellar medium is dense enough, collisional ionization equilibrium can be es…
Decadal pre-explosion activity and circumstellar interaction in a supernova
National Central University（国立中央大学）；Henan Academy of Sciences（河南省科学院）；University of Oxford（牛津大学）；National Astronomical Observatory of Japan（日本国立天文台）；SOKENDAI（综合研究大学院大学）；Monash University（蒙纳士大学）；Aarhus University（奥胡斯大学）；Max Planck Institute for Extraterrestrial Physics（马克斯·普朗克地外物理研究所）；The Australian National University（澳大利亚国立大学）
One of the key observables for determining the progenitor nature of Type Ia supernovae is provided by their immediate circumstellar medium, which according to several models should be shaped by the progenitor binary system. So far, X-ray and radio observations indicate that the surroundings are very tenuous, producing severe upper-limits on the mass loss from winds of the progenitors. In this study, we perform numerical hydro-dynamical simulations of the interaction of the SN ejecta with circumstellar structures formed by possible mass outflows from the progenitor systems and we estimate numer…
We model explosions driven by the coalescence of a black hole or neutron star with the core of its massive-star companion. Upon entering a common envelope phase, a compact object may spiral all the way to the core. The concurrent release of energy is likely to be deposited into the surrounding common envelope, powering a merger-driven explosion. We use hydrodynamic models of binary coalescence to model the common envelope density distribution at the time of coalescence. We find toroidal profiles of material, concentrated in the binary's equatorial plane and extending to many times the massive …
The nature of an emerging class of rapidly fading supernovae (RFSNe)--characterized by their short-lived light curve duration, but varying widely in peak brightness--remains puzzling. Whether the RFSNe arise from low-mass thermonuclear eruptions on white dwarfs or from the core collapse of massive stars is still a matter of dispute. We explore the possibility that the explosion of hydrogen-free massive stars could produce bright but rapidly fading transients if the effective pre-supernova radii are large and if little or no radioactive nickel is ejected. The source of radiation is then purely …
In this Letter we report a discovery of a prominent flash of a peculiar overluminous Type Ia supernova, SN 2020hvf, in about 5 hours of the supernova explosion by the first wide-field mosaic CMOS sensor imager, the Tomo-e Gozen Camera. The fast evolution of the early flash was captured by intensive intranight observations via the Tomo-e Gozen high-cadence survey. Numerical simulations show that such a prominent and fast early emission is most likely generated from an interaction between $0.01~M_{\odot}$ circumstellar material (CSM) extending to a distance of $\sim$$10^{13}~\text{cm}$ and super…
In a supernova explosion, the ejecta interacting with the surrounding circumstellar medium (CSM) give rise to variety of radiation. Since CSM is created from the mass lost from the progenitor star, it carries footprints of the late time evolution of the star. This is one of the unique ways to get a handle on the nature of the progenitor star system. Here, I will focus mainly on the supernovae (SNe) exploding in dense environments, a.k.a. Type IIn SNe. Radio and X-ray emission from this class of SNe have revealed important modifications in their radiation properties, due to the presence of high…
In this paper we present the results of the radio light curve and X-ray observations of broad-lined Type Ic SN 2007bg. The light curve shows three distinct phases of spectral and temporal evolution, implying that the SNe shock likely encountered at least 3 different circumstellar medium regimes. We interpret this as the progenitor of SN 2007bg having at least two distinct mass-loss episodes (i.e., phases 1 and 3) during its final stages of evolution, yielding a highly-stratified circumstellar medium. Modelling the phase 1 light curve as a freely-expanding, synchrotron-emitting shell, self-abso…
Observational signatures of the circumstellar material (CSM) around Type Ia supernovae (SNe Ia) provide a unique perspective on their progenitor systems. The pre-supernova evolution of the SN progenitors may naturally eject CSM in most of the popular scenarios of SN Ia explosions. In this study, we investigate the influence of dust scattering on the light curves and polarizations of SNe Ia. A Monte Carlo method is constructed to numerically solve the process of radiative transfer through the CSM. Three types of geometric distributions of the CSM are considered: spherical shell, axisymmetric di…
We investigate predicted circumstellar properties of Type Ia supernova progenitor systems with non-degenerate helium star donors. It has been suggested that systems consisting of a carbon+oxygen white dwarf and a helium star can lead to Type Ia supernova explosions. Binary evolution calculations for the helium star donor channel predict that such a progenitor system is in either a stable helium-shell burning phase or a weak helium-shell flash phase at the time of the Type Ia supernova explosion. By taking the binary evolution models from our previous study, we show that a large fraction of the…
We investigate the effect of the circumstellar medium density profile on the X-ray emission from outer ejecta knots in the Cassiopeia A supernova remnant using the 1 Ms Chandra observation. The spectra of a number of radial series of ejecta knots at various positions around the remnant are analyzed using techniques similar to those devised in previous papers. We can obtain a reasonable match to our data for a circumstellar density profile proportional to r^-2 as would arise from the steady dense wind of a red supergiant, but the agreement is improved if we introduce a small (0.2-0.3 pc) centra…
For supernova powered by the conversion of kinetic energy into radiation due to the interactions of the ejecta with a dense circumstellar shell, we show that there could be X-ray analogues of optically super-luminous SNe with comparable luminosities and energetics. We consider X-ray emission from the forward shock of SNe ejecta colliding into an optically-thin CSM shell, derive simple expressions for the X-ray luminosity as a function of the circumstellar shell characteristics, and discuss the different regimes in which the shock will be radiative or adiabatic, and whether the emission will be…
Some supernova (SN) explosions show evidence for interaction with pre-existing non-spherically symmetric circumstellar medium (CSM) in their light curves, spectral line profiles, and polarization signatures. To better understand the connection with binary stars and to aid in the interpretation of observations, we perform two-dimensional axisymmetric hydrodynamic simulations where an expanding spherical SN ejecta initialized with realistic density and velocity profiles collide with various aspherical CSM distributions. We consider CSM in the form of a circumstellar disk, colliding wind shells i…
We present optical photometry and spectroscopy of SN 2016iet, an unprecedented Type I supernova (SN) at $z=0.0676$ with no obvious analog in the existing literature. The peculiar light curve has two roughly equal brightness peaks ($\approx -19$ mag) separated by 100 days, and a subsequent slow decline by 5 mag in 650 rest-frame days. The spectra are dominated by emission lines of calcium and oxygen, with a width of only $3400$ km s$^{-1}$, superposed on a strong blue continuum in the first year, and with a large ratio of $L_{\rm [Ca\,II]}/L_{\rm [O\,I]}\approx 4$ at late times. There is no cle…
With the advent of new wide-field, high-cadence optical transient surveys, our understanding of the diversity of core-collapse supernovae has grown tremendously in the last decade. However, the pre-supernova evolution of massive stars, that sets the physical backdrop to these violent events, is theoretically not well understood and difficult to probe observationally. Here we report the discovery of the supernova iPTF13dqy = SN 2013fs, a mere ~3 hr after explosion. Our rapid follow-up observations, which include multiwavelength photometry and extremely early (beginning at ~6 hr post-explosion) …
Recently, a hydrogen-poor superluminous supernova (SLSN) iPTF15esb at redshift $z=0.224$ was reported, whose light curve (LC) and spectrum show several unusual characteristics. Its late-time spectrum shows a strong, broad H$α$ emission line and the bolometric LC exhibits two peaks and a post-peak plateau. Here we propose an ejecta-circumstellar medium (CSM) interaction model involving multiple shells and winds to explain this double-peak SN. We find that the theoretical LC reproduced by this model can well match the observations of iPTF15esb. Based on this result, we infer that the progenitor …
Type Ibn supernova SN~2010al is explored to infer parameters of supernova and a circumstellar (CS) shell. The CS interaction model combined with the spectral model of 4600Å blend suggests the explosion of a WR star with the energy of $(1-1.5)\times10^{51}$ erg inside a dense confined CS shell with the mass of $\sim0.1$\msun\ and kinetic energy of $\sim 10^{48}$ erg. The confined CS shell has been formed during the last 0.4 yr prior to the core collapse.
A possibility is explored to account for the light curve and the low expansion velocity of the supernova SN~2011ht, a member of group of three objects showing signatures of both IIn and IIP supernovae. It is argued that the radiated energy and the expansion velocity are consistent with the low energy explosion ($\approx6\times10^{49}$ erg) and $\leq 2 M_{\odot}$ ejecta interacting with the circumstellar envelope of $6-8 M_{\odot}$ and the radius of $~2\times10^{14}$ cm. The test of this scenario is proposed.
We present results of a systematic study of the mass-loss properties of Type IIn supernova progenitors within decades before their explosion. We apply an analytic light curve model to 11 Type IIn supernova bolometric light curves to derive the circumstellar medium properties. We reconstruct the mass-loss histories based on the estimated circumstellar medium properties. The estimated mass-loss rates are mostly higher than 1e-3 Msun/yr and they are consistent with those obtained by other methods. The mass-loss rates are often found to be constantly high within decades before their explosion. Thi…
Massive stars, possibly red supergiants, which retain extended hydrogen envelopes until core collapse, produce Type II Plateau (IIP) supernovae. The ejecta from these explosions shock the circumstellar matter originating from the mass loss of the progenitor during the final phases of its life. This interaction accelerates particles to relativistic energies which then lose energy via synchrotron radiation in the shock-amplified magnetic fields and inverse Compton scattering against optical photons from the supernova. These processes produce different signatures in the radio and X-ray part of th…
We present multiband optical photometric and spectroscopic observations of an unusual Type II supernova, SN 2018hfm, which exploded in the nearby (d = 34.67 Mpc) dwarf galaxy PGC 1297331 with a very low star-formation rate (0.0270 M yr-1) and a subsolar metallicity environment(~ 0.5 Z). The V-band light curve of SN 2018hfm reaches a peak with value of -18.69+/-0.64 mag, followed by a fast decline(4.42+/-0.13 mag (100d)-1). After about 50 days, it is found to experience a large flux drop (~3.0 mag in V), and then enters into an unusually faint tail, which indicates a relatively small amount of …
In this paper, we investigate two hydrogen-poor superluminous supernovae (SLSNe) iPTF15esb and iPTF13dcc whose light curves (LCs) show significant deviation from the smooth rise and fall. The LC of iPTF15esb exhibits two peaks and a post-peak plateau, and furthermore the late-time spectrum of iPTF15esb shows a strong, broad H$α$ emission line. The early-time LC of iPTF13dcc shows a long duration bump followed by the second peak. Here we propose an ejecta-circumstellar medium (CSM) interaction model involving multiple shells/winds and use it to explain the LCs of iPTF15esb and iPTF13dcc. We fin…
We constrain the explosion and circumstellar properties at the 2012b event of SN 2009ip based on its late-phase bolometric light curve recently reported. The explosion energy and ejected mass at the 2012b event are estimated as 0.01 Msun and 2e49 erg, respectively. The circumstellar medium is assumed to have two components: an inner shell and an outer wind. The inner shell which is likely created at the 2012a event has 0.2 Msun. The outer wind is created by the wind mass loss before the 2012a mass ejection, and the progenitor is estimated to have had the mass-loss rate about 0.1 Msun/yr with t…
We present a moderate-resolution spectrum of the peculiar Type II supernova iPTF14hls taken on day 1153 after discovery. This spectrum reveals the clear signature of shock interaction with dense circumstellar material (CSM). We suggest that this CSM interaction may be an important clue for understanding the extremely unusual photometric and spectroscopic evolution seen over the first 600 days of iPTF14hls. The late-time spectrum shows a double-peaked intermediate-width H-alpha line indicative of expansion speeds around 1000 km/s, with the double-peaked shape hinting at a disc-like geometry in …
A number of Type I (hydrogenless) superluminous supernova (SLSN) events have been discovered recently. However, their nature remains debatable. One of the most promising ideas is the shock-interaction mechanism, but only simplified semi-analytical models have been applied so far. We simulate light curves for several Type I SLSN (SLSN-I) models enshrouded by dense, non-hydrogen circumstellar envelopes, using a multi-group radiation hydrodynamics code that predicts not only bolometric, but also multicolor light curves. We demonstrate that the bulk of SLSNe-I including those with relatively narro…
The majority of Type II-plateau supernovae (SNe IIP) have light curves that are not compatible with the explosions of stars in a vacuum; instead, the light curves require the progenitors to be embedded in circumstellar matter (CSM). We report on the successful fitting of the well-observed SN IIP 2021yja as a core-collapse explosion of a massive star with an initial mass of ~15 Msun and a pre-explosion radius of 631 Rsun. To explain the early-time behaviour of the broad-band light curves, the presence of 0.55 Msun CSM within ~2x10^14 cm is needed. Like many other SNe IIP, SN 2021yja exhibits an…
We present observations of SN 2020fqv, a Virgo-cluster Type II core-collapse supernova (CCSN) with a high temporal resolution light curve from the Transiting Exoplanet Survey Satellite (TESS) covering the time of explosion; ultraviolet (UV) spectroscopy from the Hubble Space Telescope (HST) starting 3.3 days post-explosion; ground-based spectroscopic observations starting 1.1~days post-explosion; along with extensive photometric observations. Massive stars have complicated mass-loss histories leading up to their death as CCSNe, creating circumstellar medium (CSM) with which the SNe interact. O…
The discovery of SN 2018gep (ZTF18abukavn) challenged our understanding of the late-phase evolution of massive stars and their supernovae (SNe). The fast rise in luminosity of this SN (spectroscopically classified as a broad-lined Type Ic SN), indicates that the ejecta interacts with a dense circumstellar medium (CSM), while an additional energy source such as $^{56}$Ni-decay is required to explain the late-time light curve. These features hint at the explosion of a massive star with pre-supernova mass-loss. In this work, we examine the physical origins of rapidly evolving astrophysical transi…
We present the discovery, classification, and extensive panchromatic (from radio to X-ray) follow-up observations of PTF11qcj, a supernova discovered by the Palomar Transient Factory. PTF11qcj is located at a distance of dL ~ 124 Mpc. Our observations with the Karl G. Jansky Very Large Array show that this event is radio-loud: PTF11qcj reached a radio peak luminosity comparable to that of the famous gamma-ray-burst-associated supernova 1998bw (L_{5GHz} ~ 10^{29} erg/s/Hz). PTF11qcj is also detected in X-rays with the Chandra observatory, and in the infrared band with Spitzer. Our multi-wavelen…
Type IIn/Ia-CSM supernovae (SNe IIn/Ia-CSM) are classified by their characteristic spectra, which exhibit narrow hydrogen emission lines originating from a strong interaction with a circumstellar medium (CSM) together with broad lines of intermediate-mass elements. We performed intensive follow-up observations of SN IIn/Ia-CSM 2020uem, including photometry, spectroscopy, and polarimetry. In this paper, we focus on the results of polarimetry. We performed imaging polarimetry at $66$ days and spectropolarimetry at $103$ days after the discovery. SN 2020uem shows a high continuum polarization of …
Type II supernovae (SNe) originate from the explosion of hydrogen-rich supergiant massive stars. Their first electromagnetic signature is the shock breakout, a short-lived phenomenon which can last from hours to days depending on the density at shock emergence. We present 26 rising optical light curves of SN II candidates discovered shortly after explosion by the High cadence Transient Survey (HiTS) and derive physical parameters based on hydrodynamical models using a Bayesian approach. We observe a steep rise of a few days in 24 out of 26 SN II candidates, indicating the systematic detection …
We propose a common envelope jets supernova scenario for the enigmatic supernova iPTF14hls where a neutron star that spirals-in inside the envelope of a massive giant star accretes mass and launches jets that power the ejection of the circumstellar shell and a few weeks later the explosion itself. To account for the kinetic energy of the circumstellar gas and the explosion, the neutron star should accrete a mass of approximately 0.3 solar masses. The tens of solar masses of circumstellar gas that accounts for some absorption lines is ejected while the neutron star orbits for about one to sever…
The Fast Blue Optical Transient (FBOT) ATLAS18qqn (AT2018cow) has a light curve as bright as superluminous supernovae but rises and falls much faster. We model this light curve by circumstellar interaction of a pulsational pair-instability (PPI) supernova (SN) model based on our PPISN models studied in previous work. We focus on the 42 $M_\odot$ He star (core of a 80 $M_{\odot}$ star) which has circumstellar matter of mass 0.50 $M_\odot$. With the parameterized mass cut and the kinetic energy of explosion $E$, we perform hydrodynamical calculations of nucleosynthesis and optical light curves o…
We report on X-ray spectral evolution of the nearby Type IIn supernova (SN) 2005ip, based on Chandra and Swift observations covering from ~1 to 6 years after the explosion. X-ray spectra in all epochs are well fitted by a thermal emission model with kT > 7 keV. The somewhat high temperature suggests that the X-ray emission mainly arises from the circumstellar medium heated by the forward shock. We find that the spectra taken 2-3 years since the explosion are heavily absorbed N_H ~ 5e22 cm^{-2}, but the absorption gradually decreases to the level of the Galactic absorption N_H ~ 4e20 cm^{-2} at…
Type IIP supernova progenitors are often surrounded by dense circumstellar media that may result from mass-loss enhancement of the progenitors shortly before their explosions. Previous light-curve studies suggest that the mass-loss rates are enhanced up to ~ 0.1 Msun/yr, assuming a constant wind velocity. However, density of circumstellar media at the immediate stellar vicinity can be much higher than previously inferred for a given mass-loss rate if wind acceleration is taken into account. We show that the wind acceleration has a huge impact when we estimate mass-loss rates from early light c…
Radio Emission from Fast Blue Optical Transients Powered by Trans-relativistic Shocks in Confined Circumstellar Material
Central China Normal University（华中师范大学）；Institute of Astrophysics, Central China Normal University（华中师范大学天体物理研究所）；Laboratory for Compact Object Astrophysics and Astronomical Technology, Central China Normal University（华中师范大学致密天体天文学与技术实验室）；Education Research and Application Center, National Astronomical Data Center（国家天文台教育研究与应用中心）
I raise the possibility that the pre-explosion outburst (PEO) of the type IIn supernova 2010mc (PTF 10tel) was energized by mass accretion onto an O main-sequence stellar companion. According to this suggestion the SN progenitor suffered a rapid expansion within months before explosion. The expansion was driven by leakage of energy from the core where vigorous oxygen nuclear burning takes place within a year prior to explosion. This expansion triggered mass transfer onto the secondary star. Most of the extra energy of the outburst comes from the accretion of ~0.1Mo onto the secondary star. As …
Supernova (SN) 2014C is a unique explosion where a seemingly typical hydrogen-poor stripped envelope SN started to interact with a dense, hydrogen-rich circumstellar medium (CSM) a few months after the explosion. The delayed interaction suggests a detached CSM shell, unlike in a typical SN IIn where the CSM is much closer and the interaction commences earlier post-explosion; indicating a different mass loss history. We present near- to mid-infrared observations of SN 2014C from 1-5 years after the explosion, including uncommon 9.7 $μ$m imaging with COMICS on the Subaru telescope. Spectroscopy …
I analyse some properties of the luminous transient event SN 2019zrk and conclude that jets were the main powering sources of the pre-explosion outburst (precursor) and ejection of a massive circumstellar matter (CSM), of the very energetic explosion itself, and of the post-explosion bump in the light curve. The pre-explosion energy source is mainly a companion (main sequence, Wolf-Rayet, neutron star or black hole) star that accreted mass and launched jets. I find that the fast expansion of the CSM after acceleration by the explosion ejecta requires the explosion energy to be >10^{52} erg. On…
