Supernova explosions interacting with aspherical circumstellar material: implications for light curves, spectral line profiles, and polarization

Although all Type II supernovae (SNe) originate from massive stars possessing a hydrogen-rich envelope, their light-curve morphology is diverse, reflecting poorly characterized heterogeneity in the physical properties of their progenitor systems. Here, we present a detailed light-curve analysis of a magnitude-limited sample of 639 Type II SNe from the Zwicky Transient Facility Bright Transient Survey. Using Gaussian processes, we systematically measure empirical light-curve features (e.g. rise times, peak colours, and luminosities) in a robust sampling-independent manner. We focus on rise times as they are highly sensitive to pre-explosion progenitor properties, especially the presence of a dense circumstellar medium (CSM) shed by the progenitor in the years immediately pre-explosion. By correlating our feature measurements with physical parameters from an extensive grid of stella hydrodynamical models with varying progenitor properties (CSM structure, $\dot{M}$, $R_{\rm {CSM}}$, and $M_{\mathrm{ ZAMS}}$), we quantify the proportion of events with sufficient pre-explosion mass loss to significantly alter the initial light curve (roughly $M_{\mathrm{ CSM}} \ge 10^{-2.5}\, {\rm M}_{\odot }$) in a highly complete sample of 377 spectroscopically classified Type II SNe. We find that 67 $\pm$ 6 per cent of observed SNe in our magnitude-limited sample show evidence for substantial CSM ($M_{\rm {CSM}} \ge 10^{-2.5} {\rm M}_{\odot }$) close to the progenitor ($R_{\rm {CSM}} < 10^{15}$ cm) at the time of explosion. After applying a volumetric-correction, we find 36$^{+5}_{-7}$ per cent of all Type II SN progenitors possess substantial CSM within $10^{15}$ cm at the time of explosion. This high fraction of progenitors with dense CSM, supported by photometric and spectroscopic evidence of previous SNe, reveals mass-loss rates significantly exceeding those measured in local group red supergiants or predicted by current theoretical models.

We calculate multicolor light curves (LCs) of supernovae (SNe) from red supergiants (RSGs) exploded within dense circumstellar medium (CSM). Multicolor LCs are calculated by using a multi-group radiation hydrodynamics code STELLA. If CSM is dense enough, the shock breakout signal is delayed and smeared by CSM and kinetic energy of SN ejecta is efficiently converted to thermal energy which is eventually released as radiation. We find that explosions of RSGs are affected by CSM in early epochs when mass-loss rate just before the explosions is higher than 10^{-4} Msun/yr. Their characteristic features are that the LC has a luminous round peak followed by a flat LC, that multicolor LCs are simultaneously bright in ultraviolet and optical at the peak, and that photospheric velocity is very low at these epochs. We calculate LCs for various CSM conditions and explosion properties, i.e., mass-loss rates, radii of CSM, density slopes of CSM, explosion energies of SN ejecta, and SN progenitors inside, to see their influence on LCs. We compare our model LCs to those of ultraviolet-bright Type IIP SN 2009kf and show that the mass-loss rate of the progenitor of SN 2009kf just before the explosion is likely to be higher than 10^{-4} Msun/yr. Combined with the fact that SN 2009kf is likely to be an energetic explosion and has large 56Ni production, which implies that the progenitor of SN 2009kf is a massive RSG, our results indicate that there could be some mechanism to induce extensive mass loss in massive RSGs just before their explosions.

Type IIn supernovae (SNe IIn) are a highly heterogeneous subclass of core-collapse supernovae, spectroscopically characterized by signatures of interaction with a dense circumstellar medium (CSM). Here, we systematically model the light curves of 142 archival SNe IIn using the Modular Open Source Fitter for Transients. We find that the observed and inferred properties of SN IIn are diverse, but there are some trends. The typical supernova CSM is dense (∼10−12 g cm−3) with highly diverse CSM geometry, with a median CSM mass of ∼1 M ⊙. The ejecta are typically massive (≳10 M ⊙), suggesting massive progenitor systems. We find positive correlations between the CSM mass and the rise and fall times of SNe IIn. Furthermore, there are positive correlations between the rise time and fall times and the r-band luminosity. We estimate the mass-loss rates of our sample (where spectroscopy is available) and find a high median mass-loss rate of ∼10−2 M ⊙ yr−1, with a range between 10−3 and 1 M ⊙ yr−1. These mass-loss rates are most similar to the mass loss from great eruptions of luminous blue variables, consistent with the direct progenitor detections in the literature. We also discuss the role that binary interactions may play, concluding that at least some of our SNe IIn may be from massive binary systems. Finally, we estimate a detection rate of 1.6 × 105 yr−1 in the upcoming Legacy Survey of Space and Time at the Vera C. Rubin Observatory.

When low-mass stars form, the collapsing cloud of gas and dust goes through several stages which are usually characterized by the shape of their spectral energy distributions. Such classification is based on the cloud morphology only and does not address the dynamical state of the object. In this paper we investigate the initial cloud collapse and subsequent disk formation through the dynamical behavior as reflected in the sub-millimeter spectral emission line profiles. If a young stellar object is to be characterized by its dynamical structure it is important to know how accurately information about the velocity field can be extracted and which observables provide the best description of the kinematics. Of particular interest is the transition from infalling envelope to rotating disk, because this provides the initial conditions for the protoplanetary disk, such as mass and size. We use a hydrodynamical model, describing the collapse of a core and formation of a disk, to produce synthetic observables which we compare to calculated line profiles of a simple parameterized model. Because we know the velocity field from the hydrodynamical simulation we can determine in a quantitative way how well our best-fit parameterized velocity field reproduces the original. We use a molecular line excitation and radiation transfer code to produce spectra of both our hydro dynamical simulation as well as our parameterized model. We find that information about the velocity field can reasonably well be derived by fitting a simple model to either single-dish lines or interferometric data, but preferentially by using a combination of the two. Our result shows that it is possible to establish relative ages of a sample of young stellar objects using this method, independently of the details of the hydrodynamical model.

Interaction between a supernova (SN) ejecta and a dense circumstellar medium (CSM) can power a luminous light curve and create narrow emission lines in the spectra. While theoretical studies of interaction often assume a spherically symmetric CSM, there are observational indications that the gas surrounding some SNe has a disk-like geometry. Here, we use moving-mesh hydrodynamics simulations to study the interaction of an SN with a disk and determine how the dynamics and observable signatures may depend on the disk mass, thickness, and radial extent. We find that simple modifications to standard spherically-symmetric scaling laws can be used to describe the propagation and heating rate of the interaction shock. We use the resulting shock heating rates to derive approximate bolometric light curves, and provide analytic formulas that can be used to generate simple synthetic light curves for general supernova-disk interactions. For certain disk parameters and explosion energies, we are able to produce luminosities akin to those seen in super-luminous SNe. Because the SN ejecta can flow around and engulf the CSM disk, the interaction region may become embedded and, from certain viewing angles, the narrow emission lines indicative of interaction may be hidden.

view Abstract Citations (113) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The light variations of nonradial pulsators: theory and application to the line profile variable 53 Persei. Buta, R. J. ; Smith, M. A. Abstract The nonradial pulsator 53 Persei (B4.5 V) has been observed during 13 nights in late 1977 to determine whether its photometric variations are reminiscent of its spectral line profile changes. Inspection of the resulting light curve shows a variable amplitude with an estimated time scale of 1.9 days. Simultaneous photographic spectroscopy confirms this behavior. The light variations can be modeled successfully with a pair of sinusoidal oscillations having closely spaced periods near 1.7 and 2.1 days and amplitudes of 0.03-0.04 mag. The theory of linear, adiabatic nonradial oscillations is developed for low-order modes and applied to 53 Per. In general, sinusoidal light variations are produced by two geometric distortions of the star (the projected surface area and distorted surface normal effects) and a local compression of the gas. For the long periods observed in 53 Per, compression caused by horizontal motions in traveling waves is predicted to be the primary source of light variations. However, our predicted light amplitudes are about an order of magnitude larger than those observed. The source of the disagreement can be traced to our assumption of adiabaticity. Moreover, our observed color curve is half a cycle out of phase with the predicted light curve arising from this compression (temperature) effect. This suggests again substantial departures from adiabaticity in this long- period object. Nonradial theory also predicts that a star's rotation will split a nonradial mode into several closely spaced frequencies. An analysis of the two close frequencies in our photometric data leads to a rotational velocity which agrees to within 17% of the spectroscopic value. Our solution precludes stellar models with rapidly rotating cores. It also places a condition on the two rn-mode indices: Am = 1. We are able to place firm constraints on the physical identifications of the observed rn-mode pair, namely, m = - I, - I + 1, where 1 = 2 or 3, only. There is some difficulty in interpreting the great length of the 1.9 day period. In linear theory a single overtone of very high order (k 20) would be required. However, if one drops linearity it becomes possible to understand the long periods in terms of nonlinear coupling with a subharmonic or "stray" high-overtone mode. 53 Persei has now become the first star to show both photometric and spectroscopic variations that can best be explained in the framework of nonradial pulsation. Subject headings: stars: individual - stars: pulsation Publication: The Astrophysical Journal Pub Date: August 1979 DOI: 10.1086/157281 Bibcode: 1979ApJ...232..213B Keywords: B Stars; Light Curve; Stellar Spectrophotometry; Variable Stars; Adiabatic Conditions; Least Squares Method; Line Spectra; Sine Waves; Stellar Rotation; Astrophysics; Light Curves:Pulsating Stars; Line Profiles:Pulsating Stars; Photometry:Pulsating Stars; Pulsating Stars:Models; Pulsating Stars:Spectroscopy full text sources ADS | data products SIMBAD (4)

Context. Physical and chemical properties, such as kinetic temperature, volume density, and molecular composition of interstellar clouds are inherent in their line spectra at submillimeter wavelengths. Therefore, the spectral line profiles could be used to estimate the physical conditions of a given source. Aims. We present a new bottom-up approach, based on machine learning (ML) algorithms, to extract the physical conditions in a straightforward way from the line profiles without using radiative transfer equations. Methods. We simulated, for the typical physical conditions of dense molecular clouds and star-forming regions, the emission in spectral lines of the two isomers HCN and HNC, from J = 1–0 to J = 5–4 between 30 and 500 GHz, which are commonly observed in dense molecular clouds and star forming regions. The generated data cloud distribution has been parametrised using the line intensities and widths to enable a new way to analyse the spectral line profiles and to infer the physical conditions of the region. The line profile parameters have been charted to the HNC/HCN ratio and the excitation temperature of the molecule(s). Three ML algorithms have been trained, tested, and compared aiming to unravel the excitation conditions of HCN and HNC and their abundance ratio. Results. Machine learning results obtained with two spectral lines, one for each isomer HCN and HNC, have been compared with the local thermodynamic equilibrium (LTE) analysis for the cold source R CrA IRS 7B. The estimate of the excitation temperature and of the abundance ratio, in this case considering the two spectral lines, is in agreement with our LTE analysis. The complete optimisation procedure of the algorithms (training, testing, and prediction of the target quantities) have the potential to predict interstellar cloud properties from line profile inputs at lower computational cost than before. Conclusions. It is the first time that the spectral line profiles are mapped according to the physical conditions charting the ratio of two isomers and the excitation temperature of the molecules. In addition, a bottom-up approach starting from a set of simulated spectral data at different physical conditions is proposed to interpret line observations of interstellar regions and to estimate their physical conditions. This new approach presents the potential relevance to unravel hidden interstellar conditions with the use of ML methods.

For decades a wide variety of observations spanning the radio through optical and on to the X-ray have attempted to uncover signs of type Ia supernovae (SNe Ia) interacting with a circumstellar medium (CSM). The goal of these studies is to constrain the nature of the hypothesized SN Ia mass-donor companion. A continuous CSM is typically assumed when interpreting observations of interaction. However, while such models have been successfully applied to core-collapse SNe, the assumption of continuity may not be accurate for SNe Ia, because shells of CSM could be formed by pre-supernova eruptions (novae). In this work, we model the interaction of SNe with a spherical, low-density, finite-extent CSM and create a suite of synthetic radio synchrotron light curves. We find that CSM shells produce sharply peaked light curves. We also identify a fiducial set of models that obey a common evolution and can be used to generate radio light curves for an interaction with an arbitrary shell. The relations obeyed by the fiducial models can be used to deduce CSM properties from radio observations; we demonstrate this by applying them to the nondetections of SN 2011fe and SN 2014J. Finally, we explore a multiple shell CSM configuration and describe its more complicated dynamics and the resultant radio light curves.

We show model light curves of superluminous supernova 2006gy on the assumption that the supernova is powered by the collision of supernova ejecta and its dense circumstellar medium. The initial conditions are constructed based on the shock breakout condition, assuming that the circumstellar medium is dense enough to cause the shock breakout within it. We perform a set of numerical light curve calculations by using a one-dimensional multigroup radiation hydrodynamics code STELLA. We succeeded in reproducing the overall features of the early light curve of SN 2006gy with the circumstellar medium whose mass is about 15 Msun (the average mass-loss rate ~ 0.1 Msun/yr). Thus, the progenitor of SN 2006gy is likely a very massive star. The density profile of the circumstellar medium is not well constrained by the light curve modeling only, but our modeling disfavors the circumstellar medium formed by steady mass loss. The ejecta mass is estimated to be comparable to or less than 15 Msun and the explosion energy is expected to be more than 4e51 erg. No 56Ni is required to explain the early light curve. We find that the multidimensional effect, e.g., the Rayleigh-Taylor instability, which is expected to take place in the cool dense shell between the supernova ejecta and the dense circumstellar medium, is important in understanding supernovae powered by the shock interaction. We also show the evolution of the optical and near-infrared model light curves of high-redshift superluminous supernovae. They can be potentially used to identify SN 2006gy-like superluminous supernovae in the future optical and near-infrared transient surveys.

Supernova (SN) 2014C is unique: a seemingly typical hydrogen-poor SN that started to interact with a dense, hydrogen-rich circumstellar medium (CSM) ∼100 days post-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 infrared observations of SN 2014C 1–5 yr post-explosion, including uncommon 9.7 μm imaging with COMICS on the Subaru telescope. Spectroscopy shows the intermediate-width He I 1.083 μm emission from the interacting region up to the latest epoch 1639 days post-explosion. The last Spitzer/IRAC photometry at 1920 days confirms ongoing CSM interaction. The 1–10 μm spectral energy distributions (SEDs) can be explained by a dust model with a mixture of 62% carbonaceous and 38% silicate dust, pointing to a chemically inhomogeneous CSM. The inference of silicate dust is the first among interacting SNe. An SED model with purely carbonaceous CSM dust, while possible, requires more than 0.22 M ⊙ of dust, an order of magnitude larger than what has been observed in any SNe at this epoch. The light curve beyond 500 days is well fit by an interaction model with a wind-driven CSM and a mass-loss rate of ∼10−3 M ⊙ yr−1, which presents an additional CSM density component exterior to the constant-density shell reported previously in the literature. SN 2014C could originate in a binary system, similar to RY Scuti, which would explain the observed chemical and density profile inhomogeneity in the CSM.

We report a luminous Type II supernova, ASASSN-15nx, with a peak luminosity of mag that is between those of typical core-collapse supernovae and super-luminous supernovae. The post-peak optical light curves show a long, linear decline with a steep slope of 2.5 mag (100 day)−1 (i.e., an exponential decline in flux) through the end of observations at phase . In contrast, the light curves of hydrogen-rich supernovae (SNe II-P/L) always show breaks in their light curves at phase ∼100 day, before settling onto 56Co radioactive decay tails with a decline rate of about 1 mag (100 day)−1. The spectra of ASASSN-15nx do not exhibit the narrow emission-line features characteristic of Type IIn SNe, which can have a wide variety of light-curve shapes usually attributed to strong interactions with a dense circumstellar medium (CSM). ASASSN-15nx has a number of spectroscopic peculiarities, including a relatively weak and triangular-shaped Hα emission profile with no absorption component. The physical origin of these peculiarities is unclear, but the long and linear post-peak light curve without a break suggests a single dominant powering mechanism. Decay of a large amount of (M Ni = 1.6 ± 0.2 ) can power the light curve of ASASSN-15nx, and the steep light-curve slope requires substantial γ-ray escape from the ejecta, which is possible given a low-mass hydrogen envelope for the progenitor. Another possibility is strong CSM interactions powering the light curve, but the CSM needs to be sculpted to produce the unique light-curve shape and avoid producing SN IIn-like narrow emission lines.

Physical model light- and velocity-curve solutions for S Cancri and TT Hydrae are obtained, and analyses with incorporation of asynchronous rotation are carried out. A photometric rotation rate for the primary star of TT Hya is determined, and excellent agreement with results from spectral line profiles is found. Both separate light- and velocity-curve solutions and simultaneous light-velocity solutions are listed. The photometric rotation for S Cnc from existing light curves is indeterminate, but is compatible with line profile measures. Evidence for third light from the light curves of S Cnc is found. An explanation for the apparent conflict between the rotational states and mass-transfer activities of the two binaries is suggested.

Context. At late stages, massive stars experience strong mass-loss rates, losing their external layers and thus producing a dense H-rich circumstellar medium (CSM). After the explosion of a massive star, the collision and continued interaction of the supernova (SN) ejecta with the CSM power the SN light curve through the conversion of kinetic energy into radiation. When the interaction is strong, the light curve shows a broad peak and high luminosity that lasts for several months. For these SNe, the spectral evolution is also slower compared to non-interacting SNe. Notably, energetic shocks between the ejecta and the CSM create the ideal conditions for particle acceleration and the production of high-energy (HE) neutrinos above 1 TeV. Aims. We study four strongly interacting Type IIn SNe, 2021acya, 2021adxl, 2022qml, and 2022wed, in order to highlight their peculiar characteristics, derive the kinetic energy of their explosion and the characteristics of the CSM, infer clues on the possible progenitors and their environment, and relate them to the production of HE neutrinos. Methods. We analysed spectro-photometric data of a sample of interacting SNe to determine their common characteristics and derive the physical properties (radii and masses) of the CSM and the ejecta kinetic energies and compare them to HE neutrino production models. Results. The SNe analysed in this sample exploded in dwarf star-forming galaxies, and they are consistent with energetic explosions and strong interaction with the surrounding CSM. For SNe 2021acya and 2022wed, we find high CSM masses and mass-loss rates, linking them to very massive progenitors. For SN 2021adxl, the spectral analysis and less extreme CSM mass suggest a stripped-envelope massive star as a possible progenitor. SN 2022qml is marginally consistent with being a Type Ia thermonuclear explosion embedded in a dense CSM. The mass-loss rates for all the SNe are consistent with the expulsion of several solar masses of material during eruptive episodes in the last few decades before the explosion. Finally, we find that the SNe in our sample are marginally consistent with HE neutrino production.

{SN 2014av is a type Ibn supernova (SN) characterized by the interaction
between the SN ejecta and a helium-rich \textcolor{red}{\sout{ejecta-}}circumstellar medium (CSM).
We use the $^{56}$Ni model, the ejecta-CSM interaction (CSI) model, and the CSI plus $^{56}$Ni model to fit
the multiband light curves (LCs) of SN~2014av. For the CSI and CSI plus $^{56}$Ni models, we assume that
the CSM is a constant density shell (``shell$"$) or a steady-state stellar wind (``wind$"$) with density $\propto r^{-2}$.
We find that both the $^{56}$Ni and CSI models fail to fit the multiband LCs of SN~2014av,
while the CSI plus $^{56}$Ni model can account for the LCs.
In the last scenario, the LCs around the peaks were mainly powered by CSI,
while the flattening of the LCs was mainly powered by the \textcolor{blue}{radioactive} decay of $^{56}$Ni.
For the wind case, the derived mass-loss rate of the progenitor is $\approx \textcolor{blue}{20.5-205.5}\,\rm M_\odot$ yr$^{-1}$,
whose lower limit is significantly larger than the upper limit of the normal stellar winds, and
comparable the upper limit of hyper-winds. Hence, we suggest that the wind case is disfavored.
For the shell case, the best-fitting values of the ejecta, $^{56}$Ni, and the CSM are \textcolor{blue}{2.29} M$_{\odot}$,
\textcolor{blue}{0.09} M$_\odot$, and \textcolor{blue}{5.00} M$_{\odot}$, respectively. Provided the velocity of the CSM shell is 100$-$1000 km s$^{-1}$,
we infer that the shell might be expelled $\approx \textcolor{blue}{0.49-5.20}$ yr before the SN exploded.

NR Peg: A new highly active semi-detached binary