IIP Supernovae Research Articles

Type II-Plateau supernova radiation: dependences on progenitor and explosion properties

We explore the properties of Type II-Plateau (II-P) supernovae (SNe) together with their red supergiant (RSG) star progenitors. Using mesa star, we modulate the parameters (e.g. mixing length, overshoot, rotation, metallicity) that control the evolution of a 15 M⊙ main-sequence star to produce a variety of physical pre-SN models and SN II-P ejecta. We extend previous modelling of SN II-P radiation to include photospheric and nebular phases, as well as multiband light curves and spectra. Our treatment does not assume local thermodynamic equilibrium, is time dependent, treats explicitly the effects of line blanketing and incorporates non-thermal processes. We find that the colour properties of SNe II-P require large model atoms for Fe i and Fe ii, much larger than previously adopted. The colour properties also imply RSG progenitors of limited extent (∼500 R⊙) – larger progenitor stars produce an SN II-P radiation that remains too blue for too long. This finding calls for a reduction of RSG radii, perhaps through a strengthening of convective energy transport in RSG envelopes. Increased overshoot and rotation reduce the ratio of ejecta to helium-core mass, similarly to an increase in main-sequence mass, and thus complicate the inference of progenitor masses. In contrast to the great sensitivity on progenitor radius, SN II-P colour evolution appears insensitive to variations in explosion energy. Finally, we document the numerous SN II-P signatures that vary with progenitor metallicity, revealing their potential for metallicity determinations in the nearby and distant Universe.

CALTECH CORE-COLLAPSE PROJECT (CCCP) OBSERVATIONS OF TYPE II SUPERNOVAE: EVIDENCE FOR THREE DISTINCT PHOTOMETRIC SUBTYPES

We present R-Band light curves of Type II supernovae (SNe) from the Caltech Core Collapse Project (CCCP). With the exception of interacting (Type IIn) SNe and rare events with long rise times, we find that most light curve shapes belong to one of three distinct classes: plateau, slowly declining and rapidly declining events. The last class is composed solely of Type IIb SNe which present similar light curve shapes to those of SNe Ib, suggesting, perhaps, similar progenitor channels. We do not find any intermediate light curves, implying that these subclasses are unlikely to reflect variance of continuous parameters, but rather might result from physically distinct progenitor systems, strengthening the suggestion of a binary origin for at least some stripped SNe. We find a large plateau luminosity range for SNe IIP, while the plateau lengths seem rather uniform at approximately 100 days. As analysis of additional CCCP data goes on and larger samples are collected, demographic studies of core collapse SNe will likely continue to provide new constraints on progenitor scenarios.

Modeling Supernova Spectra

AbstractWe highlight results from a series of investigations into modeling spectra of core-collapse supernovae (SNe). We have explored the accuracy of the expanding-photosphere method, and found that it can be used to obtain distances to Type IIP SNe with an accuracy of ≲10%. We confirm the result of Utrobin and Chugai (2005) that time-dependent terms must be included in the statistical equilibrium equations in order to model Hi line evolution in Type II SNe, and show that time-dependent terms influence other spectral features (e.g., He i lines). We have initiated a study of polarization signatures from aspherical but axially-symmetric Type II SN ejecta. Hillier and Li acknowledge support from STScI theory grant HST-AR-11756.01.A and NASA theory grant NNX10AC80G. Dessart acknowledges financial support from grant PIRG04-GA-2008-239184.

The Flavours of SN II Light Curves

AbstractWe present R-Band light curves of Type II supernovae (SNe) from the Caltech Core Collapse Program (CCCP). With the exception of interacting (Type IIn) SNe and rare events with long rise times, we find that most light curve shapes belong to one of three distinct classes: plateau, slowly declining and rapidly declining events. The latter class is composed solely of Type IIb SNe which present similar light curve shapes to those of SNe Ib, suggesting, perhaps, similar progenitor channels. We do not find any intermediate light curves, implying that these subclasses are unlikely to reflect variance of continuous parameters, but rather might result from physically distinct progenitor systems, strengthening the suggestion of a binary origin for at least some stripped SNe. We find a large plateau luminosity range for SNe IIP, while the plateau lengths seem rather uniform at approximately 100 days. We present also host galaxy trends from the Palomar Transien Factory (PTF) core collapse SN sample, which augment some of the photometric results.

Identifying Supernova Progenitors and Constraining the Explosion Channels

AbstractConnecting the endpoints of massive star evolution with the various types of core-collapse supernovae (SNe) is ultimately the fundamental puzzle to be explored and solved. We can assemble clues indirectly, e.g., from information about the environments in which stars explode and establish constraints on the evolutionary phases of these stars. However, this is best accomplished through direct identification of the actual star that has exploded in pre-supernova imaging, preferably in more than one photometric band, where color and luminosity for the star can be precisely measured. We can then interpret the star's properties in light of expectations from the latest massive stellar evolutionary models, to attempt to assign an initial mass to the progenitor. So far, this has been done most successfully for SNe II-P, for which we now know that red supergiants in a relatively limited initial mass range are responsible. More recently, we have limited examples of the progenitors of SNe II-L, IIn, and IIb. The progenitors of SNe Ib and Ic, however, have been elusive so far; I will discuss the current status of our knowledge of this particular channel.

Ultraviolet-Bright Type IIP Supernovae from Massive Red Supergiants

AbstractRed supergiants (RSGs) are progenitors of Type IIP supernovae (SNe). It is suggested that RSGs can experience a mass loss with a very high mass-loss rate (even as high as 0.01 M⊙ yr−1) due to, e.g., dynamical instabilities of their envelopes (e.g., Yoon & Cantiello (2010)). Because of the extensive mass loss, RSGs can have very dense circumstellar medium (CSM) around them. If a SN explosion occurs soon after the extensive mass loss of a RSG, the SN ejecta will collide with the dense CSM. Due to the collision, the kinetic energy of the ejecta is converted to radiation energy and such SNe with collision can be brighter than usual Type IIP SNe. By performing one-dimensional multi-group radiation hydrodynamical calculations, we investigate the effects of the collision on Type IIP SN LCs. We show that if RSGs explode within a dense CSM, the SN will be very bright, especially in ultraviolet, at early epochs. We also compare our models with the ultraviolet-bright Type IIP SN 2009kf and show that the progenitor of SN 2009kf can be a massive RSG which experienced extensive mass loss just before its explosion. We conclude that this is evidence that massive RSGs experience extensive mass loss and the existence of such mass loss can actually be the cause of the contradiction between theoretical and observational mass ranges of Type IIP SN progenitors.

Non-LTE time-dependent spectroscopic modelling of Type II-plateau supernovae from the photospheric to the nebular phase: case study for 15 and 25 M⊙ progenitor stars

We present the first non-LTE time-dependent radiative-transfer simulations of supernovae (SNe) II-Plateau (II-P) covering both the photospheric and nebular phases, from ~10 to >~1000d after the explosion, and based on 1.2B piston-driven ejecta produced from a 15Msun and a 25Msun non-rotating solar-metallicity star. The radial expansion of the gradually cooling photosphere gives rise to a near-constant luminosity up to >~100d after explosion. The photosphere remains in the outer 0.5Msun of the ejecta for up to ~50d after explosion. As the photosphere reaches the edge of the helium core, the SN luminosity drops by an amount mitigated by the progenitor radius and the 56Ni mass. Synthetic light-curves exhibit a bell-shape morphology, evolving faster for more compact progenitors, and with an earlier peak and narrower width in bluer filters. UV and U-band fluxes are very sensitive to line-blanketing, the metallicity, and the adopted model atoms. During the recombination epoch synthetic spectra are dominated by HI and metal lines, and are largely insensitive to the differing H/He/C/N/O composition of our two progenitor stars. In contrast, synthetic nebular-phase spectra reveal a broader/stronger OI doublet line in the higher-mass progenitor model, reflecting the larger masses of oxygen and nickel that are ejected. Our simulations overestimate the typical luminosity and the visual rise time of standard SNe II-P, likely a consequence of our progenitor stars being too big and/or too hydrogen rich. Comparison of our simulations with photospheric-phase observations of SN1999em of the same color are satisfactory. Our neglect of non-thermal processes leads to a fast disappearance of continuum radiation and Balmer-line emission at the end of the plateau phase. With the exception of HI lines, our nebular spectra show a striking similarity to contemporaneous observations of SN1999em.

THE MASSIVE PROGENITOR OF THE TYPE II-LINEAR SUPERNOVA 2009kr

We present early-time photometric and spectroscopic observations of supernova (SN) 2009kr in NGC 1832. We find that its properties to date support its classification as Type II-linear (SN II-L), a relatively rare subclass of core-collapse supernovae (SNe). We have also identified a candidate for the SN progenitor star through comparison of pre-explosion, archival images taken with WFPC2 onboard the Hubble Space Telescope (HST) with SN images obtained using adaptive optics (AO) plus NIRC2 on the 10-m Keck-II telescope. Although the host galaxy's substantial distance (~26 Mpc) results in large uncertainties in the relative astrometry, we find that if this candidate is indeed the progenitor, it is a highly luminous (M_V = -7.8 mag) yellow supergiant with initial mass ~18-24 M_sun. This would be the first time that a SN II-L progenitor has been directly identified. Its mass may be a bridge between the upper initial mass limit for the more common Type II-plateau SNe (SNe II-P) and the inferred initial mass estimate for one Type II-narrow SN (SN IIn).

Type II-P supernovae as standardized candles: improvements using near-infrared data

Abstract We present the first near-infrared Hubble diagram for Type II-P supernovae (SNe), to further explore their value as distance indicators. We use a modified version of the standardized candle method, which relies on the tight correlation between the absolute magnitudes of Type II-P SNe and their expansion velocities during the plateau phase. Although our sample contains only 12 II-P SNe and they are necessarily local (z < 0.02), we demonstrate using near-infrared JHK photometry that it may be possible to reduce the scatter in the Hubble diagram to 0.1–0.15 mag. While this is potentially similar to the dispersion seen for Type Ia SNe, we caution that this needs to be confirmed with a larger sample of II-P SNe in the Hubble flow.

The Ultraviolet View of Supernovae

The Ultraviolet View of Supernovae

PROPERTIES OF TYPE II PLATEAU SUPERNOVA SNLS-04D2dc: MULTICOLOR LIGHT CURVES OF SHOCK BREAKOUT AND PLATEAU

Shock breakout is the brightest radiative phenomenon in a Type II supernova (SN). Although it was predicted to be bright, the direct observation is difficult due to the short duration and X-ray/ultraviolet-peaked spectra. First entire observations of the shock breakouts of Type II Plateau SNe (SNe IIP) were reported in 2008 by ultraviolet and optical observations by the {\it GALEX} satellite and supernova legacy survey (SNLS), named SNLS-04D2dc and SNLS-06D1jd. We present multicolor light curves of a SN IIP, including the shock breakout and plateau, calculated with a multigroup radiation hydrodynamical code {\sc STELLA} and an evolutionary progenitor model. The synthetic multicolor light curves reproduce well the observations of SNLS-04D2dc. This is the first study to reproduce the ultraviolet light curve of the shock breakout and the optical light curve of the plateau consistently. We conclude that SNLS-04D2dc is the explosion with a canonical explosion energy $1.2\times10^{51}$ ergs and that its progenitor is a star with a zero-age main-sequence mass $20M_\odot$ and a presupernova radius $800R_\odot$. The model demonstrates that the peak apparent $B$-band magnitude of the shock breakout would be $m_{\rm B}\sim26.4$ mag if a SN being identical to SNLS-04D2dc occurs at a redshift $z=1$, which can be reached by 8m-class telescopes. The result evidences that the shock breakout has a great potential to detect SNe IIP at $z\gsim1$.

THE NGC 300 TRANSIENT: AN ALTERNATIVE METHOD FOR MEASURING PROGENITOR MASSES

We present an alternative technique for measuring the precursor masses of transient events in stars undergoing late stage stellar evolution. We use the well-established techniques of stellar population modeling to age-date the stars surrounding the site of the recent transient event in NGC 300 (NGC 300 OT2008-1). The surrounding stars must share a common turnoff mass with the transient, since almost all stars form in stellar clusters that remain physically associated for periods longer than the lifetime of the most massive stars. We find that the precursor of NGC 300 OT2008-1 is surrounded by stars that formed in a single burst between 8-13 Myr ago, with 70% confidence. The transient was therefore likely to be due to a progenitor whose mass falls between the main sequence turnoff mass (12 Msun) and the maximum stellar mass (25 Msun) found for isochrones bounding this age range. We characterize the general applicability of this technique in identifying precursor masses of historic and future transients and supernovae (SNe), noting that it requires neither precursor imaging nor sub-arcsecond accuracy in the position of the transient. It is also based on the well-understood physics of the main sequence, and thus may be a more reliable source of precursor masses than fitting evolutionary tracks to precursor magnitudes. We speculate that if the progenitor mass is close to 17 Msun, there may be a connection between optical transients such as NGC 300 OT2008-1 and the missing type II-P SNe, known as the red supergiant problem.

Late-time photometry of two nearby type II-P supernovae: 2004dj and 2004et

We present late-time photometry for two bright type II-P supernovae (SNe) 2004dj and 2004et, extending over 400 d after the explosion, which are measured with a set of intermediate-band filters that have the advantage of tracing the strength variations of some spectral features. Although these two SNe II-P exhibit similar photometric evolution at earlier times, they diverge during the nebular phase. SN 2004dj shows a slow late-time decline rate with ∼ 0.7 ± 0.1 mag (100d)-1 during the period ranging from t ≈ 200 – 300 d after the explosion, while SN 2004et shows a much faster decline rate at a comparable phase, e.g., 1.3 ± 0.1 mag (100d)-1. The steeper decay rate seen in SN 2004et is likely due to dust formation in the explosion ejecta. Based on intermediate-band photometry, we derived the evolution of the feature lines [e.g., Ha] of SNe 2004dj and 2004et which are similar in flux at comparable phases but perhaps with significantly different decay rates. The origin of the observed variations in the continuum and the feature lines is briefly discussed.

ULTRAVIOLET LIGHT CURVES OF SUPERNOVAE WITH THESWIFTULTRAVIOLET/OPTICAL TELESCOPE

We present ultravioliet (UV) observations of supernovae (SNe) obtained with the UltraViolet/Optical Telescope (UVOT) on board the Swift spacecraft. This is the largest sample of UV light curves from any single instrument and covers all major SN types and most subtypes. The UV light curves of SNe Ia are fairly homogenous while SNe Ib/c and IIP show more variety in their light curve shapes. The UV-optical colors clearly differentiate SNe Ia and IIP, particularly at early times. The color evolution of SNe IIP, however, makes their colors similar to SNe Ia at about 20 days after explosion. SNe Ib/c are shown to have varied UV-optical colors. The use of UV colors to help type SNe will be important for high redshift SNe discovered in optical observations. These data can be added to ground based optical and near infrared data to create bolometric light curves of individual objects and as checks on generic bolometric corrections used in the absence of UV data. This sample can also be compared with rest-frame UV observations of high redshift SNe observed at optical wavelengths.

GALEX Spectroscopy of SN 2005ay Suggests Ultraviolet Spectral Uniformity among Type II-P Supernovae

We present the first results from our GALEX program designed to obtain ultraviolet (UV) spectroscopy of nearby core-collapse supernovae (SNe). Our first target, SN 2005ay in the nearby galaxy NGC 3938, is a typical member of the II-P SN subclass. Our spectra show remarkable similarity to those of the prototypical type II-P event SN 1999em, and resemble also Swift observations of the recent type II-P event SN 2005cs. Taken together, the observations of these three events trace the UV spectral evolution of SNe II-P during the first month after explosion, as required in order to interpret optical observations of high-redshift SNe II-P, and to derive cross-filter K-corrections. While still highly preliminary, the apparent UV homogeneity of SNe II-P bodes well for the use of these events as cosmological probes at high redshift.

SN 2005cs in M51 - I. The first month of evolution of a subluminous SN II plateau

Early time optical observations of supernova (SN) 2005cs in the Whirlpool Galaxy (M51), are reported. Photometric data suggest that SN 2005cs is a moderately under-luminous Type II plateau supernova (SN IIP). The SN was unusually blue at early epochs (U-B ~ -0.9 about three days after explosion) which indicates very high continuum temperatures. The spectra show relatively narrow P-Cygni features, suggesting ejecta velocities lower than observed in more typical SNe IIP. The earliest spectra show weak absorption features in the blue wing of the He I 5876A absorption component and, less clearly, of H$\beta$ and H$\alpha$. Based on spectral modelling, two different interpretations can be proposed: these features may either be due to high-velocity H and He I components, or (more likely) be produced by different ions (N II, Si II). Analogies with the low-luminosity, $^{56}$Ni-poor, low-velocity SNe IIP are also discussed. While a more extended spectral coverage is necessary in order to determine accurately the properties of the progenitor star, published estimates of the progenitor mass seem not to be consistent with stellar evolution models.

Optical and infrared observations of the Type IIP SN 2002hh from days 3 to 397

We present optical and infrared (IR) observations of the Type II SN 2002hh from 3 to 397 d after explosion. The optical spectroscopic (4-397 d) and photometric (3-278 d) data are complemented by spectroscopic (137-381 d) and photometric (137-314 d) data acquired at IR wavelengths. This is the first time L-band spectra have ever been successfully obtained for a supernova (SN) at a distance beyond the Local Group. The VRI light curves in the first 40 d reveal SN 2002hh to be an SN IIP (plateau) - the most common of all core-collapse SNe. SN 2002hh is one of the most highly extinguished SNe ever investigated. To provide a match between its early-time spectrum and a coeval spectrum of the Type IIP SN 1999em, as well as maintaining consistency with K I interstellar absorption, we invoke a two-component extinction model. One component is due to the combined effect of the interstellar medium (ISM) of our Milky Way Galaxy and the SN host galaxy, while the other component is due to a 'dust pocket' where the grains have a mean size smaller than in the ISM. The early-time optical light curves of SNe 1999em and 2002hh are generally well matched, as are the radioactive tails of these two SNe and SN 1987A. The late-time similarity of the SN 2002hh optical light curves to those of SN 1987A, together with measurements of the optical/IR luminosity and [Fe II] 1.257 mu m emission indicate that 0.07 +/- 0.02 M-circle dot of Ni-56 was ejected by SN 2002hh. However, during the nebular phase the HKL' luminosities of SN 2002hh exhibit a growing excess with respect to those of SN 1987A. We attribute much of this excess to an IR-echo from a pre-existing, dusty circumstellar medium. Based on an IR-echo interpretation of the near-IR (NIR) excess, we deduce that the progenitor of SN 2002hh underwent recent mass-loss of similar to 0.3 M-circle dot. A detailed comparison of the late-time optical and NIR spectra of SNe 1987A and 2002hh is presented. While the overall impression is one of similarity between the spectra of the two events, there are notable differences. The Mg I 1.503 mu m luminosity of SN 2002hh is a factor of 2.5 greater than in SN 1987A at similar epochs, yet coeval silicon and calcium lines in SN 2002hh are fainter. Interpreting these differences as being due to abundance variations, the overall abundance trend between SN 1987A and 2002hh is not consistent with explosion model predictions. It appears that during the burning to intermediate-mass elements, the nucleosynthesis did not progress as far as might have been expected given the mass of iron ejected. Evidence for mixing in the ejecta is presented. Pronounced blueshifts seen in the more isolated lines are attributed to asymmetry in the ejecta. However, during the time-span of these observations (similar to 1-yr post-explosion) we find no evidence of dust condensation in the ejecta such as might have been revealed by an increasing blueshift and/or attenuation of the red wings of the emission lines. Nevertheless, the clear detection of first overtone COemission by 200 d and the reddening trend in (K-L')(0) suggest that dust formation in the ejecta may occur at later epochs. From the[OI] lambda lambda 6300, 6364 angstrom doublet luminosity we infer a 16-18 M-circle dot main-sequence progenitor star. The progenitor of SN 2002hh was probably a red supergiant with a substantial, dusty wind.

Optical Photometry of the Type II-P Supernova 2004dj in NGC 2403

We present photometric data of the Type II-P supernova (SN) 2004dj in NGC 2403. The multicolor light curves cover the SN from ∼60 to 200 days after explosion and are measured with a set of intermediate-band filters that have the advantage of tracing the strength variations of some spectral features. The light curves show a flat evolution in the middle of the plateau phase, then decline exponentially at the late times, with a rate of 0.10 ± 0.03 mag (10 days)-1 in most of the filters. In the nebular phase, the spectral energy distribution of SN 2004dj shows a steady increase in the flux near 6600 and 8500 Å, which may correspond to the emission lines of Hα and the Ca II near-IR triplet, respectively. The photometric behavior suggests that SN 2004dj is a normal SN II-P. Compared with the light curves of another typical SN II-P, 1999em, we estimate the explosion date to be 2004 June 10 ± 21 UT (JD 2,453,167 ± 21) for SN 2004dj. We also estimate the ejected nickel mass during the explosion to be M(56Ni) = 0.023 ± 0.005 M⊙ from two different methods, which is typical for a SN II-P. We derive the explosion energy to be E ≈ 0.75 × 1051 ergs, the ejecta mass to be M ≈ 10.0 M⊙, and the initial radius to be R ≈ 282 R⊙ for the presupernova star of SN 2004dj, which are consistent with other typical SNe II-P.

The Progenitor of SN 2004dj in a Star Cluster

The progenitor of Type II-P (P p plateau) supernova SN 2004dj is identified with a supergiant in a compact star cluster known as “Sandage’s star 96” (S96) in the nearby spiral galaxy NGC 2403, which was fortuitously imaged as part of the Beijing-Arizona-Taiwan-Connecticut (BATC) Multicolor Sky Survey from 1995 February to 2003 December prior to SN 2004dj. The superior photometry of BATC images for S96, taken with 14 intermediate-band filters covering 3000–10000 , unambiguously establishes the star cluster nature of S96, with u A an age of ∼20 Myr, a reddening of mag, and a total mass of ∼96,000 M,. The compact star E(B V) ∼ 0.35 cluster nature of S96 is also consistent with the lack of light variations in the past decade. The SN progenitor is estimated to have a main-sequence mass of ∼12 M,. The comparison of our intermediate-band data of S96 with the postoutburst photometry obtained as the SN significantly dims with time may hopefully conclusively establish the nature of the progenitor. Subject headings: galaxies: individual (NGC 2403) — galaxies: star clusters — stars: evolution — supergiants — supernovae: general — supernovae: individual (SN 2004dj)

Extragalactic Binaries as Core-Collapse Supernova Progenitors

Core-collapse supernovae (SNe) come in a variety of subtypes. The SNe II-plateau (II-P) show a long plateau in their light curves, as well as classical P Cygni Balmer line profiles in their spectra. The SNe Il-linear (II-L) show a linear decline in their light curves after maximum, and the blue absorption trough in the Balmer lines is missing, leaving only broad emission profiles. The SNe II-narrow (IIn) show a narrow profile atop a broad base to the Balmer emission. The SNe lb exhibit no hydrogen lines, but prominent He lines instead. The SNe Ic also show no H, but also weak or no He, with their spectra dominated by intermediate-mass elements. The SNe lib start out appearing as SNe II(P), but in time evolve spectrally to resemble SNe lb, with a later resumption of broad Balmer profiles, as in the case of SN 1993J (see Filippenko 1997 for a review of SN types). The progression from SNe II-P, II-L, Iln, lib, lb, through Ic may be due to the degree of stripping of the H-rich stellar envelope. Binary star systems are likely the progenitors of many core-collapse SNe. In fact, we might expect ≳40-50% of all such SNe to arise from binaries (e.g., De Donder & Vanbeveren 1998).