Hydrogen-rich (type II) supernovae (SNe) exhibit considerable photometric and spectroscopic diversity. Extending previous work that focused exclusively on photometry, we simultaneously model the multi-band light curves and optical spectra of Type II SNe using RSG progenitors that are characterized by their H-rich envelope masses or the mass and extent of an enshrouding cocoon at the star's surface. Reducing the H-rich envelope mass yields faster declining light curves, a shorter duration of the photospheric phase, broader line profiles at early times, but only a modest boost in early-time optical brightness. Increasing the mass of the circumstellar material (CSM) is more effective at boosting the early-time brightness and producing a fast-declining light curve while leaving the duration of the photospheric phase intact. It also makes the optical color bluer, delays the onset of recombination, and can severely reduce the speed of the fastest ejecta material. The early ejecta interaction with CSM is conducive to producing featureless spectra at $10-20$ d and a weak or absent H$α$ absorption during the recombination phase. The slow decliners SNe 1999em, 2012aw, and 2004et can be explained with a $1.2 \times 10^{51}$ erg explosion in a compact ($\sim$600 R$_\odot$) RSG star from a 15 M$_\odot$ stellar evolution model. A small amount of CSM ($<0.2$ M$_\odot$) improves the match to the SN photometry at times $<$ 10 d. With more extended RSG progenitors, one predicts lower ejecta kinetic energies, but the SN color stays blue for too long and the spectral line widths are too narrow. The fast decliners SNe 2013ej and 2014G may require $0.5-1.0$ M$_\odot$ of CSM, although this depends on the CSM structure. A larger boost to the luminosity (as for fast decliners SNe 1979C or 1998S) requires interaction with a more spatially extended CSM, which might also be detached from the star.
We present a Hubble diagram of type II supernovae using corrected magnitudes derived only from photometry, with no input of spectral information. We use a data set from the Carnegie Supernovae Project I (CSP) for which optical and near-infrared light-curves were obtained. The apparent magnitude is corrected by two observables, one corresponding to the slope of the plateau in the $V$ band and the second a colour term. We obtain a dispersion of 0.44 mag using a combination of the $(V-i)$ colour and the $r$ band and we are able to reduce the dispersion to 0.39 mag using our golden sample. A compa…
We study a sample of 23 Type II Plateau supernovae (SNe II-P), all observed with the same set of instruments. Analysis of their photometric evolution confirms that their typical plateau duration is 100 days with little scatter, showing a tendency to get shorter for more energetic SNe. The rise time from explosion to plateau does not seem to correlate with luminosity. We analyze their spectra, measuring typical ejecta velocities, and confirm that they follow a well behaved power-law decline. We find indications of high-velocity material in the spectra of six of our SNe. We test different dust e…
We present survey results obtained from the UBVRI optical photometric follow-up of 19 bright core-collapse SNe during 2002-2012 using 1-m class optical telescopes operated by the Aryabhatta Research Institute of Observational Science (acronym ARIES), Nainital India. This homogeneous set of data have been used to study behavior of optical light/color curve, and to gain insight into object-to-object peculiarity. We derive integrated luminosities for types IIP, Ibc and luminous SNe. Two peculiar type IIP events having photometric properties similar to normal IIP and spectroscopic properties simil…
Using radiation-hydrodynamics and radiative-transfer simulations, we explore the origin of the spectral diversity of interacting supernovae (SNe) of type IIn. We revisit SN1994W and investigate the dynamical configurations that can give rise to spectra with narrow lines at all times. We find that a standard ~10Msun 10^51erg SN ejecta ramming into a 0.4Msun dense CSM is inadequate for SN1994W, as it leads to the appearance of broad lines at late times. This structure, however, generates spectra that exhibit the key morphological changes seen in SN1998S. For SN1994W, we consider a completely dif…
CCD BVRI photometry is presented for the type Ic-BL Supernovae 2016coi and 2018ebt. The shape of the light curves for both objects is typical for this class of SNe. A change of brightness decline rate at about 100 days after maximum light is observed for SN 2016coi. The light curves of SN 2018ebt are best matched by those of SN Ic-BL 2002ap. For SN 2018ebt, we derived the dates and magnitudes of maximum light, rates of decline at late stages of evolution and presented evidence for extinction in the host galaxy being negligible.
Hydrogen-rich Type II-Plateau supernovae exhibit correlations between the plateau luminosity $L_{\rm pl}$, the nickel mass $M_{\rm Ni}$, the explosion energy $E_{\rm exp}$, and the ejecta mass $M_{\rm ej}$. Using our global, self-consistent, multi-band model of nearby well-observed supernovae, we find that the covariances of these quantities are strong and that the confidence ellipsoids are oriented in the direction of the correlations, which reduces their significance. By proper treatment of the covariance matrix of the model, we discover a significant intrinsic width to the correlations betw…
We present a spectroscopic analysis of the H-alpha profiles of hydrogen-rich type II supernovae. A total of 52 type II supernovae having well sampled optical light curves and spectral sequences were analyzed. Concentrating on the H-alpha P-Cygni profile we measure its velocity from the FWHM of emission and the ratio of absorption to emission (a/e) at a common epoch at the start of the recombination phase, and search for correlations between these spectral parameters and photometric properties of the V-band light curves. Testing the strength of various correlations we find that a/e appears to b…
Type Ia Supernovae (SNe Ia) form an observationally uniform class of stellar explosions, in that more luminous objects have smaller decline-rates. This one-parameter behavior allows SNe Ia to be calibrated as cosmological `standard candles', and led to the discovery of an accelerating Universe. Recent investigations, however, have revealed that the true nature of SNe Ia is more complicated. Theoretically, it has been suggested that the initial thermonuclear sparks are ignited at an offset from the centre of the white-dwarf (WD) progenitor, possibly as a result of convection before the explosio…
We search for the reasons behind the spectroscopic diversity of hydrogen-poor superluminous supernovae (SLSNe-I) in the pre-maximum phase. Our analysis is a continuation of the paper of \citet{ktr21}, who disclosed two new subtypes of SLSNe-I characterized by the presence/absence of a W-shaped absorption feature in their pre-maximum spectra between 4000 and 5000 Å(called Type~W and Type~15bn, respectively). However, the physical cause of this bimodality is still uncertain. Here we present pre-maximum spectral synthesis of 27 SLSNe-I with special attention to the photospheric temperature ($T_{ …
Photometric classification of supernovae (SNe) is imperative as recent and upcoming optical time-domain surveys, such as the Large Synoptic Survey Telescope (LSST), overwhelm the available resources for spectrosopic follow-up. Here we develop a range of light curve classification pipelines, trained on 518 spectroscopically-classified SNe from the Pan-STARRS1 Medium-Deep Survey (PS1-MDS): 357 Type Ia, 93 Type II, 25 Type IIn, 21 Type Ibc, and 17 Type I SLSNe. We present a new parametric analytical model that can accommodate a broad range of SN light curve morphologies, including those with a pl…
Observational surveys are now able to detect an increasing number of transients, such as core-collapse supernovae (SN) and powerful non-terminal outbursts (SN impostors). Dedicated spectroscopic facilities can follow up these events shortly after detection. Here we investigate the properties of these explosions at early times. We use the radiative transfer code CMFGEN to build an extensive library of spectra simulating the interaction of supernovae and their progenitor's winds/circumstellar medium (CSM). We consider a range of progenitor mass-loss rates (Mdot = 5e-4 to 1e-2 Msun/yr), abundance…
We present extensive spectroscopic observations for one of the closest type Ia supernovae (SNe Ia), SN 2014J discovered in M82, ranging from 10.4 days before to 473.2 days after B-band maximum light. The diffuse interstellar band (DIB) features detected in a high-resolution spectrum allow an estimate of line-of-sight extinction as Av=1.9+/-0.6 mag. Spectroscopically, SN 2014J can be put into the high-velocity (HV) subgroup in Wang's classification with a velocity of Si~II 6355 at maximum light as about 12200 km/s, but has a low velocity gradient (LVG, following Benetti's classification) as 41+…
Near maximum brightness, the spectra of Type Ia supernovae (SNe Ia) present typical absorption features of Silicon II observed at roughly 6100A and 5750A. The 2-D distribution of the pseudo-equivalent widths (pEWs) of these features is a useful tool for classifying SNe Ia spectra (Branch plot). Comparing the observed distribution of SNe on the Branch plot to results of simulated explosion models, we find that 1-D models fail to cover most of the distribution. In contrast, we find that TARDIS radiative transfer simulations of the WD head-on collision models along different lines of sight almost…
Type Ibn supernovae (SNe) are a small yet intriguing class of explosions whose spectra are characterized by low-velocity helium emission lines with little to no evidence for hydrogen. The prevailing theory has been that these are the core-collapse explosions of very massive stars embedded in helium-rich circumstellar material (CSM). We report optical observations of six new SNe Ibn: PTF11rfh, PTF12ldy, iPTF14aki, iPTF15ul, SN 2015G, and iPTF15akq. This brings the sample size of such objects in the literature to 22. We also report new data, including a near-infrared spectrum, on the Type Ibn SN…
Rapid variability before and near the maximum brightness of supernovae has the potential to provide a better understanding of nearly every aspect of supernovae, from the physics of the explosion up to their progenitors and the circumstellar environment. Thanks to modern time-domain optical surveys, which are discovering supernovae in the early stage of their evolution, we have the unique opportunity to capture their intraday behavior before maximum. We present high-cadence photometric monitoring (on the order of seconds-minutes) of the optical light curves of three Type Ia and two Type II SNe …
Ultraviolet (UV) observations of Type Ia supernovae (SNe Ia) probe the outermost layers of the explosion, and UV spectra of SNe Ia are expected to be extremely sensitive to differences in progenitor composition and the details of the explosion. Here we present the first study of a sample of high signal-to-noise ratio SN Ia spectra that extend blueward of 2900 A. We focus on spectra taken within 5 days of maximum brightness. Our sample of ten SNe Ia spans the majority of the parameter space of SN Ia optical diversity. We find that SNe Ia have significantly more diversity in the UV than in the o…
SNe II show great photometric and spectroscopic diversity which is attributed to the varied physical characteristics of their progenitor and explosion properties. In this study, the third of a series of papers where we analyse a sample of SNe II observed by the Carnegie Supernova Project-I, we present correlations between their observed and physical properties. Our analysis shows that explosion energy is the physical property that correlates with the highest number of parameters. We recover previously suggested relationships between the hydrogen-rich envelope mass and the plateau duration, and…
We present a densely-sampled, homogeneous set of light curves of 64 low redshift (z < 0.05) stripped-envelope supernovae (SN of type IIb, Ib, Ic and Ic-bl). These data were obtained between 2001 and 2009 at the Fred L. Whipple Observatory (FLWO) on Mt. Hopkins in Arizona, with the optical FLWO 1.2-m and the near-infrared PAIRITEL 1.3-m telescopes. Our dataset consists of 4543 optical photometric measurements on 61 SN, including a combination of UBVRI, UBVr'i', and u'BVr'i', and 2142 JHKs near-infrared measurements on 25 SN. This sample constitutes the most extensive multi-color data set of str…
WFST Supernovae in the First Year: I. Statistical Study of 16 Early-phase Type Ia Supernovae from the Pilot Survey
University of Science and Technology of China（中国科学技术大学）；National Astronomical Observatory of Japan（日本国立天文台）；Kyoto University（京都大学）；University of Turku（图尔库大学）
Type Ib supernovae are bluer than Type Ic supernovae
Max Planck Institute for Astrophysics（马普天体物理研究所）；European Southern Observatory（欧洲南方天文台）；Technische Universität München（慕尼黑工业大学）；Seoul National University（首尔大学）；Tel Aviv University（特拉维夫大学）；Michigan State University（密歇根州立大学）
We present photometry and spectroscopy of SN2013fs and SN2013fr in the first 100 days post-explosion. Both objects showed transient, relatively narrow H$α$ emission lines characteristic of SNeIIn, but later resembled normal SNeII-P or SNeII-L, indicative of fleeting interaction with circumstellar material (CSM). SN2013fs was discovered within 8hr of explosion. Its light curve exhibits a plateau, with spectra revealing strong CSM interaction at early times. It is a less luminous version of the transitional SNIIn PTF11iqb, further demonstrating a continuum of CSM interaction intensity between SN…
We present results of a supernova light-curve population synthesis, predicting the range of possible supernova lightcurves arising from a population of progenitor stars that include interacting binary systems. We show that the known diversity of supernova lightcurves can be interpreted as arising from binary interactions. Given detailed models of the progenitor stars, we are able to the determine what parameters within these stars determine the shape of their supernova lightcurve. The primary factors are the mass of supernova ejecta and the mass of hydrogen in the final progenitor. We find tha…
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…
The effect of metallicity on the observed light of Type Ia supernovae (SNe Ia) could lead to systematic errors as the absolute magnitudes of local and distant SNe Ia are compared to measure luminosity distances and determine cosmological parameters. The UV light may be especially sensitive to metallicity, though different modeling methods disagree as to the magnitude, wavelength dependence, and even the sign of the effect. The outer density structure, ^56 Ni, and to a lesser degree asphericity, also impact the UV. We compute synthetic photometry of various metallicity-dependent models and comp…
We present $81$ near-infrared (NIR) spectra of $30$ Type II supernovae (SNe II) from the Carnegie Supernova Project-II (CSP-II), the largest such dataset published to date. We identify a number of NIR features and characterize their evolution over time. The NIR spectroscopic properties of SNe II fall into two distinct groups. This classification is first based on the strength of the He I $\lambda1.083\,μ$m absorption during the plateau phase; SNe II are either significantly above (spectroscopically strong) or below $50$ angstroms (spectroscopically weak) in pseudo equivalent width. However bet…
The existence of multiple subclasses of type Ia supernovae (SNeIa) has been the subject of great debate in the last decade. One major challenge inevitably met when trying to infer the existence of one or more subclasses is the time consuming, and subjective, process of subclass definition. In this work, we show how machine learning tools facilitate identification of subtypes of SNeIa through the establishment of a hierarchical group structure in the continuous space of spectral diversity formed by these objects. Using Deep Learning, we were capable of performing such identification in a 4 dime…
We present a new self-consistent and versatile method that derives photospheric radius and temperature variations of Type II-Plateau supernovae based on their expansion velocities and photometric measurements. We apply the method to a sample of 26 well-observed, nearby supernovae with published light curves and velocities. We simultaneously fit ~230 velocity and ~6800 magnitude measurements distributed over 21 photometric passbands spanning wavelengths from 0.19 to 2.2 microns. The light curve differences among the Type II-Plateau supernovae are well-modeled by assuming different rates of phot…
The power of binaries on stripped-envelope supernovae across metallicity: uniform progenitor parameter space and persistently low ejecta masses, but subtype diversity
Over its lifespan, the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will monitor millions of supernovae (SNe) from explosion to oblivion, yielding an unprecedented ugrizy photometric dataset on their late-time evolution. Here, we show that the photometric evolution of Type Ibc SNe can be used to constrain numerous properties of their ejecta, without the need for expensive spectroscopic observations. Using radiative-transfer simulations for explosions of He-star progenitors of different initial masses, we show that the g-band filter follows primarily the strength of the FeII…
Time-domain astronomy is entering a new era as wide-field surveys with higher cadences allow for more discoveries than ever before. The field has seen an increased use of machine learning and deep learning for automated classification of transients into established taxonomies. Training such classifiers requires a large enough and representative training set, which is not guaranteed for new future surveys such as the Vera Rubin Observatory, especially at the beginning of operations. We present the use of Gaussian processes to create a uniform representation of supernova light curves from multip…
In the ultraviolet (UV), Type Ia supernovae (SNe Ia) show a much larger diversity in their properties than in the optical. Using a stationary Monte-Carlo radiative transfer code, a grid of spectra at maximum light was created varying bolometric luminosity and the amount of metals in the outer layers of the SN ejecta. This model grid is then compared to a sample of high-redshift SNe Ia in order to test whether the observed diversities can be explained by luminosity and metallicity changes alone. The dispersion in broadband UV flux and colours at approximately constant optical spectrum can be re…
Investigating interstellar (IS) dust properties in external galaxies is important not only to infer the intrinsic properties of astronomical objects but also to understand the star/planet formation in the galaxies. From the non-Milky-Way-like extinction and interstellar polarization (ISP) observed in reddened Type Ia supernovae (SNe), it has been suggested that their host galaxies contain dust grains whose properties are substantially different from the Milky-Way (MW) dust. It is important to investigate the universality of such non-MW-like dust in the universe. Here we report spectropolarimet…
Using our new general-relativistic, radiation hydrodynamics, Lagrangian code, we computed a rather extended grid of hydrogen-rich core-collapse supernova (CC-SN) models and explored the potentials of their "standardization" as distance indicators. We discuss the properties of some calibrations previously reported in the literature and present new correlations based on the behavior of the light curve, that can be employed for calibrating hydrogen-rich CC-SNe using only photometric data.
We present an investigation of the optical spectra of 264 low-redshift (z < 0.2) Type Ia supernovae (SNe Ia) discovered by the Palomar Transient Factory, an untargeted transient survey. We focus on velocity and pseudo-equivalent width measurements of the Si II 4130, 5972, and 6355 A lines, as well those of the Ca II near-infrared (NIR) triplet, up to +5 days relative to the SN B-band maximum light. We find that a high-velocity component of the Ca II NIR triplet is needed to explain the spectrum in ~95 per cent of SNe Ia observed before -5 days, decreasing to ~80 per cent at maximum. The averag…
We assemble a sample of 24 hydrogen-poor super-luminous supernovae (SLSNe). Parameterizing the light curve shape through rise and decline timescales shows that the two are highly correlated. Magnetar-powered models can reproduce the correlation, with the diversity in rise and decline rates driven by the diffusion timescale. Circumstellar interaction models can exhibit a similar rise-decline relation, but only for a narrow range of densities, which may be problematic for these models. We find that SLSNe are approximately 3.5 magnitudes brighter and have light curves 3 times broader than SNe Ibc…
It is now firmly established that at a significant fraction of hydrogen-rich type II supernovae (SNe II) arise from red supergiant progenitors. However, a large diversity of SN properties exist, and it is presently unclear how this can be understood in terms of progenitor differences and pre-SN stellar evolution. In this contribution, I present the diversity of SN II V-band light-curves for a large sample of SNe II, and compare these to photometry of SNe II which have progenitor mass constraints from pre-explosion imaging.
This paper investigates on the possible systematic difference of Supernovae Ia (SN Ia) properties related to the age and masses of the progenitors that could introduce a systematic bias between low and high redshift SN Ia's. The relation between the main features of the distribution of the delay times (DTD) and the masses of the progenitors is illustrated for the single (SD) and double degenerate (DD) models. Mixed models, which assume contributions from both the SD and DD channels, are also presented and tested versus the observed correlations between the SN Ia rates and the parent galaxy pro…
The LaSilla/QUEST Variability Survey (LSQ) and the Carnegie Supernova Project (CSP II) are collaborating to discover and obtain photometric light curves for a large sample of low redshift (z < 0.1) Type Ia supernovae. The supernovae are discovered in the LSQ survey using the 1 m ESO Schmidt telescope at the La Silla Observatory with the 10 square degree QUEST camera. The follow-up photometric observations are carried out using the 1 m Swope telescope and the 2.5 m du Pont telescopes at the Las Campanas Observatory. This paper describes the survey, discusses the methods of analyzing the data an…
We present the first detailed chemical abundance study of the ultra-faint dwarf galaxy Tucana II based on high-resolution Magellan/MIKE spectra of four red giant stars. The metallicity of these stars ranges from [Fe/H] = -3.2 to -2.6, and all stars are low in neutron-capture abundances ([Sr/Fe] and [Ba/Fe] < -1). However, a number of anomalous chemical signatures are present. Three stars are carbon-enhanced, including the most metal-rich star. This star ([Fe/H]=-2.6) shows [Na,$α$,Sc/Fe] < 0, suggesting an extended star formation history with contributions from AGB stars and Type Ia supernovae…
Type II-plateau supernovae (SNe IIP) are the results of the explosions of red supergiants and are the most common subclass of core-collapse supernovae. Past observations have shown that the outer layers of the ejecta of SNe IIP are largely spherical, but the degree of asphericity increases toward the core. We present evidence for high degrees of asphericity in the inner cores of three recent SNe IIP (SNe 2006my, 2006ov, and 2007aa), as revealed by late-time optical spectropolarimetry. The three objects were all selected to have very low interstellar polarization (ISP), which minimizes the unce…
We study a sample of 16 Type Ia supernovae (SNe Ia) having both spectroscopic and photometric observations within 2 $-$ 3 days after the first light. The early $B-V$ colors of such a sample tends to show a continuous distribution. For objects with normal ejecta velocity (NV), the C~II $λ$6580 feature is always visible in the early spectra while it is absent or very weak in the high-velocity (HV) counterpart. Moreover, the velocities of the detached high-velocity features (HVFs) of Ca~II NIR triplet (CaIR3) above the photosphere are found to be much higher in HV objects than in NV objects, with…
