Direct evidence of two-component ejecta in supernova 2016gkg from nebular spectroscopy
Hanindyo Kuncarayakti, Gaston Folatelli, Keiichi Maeda, Luc Dessart, Anders Jerkstrand, Joseph P. Anderson, Kentaro Aoki, Melina C. Bersten, Lucia Ferrari, Llui… 展开作者
Hanindyo Kuncarayakti, Gaston Folatelli, Keiichi Maeda, Luc Dessart, Anders Jerkstrand, Joseph P. Anderson, Kentaro Aoki, Melina C. Bersten, Lucia Ferrari, Lluis Galbany, Federico Garcia, Claudia P. Gutierrez, Takashi Hattori, Koji S. Kawabata, Timo Kravtsov, Joseph D. Lyman, Seppo Mattila, Felipe Olivares E., Sebastian F. Sanchez, Schuyler D. Van Dyk
Spectral observations of the type-IIb supernova (SN) 2016gkg at 300-800 days are reported. The spectra show nebular characteristics, revealing emission from the progenitor star's metal-rich core and providing clues to the kinematics and physical conditions of the explosion. The nebular spectra are dominated by emission lines of [O I] $λ\lambda6300, 6364$ and [Ca II] $λ\lambda7292, 7324$. Other notable, albeit weaker, emission lines include Mg I] $\lambda4571$, [Fe II] $\lambda7155$, O I $\lambda7774$, Ca II triplet, and a broad, boxy feature at the location of H$α$. Unlike in other stripped-envelope SNe, the [O I] doublet is clearly resolved due to the presence of strong narrow components. The doublet shows an unprecedented emission line profile consisting of at least three components for each [O I]$\lambda6300, 6364$ line: a broad component (width $\sim2000$ km s$^{-1}$), and a pair of narrow blue and red components (width $\sim300$ km s$^{-1}$) mirrored against the rest velocity. The narrow component appears also in other lines, and is conspicuous in [O I]. This indicates the presence of multiple distinct kinematic components of material at low and high velocities. The low-velocity components are likely to be produced by a dense, slow-moving emitting region near the center, while the broad components are emitted over a larger volume. These observations suggest an asymmetric explosion, supporting the idea of two-component ejecta that influence the resulting late-time spectra and light curves. SN 2016gkg thus presents striking evidence for significant asymmetry in a standard-energy SN explosion. The presence of material at low velocity, which is not predicted in 1D simulations, emphasizes the importance of multi-dimensional explosion modeling of SNe.
V906 Carinae was one of the best observed novae of recent times. It was a prolific dust producer and harboured shocks in the early evolving ejecta outflow. Here, we take a close look at the consequences of these early interactions through study of high-resolution UVES spectroscopy of the nebular stage and extrapolate backwards to investigate how the final structure may have formed. A study of ejecta geometry and shaping history of the structure of the shell is undertaken following a spectral line SHAPE model fit. A search for spectral tracers of shocks in the nova ejecta is undertaken and an a…
When supernovae enter the nebular phase after a few months, they reveal spectral fingerprints of their deep interiors, glowing by radioactivity produced in the explosion. We are given a unique opportunity to see what an exploded star looks like inside. The line profiles and luminosities encode information about physical conditions, explosive and hydrostatic nucleosynthesis, and ejecta morphology, which link to the progenitor properties and the explosion mechanism. Here, the fundamental properties of spectral formation of supernovae in the nebular phase are reviewed. The formalism between eject…
In this study, we present one-dimensional, non-local-thermodynamic-equilibrium, radiative transfer simulations (using CMFGEN) in which we introduce micro-clumping at nebular times into two Type Ia supernova ejecta models. We use one sub-Chandrasekhar (sub-M$_{\rm Ch}$) ejecta with 1.02 M$_\odot$ and one M$_{\rm Ch}$ ejecta model with 1.40 M$_\odot$. We introduce clumping factors $f=$0.33,0.25, and 0.10 which are constant throughout the ejecta and compared to the unclumped $f=1.0$ case. We find that clumping is a natural mechanism to reduce the ionization of the ejecta, reducing emission from […
The classic single-degenerate model for the progenitors of Type Ia Supernova (SN Ia) predicts that the supernova ejecta should be enriched with solar-like abundance material stripped from the companion star. Spectroscopic observations of normal SNe Ia at late times, however, have not resulted in definite detection of hydrogen. In this Letter, we study line formation in SNe Ia at nebular times using non-LTE spectral modeling. We present, for the first time, multidimensional radiative transfer calculations of SNe Ia with stripped material mixed in the ejecta core, based on hydrodynamical simulat…
Optical and near-infrared nebular-phase spectroscopy of SN 2024ggi: constraints on the structure of the inner ejecta, progenitor mass, and dust
Millennium Institute of Astrophysics MAS（天体物理学千年研究所）；Gemini Observatory, NSF's National Optical-Infrared Astronomy Research Laboratory（Gemini 天文台，美国国家光学红外天文研究实验室）
Nova Cen 2013 (V1369 Cen) is the fourth bright nova observed panchromatically through high resolution UV+optical multi epoch spectroscopy. It is also the nova with the richest set of spectra (both in terms of data quality and number of epochs) thanks to its exceptional brightness. Here, we use the late nebular spectra taken between day ~250 and day ~837 after outburst to derive the physical, geometrical and kinematical properties of the nova. We compare the results with those determined for the other panchromatic studies in this series: T Pyx, V339 Del (nova Del 2013), and V959 Mon (nova Mon 2…
Supernova (SN) explosions, through the metals they release, play a pivotal role in the chemical evolution of the Universe and the origin of life. Nebular phase spectroscopy constrains such metal yields, for example through forbidden line emission associated with OI, CaII, FeII, or FeIII. Fluid instabilities during the explosion produce a complex 3D ejecta structure, with considerable macroscopic, but no microscopic, mixing of elements. This structure sets a formidable challenge for detailed nonlocal thermodynamic equilibrium radiative transfer modeling, which is generally limited to 1D in grid…
Nebular phase spectra of core-collapse supernovae (SNe) provide critical and unique information on the progenitor massive star and its explosion. We present a set of 1-D steady-state non-local thermodynamic equilibrium radiative transfer calculations of type II SNe at 300d after explosion. Guided by results for a large set of stellar evolution simulations, we craft ejecta models for type II SNe from the explosion of a 12, 15, 20, and 25Msun star. The ejecta density structure and kinetic energy, the 56Ni mass, and the level of chemical mixing are parametrized. Our model spectra are sensitive to…
SN2023ixf: ultraviolet-to-infrared radiative-transfer modeling of the nebular-phase evolution until 1000 days
Institut d’Astrophysique de Paris, CNRS-Sorbonne Université（巴黎天体物理研究所，法国国家科学研究中心-索邦大学）；French-Chilean Laboratory for Astronomy, IRL 3386, CNRS and Instituto de Astrofísica, Pontificia Universidad Católica de Chile（中法天文实验室，法国国家科学研究中心和智利天主教Pontificia大学天体物理研究所）；Cahill Center for Astrophysics, California Institute of Technology（加州理工学院卡希尔天体物理学中心）；Steward Observatory, University of Arizona（亚利桑那大学斯图尔德天文台）；Department of Astronomy, University of California, Berkeley（加州大学伯克利分校天文学系）；Institute of Space Sciences (ICE, CSIC)（空间科学研究所（CSIC））；Institut d’Estudis Espacials de Catalunya (IEEC)（加泰罗尼亚空间研究研究所）；Department of Physics and Astronomy, University of California, Davis（加州大学戴维斯分校物理与天文学系）
We report distinctly double-peakedH-alpha and H-beta emission lines in the late-time, nebular-phase spectra (>~200 d) of the otherwise normal at early phases (<~ 100 d) Type IIP supernova ASASSN-16at (SN 2016X). Such distinctly double-peaked nebular Balmer lines have never been observed for a Type II SN. The nebular-phase Balmer emission is driven by the radioactive Co56 decay, so the observed line-profile bifurcation suggests a strong bipolarity in the Ni56 distribution or in the line-forming region of the inner ejecta. The strongly bifurcated blue- and red-shifted peaks are separated by ~3x1…
We present deep, nebular-phase spectropolarimetry of the Type II-P/L SN 2013ej, obtained 167 days after explosion with the European Southern Observatory's Very Large Telescope. The polarized flux spectrum appears as a nearly perfect (92% correlation), redshifted (by ~4,000 km/sec) replica of the total flux spectrum. Such a striking correspondence has never been observed before in nebular-phase supernova spectropolarimetry, although data capable of revealing it have heretofore been only rarely obtained. Through comparison with 2D polarized radiative transfer simulations of stellar explosions, w…
Numerous superluminous supernovae (SLSNe) of Type Ic have been discovered and monitored in the last decade. The favored mechanism at their origin is a sustained power injection from a magnetar. This study presents non-local thermodynamic equilibrium time-dependent radiative transfer simulations of various single carbon-rich Wolf-Rayet star explosions influenced by magnetars of diverse properties and covering from a few days to one or two years after explosion. Nonthermal processes are treated; the magnetar-power deposition profile is prescribed; dynamical effects are ignored. In this context, …
We present near infrared (NIR) spectroscopy of the nearby supernova 2014J obtained $\sim$450 d after explosion. We detect the [Ni II] 1.939 $μ$m line in the spectra indicating the presence of stable $^{58}$Ni in the ejecta. The stable nickel is not centrally concentrated but rather distributed as the iron. The spectra are dominated by forbidden [Fe II] and [Co II] lines. We use lines, in the NIR spectra, arising from the same upper energy levels to place constraints on the extinction from host galaxy dust. We find that that our data are in agreement with the high $A_V$ and low $R_V$ found in e…
Following our recent work on Type II supernovae (SNe), we present a set of 1D nonlocal thermodynamic equilibrium radiative transfer calculations for nebular-phase Type Ibc SNe starting from state-of-the-art explosion models with detailed nucleosynthesis. Our grid of progenitor models is derived from He stars that were subsequently evolved under the influence of wind mass loss. These He stars, which most likely form through binary mass exchange, synthesize less oxygen than their single-star counterparts with the same zero-age main sequence (ZAMS) mass. This reduction is greater in He-star model…
Key information about the progenitor system and the explosion mechanism of Type Ia supernovae (SNe~Ia) can be obtained from early observations, within a few days from explosion. iPTF16abc was discovered as a young SN~Ia with excellent early time data. Here, we present photometry and spectroscopy of the SN in the nebular phase. A comparison of the early time data with a sample of SNe~Ia shows distinct features, differing from normal SNe~Ia at early phases but similar to normal SNe~Ia at a few weeks after maximum light (i.e. the transitional phase) and well into the nebular phase. The transparen…
The spectroscopic evolution of the recurrent nova T Pyxidis during its 2011 outburst. II.The optically thin phase and the structure of the ejecta in recurrent novae
We study the spectroscopic evolution of superluminous supernovae (SLSNe) later than 100 days after maximum light. We present new data for Gaia16apd and SN2017egm, and analyse these with a larger sample comprising 41 spectra of 12 events. The spectra become nebular within 2-4 $e$-folding times after light curve peak, with the rate of spectroscopic evolution correlated to the light curve timescale. Emission lines are identified with well-known transitions of oxygen, calcium, magnesium, sodium and iron. SLSNe are differentiated from other Type Ic SNe by a prominent O I $λ$7774 line and higher-ion…
We analyze a KeckI/LRIS nebular spectrum taken 268 days after $B$-band maximum of ASASSN-18bt (SN~2018oh), a Type Ia supernova (SN Ia) observed by {\it K2} at the time of explosion. ASASSN-18bt exhibited a two-component rise to peak brightness, possibly the signature of an interaction between the SN ejecta and a large ($\gtrsim 20~R_\odot$) nearby, non-degenerate companion. We search for emission signatures of stripped material from a non-degenerate companion in the nebular spectrum and find no evidence for any unbound material. We place an upper limit of $< 0.006~M_\odot$ on the amount of str…
We present nebular phase optical and near-infrared spectroscopy of the Type Ia supernova (SN) 2017cbv. The early light curves of SN~2017cbv showed a prominent blue bump in the $U$, $B$ and $g$ bands lasting for $\sim$5 d. One interpretation of the early light curve was that the excess blue light was due to shocking of the SN ejecta against a nondegenerate companion star -- a signature of the single degenerate scenario. If this is the correct interpretation, the interaction between the SN ejecta and the companion star could result in significant H$α$ (or helium) emission at late times, possibly…
This work examines the relationships between the properties (flux ratios, full width at half-maximum velocities) of the [O I] $λλ$6300, 6364, [Ca II] $λλ$7291, 7323, and the Ca II near-infrared triplet, emission lines of a large sample of core-collapse supernovae (SNe) and Ca-rich transients (509 spectra of 86 transients, of which 10 transients are Ca-rich events). Line-flux ratios as a function of time were investigated with differences identified between the transient classes, in particular the Type II SNe were found to have distinct line-flux ratios compared to stripped-envelope (SE) SNe. N…
Aquila X-1 is a prototypical neutron star low mass X-ray binary and one of the most studied X-ray transients. We present optical spectroscopy obtained with the Gran Telescopio Canarias (10.4 m) during the 2016 outburst, the brightest in recent times, which showed a standard evolution with hard and soft accretion states. Our data set includes a dense coverage of the brightest phases of the event, as well as the decay towards quiescence. We searched for optical winds by studying the profiles and evolution of the main emission lines and found no indisputable wind signatures, such as P-Cyg profile…
Non-LTE time-dependent spectroscopic modelling of type II-plateau supernovae from the photospheric to the nebular phase: case study for 15 and 25Msun progenitor stars
As the closest Type Ia supernova in decades, SN 2014J provides a unique opportunity for detailed investigation into observational signatures of the progenitor system and explosion mechanism in addition to burning product distribution. We present a late-time near-infrared spectral series from Gemini-N at $307-466$ days after the explosion. Following the $H$-band evolution probes the distribution of radioactive iron group elements, the extent of mixing, and presence of magnetic fields in the expanding ejecta. Comparing the isolated $1.6440$ $μ$m [Fe II] emission line with synthetic models shows …
We present multi-band ultraviolet, optical, and near-infrared photometry, along with visual-wavelength spectroscopy, of supernova (SN) 2014G in the nearby galaxy NGC 3448 (25 Mpc). The early-phase spectra show strong emission lines of the high ionisation species He II/N IV/C IV during the first 2-3 d after explosion, traces of a metal-rich CSM probably due to pre-explosion mass loss events. These disappear by day 9 and the spectral evolution then continues matching that of normal Type II SNe. The post-maximum light curve declines at a rate typical of Type II-L class. The extensive photometric …
Using 1-D non-Local-Thermodynamic-Equilibrium time-dependent radiative-transfer simulations, we study the ejecta properties required to match the early and late-time photometric and spectroscopic properties of supernovae (SNe) associated with long-duration gamma-ray bursts (LGRBs). To match the short rise time, narrow light curve peak, and extremely broad spectral lines of SN1998bw requires a model with <3Msun ejecta but a high explosion energy of a few 1e52erg and 0.5Msun of Ni56. However the relatively high luminosity, the presence of narrow spectral lines of intermediate mass elements, and …
SN 2017ein is a narrow-lined Type Ic SN that was found to share a location with a point-like source in the face on spiral galaxy NGC 3938 in pre-supernova images, making SN 2017ein the first credible detection of a Type Ic progenitor. Results in the literature suggest this point-like source is likely a massive progenitor of 60-80 M$_{\odot}$, depending on if the source is a binary, a single star, or a compact cluster. Using new photometric and spectral data collected for 200 days, including several nebular spectra, we generate a consistent model covering the photospheric and nebular phase usin…
We present nebular-phase spectra of the Type Ia supernova (SN Ia) 2016brx, a member of the 1991bg-like subclass that lies at the faint end of the SN Ia luminosity function. Nebular spectra are available for only three other 1991bg-like SNe, and their Co line centers are all within <~ 500 km/s of each other. In contrast, the nebular Co line center of SN 2016brx is blue-shifted by >1500 km/s compared to them and by ~1200 km/s compared to the rest frame. This is a significant shift relative to the narrow nebular line velocity dispersion of <~ 2000 km/s of these SNe. The large range of nebular lin…
The enigmatic type IIP SN 2016X demonstrates the unprecedented asphericity in the nebular H-alpha line profile, the absence of nebular [O I] emission, and the unusual occultation effect due to the internal dust. The hydrodynamic modelling of the bolometric light curve and expansion velocities suggests that the event is an outcome of the massive star explosion that ejected 28 Msun with the kinetic energy of 1.7x10^51 erg and 0.03 Msun of radioactive Ni-56. We recover the bipolar distribution of Ni-56 from the H-alpha profile via the simulation of the emissivity produced by non-spherical Ni-56 e…
We present the first images of the nebula around eta Carinae obtained with HST/WFC3, including a UV image in the F280N filter that traces MgII emission, plus contemporaneous imaging in the F336W, F658N, and F126N filters that trace near-UV continuum, [NII], and [FeII], respectively. The F336W and F658N images are consistent with previous images in these filters, and F126N shows that for the most part, [FeII] 12567 traces clumpy shocked gas seen in [NII]. The F280N image, however, reveals MgII emission from structures that have not been seen in any previous line or continuum images of eta Carin…
We present nebular-phase imaging and spectroscopy for the hydrogen-poor superluminous supernova SN 2015bn, at redshift z=0.1136, spanning +250-400 d after maximum light. The light curve exhibits a steepening in the decline rate from 1.4 mag/(100 d) to 1.7 mag/(100 d), suggestive of a significant decrease in the opacity. This change is accompanied by a transition from a blue continuum superposed with photospheric absorption lines to a nebular spectrum dominated by emission lines of oxygen, calcium and magnesium. There are no obvious signatures of circumstellar interaction or large nickel mass. …
As a candidate 'super-Chandrasekhar' or 09dc-like Type Ia supernova (SN Ia), SN 2012dn shares many characteristics with other members of this remarkable class of objects but lacks their extraordinary luminosity. Here, we present and discuss the most comprehensive optical data set of this SN to date, comprised of a densely sampled series of early-time spectra obtained within the Nearby Supernova Factory project, plus photometry and spectroscopy obtained at the VLT about 1 yr after the explosion. The light curves, colour curves, spectral time series and ejecta velocities of SN 2012dn are compare…
We present SN 2020jfo, a Type IIP supernova in the nearby galaxy M61. Optical light curves from the Zwicky Transient Facility, complemented with data from Swift and near-IR photometry are presented. The 350-day duration bolometric light curve exhibits a relatively short (~ 65 days) plateau. This implies a moderate ejecta mass (~ 5 Msun). A series of spectroscopy is presented, including spectropolarimetric observations. The nebular spectra are dominated by Halpha but also reveal emission lines from oxygen and calcium. Comparisons to synthetic nebular spectra indicate an initial progenitor mass …
