arXiv subjects

Sergei I. Blinnikov

Publications and source records attributed to Sergei I. Blinnikov.

At least 19 recordsLinked to original sources

arXiv2026

Properties of the circumstellar matter around the pair-instability supernova candidate SN 2018ibb revealed by its light curve

SN 2018ibb is one of the best pair-instability supernova (PISN) candidates identified to date. It, however, showed unexpected blue flux excess in late-phase spectra, likely originating from the interaction between supernova (SN) ejecta and dense circumstellar matter (CSM). We develop synthetic light-curve models of PISNe interacting with dense CSM and estimate the CSM properties of SN 2018ibb by comparing the synthetic and observed light curves. We found that the bolometric luminosity evolution of SN 2018ibb from 150 d after the peak can be well reproduced by the interaction with the CSM formed by a mass-loss rate of 0.01(v_CSM/1,000 km/s) Msun/yr, where v_CSM is the CSM velocity. The observed luminosity break at around 300 d from the peak indicates that the CSM interaction ended at this time and the dense CSM radius was 8.5e16 cm. The CSM radius then implies that the mass loss of the progenitor was enhanced for 28/(v_CSM/1,000 km/s) yr before explosion. We conclude that PISN progenitors may experience short-term mass-loss enhancement within decades before explosion, similar to what is often observed in progenitors of core-collapse SNe.

astro-ph.HE↗

arXiv2026

Superlinear Type II Superluminous Supernovae 2017fck and 2019cmv: A Possible Origin from Interacting Thermonuclear Supernovae

Additional power sources to traditional supernovae (SNe) are necessary to account for the extreme luminosities of superluminous SNe (SLSNe). A main power source for hydrogen-rich SLSNe (SLSNe-II) is thought to be circumstellar material (CSM) interaction. However, the nature of underlying SNe and their progenitor systems remain elusive as they are hidden below strong CSM signatures. Here, we present optical photometry and spectroscopy of SLSNe-II 2017fck and 2019cmv. They are characterized by post-maximum "superlinear" light curves which we also identify in a sample of Type Ia SNe interacting with CSM (SNe Ia-CSM), along with their light-curve correlations and spectral similarities. Thus, we compute a numerical light-curve model grid of SNe Ia-CSM with various SN Ia subtypes and CSM distributions. Our model grid spans the observed parameter space of SNe Ia-CSM in terms of their rise times, peak luminosities, and decline rates with a wide CSM mass range of $\sim2-11$ M$_\odot$, indicating the diversity in their progenitor systems. For SNe 2017fck and 2019cmv, we infer high CSM masses of $\sim11$ and $6$ M$_\odot$, respectively, which might be produced during the common envelope evolution of a white dwarf and massive ($\geq8$ M$_\odot$) or intermediate-mass ($<8$ M$_\odot$) companion. Together with the proposed connection of SLSN-II 2006gy to SNe Ia-CSM, SNe 2017fck and 2019cmv may offer a possible thermonuclear origin for superlinear SLSNe-II with peak optical luminosities up to $10^{44}$ erg s$^{-1}$.

astro-ph.HE↗

arXiv2026

Electron-capture Supernova Candidates from Light Curves: Implications for Their Progenitors and Explosion Properties

Core-collapse supernovae are explosions of massive stars. While most massive stars end as iron-core-collapse supernovae, less massive stars are expected to explode as electron-capture supernovae (ECSNe), defining the low-mass boundary of core-collapse supernovae. ECSNe were proposed $\sim 40$ years ago, and first-principles simulations predict their successful explosions with low energies of $\sim 10^{50}$~erg. Nevertheless, only one convincing candidate, SN~2018zd, has been proposed other than SN~1054, the progenitor of the Crab Nebula. We search for ECSN candidates among Type~II SNe from the literature and a public Zwicky Transient Facility sample, using a color-based diagnostic, selecting ten candidates with blue colors at the middle of the plateau. We classify three as \textit{gold}, for which a spectrum around the middle of the plateau disfavors strong circumstellar-medium interaction that would make the SN bluer, and seven as \textit{silver} without such spectra. Comparing the observed multicolor light curves with radiation-hydrodynamical models, we infer the explosion energies, $(0.4-1.7)\times10^{50}$~erg for the \textit{gold candidates} and $(0.4-2.7)\times10^{50}$~erg including the \textit{silver candidates}, consistent with first-principles predictions and the mass-loss rates, $3\times10^{-3} - 3 \times 10^{-2}~M_{\odot}~{\rm yr}^{-1}$ for the \textit{gold candidates}, which remain similar when the \textit{silver candidates} are included, higher than those expected for the early super-asymptotic-giant-branch phase. The ECSN occurrence ratios among SNe~II are inferred as $3.0^{+10.6}_{-2.9}$ and $15.7^{+17.3}_{-12.7}~\%$ from the \textit{gold} and \textit{silver candidates}, respectively, which we interpret as lower and upper limits. To robustly identify ECSNe and refine this ratio, spectroscopic follow-ups of ECSN candidates around the middle of the plateau are essential.

astro-ph.HE↗

arXiv2025

Analytical approaches for rapid prediction of gravitational waveforms for relativistic binary systems

We present a fast method for obtaining fully analytical approximations for gravitational waveforms produced by merging of neutron stars and/or black holes for the earliest stages of the merger process. The obtained analytical formula is compared with numerical calculations, its accuracy and limits of applicability are evaluated. Our results may be useful not only for the earliest evalution of properties of the nature of binary system in gravitational-wave detectors but also will give early alerts for gamma-ray, optical and neutrino observatories.

astro-ph.HE↗

arXiv2025

Type Ibn supernovae from ultra-stripped supernova progenitors

Ultra-stripped supernovae are core-collapse supernovae from progenitors that lose a significant fraction of mass because of the binary interactions with their compact companion stars. Ultra-stripped supernovae have been connected to fast-evolving faint Type Ib or Ic supernovae. Here, we show that in some cases ultra-stripped supernovae can result in Type Ibn supernovae. Progenitors of ultra-stripped supernovae may trigger violent silicon burning shortly before the core collapse, leading to mass ejection that results in a dense circumstellar matter. By taking an ultra-stripped supernova progenitor that loses 0.2 Msun at 78 days before the core collapse, we compute the light-curve evolution of the ultra-stripped supernova within the dense circumstellar matter. The core collapse results in a supernova explosion with an ejecta mass of 0.06 Msun and an explosion energy of 9e49 erg. Because the dense circumstellar matter is more massive than the supernova ejecta, the ejecta are immediately decelerated and the light curve is powered mainly by the circumstellar interaction. Therefore, this ultra-stripped supernova is likely observed as a Type Ibn supernova. We suggest that some Type Ibn supernovae may originate from ultra-stripped supernova progenitors losing significant mass shortly before their explosion due to violent silicon burning.

astro-ph.HE↗

arXiv2024

A Robust Light-Curve Diagnostic for Electron-Capture Supernovae and Low-Mass Fe-Core-Collapse Supernovae

Core-collapse supernovae (CCSNe) are the terminal explosions of massive stars. While most massive stars explode as iron-core-collapse supernovae (FeCCSNe), slightly less massive stars explode as electron-capture supernovae (ECSNe), shaping the low-mass end of CCSNe. ECSNe was proposed $\sim 40$ years ago and first-principles simulations also predict their successful explosions. Observational identification and investigation of ECSNe are important for the completion of stellar evolution theory. To date, only one promising candidate has been proposed, SN 2018zd, other than the historical progenitor of the Crab Nebula, SN 1054. We present representative synthetic light curves of low-mass FeCCSNe and ECSNe exploding with energies in circumstellar media (CSM) estimated with theoretically or observationally plausible methods. The plateaus of the ECSNe are shorter, brighter, and bluer than those of the FeCCSNe. To investigate the robustness of their intrinsic differences, we adopted various explosion energies and CSM. Although they may have similar bolometric light-curve plateaus, ECSNe are bluer than FeCCSNe in the absence of strong CSM interaction, illustrating that multicolor observations are essential to identify ECSNe. This provides a robust indicator of ECSNe because the bluer plateaus stem from the low-density envelopes of their super-asymptotic-giant-branch progenitors. Furthermore, we propose a distance-independent method to identify ECSNe: $(g-r)_{t_{\rm PT}/2} < 0.008 \times t_{\rm PT} - 0.4$, i.e., blue $g-r$ at the middle of the plateau $(g-r)_{t_{\rm PT}/2}$, where $t_{\rm PT}$ is the transition epoch from plateau to tail. Using this method, we identified SN 2018zd as an ECSN, which we believe to be the first ECSN identified with modern observing techniques.

astro-ph.HE↗

arXiv2023

Synthetic red supergiant explosion model grid for systematic characterization of Type II supernovae

A new model grid containing 228,016 synthetic red supergiant explosions (Type II supernovae) is introduced. Time evolution of spectral energy distributions from 1 A to 50,000 A (100 frequency bins in a log scale) is computed at each time step up to 500 days after explosion in each model. We provide light curves for the filters of the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST), Zwicky Transient Facility (ZTF), Sloan Digital Sky Servey (SDSS), and the Neil Gehrels Swift Observatory, but light curves for any photometric filters can be constructed by convolving any filter response functions to the synthetic spectral energy distributions. We also provide bolometric light curves and photosphere information such as photospheric velocity evolution. The parameter space covered by the model grid is five progenitor masses (10, 12, 14, 16, and 18 Msun at the zero-age main sequence, solar metallicity), ten explosion energies (0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, and 5.0 x 10^51 erg), nine 56Ni masses (0.001, 0.01, 0.02, 0.04, 0.06, 0.08, 0.1, 0.2, and 0.3 Msun), nine mass-loss rates (1e-5.0, 1e-4.5, 1e-4.0, 1e-3.5, 1e-3.0, 1e-2.5, 1e-2.0, 1e-1.5, and 1e-1.0 Msun/yr with a wind velocity of 10 km/s), six circumstellar matter radii (1, 2, 4, 6, 8, and 10 x 10^14 cm), and ten circumstellar structures (beta = 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, and 5.0). 56Ni is assumed to be uniformly mixed up to the half mass of a hydrogen-rich envelope. This model grid can be a base for rapid characterizations of Type II supernovae with sparse photometric sampling expected in LSST through a Bayesian approach, for example. The model grid is available at https://doi.org/10.5061/dryad.pnvx0k6sj.

astro-ph.HE↗

arXiv2023

SN 2018hna: Adding a Piece to the Puzzles of the Explosion of Blue Supergiants

We present extensive optical/ultraviolet observations and modelling analysis for the nearby SN 1987A-like peculiar Type II supernova (SN) 2018hna. Both photometry and spectroscopy covered phases extending to $>$500 days after the explosion, making it one of the best-observed SN II of this subtype. SN 2018hna is obviously bluer than SN 1987A during the photospheric phase, suggesting higher photospheric temperature, which may account for weaker BaII $\mathrmλ$6142 lines in its spectra. Analysis of early-time temperature evolution suggests a radius of $\sim$45 $\mathrm{R_{\odot}}$ for the progenitor of SN 2018hna, consistent with a blue supergiant (BSG). By fitting the bolometric light curve with hydrodynamical models, we find that SN 2018hna has an ejecta mass of $\sim$(13.7--17.7) $\mathrm{M_{\odot}}$, a kinetic energy of $\sim$ (1.0--1.2) $\times 10^{51}$ erg, and a $^{56}$Ni mass of about 0.05 $\mathrm{M_{\odot}}$. Moreover, based on standard stellar evolution and the oxygen mass (0.44--0.73 $\mathrm{M_{\odot}}$) deduced from nebular [OI] lines, the progenitor of SN 2018hna is expected to have an initial main-sequence mass $<$16 $\mathrm{M_{\odot}}$. In principle, such a relatively low-mass star cannot end as a BSG just before core-collapse, except some unique mechanisms are involved, such as rapid rotation, restricted semiconvection, etc. On the other hand, binary scenario may be more favourable, like in the case of SN 1987A. While the much lower oxygen mass inferred for SN~2018hna may imply that its progenitor system also had much lower initial masses than that of SN 1987A.

astro-ph.HE↗

arXiv2022

Light Curves and Event Rates of Axion Instability Supernovae

It was recently proposed that exotic particles can trigger a new stellar instability which is analogous to the e-e+ pair instability if they are produced and reach equilibrium in the stellar plasma. In this study, we construct axion instability supernova (AISN) models caused by the new instability to predict their observational signatures. We focus on heavy axion-like particles (ALPs) with masses of ~400 keV--2 MeV and coupling with photons of g_{ag}~10^{-5} GeV^{-1}. It is found that the 56Ni mass and the explosion energy are significantly increased by ALPs for a fixed stellar mass. As a result, the peak times of the light curves of AISNe occur earlier than those of standard pair-instability supernovae by 10--20 days when the ALP mass is equal to the electron mass. Also, the event rate of AISNe is 1.7--2.6 times higher than that of pair-instability supernovae, depending on the high mass cutoff of the initial mass function.

astro-ph.HE↗

arXiv2022

Variable thermal energy injection from magnetar spin down as a possible cause of stripped-envelope supernova light-curve bumps

Luminosity evolution of some stripped-envelope supernovae such as Type I superluminous supernovae is difficult to be explained by the canonical 56Ni nuclear decay heating. A popular alternative heating source is rapid spin down of strongly-magnetized rapidly-rotating neutron stars (magnetars). Recent observations have indicated that Type I superluminous supernovae often have bumpy light curves with multiple luminosity peaks. The cause of bumpy light curves is unknown. In this study, we investigate the possibility that the light-curve bumps are caused by variations of the thermal energy injection from magnetar spin down. We find that a temporal increase in the thermal energy injection can lead to multiple luminosity peaks. The multiple luminosity peaks caused by the variable thermal energy injection is found to be accompanied by significant increase in photospheric temperature, and photospheric radii are not significantly changed. We show that the bumpy light curves of SN 2015bn and SN 2019stc can be reproduced by temporarily increasing magnetar spin-down energy input by a factor of 2-3 for 5-20 days. However, not all the light-curve bumps are accompanied by the clear photospheric temperature increase as predicted by our synthetic models. In particular, the secondary light-curve bump of SN 2019stc is accompanied by a temporal increase in photospheric radii rather than temperature, which is not seen in our synthetic models. We, therefore, conclude that not all the light-curve bumps observed in luminous supernovae are caused by the variable thermal energy injection from magnetar spin down and some bumps are likely caused by a different mechanism.

astro-ph.HE↗

arXiv2021

Properties of Thorne-Zytkow object explosions

Thorne-Zytkow objects are stars that have a neutron star core with an extended hydrogen-rich envelope. Massive Thorne-Zytkow objects are proposed to explode when the nuclear reactions sustaining their structure are terminated by the exhaustion of the seed elements. In this paper, we investigate the observational properties of the possible Thorne-Zytkow object explosions. We find that Thorne-Zytkow object explosions are observed as long-duration transients lasting for several years. If the accretion disk triggering the explosions does not last for a long time, Thorne-Zytkow object explosions have a luminosity plateau with about 1e39 erg/s lasting for a few years, and then they suddenly become faint. They would be observed as vanished stars after a bright phase lasting for a few years. If the accretion disk is sustained for long time, the Thorne-Zytkow object explosions become as bright as supernovae. They would be observed as supernovae with rise times of several hundred days. We found that their photospheric velocities are 2000 km/s at most, much smaller than those found in supernovae. Supernovae with extremely long rise times such as HSC16aayt and SN 2008iy may be related to the explosions of Thorne-Zytkow objects.

astro-ph.HE↗

arXiv2021

Non-steady state model of global temperature change: Can we keep temperature from rising more than on two degrees?

We propose a non-steady state model of the global temperature change. The model describes Earth's surface temperature dynamics under main climate forcing. The equations were derived from basic physical relationships and detailed assessment of the numeric parameters used in the model. It shows an accurate fit with observed changes in the surface mean annual temperature (MAT) for the past 116 years. Using our model, we analyze the future global temperature change under scenarios of drastic reductions of CO\textsubscript{2}. The presence of non-linear feed-backs in the model indicates on the possibility of exceeding two degrees threshold even under the carbon dioxide drastic reduction scenario. We discuss the risks associated with such warming and evaluate possible benefits of developing CO\textsubscript{2}-absorbing deciduous tree plantations in the boreal zone of Northern Hemisphere.

physics.ao-ph↗

arXiv2021

Optical and spectral observations and hydrodynamic modelling of Type IIb Supernova 2017gpn

In this work we present the photometric and spectroscopic observations of Type IIb Supernova 2017gpn. This supernova was discovered in the error-box of LIGO/Virgo G299232 gravitational-wave event. We obtained the light curves in B and R passbands and modelled them numerically using the one-dimensional radiation hydrocode STELLA. The best-fit model has the following parameters: the pre-SN star mass and the radius are 3.5 Msun and 50 Rsun, respectively; the explosion energy is Eexp = 1.2 * 10^51 erg; the mass of radioactive nickel is M56Ni =0.11 Msun, which is totally mixed through the ejecta, the mass of the hydrogen envelope 0.06 Msun. Moreover, SN 2017gpn is a confirmed SN IIb that is located at the farthest distance from the center of its host galaxy NGC 1343 (i.e. the projected distance is about 21 kpc). This challenges the scenario of the origin of Type IIb Supernovae from massive stars.

astro-ph.HE↗

arXiv2021

Observational properties of a general relativistic instability supernova from a primordial supermassive star

We present the expected observational properties of a general relativistic instability supernova (GRSN) from the 55,500 Msun primordial (Population III) star. Supermassive stars exceeding 1e4 Msun may exist in the early Universe. They are generally considered to collapse through the general relativistic instability to be seed black holes to form supermassive (~ 1e9 Msun) black holes observed as high-redshift quasars. Some of them, however, may explode as GRSNe if the explosive helium burning unbinds the supermassive stars following the collapse triggered by the general relativistic instability. We perform the radiation hydrodynamics simulation of the GRSN starting shortly before the shock breakout. We find that the GRSN is characterized by a long-lasting (550 d) luminous (1.5e44 erg/s) plateau phase with the photospheric temperature of around 5000 K in the rest frame. The plateau phase lasts for decades when it appears at high redshifts and it will likely be observed as a persistent source in the future deep near-infrared imaging surveys. Especially, the near-infrared images reaching 29 AB magnitude that can be obtained by Galaxy and Reionization EXplorer (G-REX) and James Webb Space Telescope (JWST) allow us to identify GRSNe up to z ~ 15. Deeper images enable us to discover GRSNe at even higher redshifts. Having extremely red color, they can be distinguished from other persistent sources such as high-redshift galaxies by using color information. We conclude that the deep near-infrared images are able to constrain the existence of GRSNe from the primordial supermassive stars in the Universe even without the time domain information.

astro-ph.HE↗

arXiv2020

Cosmological acceleration

An overview is given of the current status of the theory and observations of the acceleration of the expansion of the observable part of the Universe. Contents 1. Historical Introduction 2. Friedmann equations and cosmological acceleration 3. Vacuum energy problem 4. Data in favor of cosmological acceleration 5.Data on supernovae and baryon acoustic oscillations 5.1 Cosmography primer: distances in the Universe; 5.2 Photometric distance; 5.3 Cosmic distance ladder; 5.4 Variety of type-Ia supernovae light curves and their usage in cosmography; 5.5 Baryon acoustic oscillations (BAOs); 5.6 BAOs in the correlation function of galaxies; 5.7 Summary of results on supernovae combined with BAOs; 5.8 Systematics and dependence on z; 5.9 Supernovae as primary distance indicators; 5.10 Merging of neutron stars and the standard siren method 6. Dark energy 7. Modified gravity 8.Conclusion 9.Appendices 9.1 Derivation of the Friedmann equations; 9.2 Cosmological parameters; 9.3 Scalar field

astro-ph.CO↗

arXiv2020

Luminous supernovae associated with ultra-long gamma-ray bursts from hydrogen-free progenitors extended by pulsational pair-instability

We show that the luminous supernovae (SNe) associated with ultra-long gamma-ray bursts (GRBs) can be related to the slow cooling from the explosions of hydrogen-free progenitors extended by pulsational pair-instability. In the accompanying paper (Marchant & Moriya 2020), we have shown that some rapidly-rotating hydrogen-free GRB progenitors that experience pulsational pair-instability can keep an extended structure caused by pulsational pair-instability until the core collapse. Such progenitors have large radii exceeding 10 Rsun and they sometimes reach beyond 1000 Rsun at the time of the core collapse. They are, therefore, promising progenitors of ultra-long GRBs. We here perform the light-curve modeling of the explosions of one extended hydrogen-free progenitor with a radius of 1962 Rsun. Thanks to the large progenitor radius, the ejecta experience slow cooling after the shock breakout and they become rapidly evolving (<~ 10 days) luminous (>~ 1e43 erg/s) SNe in optical even without the energy input from the 56Ni nuclear decay when the explosion energy is more than 1e52 erg. The 56Ni decay energy input can affect the light curves after the optical light-curve peak and make the light-curve decay slow when the 56Ni mass is around 1 Msun. They also have fast photospheric velocity above 10,000 km/s and hot photospheric temperature above 10,000 K at around the peak luminosity. We find that the rapid rise and luminous peak found in the optical light curve of SN 2011kl, which is associated with the ultra-long GRB 111209A, can be explained as the cooling phase of the extended progenitor. The ultra-long GRB progenitors proposed in Marchant & Moriya (2020) can explain both the ultra-long GRB duration and the accompanying SN properties. When the GRB jet is off-axis or choked, the luminous SNe could be observed as fast blue optical transients without accompanying GRBs. (abridged)

astro-ph.HE↗

arXiv2020

Systematic investigation of the effect of 56Ni mixing in the early photospheric velocity evolution of stripped-envelope supernovae

Mixing of 56Ni, whose nuclear decay energy is a major luminosity source in stripped-envelope supernovae, is known to affect the observational properties of stripped-envelope supernovae such as light-curve and color evolution. Here we systematically investigate the effect of 56Ni mixing on the photospheric velocity evolution in stripped-envelope supernovae. We show that 56Ni mixing significantly affects the early photospheric velocity evolution. The photospheric velocity, which is often used to constrain the ejecta mass and explosion energy, significantly varies by just changing the degree of 56Ni mixing. In addition, the models with a small degree of 56Ni mixing show a flattening in the early photospheric velocity evolution, while the fully mixed models show a monotonic decrease. The velocity flattening appears in both helium and carbon+oxygen progenitor explosions with a variety of ejecta mass, explosion energy, and 56Ni mass. Some stripped-envelope supernovae with early photospheric velocity information do show such a flattening. We find that Type Ib SN 2007Y, which has early photospheric velocity information, has a signature of a moderate degree of 56Ni mixing in the photospheric velocity evolution and about a half of the ejecta is mixed in it. The immediate spectroscopic follow-up observations of stripped-envelope supernovae shortly after the explosion providing the early photospheric evolution give an important clue to constrain 56Ni mixing in the ejecta.

astro-ph.HE↗

arXiv2019

SN 2018hna: 1987A-like supernova with a signature of shock breakout

High cadence ultraviolet, optical and near-infrared photometric and low-resolution spectroscopic observations of the peculiar Type II supernova (SN) 2018hna are presented. The early phase multiband light curves exhibit the adiabatic cooling envelope emission following the shock breakout up to ~14 days from the explosion. SN~2018hna has a rise time of $\sim$\,88 days in the V-band, similar to SN 1987A. A $\rm^{56}Ni$ mass of ~0.087$\pm$0.004 $\rm M_{\odot}$ is inferred for SN 2018hna from its bolometric light curve. Hydrodynamical modelling of the cooling phase suggests a progenitor with a radius ~50 $\rm R_{\odot}$, a mass of ~14-20 $\rm M_{\odot}$ and explosion energy of ~1.7-2.9$\rm \times$ $\rm 10^{51}\ erg$. The smaller inferred radius of the progenitor than a standard red supergiant is indicative of a blue supergiant progenitor of SN 2018hna. A sub-solar metallicity (~0.3 $\rm Z_{\odot}$) is inferred for the host galaxy UGC 07534, concurrent with the low-metallicity environments of 1987A-like events.

astro-ph.HE↗