Properties of Thorne–Żytkow object explosions Moriya, Takashi J; Blinnikov, Sergei I
Monthly notices of the Royal Astronomical Society,
09/2021, Letnik:
508, Številka:
1
Journal Article
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ABSTRACT
Thorne–Żytkow objects are stars that have a neutron star core with an extended hydrogen-rich envelope. Massive Thorne–Żytkow 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–Żytkow object explosions. We find that Thorne–Żytkow object explosions are observed as long-duration transients lasting for several years. If the accretion disc triggering the explosions does not last for a long time, Thorne–Żytkow object explosions have a luminosity plateau with about $10^{39}\, \mathrm{erg\, s^{-1}}$ 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 disc is sustained for long time, the Thorne–Żytkow 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 $2000\, \mathrm{km\, s^{-1}}$ 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–Żytkow objects.
ABSTRACT
Luminosity evolution of some stripped-envelope supernovae such as Type I superluminous supernovae is difficult to explain 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 d. 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.
Abstract
Type IIP supernova progenitors are often surrounded by dense circumstellar media that may result from mass-loss enhancement of the progenitors shortly before their explosions. Previous ...light-curve studies suggest that the mass-loss rates are enhanced up to ∼0.1 M⊙ yr−1, assuming a constant wind velocity. However, the density of circumstellar media at the immediate stellar vicinity can be much higher than previously inferred for a given mass-loss rate if wind acceleration is taken into account. We show that the wind acceleration has a huge impact when we estimate mass-loss rates from early light curves of Type IIP supernovae by taking SN 2013fs as an example. We perform numerical calculations of the interaction between supernova ejecta and circumstellar media with a constant mass-loss rate but with a β-law wind velocity profile. We find that the mass-loss rate of the progenitor of SN 2013fs shortly before the explosion, which was inferred to be ∼0.1 M⊙ yr−1 with a constant wind velocity of 10 km s−1 by a previous light-curve modelling, can be as low as ∼10−3 M⊙ yr−1 with the same terminal wind velocity of 10 km s−1 but with a wind velocity profile with β ≃ 5. In both cases, the mass of the circumstellar medium is similar (≃0.5 M⊙). Therefore, the beginning of the progenitor’s mass-loss enhancement in our interpretation is ∼100 yr before the explosion, not several years. Our result indicates that the immediate dense environment of Type II supernova progenitors may be significantly influenced by wind acceleration.
ABSTRACT
We present the expected observational properties of a general relativistic instability supernova (GRSN) from the 55 500 M⊙ primordial (Population III) star. Supermassive stars exceeding ...$10^4\, \mathrm{M}_\odot$ 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 ($\sim 10^9\, \mathrm{M}_\odot$) 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 ($1.5\times 10^{44}\, \mathrm{erg\, s^{-1}}$) 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 colour, they can be distinguished from other persistent sources such as high-redshift galaxies by using colour 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.
We investigate light-curve and spectral properties of ultrastripped core-collapse supernovae. Ultrastripped supernovae are the explosions of heavily stripped massive stars that lost their envelopes ...via binary interactions with a compact companion star. They eject only ~0.1 M... and may be the main way to form double neutron-star systems that eventually merge emitting strong gravitational waves. We follow the evolution of an ultrastripped supernova progenitor until iron core collapse and perform explosive nucleosynthesis calculations. We then synthesize light curves and spectra of ultrastripped supernovae using the nucleosynthesis results and present their expected properties. Ultrastripped supernovae synthesize ~0.01 M... of radioactive 56Ni, and their typical peak luminosity is around 10 super( 42) erg s super( -1) or -16 mag. Their typical rise time is 5-10 d. Comparing synthesized and observed spectra, we find that SN 2005ek, some of the so-called calcium-rich gap transients, and SN 2010X may be related to ultrastripped supernovae. If these supernovae are actually ultrastripped supernovae, their event rate is expected to be about 1 per cent of core-collapse supernovae. Comparing the double neutron-star merger rate obtained by future gravitational-wave observations and the ultrastripped supernova rate obtained by optical transient surveys identified with our synthesized light-curve and spectral models, we will be able to judge whether ultrastripped supernovae are actually a major contributor to the binary neutron-star population and provide constraints on binary stellar evolution. (ProQuest: ... denotes formulae/symbols omitted.)
We present an analytic model for bolometric light curves which are powered by the interaction between supernova ejecta and a dense circumstellar medium. This model is aimed at modelling Type IIn ...supernovae to determine the properties of their supernova ejecta and circumstellar medium. Our model is not restricted to the case of steady mass loss and can be applied broadly. We only consider the case in which the optical depth of the unshocked circumstellar medium is not high enough to affect the light curves. We derive the luminosity evolution based on an analytic solution for the evolution of a dense shell created by the interaction. We compare our model bolometric light curves to observed bolometric light curves of three Type IIn supernovae (2005ip, 2006jd, 2010jl) and show that our model can constrain their supernova ejecta and circumstellar medium properties. Our analytic model is supported by numerical light curves from the same initial conditions.
We show that the luminous supernovae associated with ultra-long gamma-ray bursts can be related to the slow cooling from the explosions of hydrogen-free progenitors that are extended by pulsational ...pair-instability. We have recently shown that some rapidly-rotating hydrogen-free gamma-ray burst progenitors that experience pulsational pair-instability can keep an extended structure caused by pulsational pair-instability until the core collapse. These types of progenitors have large radii exceeding 10
R
⊙
and they sometimes reach beyond 1000
R
⊙
at the time of the core collapse. They are, therefore, promising progenitors of ultra-long gamma-ray bursts. Here, we perform light-curve modeling of the explosions of one extended hydrogen-free progenitor with a radius of 1962
R
⊙
. The progenitor mass is 50
M
⊙
and 5
M
⊙
exists in the extended envelope. We use the one-dimensional radiation hydrodynamics code
STELLA
in which the explosions are initiated artificially by setting given explosion energy and
56
Ni mass. Thanks to the large progenitor radius, the ejecta experience slow cooling after the shock breakout and they become rapidly evolving (≲10 days), luminous (≳10
43
erg s
−1
) supernovae in the optical even without energy input from the
56
Ni nuclear decay when the explosion energy is more than 10
52
erg. The
56
Ni decay energy input can affect the light curves after the optical light-curve peak and make the light-curve decay slowly when the
56
Ni mass is around 1
M
⊙
. They also have a fast photospheric velocity above 10 000 km s
−1
and a 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 gamma-ray burst GRB 111209A, can be explained as the cooling phase of the extended progenitor. The subsequent slow light-curve decline can be related to the
56
Ni decay energy input. The ultra-long gamma-ray burst progenitors we proposed recently can explain both the ultra-long gamma-ray burst duration and the accompanying supernova properties. When the gamma-ray burst jet is off-axis or choked, the luminous supernovae could be observed as fast blue optical transients without accompanying gamma-ray bursts.
Abstract
We investigate the possibility that the energetic Type II supernova OGLE-2014-SN-073 is powered by a fallback accretion following the failed explosion of a massive star. Taking massive ...hydrogen-rich supernova progenitor models, we estimate the fallback accretion rate and calculate the light-curve evolution of supernovae powered by the fallback accretion. We find that such fallback accretion powered models can reproduce the overall observational properties of OGLE-2014-SN-073. It may imply that some failed explosions could be observed as energetic supernovae like OGLE-2014-SN-073 instead of faint supernovae as previously proposed.
An electron-capture supernova (ECSN) is a core-collapse supernova (CCSN) explosion of a super-asymptotic giant branch (SAGB) star with a main-sequence mass M sub(MS) ~ 7-9.5 M sub(middot in circle). ...The explosion takes place in accordance with core bounce and subsequent neutrino heating and is a unique example successfully produced by first-principle simulations. This allows us to derive a first self-consistent multicolor light curve of a CCSN. Adopting the explosion properties derived by the first-principle simulation, i.e., the low explosion energy of 1.5 x 10 super(50) erg and the small super(56)Ni mass of 2.5 x 10 super(3) M sub(middot in circle), we perform a multi-group radiation hydrodynamics calculation of ECSNe and present multicolor light curves of ECSNe of SAGB stars with various envelope masses and hydrogen abundances. We demonstrate that a shock breakout has a peak luminosity of L ~ 2 x 10 super(44) erg s super(?1) and can evaporate circumstellar dust up to R ~ 10 super(17) cm for the case of carbon dust, that the plateau luminosity and plateau duration of ECSNe are L ~ 10 super(42) erg s super(?1) and t ~ 60-100 days, respectively, and that a plateau is followed by a tail with a luminosity drop by ~4 mag. The ECSN shows a bright and short plateau that is as bright as typical Type II plateau supernovae, and a faint tail that might be influenced by the spin-down luminosity of a newborn pulsar. Furthermore, the theoretical models are compared with ECSN candidates: SN 1054 and SN 2008S. We find that SN 1054 shares the characteristics of the ECSNe. For SN 2008S, we find that its faint plateau requires an ECSN model with a significantly low explosion energy of E ~ 1048 erg.
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