Keywords

Under the assumption that jets explode all core collapse supernovae (CCSNe), I classify 14 CCSN remnants (CCSNRs) into five groups according to their morphology as shaped by jets, and attribute the classes to the specific angular momentum of the pre-collapse core. Point-symmetry (one CCSNR): According to the jittering jets explosion mechanism (JJEM) when the pre-collapse core rotates very slowly, the newly born neutron star (NS) launches tens of jet-pairs in all directions. The last several jet-pairs might leave an imprint of several pairs of "ears," i.e., a point-symmetric morphology. One pair of ears (eight CCSNRs): More rapidly rotating cores might force the last pair of jets to be long-lived and shape one pair of jet-inflated ears that dominates the morphology. S-shaped (one CCSNR): The accretion disk might precess, leading to an S-shaped morphology. Barrel-shaped (three CCSNRs): Even more rapidly rotating pre-collapse cores might result in a final energetic pair of jets that clear the region along the axis of the pre-collapse core rotation and form a barrel-shaped morphology. Elongated (one CCSNR): A very rapidly rotating pre-collapse core forces all jets to be along the same axis such that the jets are inefficient in expelling mass from the equatorial plane and the long-lasting accretion process turns the NS into a black hole. The two new results of this study are the classification of CCSNRs into five classes based on jet-shaped morphological features, and the attribution of the morphological classes mainly to the pre-collapse core rotation in the frame of the JJEM.

I build a toy model in the frame of the jittering jets explosion mechanism (JJEM) of core collapse supernovae that incorporates both the stochastically varying angular momentum component of the material that the newly born neutron star (NS) accretes and the constant angular momentum component, and show that the JJEM can account for the ≃2.5–5M_⊙ mass gap between NSs and black holes (BHs). The random component of the angular momentum results from pre-collapse core convection fluctuations that are amplified by post-collapse instabilities. The fixed angular momentum component results from pre-collapse core rotation. For slowly rotating pre-collapse cores the stochastic angular momentum fluctuations form intermittent accretion disks (or belts) around the NS with varying angular momentum axes in all directions. The intermittent accretion disk/belt launches jets in all directions that expel the core material in all directions early on, hence leaving an NS remnant. Rapidly rotating pre-collapse cores form an accretion disk with angular momentum axis that is about the same as the pre-collapse core rotation. The NS launches jets along this axis and hence the jets avoid the equatorial plane region. Inflowing core material continues to feed the central object from the equatorial plane increasing the NS mass to form a BH. The narrow transition from slow to rapid pre-collapse core rotation, i.e., from an efficient to inefficient jet feedback mechanism, accounts for the sparsely populated mass gap.

In this work, we present the probabilities of mergers of binary black holes (BBHs) and binary neutron stars (BNSs) as functions of stellar mass, metallicity, specific star formation rate (sSFR), and age for galaxies with redshift z ≤ 0.1. Using the binary-star evolution (BSE) code and some fitting formulae, we construct a phenomenological model of cosmic gravitational wave (GW) merger events. By using the Bayesian analysis method and the observations from Advanced LIGO and Virgo, we obtain the relevant parameters of the phenomenological model (such as the maximum black hole mass is ${93}_{-22}^{+73}\,{M}_{\odot }$). Combining the above model results with the galaxy catalog given by the EMERGE empirical galaxy model, we find the normalized probability of occurrence of a merger event varying with ${\mathrm{log}}_{10}(\mathrm{sSFR}/{\mathrm{yr}}^{-1})$ for galaxies with z ≤ 0.1 is different from that in previous studies, that is, two peaks exist in this work while there is only one peak (log₁₀(sSFR/yr ⁻¹) = −10) in the previous work. The sSFR value corresponding to the new peak is log₁₀(sSFR/yr ⁻¹) = −12 and in line with the value (${\mathrm{log}}_{10}(\mathrm{sSFR}/{\mathrm{yr}}^{-1})=-{12.65}_{-0.66}^{+0.44}$) of NGC 4493, the host galaxy of BNS merger event GW170817. The new peak is caused by today's quenched galaxies, which give a large contribution to the total SFR at high redshift in the EMERGE empirical galaxy model. Moreover, we find that the BNS mergers are most likely detected in galaxies with age ∼11 Gyr, which is greater than previous results (6−8 Gyr) and close to the age of NGC 4993, ${13.2}_{-0.9}^{+0.5}$ Gyr.

I present the effervescent zone model to account for the compact dense circumstellar material (CSM) around the progenitor of the core collapse supernova (CCSN) SN 2023ixf. The effervescent zone is composed of bound dense clumps that are lifted by stellar pulsation and envelope convection to distances of ≈tens × au, and then fall back. The dense clumps provide most of the compact CSM mass and exist alongside the regular (escaping) wind. I crudely estimate that for a compact CSM within R_CSM ≈ 30 au that contains M_CSM ≈ 0.01 M_⊙, the density of each clump is k_b ≳ 3000 times the density of the regular wind at the same radius and that the total volume filling factor of the clumps is several percent. The clumps might cover only a small fraction of the CCSN photosphere in the first days post-explosion, accounting for the lack of strong narrow absorption lines. The long-lived effervescent zone is compatible with no evidence for outbursts in the years prior to the SN 2023ixf explosion and the large-amplitude pulsations of its progenitor, and it is an alternative to the CSM scenario of several-years-long high mass loss rate wind.

We conduct one-dimensional stellar evolution simulations of red supergiant (RSG) stars that mimic common envelope evolution (CEE) and find that the inner boundary of the envelope convective zone moves into the initial envelope radiative zone. The envelope convection practically disappears only when the RSG radius decreases by about an order of magnitude or more. The implication is that one cannot split the CEE into one stage during which the companion spirals-in inside the envelope convective zone and removes it, and a second slower phase when the companion orbits the initial envelope radiative zone and a stable mass transfer takes place. At best, this might take place when the orbital separation is about several solar radii. However, by that time other processes become important. We conclude that as of yet, the commonly used alpha-formalism that is based on energy considerations is the best phenomenological formalism.

The range of the U bosonic coupling constants in neutron star matter is a very interesting but still unsolved problem which has multifaceted influences in nuclear physics, particle physics, astrophysics and cosmology. The combination of the theoretical numerical simulation and the recent observations provides a very good opportunity to solve this problem. In the present work, the range of the U bosonic coupling constants is inferred based on the three relations of the mass–radius, mass-frequency and mass-tidal deformability in neutron stars containing hyperons using the GM1, TM1 and NL3 parameter sets under the two flavor symmetries of SU(6) and SU(3) in the framework of the relativistic mean field theory. Combined with observations from PSRs J1614-2230, J0348+0432, J2215-5135, J0952-0607, J0740+6620, J0030-0451, J1748-2446ad, XTE J1739-285, GW170817 and GW190814 events, our numerical results show that the U bosonic coupling constants may tend to be within the range from 0 to 20 GeV⁻² in neutron star containing hyperons. Moreover, the numerical results of the three relations obtained by the SU(3) symmetry are better in accordance with observation data than those obtained by the SU(6) symmetry. The results will help us to improve the strict constraints of the equation of state for neutron stars containing hyperons.

Motivated by the determination of black hole masses with gravitational-wave observations, we calculate the evolution of massive stars through presupernova stages and obtain the mass distribution of black holes. In the first part, we calculate the evolution of He stars with masses of 30–120 M_⊙. We study in detail how convective carbon shell burning controls pair-instability pulsations before and during oxygen burning and determine their final fates. In the second part, we calculate the evolution of H-rich stars with initial masses of 13–80 M_⊙ until Fe core collapse and obtain the possible black hole mass range by applying the criterion of the compactness parameters. From these models, we predict the mass distribution of black holes for stars that undergo Fe core collapse and pair-instability pulsation. The predicted masses for black holes range from 4.2 to 46 M_⊙, which are consistent with the gravitational-wave observations.

The growing observed evidence shows that the long- and short-duration gamma-ray bursts (GRBs) originate from massive star core-collapse and the merger of compact stars, respectively. GRB 201221D is a short-duration GRB lasting ∼0.1 s without extended emission at high redshift z = 1.046. By analyzing data observed with the Swift/BAT and Fermi/GBM, we find that a cutoff power-law model can adequately fit the spectrum with a soft ${E}_{{\rm{p}}}={113}_{-7}^{+9}$ keV, and isotropic energy ${E}_{\gamma ,\mathrm{iso}}={1.36}_{-0.14}^{+0.17}\times {10}^{51}\,\mathrm{erg}$. In order to reveal the possible physical origin of GRB 201221D, we adopted multi-wavelength criteria (e.g., Amati relation, ε-parameter, amplitude parameter, local event rate density, luminosity function, and properties of the host galaxy), and find that most of the observations of GRB 201221D favor a compact star merger origin. Moreover, we find that $\hat{\alpha }$ is larger than $2+\hat{\beta }$ in the prompt emission phase which suggests that the emission region is possibly undergoing acceleration during the prompt emission phase with a Poynting-flux-dominated jet.

We present a systematic study of the most luminous (M_IR [Vega magnitudes] brighter than −14) infrared (IR) transients discovered by the SPitzer InfraRed Intensive Transients Survey (SPIRITS) between 2014 and 2018 in nearby galaxies (D < 35 Mpc). The sample consists of nine events that span peak IR luminosities of M_[4.5],peak between −14 and −18.2, show IR colors between 0.2 < ([3.6]–[4.5]) < 3.0, and fade on timescales between 55 days < t_fade < 480 days. The two reddest events (A_V > 12) show multiple, luminous IR outbursts over several years and have directly detected, massive progenitors in archival imaging. With analyses of extensive, multiwavelength follow-up, we suggest the following possible classifications: five obscured core-collapse supernovae (CCSNe), two erupting massive stars, one luminous red nova, and one intermediate-luminosity red transient. We define a control sample of all optically discovered transients recovered in SPIRITS galaxies and satisfying the same selection criteria. The control sample consists of eight CCSNe and one Type Iax SN. We find that 7 of the 13 CCSNe in the SPIRITS sample have lower bounds on their extinction of 2 < A_V < 8. We estimate a nominal fraction of CCSNe in nearby galaxies that are missed by optical surveys as high as ${38.5}_{-21.9}^{+26.0} \%$ (90% confidence). This study suggests that a significant fraction of CCSNe may be heavily obscured by dust and therefore undercounted in the census of nearby CCSNe from optical searches.

Type IIb supernovae (SNe) are important candidates to understand mechanisms that drive the stripping of stripped-envelope (SE) supernova (SN) progenitors. While binary interactions and their high incidence are generally cited to favor them as SN IIb progenitors, this idea has not been tested using models covering a broad parameter space. In this paper, we use non-rotating single- and binary-star models at solar and low metallicities spanning a wide parameter space in primary mass, mass ratio, orbital period, and mass transfer efficiencies. We find that our single- and binary-star models contribute to roughly equal, however small, numbers of SNe IIb at solar metallicity. Binaries only dominate as progenitors at low metallicity. We also find that our models can account for less than half of the observationally inferred rate for SNe IIb at solar metallicity, with computed rates ≲4% of core-collapse (CC) SNe. On the other hand, our models can account for the rates currently indicated by observations at low metallicity, with computed rates as high as 15% of CC SNe. However, this requires low mass transfer efficiencies (≲0.1) to prevent most progenitors from entering contact. We suggest that the stellar wind mass-loss rates at solar metallicity used in our models are too high. Lower mass-loss rates would widen the parameter space for binary SNe IIb at solar metallicity by allowing stars that initiate mass transfer earlier in their evolution to reach CC without getting fully stripped.