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Supernovae are nature's grandest explosions and an astrophysical laboratory
in which unique conditions exist that are not achievable on Earth. They are
also the furnaces in which most of the elements heavier than carbon have been
forged. Scientists have argued for decades about the physical mechanism
responsible for these explosions. It is clear th...
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Recent nucleosynthesis calculations of Type II supernovae using advanced neutrino transport determine that the early neutrino winds are proton-rich. However, a fraction of the ejecta emitted at the same time is composed of neutron-rich pockets. In this paper we calculate the nucleosynthesis contribution from the neutron-rich pockets in the hot conv...
We study thermal effects on neutrino-nucleus reactions occurring under supernova conditions. The approach we use is based on the QRPA extended to finite temperature by the thermofield dynamics formalism. For the relevant supernova conditions we calculate inelastic neutrino scattering and neutrino absorption cross sections for two sample nuclei, 56F...
We present 42 rapidly evolving (time spent above half-maximum brightness $t_{1/2}<12$d) extragalactic transients from Phase I of the Zwicky Transient Facility (ZTF), of which 22 have spectroscopic classifications. This is one of the largest systematically selected samples of day-timescale transients, and the first with spectroscopic classifications...
Some hydrogen poor superluminous supernovae (SLSNe) exhibit bumps in the tails of their light-curves associated with hydrogen features in their late time spectra. Here we use the explosion parameters of one such SLSN -- SN 2017gci -- to search the stellar models of the Binary Population And Spectral Synthesis (BPASS) code for potential progenitors....
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... Another source of chemical enhancement are supernovae Type II (SNe II) explosions of massive stars (8 -40 M ⊙ ); producing O, Ne, Mg, Al, and other nucleosynthesis products, with reference timescales of 10 7 years for a 15 M ⊙ star (Woosley & Janka 2005). SNe II explosions are highly energetic episodes that release metals in the hot diffuse phase (T ∼ 10 6−7 K), which are detectable in radio and X-ray observations. ...
We present a pioneering spatially-resolved, multi-phase gas abundance study on the blue compact dwarf galaxy NGC~5253, targeting 10 star-forming (SF) clusters inside six FUV HST/COS pointings with co-spatial optical VLT/MUSE observations throughout the galaxy. The SF regions span a wide range of ages (1--15 Myr) and are distributed at different radii (50 -- 230 pc). We performed robust absorption-line profile fitting on the COS spectra, covering 1065--1430 \AA\ in the FUV, allowing an accurate computation of neutral-gas abundances for 13 different ions sampling 8 elements. These values were then compared with the ionized-gas abundances, measured using the direct method on MUSE integrated spectra inside analog COS apertures. Our multi-phase, spatially resolved comparisons find abundances which are lower in the neutral gas than the ionized gas by 0.22 dex, 0.80 dex and 0.58 dex for log(O/H), log(N/H) and log(N/O), respectively. We modeled the chemical abundance distributions and evaluated correlations as a function of radius and age. It was found that while N, O and N/O abundances decrease as a function of age in the ionized gas, they increase with age in the neutral gas. No strong correlations for N, O or N/O were observed as a function of radius. The N/O and N/H offsets between the phases were found to decrease with age, providing evidence that chemical enrichment happens differentially, first in the ionized-gas phase around 2--5 Myrs (due to N-rich Wolf-Rayet stars) and then mixing out into the cold neutral gas on longer timescales of 10--15 Myr.
... First detected as short transient bursts of high-energy photons (Klebesadel et al. 1973), observations of afterglows (Costa et al. 1997;Groot et al. 1998) and supernova counterparts Bloom et al. 1999;Hjorth et al. 2003;Woosley & Bloom 2006) have facilitated a deeper understanding of these otherwise mysterious events. Long-duration gamma-ray bursts (LGRBs) are now thought to occur during core-collapse supernovae, a process in which stars more massive than about 8 M e end their lives in a violent explosion, resulting in the formation of either a black hole (BH) or a neutron star (NS; Woosley & Janka 2005). After the formation of either a BH or an NS, material from the preceding collapse can accrete around the compact object, providing a possible power source for an ensuing LGRB (e.g., Narayan et al. 2001). ...
Long-duration gamma-ray bursts (LGRBs), thought to be produced during core-collapse supernovae, may have a prominent neutron component in the outflow material. If present, neutrons can change how photons scatter in the outflow by reducing its opacity, thereby allowing the photons to decouple sooner than if there were no neutrons present. Understanding the details of this process could therefore allow us to probe the central engine of LGRBs, which is otherwise hidden. Here, we present results of the photospheric emission from an LGRB jet, using a combination of relativistic hydrodynamic simulations and radiative transfer postprocessing using Monte Carlo radiation transfer code. We control the size of the neutron component in the jet material by varying the equilibrium electron fraction Y e , and we find that the presence of neutrons in the GRB fireball affects the Band parameters α and E 0 , while the picture with the β parameter is less clear. In particular, the break energy E 0 is shifted to higher energies. Additionally, we find that increasing the size of the neutron component also increases the total radiated energy of the outflow across multiple viewing angles. Our results not only shed light on LGRBs but are also relevant to short-duration gamma-ray bursts associated with binary neutron star mergers due to the likelihood of a prominent neutron component in such systems.
... The blue curves represent chemical evolution models (Watanabe et al. 2023) with different metallicities. The cyan lines denote isochrones of the chemical evolution models at the model ages of 10 6.7 , 10 6.8 , 10 6.9 , and 10 7.0 yr that correspond to the lifetime of progenitor stars with 40, 30, 25, and 20 M e , respectively (Portinari et al. 1998). in the carbon-burning layer (e.g., Woosley & Janka 2005), which reduces neon abundance. ...
We present chemical abundance ratios of 70 star-forming galaxies at z ∼ 4–10 observed by the JWST/NIRSpec Early Release Observations, GLASS, and CEERS programs. Among the 70 galaxies, we have pinpointed two galaxies, CEERS_01019 at z = 8.68 and GLASS_150008 at z = 6.23, with extremely low C/N ([C/N] ≲ −1), evidenced with C iii ] λλ 1907,1909, N iii ] λ 1750, and N iv ] λλ 1483,1486, which show high N/O ratios ([N/O] ≳ 0.5) comparable with the one of GN-z11, regardless of whether stellar or active galactic nucleus radiation is assumed. Such low C/N and high N/O ratios found in CEERS_01019 and GLASS_150008 (additionally identified in GN-z11) are largely biased toward the equilibrium of the CNO cycle, suggesting that these three galaxies are enriched by metals processed by the CNO cycle. On the C/N versus O/H plane, these three galaxies do not coincide with Galactic H ii regions, normal star-forming galaxies, and nitrogen-loud quasars with asymptotic giant branch stars, but with globular-cluster (GC) stars, indicating a connection with GC formation. We compare the C/O and N/O of these three galaxies with those of theoretical models and find that these three galaxies are explained by scenarios with dominant CNO-cycle materials, i.e., Wolf–Rayet stars, supermassive (10 ³ –10 ⁵ M ⊙ ) stars, and tidal disruption events, interestingly with a requirement of frequent direct collapses. For all the 70 galaxies, we present measurements of Ne/O, S/O, and Ar/O, together with C/O and N/O. We identify four galaxies with very low Ne/O, log(Ne/O) < −1.0, indicating abundant massive (≳30 M ⊙ ) stars.
... In hot and dense astrophysical environments such as core collapse supernovae and binary neutron star mergers, neutrinos are emitted in such large number fluxes that the average flavor content is important to the dynamic and chemical evolution. Through weak interactions with local nucleons, electron flavor neutrinos and antineutrinos can alter the local proton-to-neutron ratio in these environments, thereby affecting, for example, r-process nucleosynthesis [1][2][3][4][5][6][7]. It is therefore crucial to understand the flavor content of the neutrinos if one wishes to perform detailed studies of the evolution of these systems [8][9][10][11][12][13][14][15]. ...
Neutrino gases are expected to form in high-density astrophysical environments, and accurately modeling their flavor evolution is critical to understanding such environments. In this work, we study a simplified model of such a dense neutrino gas in the regime for which neutrino-neutrino coherent forward scattering is the dominant mechanism contributing to the flavor evolution. We show evidence that the generic potential induced by this effect is nonintegrable and that the statistics of its energy level spaces are in good agreement with the Wigner surmise. We also find that individual neutrinos rapidly entangle with all of the others present, which results in an equilibration of the flavor content of individual neutrinos. We show that the average neutrino flavor content can be predicted utilizing a thermodynamic partition function. A random phase approximation to the evolution gives a simple picture of this equilibration. In the case of neutrinos and antineutrinos, processes like νeν¯e⇆νμν¯μ yield a rapid equilibrium satisfying n(νe)n(ν¯e)=n(νμ)n(ν¯μ)=n(ντ)n(ν¯τ) in addition to the standard lepton number conservation in regimes where off-diagonal vacuum oscillations are small compared to ν−ν interactions.
... The silicate absorption feature may indicate that this galaxy once hosted massive stars (type O or B) capable of burning silicon in their final stages (Vollmer et al 2008). Supernova explosions may also have created a silicon-rich interstellar medium around the galaxy's core (Woosley, 2005). ...
Messier 104, NGC 4594, also known as the Sombrero Galaxy, has been extensively studied, especially its structure and stellar halo. Its abundance of globular clusters has given rise to many theories and much speculation. However, other objects in the vicinity of such a spectacular galaxy are sometimes ignored. While studying HST images available on the HST Legacy website of the halo of M104 (HST proposal 9714, PI: Keith Noll), the author observed at 12:40:07.829 -11:36:47.38 (in j2000) an object about 4 arc seconds in diameter. A study with VO tools suggests that the object is a SBc galaxy with an AGN (Seyfert).
... In hot and dense astrophysical environments such as core collapse supernovae (CCSNe) and binary neutron star mergers (BNSMs), neutrinos are emitted in such large number fluxes that the average flavor content is important to the dynamic and chemical evolution. Through weak interactions with local nucleons electron flavor neutrinos and antineutrinos can alter the local proton-toneutron ratio in these environments thereby affecting, for example, r-process nucleosynthesis [1][2][3][4][5][6][7]. It is therefore crucial to understand the flavor content of the neutrinos if one wishes to perform detailed studies of the evolution of these systems [8][9][10][11][12][13][14][15]. ...
In hot and dense astrophysical environments, neutrinos are emitted in such numbers that their flavor content is expected to have an appreciable effect on the local system's dynamic and chemical evolution. In this work, we consider such a gas in the regime for which neutrino-neutrino coherent forward scattering dominates the flavor evolution. We show evidence that the generic potential induced by this effect is non-integrable and that the statistics of its energy level spaces are in good agreement with the Wigner surmise. We also find that individual neutrinos rapidly entangle with all of the others present which results in an equilibration of the flavor content of individual neutrinos. We show that the average neutrino flavor content can be predicted utilizing a thermodynamic partition function. A random phase approximation to the evolution gives a simple picture of this equilibration. In the case of neutrinos and antineutrinos, processes like $\nu_e {\bar{\nu}}_e \leftrightarrows \nu_\mu {\bar{\nu}_\mu} $ yield a rapid equilibrium satisfying $n( \nu_e) n({\bar \nu}_e) = n( \nu_\mu) n({\bar \nu}_\mu) = n( \nu_\tau) n({\bar \nu}_\tau)$ in addition to the standard lepton number conservation in regimes where off-diagonal vacuum oscillations are small compared to $\nu-\nu$ interactions.
... Here the spectral index and cutoff energy of the protons are adopted to be Γ = 2.0 and E cut = 3 PeV, respectively. And the total energy of the injected protons is assumed to be W p, inj = E SN h , where η is the fraction of the kinetic energy of the SNR, E SN , converted into the escaped proton energy, and the typical value of E SN is adopted to be 10 51 erg (Woosley & Janka 2005;Vink & Kuiper 2006). ...
Motivated by the recent discovery of a low-surface-brightness diffuse emission, a supernova remnant (SNR) candidate, surrounding the young pulsar PSR J0837–2454, we carry out a likelihood analysis of the γ -ray data obtained by the Fermi Gamma-ray Space Telescope from 2008 August to 2022 November. Using a 2D Gaussian spatial template, we detect a significant extended γ -ray emission with a 68% containment radius of ∼1.°8, which is spatially coincident with the new SNR candidate at the ∼12 σ confidence level. The spectrum of the extended γ -ray emission, obtained in the energy range of 0.1-500.0 GeV, shows a significant spectral curvature at ∼1 GeV, with a log-parabola spectral shape. Several scenarios, such as an SNR, pulsar wind nebula, and pulsar halo, are discussed as the potential origins of the extended γ -ray emission, and our model fitting results are preferred for the SNR scenario.
... Core-collapse supernovae (CCSNe) provide a unique opportunity to study the last stages of stellar life cycles, the synthesis of heavy elements, and the birth of compact objects (Burrows & Lattimer 1986;Woosley et al. 2002;Woosley & Janka 2005). However, the presence of intervening opaque stellar gas limits the prospects for learning about the underlying physics of the explosion mechanism and the compact object environment from electromagnetic signals alone. ...
Upcoming LIGO–Virgo–KAGRA (LVK) observing runs are expected to detect a variety of inspiralling gravitational-wave (GW) events that come from black hole and neutron star binary mergers. Detection of noninspiral GW sources is also anticipated. We report the discovery of a new class of noninspiral GW sources—the end states of massive stars—that can produce the brightest simulated stochastic GW burst signal in the LVK bands known to date, and could be detectable in LVK run A+. Some dying massive stars launch bipolar relativistic jets, which inflate a turbulent energetic bubble—cocoon—inside of the star. We simulate such a system using state-of-the-art 3D general relativistic magnetohydrodynamic simulations and show that these cocoons emit quasi-isotropic GW emission in the LVK band, ∼10–100 Hz, over a characteristic jet activity timescale ∼10–100 s. Our first-principles simulations show that jets exhibit a wobbling behavior, in which case cocoon-powered GWs might be detected already in LVK run A+, but it is more likely that these GWs will be detected by the third-generation GW detectors with an estimated rate of ∼10 events yr ⁻¹ . The detection rate drops to ∼1% of that value if all jets were to feature a traditional axisymmetric structure instead of a wobble. Accompanied by electromagnetic emission from the energetic core-collapse supernova and the cocoon, we predict that collapsars are powerful multimessenger events.
... As shown in the top left panel of Figure 5, the models predict an increase in Ne/O with Age mod . This increase can originate from the prediction that CCSNe with more massive progenitors have higher temperatures in the carbon-burning layer (e.g., Woosley & Janka 2005), which reduces neon abundance. ...
We present chemical abundance ratios of 70 star-forming galaxies at $z\sim4$-10 observed by the JWST/NIRSpec ERO, GLASS, and CEERS programs. Among the 70 galaxies, we have pinpointed 2 galaxies, CEERS_01019 at $z=8.68$ and GLASS_150008 at $z=6.23$, with extremely low C/N ([C/N]$\lesssim -1$), evidenced with CIII]$\lambda\lambda$1907,1909, NIII]$\lambda$1750, and NIV]$\lambda\lambda$1483,1486, which show high N/O ratios ([N/O]$\gtrsim 0.5$) comparable with the one of GN-z11. CEERS_01019 (GLASS_150008) has (does not have) a strong high ionization line that is explained by AGN (star-formation) photoionization models, which is (not) similar to GN-z11. Such low C/N and high N/O ratios found in CEERS_01019 and GLASS_150008 (additionally identified in GN-z11) are close to the equilibrium of the CNO cycle, suggesting that these 3 galaxies are enriched by metals processed by the CNO cycle. On the C/N vs. O/H plane, these 3 galaxies do not coincide with Galactic HII regions, normal star-forming galaxies, and nitrogen-loud quasars with AGB stars, but globular-cluster (GC) stars, indicating a connection with GC formation. We compare C/O and N/O of these 3 galaxies with those of theoretical models, and find that these 3 galaxies are explained by scenarios with dominant CNO-cycle materials, i.e. Wolf-Rayet stars, supermassive ($10^{3}-10^{5}\ M_{\odot}$) stars, and tidal disruption events, interestingly with a requirement of frequent direct collapses. For all the 70 galaxies, we present measurements of Ne/O, S/O, and Ar/O, together with C/O and N/O. We identify 4 galaxies with very low Ne/O, $\log(\rm Ne/O)<-1.0$, indicating abundant massive ($\gtrsim30\ M_\odot$) stars.
... It is well known that stars having M 8 M initial mass are able to reach the evolutionary stage of Si burning, thus forming an Fe core that is supported mostly by the pressure of degenerate electrons. While approaching the Chandrasekhar mass, the core becomes unstable due to either the loss of high-energy γ-photons by the photodisintegration of Fe nuclei into He, or the disappearance of electrons due to neutronization (inverse βdecay), i.e., the fusing of protons and electrons into neutrons [30]. The sudden lack of pressure supporting the core initiates a gravitational collapse that can be stopped only by the immense pressure of the degenerate neutrons in the freshly born neutron star. ...
The violent stellar explosions known as supernovae have received especially strong attention in both the research community and the general public recently. With the advent of space telescopes, the study of these extraordinary events has switched gears and it has become one of the leading fields in modern astrophysics. In this paper, we review some of the recent developments, focusing mainly on studies related to space-based observations.
