scholarly journals Low-luminosity Type II supernovae – III. SN 2018hwm, a faint event with an unusually long plateau

2020 ◽  
Vol 501 (1) ◽  
pp. 1059-1071
Author(s):  
A Reguitti ◽  
M L Pumo ◽  
P A Mazzali ◽  
A Pastorello ◽  
G Pignata ◽  
...  
Keyword(s):  
Spectroscopic Data ◽  
Low Energy ◽  
Explosion Energy ◽  
Iron Core ◽  
Core Collapse ◽  
Type Ii ◽  
Balmer Lines ◽  
Hydrodynamical Simulations ◽  
Best Fit ◽  
Branch Star

ABSTRACT In this work, we present photometric and spectroscopic data of the low-luminosity (LL) Type IIP supernova (SN) 2018hwm. The object shows a faint (Mr = −15 mag) and very long (∼130 d) plateau, followed by a 2.7 mag drop in the r band to the radioactive tail. The first spectrum shows a blue continuum with narrow Balmer lines, while during the plateau the spectra show numerous metal lines, all with strong and narrow P-Cygni profiles. The expansion velocities are low, in the 1000–1400 km s−1 range. The nebular spectrum, dominated by H α in emission, reveals weak emission from [O i] and [Ca ii] doublets. The absolute light curve and spectra at different phases are similar to those of LL SNe IIP. We estimate that 0.002 M⊙ of 56Ni mass were ejected, through hydrodynamical simulations. The best fit of the model to the observed data is found for an extremely low explosion energy of 0.055 foe, a progenitor radius of 215 R⊙, and a final progenitor mass of 9–10 M⊙. Finally, we performed a modelling of the nebular spectrum, to establish the amount of oxygen and calcium ejected. We found a low M(16O)$\approx 0.02\, \mathrm{ M}_{\odot }$, but a high M(40Ca) of 0.3 M⊙. The inferred low explosion energy, the low ejected 56Ni mass, and the progenitor parameters, along with peculiar features observed in the nebular spectrum, are consistent with both an electron-capture SN explosion of a superasymptotic giant branch star and with a low-energy, Ni-poor iron core-collapse SN from a 10–12 M⊙ red supergiant.

scholarly journals Dynamics of Type-II Supernovae

1996 ◽  
Vol 145 ◽  
pp. 109-117 ◽  
Author(s):  
H.-Th. Janka ◽  
E. M. Müller
Keyword(s):  
Large Scale ◽  
Energy Deposition ◽  
Supernova Explosion ◽  
Threshold Value ◽  
Neutrino Energy ◽  
Two Dimensions ◽  
Iron Core ◽  
Type Ii ◽  
Convective Processes ◽  
Hydrodynamical Simulations

Hydrodynamical simulations of type-II supernovae in one and two dimensions are performed for the revival phase of the delayed shock by neutrino energy deposition. Starting with a post-collapse model of the 1.31 Mʘ iron core of a 15 Mʘ star immediately after the stagnation of the prompt shock about 10 ms after core bounce, the models are followed for several hundred milliseconds with varied neutrino fluxes from the neutrino sphere. The variation of the neutrino luminosities is motivated by the considerable increase of the neutrino emission due to convective processes inside and close to the neutrino sphere (see Janka 1993), which are driven by negative gradients of entropy and electron concentration left behind by the prompt shock (Burrows & Fryxell 1992, Janka & Müller 1992). The size of this luminosity increase remains to be quantitatively analyzed yet and may require multi-dimensional neutrino transport. However, in the presented simulations the region below the neutrino sphere is cut out and replaced by an inner boundary condition, so that the convective zone is only partially included and the neutrino flows are treated as a freely changeable energy source.For small neutrino luminosities the energy transfer to the matter is insufficient to revive the stalled shock. However, there is a sharp transition to successful explosions, when the neutrino luminosities lie above some ‘threshold value’. Once the shock is driven out and the density and temperature of the matter between neutrino sphere and shock start to decrease during the expansion, suitable conditions for further neutrino energy deposition are maintained, and an explosion results. With the neutrino energy deposition the entropy per nucleon in the region between neutrino sphere and shock grows, and convective overturn will set in. Multi-dimensional simulations show that due to the large pressure scale height a large-scale pattern of up-flows and down-flows with velocities close to the local speed of sound develops. Consequently, cold, postshock material is advected down into the neutrino heating layer close to the neutrino sphere and hot material is transported outwards, thus reducing energy losses by re-emission of neutrinos and increasing the pressure behind the shock. Therefore these convective processes are found to be a very important aid to the delayed supernova explosion. In fact, two-dimensional models explode even in cases where spherically symmetrical computations fail.

scholarly journals Exploding SNe with jets: time-scales

2011 ◽  
Vol 7 (S279) ◽  
pp. 377-379
Author(s):  
Oded Papish ◽  
Noam Soker
Keyword(s):  
Time Scales ◽  
Time Scale ◽  
Explosion Energy ◽  
Numerical Code ◽  
Core Collapse ◽  
Typical Time ◽  
Order Of Magnitude ◽  
Hydrodynamical Simulations

AbstractWe perform hydrodynamical simulations of core collapse supernovae (CCSNe) with a cylindrically-symmetrical numerical code (FLASH) to study the inflation of bubbles and the initiation of the explosion within the frame of the jittering-jets model. We study the typical time-scale of the model and compare it to the typical time-scale of the delayed neutrino mechanism. Our analysis shows that the explosion energy of the delayed neutrino mechanism is an order of magnitude less than the required 1051 erg.

scholarly journals Blue supergiant progenitors from binary mergers for SN 1987A and other Type II-peculiar supernovae

2016 ◽  
Vol 12 (S329) ◽  
pp. 64-68
Author(s):  
Athira Menon ◽  
Alexander Heger
Keyword(s):  
Stellar Evolution ◽  
Evolutionary Model ◽  
Iron Core ◽  
Core Collapse ◽  
Type Ii ◽  
Sn 1987A ◽  
Ring Nebula ◽  
Binary Mergers ◽  
Evolution Study ◽  
Different Depths

AbstractWe present results of a systematic and detailed stellar evolution study of binary mergers for blue supergiant (BSG) progenitors of Type II supernovae, particularly for SN 1987A. We are able to reproduce nearly all observational aspects of the progenitor of SN 1987A, Sk –69 °202, such as its position in the HR diagram, the enrichment of helium and nitrogen in the triple-ring nebula and its lifetime before its explosion. We build our evolutionary model based on the merger model of Podsiadlowski et al. (1992), Podsiadlowski et al. (2007) and empirically explore an initial parameter consisting of primary masses, secondary masses and different depths up to which the secondary penetrates the He core during the merger. The evolution of the post-merger star is continued until just before iron-core collapse. Of the 84 pre-supernova models (16 M⊙ − 23 M⊙) computed, the majority of the pre-supernova models are compact, hot BSGs with effective temperature >12 kK and 30 R⊙ − 70 R⊙ of which six match nearly all the observational properties of Sk –69 °202.

scholarly journals Core Collapse, Bounce and Shock Propagation

1980 ◽  
Vol 58 ◽  
pp. 537-544
Author(s):  
Richard L. Bowers ◽  
James R. Wilson
Keyword(s):  
Inner Core ◽  
Shock Propagation ◽  
Iron Core ◽  
Core Collapse ◽  
Nuclear Density ◽  
Type Ii ◽  
Specific Entropy ◽  
Collapse Models ◽  
Recent Developments

Abstract.Recent developments in the physics input for iron core collapse models of type II supernovae are reviewed. The effect of these developments on collapse calculations is also discussed. The inner core collapses homologously, with little change in specific entropy, bounces in the neighborhood of nuclear density, and sets up; an outward moving shock. In adiabatic models an explosion may result. The inclusion of neutrino effects may produce substantial shock damping. Current results indicate that core collapse, bounce and shock propagation does not produce an explosion when neutrino effects are included.

scholarly journals Nothing is certain in string compactifications

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Iñaki García Etxebarria ◽  
Miguel Montero ◽  
Kepa Sousa ◽  
Irene Valenzuela
Keyword(s):  
Flux Compactifications ◽  
Spin Structure ◽  
Energy Condition ◽  
Low Energy ◽  
Type Ii ◽  
String Compactifications ◽  
Compact Dimension ◽  
Bordism Group ◽  
Topological Obstruction ◽  
M Theory

Abstract A bubble of nothing is a spacetime instability where a compact dimension collapses. After nucleation, it expands at the speed of light, leaving “nothing” behind. We argue that the topological and dynamical mechanisms which could protect a compactification against decay to nothing seem to be absent in string compactifications once supersymmetry is broken. The topological obstruction lies in a bordism group and, surprisingly, it can disappear even for a SUSY-compatible spin structure. As a proof of principle, we construct an explicit bubble of nothing for a T3 with completely periodic (SUSY-compatible) spin structure in an Einstein dilaton Gauss-Bonnet theory, which arises in the low-energy limit of certain heterotic and type II flux compactifications. Without the topological protection, supersymmetric compactifications are purely stabilized by a Coleman-deLuccia mechanism, which relies on a certain local energy condition. This is violated in our example by the nonsupersymmetric GB term. In the presence of fluxes this energy condition gets modified and its violation might be related to the Weak Gravity Conjecture.We expect that our techniques can be used to construct a plethora of new bubbles of nothing in any setup where the low-energy bordism group vanishes, including type II compactifications on CY3, AdS flux compactifications on 5-manifolds, and M-theory on 7-manifolds. This lends further evidence to the conjecture that any non-supersymmetric vacuum of quantum gravity is ultimately unstable.

scholarly journals Clumps and Rings of Ejecta in SNR 0540–69.3 as Seen in 3D

2021 ◽  
Vol 922 (2) ◽  
pp. 265
Author(s):  
J. Larsson ◽  
J. Sollerman ◽  
J. D. Lyman ◽  
J. Spyromilio ◽  
L. Tenhu ◽  
...  
Keyword(s):  
3D Reconstruction ◽  
Supernova Remnants ◽  
Alternative Explanation ◽  
Type Ii ◽  
Large Telescope ◽  
Very Large Telescope ◽  
Balmer Lines ◽  
Pulsar Wind

Abstract The distribution of ejecta in young supernova remnants offers a powerful observational probe of their explosions and progenitors. Here we present a 3D reconstruction of the ejecta in SNR 0540-69.3, which is an O-rich remnant with a pulsar wind nebula located in the LMC. We use observations from the Very Large Telescope (VLT)/MUSE to study Hβ, [O iii] λ λ4959, 5007, Hα, [S ii] λ λ6717, 6731, [Ar iii] λ7136, and [S iii] λ9069. This is complemented by 2D spectra from VLT/X-shooter, which also cover [O ii] λ λ3726, 3729, and [Fe ii] λ12567. We identify three main emission components: (i) clumpy rings in the inner nebula (≲1000 km s−1) with similar morphologies in all lines; (ii) faint extended [O iii] emission dominated by an irregular ring-like structure with radius ∼1600 km s−1 and inclination ∼40°, but with maximal velocities reaching ∼3000 km s−1; and (iii) a blob of Hα and Hβ located southeast of the pulsar at velocities ∼1500–3500 km s−1. We analyze the geometry using a clump-finding algorithm and use the clumps in the [O iii] ring to estimate an age of 1146 ± 116 yr. The observations favor an interpretation of the [O iii] ring as ejecta, while the origin of the H-blob is more uncertain. An alternative explanation is that it is the blown-off envelope of a binary companion. From the detection of Balmer lines in the innermost ejecta we confirm that SNR 0540 was a Type II supernova and that hydrogen was mixed down to low velocities in the explosion.

scholarly journals A low-energy core-collapse supernova without a hydrogen envelope

Nature ◽  
2009 ◽  
Vol 459 (7247) ◽  
pp. 674-677 ◽  
Author(s):  
S. Valenti ◽  
A. Pastorello ◽  
E. Cappellaro ◽  
S. Benetti ◽  
P. A. Mazzali ◽  
...  
Keyword(s):  
Low Energy ◽  
Core Collapse ◽  
Core Collapse Supernova

scholarly journals Stellar Core Collapse and Exotic Matter

2011 ◽  
Vol 7 (S279) ◽  
pp. 367-368
Author(s):  
Ken'ichiro Nakazato ◽  
Kohsuke Sumiyoshi
Keyword(s):  
Black Hole ◽  
Degrees Of Freedom ◽  
Gamma Ray ◽  
Dense Matter ◽  
Gamma Ray Bursts ◽  
Core Collapse ◽  
Hole Formation ◽  
Stellar Core ◽  
Black Hole Formation ◽  
Hydrodynamical Simulations

AbstractSome supernovae and gamma-ray bursts are thought to accompany a black hole formation. In the process of a black hole formation, a central core becomes hot and dense enough for hyperons and quarks to appear. In this study, we perform neutrino-radiation hydrodynamical simulations of a stellar core collapse and black hole formation taking into account such exotic components. In our computation, general relativity is fully considered under spherical symmetry. As a result, we find that the additional degrees of freedom soften the equation of state of matter and promote the black hole formation. Furthermore, their effects are detectable as a neutrino signal. We believe that the properties of hot and dense matter at extreme conditions are essential for the studies on the astrophysical black hole formation. This study will be hopefully a first step toward a physics of the central engine of gamma-ray bursts.

scholarly journals The diverse lives of progenitors of hydrogen-rich core-collapse supernovae: the role of binary interaction

2019 ◽  
Vol 631 ◽  
pp. A5 ◽  
Author(s):  
Emmanouil Zapartas ◽  
Selma E. de Mink ◽  
Stephen Justham ◽  
Nathan Smith ◽  
Alex de Koter ◽  
...  
Keyword(s):  
Binary Stars ◽  
Binary Interaction ◽  
Core Collapse ◽  
Relative Importance ◽  
Type Ii ◽  
Population Synthesis ◽  
Binary Channel ◽  
History Of ◽  
Binary Channels

Hydrogen-rich supernovae, known as Type II (SNe II), are the most common class of explosions observed following the collapse of the core of massive stars. We used analytical estimates and population synthesis simulations to assess the fraction of SNe II progenitors that are expected to have exchanged mass with a companion prior to explosion. We estimate that 1/3 to 1/2 of SN II progenitors have a history of mass exchange with a binary companion before exploding. The dominant binary channels leading to SN II progenitors involve the merger of binary stars. Mergers are expected to produce a diversity of SN II progenitor characteristics, depending on the evolutionary timing and properties of the merger. Alternatively, SN II progenitors from interacting binaries may have accreted mass from their companion, and subsequently been ejected from the binary system after their companion exploded. We show that the overall fraction of SN II progenitors that are predicted to have experienced binary interaction is robust against the main physical uncertainties in our models. However, the relative importance of different binary evolutionary channels is affected by changing physical assumptions. We further discuss ways in which binarity might contribute to the observed diversity of SNe II by considering potential observational signatures arising from each binary channel. For supernovae which have a substantial H-rich envelope at explosion (i.e., excluding Type IIb SNe), a surviving non-compact companion would typically indicate that the supernova progenitor star was in a wide, non-interacting binary. We argue that a significant fraction of even Type II-P SNe are expected to have gained mass from a companion prior to explosion.

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