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We report detections of thermal X-ray line emission and proper motions in the supernova remnant (SNR) RX J1713.7-3946, the prototype of the small class of synchrotron dominated SNRs. Based on deep XMM-Newton observations, we find clear line features including Ne Lyα, Mg Heα, and Si Heα from the central portion of the remnant. The metal abundance ratios suggest that the thermal emission originates from core-collapse SN ejecta arising from a relatively low-mass (≲20 M⊙) progenitor. In addition, using XMM-Newton observations on a 13 yr time interval, we have measured expansion in the southeastern rim to be ~0.75″ yr−1 or ~3500 km s−1 at a distance of 1 kpc. Given this, we derive an upstream density to be ~0.01 cm−3, compatible with the lack of thermal X-rays from the shocked ambient medium. We also estimate the age of the remnant to be ~1200–1600 yr, roughly consistent with the idea that RX J1713.7-3946 is the remnant of SN 393.
The properties of the first generation of stars and their supernova (SN) explosions remain unknown due to the lack of their actual observations. Pop III stars may have been very massive and predicted to be exploded as pair-instability SNe, but the observed metal-poor stars show the abundance patterns which are more consistent with yields of core-collapse SNe. We study the multicolor light curves for a metal-free core-collapse SN models (massive stars of 25-100 solar mass range) to determine the indicators for the detection and identification of first generation SNe. We use mixing-fallback supernova explosion models which explain the observed abundance patterns of metal poor stars. Numerical calculations of the multicolor light curves are performed using the multigroup radiation hydrodynamic code STELLA. The calculated light curves of metal-free SNe are compared with our calculations of non-zero metallicity models and observed SNe.
Origins of superluminous supernovae (SLSNe) discovered by recent SN surveys are still not known well. One idea to explain the huge luminosity is the collision of dense CSM and SN ejecta. If SN ejecta is surrounded by dense CSM, the kinetic energy of SN ejecta is efficiently converted to radiation energy, making them very bright. To see how well this idea works quantitatively, we performed numerical simulations of collisions of SN ejecta and dense CSM by using one-dimensional radiation hydrodynamics code STELLA and obtained light curves (LCs) resulting from the collision. First, we show the results of our LC modeling of SLSN 2006gy. We find that physical parameters of dense CSM estimated by using the idea of shock breakout in dense CSM (e.g., Chevalier & Irwin 2011, Moriya & Tominaga 2012) can explain the LC properties of SN 2006gy well. The dense CSM's radius is about 1016 cm and its mass about 15 M⊙. It should be ejected within a few decades before the explosion of the progenitor. We also discuss how LCs change with different CSM and SN ejecta properties and origins of the diversity of H-rich SLSNe. This can potentially be a probe to see diversities in mass-loss properties of the progenitors. Finally, we also discuss a possible signature of SN ejecta-CSM interaction which can be found in H-poor SLSN.
Type II-plateau supernovae (SNe II-P) are fainter than Type Ia SNe and thus have so far been observed only at z < 1. We introduce shock breakout and propose a distant SN II-P survey at z > 1 with shock breakout. The first observation of shock breakout from the rising phase is reported in 2008. We first construct a theoretical model reproducing the UV-optical light curves (LCs) of the first example and demonstrate that the peak apparent g-band magnitude of the shock breakout would be mg ~ 26.4 mag if an identical SN occurs at a redshift z = 1, which can be reached by 8m-class telescopes. Furthermore, we present LCs of shock breakout of SN explosions with various main-sequence masses, metallicities, and explosion energies and derive the observable SN rate and reachable redshift as functions of filter and limiting magnitude by taking into account an initial mass function, cosmic star formation history, intergalactic absorption, and host galaxy extinction. The g-band observable SN rate with limiting magnitude 27.5 mag is 3.3 SNe deg−2 day−1 and half of them are located at z > 1.2.
Ultra-high energy cosmic rays (UHECRs) are the most energetic particles flying from space and their source is not clarified yet. Recently, the Pierre Auger Observatory (PAO) suggests that UHECRs involve heavy nuclei. The PAO results require that a considerable fraction of metal nuclei must exist in the accelerating site, which can be realized only in the stellar interior. This puts strong constraints on the origin of UHECRs. In order to definitize the constraints from PAO results, we investigate the fraction of metal nuclei in a relativistic jet in gamma-ray burst associated with core-collapse supernova. If the jet is initially dominated by radiation field, quasi-statistical equilibrium (QSE) is established and heavy nuclei are dissociated to light particles such as 4He during the acceleration and expansion. On the other hand, if the jet is mainly accelerated by magnetic field heavy or intermediate mass nuclei can survive. The criterion to contain the metal nuclei is that the temperature at the launch site is below 4.5 × 109K. Therefore, if the composition of UHECRs is dominated by metal nuclei, a GRB with the magnetized jet is the most plausible candidate of the accelerating site.
Red supergiants (RSGs) are progenitors of Type IIP supernovae (SNe). It is suggested that RSGs can experience a mass loss with a very high mass-loss rate (even as high as 0.01 M⊙ yr−1) due to, e.g., dynamical instabilities of their envelopes (e.g., Yoon & Cantiello (2010)). Because of the extensive mass loss, RSGs can have very dense circumstellar medium (CSM) around them. If a SN explosion occurs soon after the extensive mass loss of a RSG, the SN ejecta will collide with the dense CSM. Due to the collision, the kinetic energy of the ejecta is converted to radiation energy and such SNe with collision can be brighter than usual Type IIP SNe. By performing one-dimensional multi-group radiation hydrodynamical calculations, we investigate the effects of the collision on Type IIP SN LCs. We show that if RSGs explode within a dense CSM, the SN will be very bright, especially in ultraviolet, at early epochs. We also compare our models with the ultraviolet-bright Type IIP SN 2009kf and show that the progenitor of SN 2009kf can be a massive RSG which experienced extensive mass loss just before its explosion. We conclude that this is evidence that massive RSGs experience extensive mass loss and the existence of such mass loss can actually be the cause of the contradiction between theoretical and observational mass ranges of Type IIP SN progenitors.
We performed a 1D LTE chemical abundance analysis of an extremely metal-poor star BD+44°493 ([Fe/H]= −3.7), and set a very low upper limit for its Be abundance: A(Be) < −2.0. It may indicate that the decreasing trend of Be abundances with lower [Fe/H] still holds at [Fe/H] < −3.5, and demonstrate that high C and O abundances do not necessarily imply high Be abundances. However, since the star is a subgiant with Teff ~ 5500K, Be may be depleted.
We review the properties of supernovae (SNe) as a function of the progenitor's mass M. (1) Mup - 10 M⊙ stars are super-AGB stars and resultant electron capture SNe may be Faint supernovae like Type IIn SN 2008S. (2) 10 - 12 M⊙ stars undergo Fe-core collapse to form neutron stars (NSs) and Faint supernovae. (3) 12 M⊙ - MBN stars undergo Fe-core collapse to form NSs and normal core-collapse supernovae. (4) MBN - 90 M⊙ stars undergo Fe-core collapse to form Black Holes. Resultant supernovae are bifurcate into Hypernovae and Faint supernovae. The observed properties of SN 2008ha can be explained with this type of Faint supernovae. (5) 90 - 140 M⊙ stars produce Luminous SNe, like SNe 2007bi and 2006gy. (6) 140 - 300 M⊙ stars become pair-instability supernovae which could be Luminous supernovae (SNe 2007bi and 2006gy). (7) Very massive stars with M ≳ 300 M⊙ undergo core-collapse to form intermediate mass black holes. Some SNe could be more Luminous supernovae (like SN 2006gy).
We performed a chemical abundance analysis of the very bright (V = 9.1) carbon-enhanced metal-poor (CEMP) star BD+44°493, which is the first star found with metallicity [Fe/H] < −3.5 and an apparent magnitude V < 12. The star is classified as a CEMP-no” subgiant, and its abundance pattern implies that a first-generation faint supernova is the most likely origin of its carbon excess. We set an very low upper limit on this star's beryllium abundance, which demonstrates that high C and O abundances do not necessarily imply high Be abundances.
The first metal enrichment in the universe was made by supernova (SN) explosions of population (Pop) III stars. The history of chemical evolution is recorded in abundance patterns of extremely metal-poor (EMP) stars. We investigate the properties of nucleosynthesis in Pop III SNe by comparing their yields with the abundance patterns of the EMP stars. We focus on (1) jet-induced SNe with various properties of the jets, especially energy deposition rates [Ėdep = (0.3 − 1500) × 1051 ergs s−1], and (2) SNe of stars with various main-sequence masses (Mms = 13 − 50M⊙) and explosion energies [E = (1 − 40) × 1051ergs]. The varieties of Pop III SNe can explain the observations of the EMP stars: (1) higher [C/Fe] for lower [Fe/H] and (2) trends of abundance ratios [X/Fe] against [Fe/H].
We investigate the evolution of dust formed in Population III supernovae (SNe) by considering its transport and processing by sputtering within the SN remnants (SNRs). We find that the fate of dust grains within SNRs heavily depends on their initial radii aini. For Type II SNRs expanding into the ambient medium with density of nH,0 = 1 cm−3, grains of aini < 0.05 μm are detained in the shocked hot gas and are completely destroyed, while grains of aini > 0.2 μm are injected into the surrounding medium without being significantly destroyed. Grains with aini = 0.05–0.2 μm are finally trapped in the dense shell behind the forward shock. We show that the grains piled up in the dense shell enrich the gas up to 10−6–10−4Z⊙, high enough to form low-mass stars with 0.1–1 M⊙. In addition, [Fe/H] in the dense shell ranges from −6 to −4.5, which is in good agreement with the ultra-metal-poor stars with [Fe/H] < −4. We suggest that newly formed dust in a Population III SN can have great impact on the stellar mass and elemental composition of Population II.5 stars formed in the shell of the SNR.
We review the final stages of stellar evolution, supernova properties, and chemical yields as a function of the progenitor's mass. (1) 8 - 10 M⊙ stars are super-AGB stars when the O+Ne+Mg core collapses due to electron capture. These AGB-supernovae may constitute an SN 2008S-like sub-class of Type IIn supernovae. These stars produce little α-elements and Fe-peak elements, but are important sources of Zn and light p-nuclei. (2) 10 - 90 M⊙ stars undergo Fe-core collapse. Nucleosynthesis in aspherical explosions is important, as it can well reproduce the abundance patterns observed in extremely metal-poor stars. (3) 90 - 140 M⊙ stars undergo pulsational nuclear instabilities at various nuclear burning stages, including O and Si-burning. (4) Very massive stars with M ≳ 140 M⊙ either become pair-instability SNe, or undergo core-collapse to form intermediate mass black holes if the mass loss is small enough.
The very peculiar abundance patterns observed in extremely metal-poor (EMP) stars can not be explained by conventional normal supernova nucleosynthesis but can be well-reproduced by nucleosynthesis in hyper-energetic and hyper-aspherical explosions, i.e., Hypernovae (HNe). Previously, such HNe have been observed only as Type Ic supernovae. Here, we examine the properties of recent Type Ib supernovae (SNe Ib). In particular, SN Ib 2008D associated with the luminous X-ray transient 080109 is found to be a more energetic explosion than normal core-collapse supernovae. We estimate that the progenitor's main sequence mass is MMS = 20 − 25M⊙ with an explosion of kinetic energy of EK ~ 6.0 × 1051 erg. These properties are intermediate between those of normal SNe and hypernovae associated with gamma-ray bursts. Therefore, such energetic SNe Ib could also make an important contribution to the chemical enrichment in the early Universe.
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