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IRAS 00500+6713 is a hypothesized remnant of a Type Iax supernova SN 1181. Multiwavelength observations have revealed its complicated morphology; a dusty infrared ring is sandwiched by the inner and outer X-ray nebulae. We analyze the archival X-ray data taken by XMM-Newton and Chandra X-ray Observatory to constrain the angular radius, mass, and metal abundance of the X-ray nebulae, and construct a theoretical model describing the dynamical evolution of IRAS 00500+6713, including the effects of the interaction between the SN ejecta and the intense wind enriched with carbon-burning ashes from the central white dwarf (WD) J005311. We show that the inner X-ray nebula corresponds to the wind termination shock while the outer X-ray nebula to the shocked interface between the SN ejecta and the interstellar matter. The observed X-ray properties can be explained by our model with an ejecta kinetic energy of E _ej = (0.77–1.1) × 10 ^48 erg, an ejecta mass of M _ej = 0.18–0.53 M _⊙ , if the currently observed wind from WD J005311 started to blow t _w ≳ 810 yr after the explosion, i.e., approximately after 1990 CE. The inferred SN properties are compatible with those of Type Iax SNe and the timing of the wind launch may correspond to the Kelvin–Helmholtz contraction of the oxygen–neon core of WD J005311 that triggered a surface carbon burning. Our analysis supports that IRAS 00500+6713 is the remnant of SN Iax 1181 produced by a double degenerate merger of oxygen–neon and carbon–oxygen WDs, and WD J005311 is the surviving merger product.

We numerically construct a series of axisymmetric rotating magnetic wind solutions, aiming at exploring the observation properties of massive white dwarf (WD) merger remnants with a strong magnetic field, a fast spin, and an intense mass loss, as inferred for WD J005311. We investigate the magnetospheric structure and the resultant spin-down torque exerted to the merger remnant with respect to the surface magnetic flux Φ _* , spin angular frequency Ω _* and the mass-loss rate $\dot{M}$ . We confirm that the wind properties for $\sigma \equiv {{\rm{\Phi }}}_{* }^{2}{{\rm{\Omega }}}_{* }^{2}/\dot{M}{v}_{\mathrm{esc}}^{3}\gtrsim 1$ significantly deviate from those of the spherical Parker wind, where v _esc is the escape velocity at stellar surface. For such a rotating magnetic wind sequence, we find (i) a quasiperiodic mass eruption triggered by magnetic reconnection along with the equatorial plane and (ii) a scaling relation for the spin-down torque $T\approx (1/2)\times \dot{M}{{\rm{\Omega }}}_{* }{R}_{* }^{2}{\sigma }^{1/4}$ . We apply our results to discuss the spin-down evolution and wind anisotropy of massive WD merger remnants, the latter of which could be probed by a successive observation of WD J005311 using Chandra.

We present the updated open-source code Complete History of Interaction-Powered Supernovae ( CHIPS ) that can be applied to modeling supernovae (SNe) arising from an interaction with the massive circumstellar medium (CSM) as well as the formation process of the CSM. Our update mainly concerns extensions to hydrogen-poor SNe from stripped progenitors, targeting the modeling of interaction-powered SNe Ibc, such as Type Ibn and Icn SNe. We successfully reproduce the basic properties of the light curves of these types of SNe that occur after the partial eruption of the outermost layer with a mass of 0.01–0.1 M _⊙ at ≲1 year before explosion. We also find that the luminosity of the observed precursors can be naturally explained by the outburst that creates the dense CSM, given that the energy of the outburst is efficiently dissipated by collision with an external material, possibly generated by a previous mass eruption. We discuss possible scenarios causing eruptive mass loss based on our results.

Some supernovae (SNe) are powered by the collision of the SN ejecta with dense circumstellar matter (CSM). Their emission spectra show characteristic line shapes of combined broad emission and narrow P Cygni lines, which should closely relate to the CSM structure and the mass-loss mechanism that creates the dense CSM. We quantitatively investigate the relationship between the line shape and the CSM structure by Monte Carlo radiative transfer simulations, considering two representative cases of dense CSM formed by steady and eruptive mass loss. Comparing the H α emission between the two cases, we find that a narrow P Cygni line appears in the eruptive case but does not appear in the steady case due to the difference in the velocity gradient in the dense CSM. We also reproduce the blueshifted photon excess observed in some Type IIn SNe, which is formed by photon transport across the shock wave, and find the relationship between the velocity of the shocked matter and the amount of blueshift of the photon excess. We conclude that the presence or absence of narrow P Cygni lines can distinguish the mass-loss mechanism and suggest high-resolution spectroscopic observations with λ /Δ λ ≳ 10 ^4 after the light-curve peak for applying this diagnostic method.

We present timing and spectral analysis results of the NICER and NuSTAR observations of the dwarf nova MASTER OT J030227.28+191754.5 during the 2021–2022 outburst. The soft X-ray component was found to be dominated by blackbody radiation with a temperature of ∼30 eV and also showed prominent oxygen and neon emission lines. The blackbody luminosity exceeded 10 ^34 erg s ^−1 , which is consistent with theoretical predictions, and then decreased more than an order of magnitude in 3.5 days. The inferred abundances of oxygen and neon in the optically thin coronal region surrounding the central white dwarf (WD) are several times higher than the respective solar values. Although inconclusive, the abundance enrichment may originate from the WD, indicating that it may be mainly composed of oxygen and neon. Assuming that the blackbody radiation comes from the belt-shaped boundary layer between the WD and the accretion disk, we estimated the WD radius to be (2.9 ± 1.1) × 10 ^8 cm, which corresponds to the WD mass range of 1.15–1.34 M _⊙ . If the accretion continues for another ∼1 Gyr, the WD may experience an accretion-induced collapse into a neutron star and form a so-called black widow pulsar system.

Recent observations of a large fraction of Type II supernovae (SNe) show traces of dense circumstellar medium (CSM) very close to the progenitor star. If this CSM is created by eruptive mass loss several months before core collapse, the eruption itself may be visible as a precursor, helpful as an early warning of a near-future SN. Using radiation hydrodynamical simulations based on the open-source code CHIPS, we theoretically model the emission from the mass eruption of a red supergiant star. We find that for a modest mass eruption the luminosity is typically on the order of 10 ^39 erg s ^−1 , can last as long as hundreds of days until the star explodes, and is mainly bright in the infrared (from −9 to −11 mag around peak). We discuss observational strategies to find these signatures from Galactic and local Type II SNe.

Context. Observations suggest that some massive stars experience violent and eruptive mass loss associated with significant brightening that cannot be explained by hydrostatic stellar models. This event seemingly forms dense circumstellar matter (CSM). The mechanism of eruptive mass loss has not been fully explained. We focus on the fact that the timescale of nuclear burning gets shorter than the dynamical timescale of the envelope a few years before core collapse for some massive stars. Aims. To reveal the properties of the eruptive mass loss, we investigate its relation to the energy injection at the bottom of the envelope supplied by nuclear burning taking place inside the core. In this study, we do not specify the actual mechanism for transporting energy from the site of nuclear burning to the bottom of the envelope. Instead, we parameterize the amount of injected energy and the injection time and try to extract information on these parameters from comparisons with observations. Methods. We carried out 1D radiation hydrodynamical simulations for progenitors of red, yellow, and blue supergiants, and Wolf- Rayet stars. We calculated the evolution of the progenitors with a public stellar evolution code. Results. We obtain the light curve associated with the eruption, the amount of ejected mass, and the CSM distribution at the time of core-collapse. Conclusions. The energy injection at the bottom of the envelope of a massive star within a period shorter than the dynamical timescale of the envelope could reproduce some observed optical outbursts prior to the core-collapse and form the CSM, which can power an interaction supernova classified as Type IIn. [ABSTRACT FROM AUTHOR]

Recent observations found that electrons are accelerated to ~10 GeV and emit synchrotron hard X-rays in two magneticwhite dwarfs (WDs), also known as cataclysmic variables (CVs). In nova outbursts of WDs, multi-GeV gamma-rays were detected, implying that protons are accelerated to 100 GeV or higher. In recent optical surveys, the WD density is found to be higher near the Sun than in the Galactic disk by a factor ~2.5. The cosmic rays (CRs) produced by local CVs and novae will accumulate in the local bubble for 106-107 yr. On these findings, we search for CRs from historic CVs and novae in the observed CR spectra. We model the CR spectra at the heliopause as sums of Galactic and local components based on observational data as much as possible. The initial Galactic CR electron and proton spectra are deduced from the gamma-ray emissivity, the local electron spectrum from the hard X-ray spectra at the CVs, and the local proton spectrum from gamma-ray spectra at novae. These spectral shapes are then expressed in a simple set of polynomial functions of CR energy and regressively fitted until the highenergy (>100 GeV) CR spectra near Earth and the Voyager-1 spectra at the heliopause are reproduced. We then extend the modeling to nuclear CR spectra and find that one spectral shape fits all local nuclear CRs, and that the apparent hardening of the nuclear CR spectra is caused by the roll-down of local nuclear spectra around 100-200 GeV. All local CR spectra populate a limited energy band below 100-200 GeV and enhance gamma-ray emissivity below ~10 GeV. Such an enhancement is observed in the inner Galaxy, suggesting the CR fluxes from CVs and novae are substantially higher there. [ABSTRACT FROM AUTHOR]

We present a study of the progenitor of the magnetar 1E 2259+586, from Suzaku observations of the associated supernova remnant CTB 109. The Suzaku spectra, either spatially integrated or spatially resolved, were successfully described by a two-component plasma model, which reconfirms a previous Chandra result on the northwestern part of this remnant (Sasaki et al. 2013, A&A, 552, A45). The hotter component, with a temperature of ~0.7 keV, can be identified as the stellar ejecta heated by reverse shock, because its contribution increases towards the remnant center. The cooler one, with a temperature of ~0.25 keV, can be identified as the shocked interstellar matter. The abundances of Ne, Mg, Si, and S of the hotter component support these identifications. The total masses of the cooler and hotter components are estimated to be 220±40M⊙ and 42±11M⊙, respectively. The remnant is considered to be adiabatically expanding as in the Sedov- Taylor phase. The explosion energy, estimated to be 1.0 × 1051 erg by a canonical Sedov model, is typical of a core-collapse supernova explosion. Assuming that the hotter component includes the ejecta as well as the matter lost by the progenitor star via stellar winds, 1E 2259+586 is inferred to have originated from a very massive star. [ABSTRACT FROM AUTHOR]

We present a novel semi-analytic solution that describes the propagation of a spherical blast wave driven by a central energy source. The initial density profile has a power-law function of the distance from the center and the energy is injected only into the central region at a rate given by a power-law function of time. This solution is composed of three regions separated by the contact surface and the shock front. The innermost region is assumed to be uniform and the outside of the contact surface includes the shocked matter described by self-similar solutions. We analytically derive the applicable range of parameters of this solution from requirements needed to satisfy the boundary conditions. We perform numerical simulations for flows with various values of parameters, some of which reside out of the thus-derived applicable range, and compare the results with the semi-analytic solutions. [ABSTRACT FROM AUTHOR]

The progenitor systems for type Ia supernovae are still controversial. One of the methods used to test the proposed scenario for the progenitor systems is to identify companions that are supposed to survive according to the so-called single degenerate scenario. These companions might be affected by supernova ejecta. We present several numerical simulations of surviving red giant companions whose envelopes were stripped and heated. We find that red giants with less-massive helium cores (≲0.30M⊙) can be so faint after the supernovae that we cannot detect them. In addition, we apply the results to the case of SNR0509-67.5, and put constraints on the helium core mass, envelope stripping, and energy injection under the single degenerate scenario for type Ia supernovae. [ABSTRACT FROM AUTHOR]

In the single degenerate (SD) scenario of type Ia supernovae (SNe Ia), the collision of the ejecta with its companion results in stripping hydrogen-rich matter from the companion star. This hydrogen-rich matter might leave its trace in the light curves and/or spectra. In this paper, we perform radiation hydrodynamical simulations of this collision for three binary systems. As a result, we find that the emission from the shock-heated region is not as strong as in previous studies. This weak emission, however, may be a result of our underestimation of the coupling between the gas and radiation in the shock interaction. Therefore, though our results suggest that the observed early light curves of SNeIa cannot rule out a binary system with a short separation as the progenitor system, more elaborate numerical studies will be needed to reach a fair conclusion. Alternatively, our results indicate that the feature observed in the early phase of a recent type Ia SN2014J might result from interaction of the ejecta with a red giant companion star. We also discuss the dependence of spectral features of Hα and Si II absorption lines on viewing angles and investigate whether they can constrain the event rate of the SD progenitor. [ABSTRACT FROM AUTHOR]

The chemical abundance of r-process elements in nearby dwarf spheroidal (dSph) galaxies is a powerful tool to probe the site of r-process since their small-mass scale can assess the potential rarity of events associated with the r-process production. A merger of binary neutron stars is a promising candidate for such a site. In faint, or less-massive, dSph galaxies such as the Draco, a few binary neutron star mergers are expected to have occurred at most over the whole past. We have measured the chemical abundance, including Eu and Ba, of three red giants in the Draco dSph by Subaru High-Dispersion Spectrograph observation. The Eu detection for one star with [Fe/H] = -1.45 confirms a broadly constant [Eu/H] of ~-1.3 for stars with [Fe/H] ≳ - 2. This feature is shared by other dSphs with similar masses, i.e., the Sculptor and the Carina, and suggests that a neutron star merger is the origin of r-process elements in terms of the rarity of this event. In addition, two very metal-poor stars with [Fe/H]=-2.12 and -2.51 are found to exhibit very low Eu abundances, such as [Eu/H] < -2, with the suggestion of a sudden increase of Eu abundance by more than 0.7 dex at [Fe/H] ≈ -2.2 in the Draco dSph. The detection of Ba abundances for these stars suggests that the r-process enrichment began no later than the time when only a few percent of stars in the present-day Draco dSph were formed. Though identifying the origin of an early Eu production inside the Draco dSph should be left until more abundant data of stars with [Fe/H] ≲ -2 in Draco, as well as other faint dSphs, become available, the implied early emergence of an Eu production event might be reconciled with the presence of extremely metal-poor stars enriched by r-process elements in the Galactic halo. [ABSTRACT FROM AUTHOR]