arXiv subjects

I. R. Seitenzahl

Publications and source records attributed to I. R. Seitenzahl.

At least 19 recordsLinked to original sources

arXiv2026

Multi-dimensional NLTE radiative transfer for a double detonation Type Ia explosion model in the photospheric phase

Previous radiative transfer calculations have shown that both multi-dimensionality and NLTE (non local thermodynamic equilibrium) effects impact the synthetic observables predicted for Type Ia supernova explosion models. Here we carry out a 2D NLTE radiative transfer simulation in the photospheric phase for a double detonation model with a 1 M$_{\odot}$ carbon-oxygen core and 0.02 M$_{\odot}$ helium shell. The predicted observables demonstrate that departures from both spherical symmetry and local thermodynamic equilibrium are significant on scales relevant to comparisons with observations. The NLTE treatment leads to a bluer spectral energy distribution, more slowly declining optical-band light curves, changes to the near-infrared light curve shapes, and differences in the evolution of key spectral features. Although substantial viewing-angle variation is predicted for the model, the scale of the variation is not significantly impacted by NLTE effects up to peak. However, after peak, our 2D NLTE simulation retains a strong viewing-angle dependence in its spectra whereas our simulation of the same ejecta model using an approximate NLTE treatment predicts significantly reduced spectroscopic viewing-angle variation. The NLTE treatment leads to improved agreement with normal Type Ia supernovae, primarily due to the increased ionisation state of the simulation, although the absence of a secondary near-infrared maximum suggests that the ejecta remain over-ionised relative to observations after peak. Despite the improved agreement, many viewing angles still show excessive line blanketing, suggesting that the 0.02 M$_{\odot}$ helium-shell mass of the current model is too large to reproduce normal Type Ia supernovae over the majority of lines of sight.

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arXiv2025

Exploring the range of impacts of helium in the spectra of double detonation models for Type Ia supernovae

Models of sub-Chandrasekhar mass double detonations for Type Ia supernovae (SNe Ia) suggest a distinguishing property of this scenario is unburnt helium in the outer ejecta. However, modern explosion simulations suggest there may be significant variations in its mass and velocity distribution. We recently presented a NLTE (non local thermodynamic equilibrium) radiative transfer simulation for one realisation of the double detonation scenario with a modest He mass (0.018 M${\odot}$) present in the ejecta at relatively high velocities (${\sim}18000\,\mathrm{km}\,\mathrm{s}^{-1}$). That simulation predicted a He I 10830$\,Å$ feature blueward of Mg II 10927$\,Å$ consistent with near-infrared observations of "transitional" SNe Ia. To demonstrate the expected diversity in the helium signature, here we present a calculation for a double detonation model with a higher He mass (${\sim}$0.04 M${\odot}$) ejected at lower velocities (${\sim}13000\,\mathrm{km}\,\mathrm{s}^{-1}$). Despite our simulation predicting no clear optical or 2 micron helium features, a strong and persistent He I 10830$\,Å$ absorption is present. The feature appears at wavelengths consistent with the extended blue wing of the Mg II 10927$\,Å$ feature sometimes present in observations, suggesting this is a helium spectral signature (although for this particular model it is too strong and persistent to be consistent with normal SNe Ia). The significant differences in He I 10830$\,Å$ predicted by the two simulations suggests helium spectral signatures likely show significant variation throughout the SNe Ia population. This motivates further work to use this observable signature to test the parameter space for double detonation models.

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arXiv2024

Investigating Unusual H$α$ Features towards the Scutum Supershell

We investigate the unusual H$α$ features found towards the Scutum Supershell via recent arc-minute and arc-second resolution imaging. These multi-degree features resemble a long central spine ending in a bow-shock morphology. We performed a multi-wavelength study in [SII] optical, radio continuum, infrared continuum, HI, CO, X-ray and gamma-ray emissions. Interestingly, we found the Galactic worm GW16.9$-$3.8 HI feature appears within the Scutum Supershell, and likely influences the spine morphology. Furthermore, the rightmost edge of the bow-shock H$α$ emission overlaps with [S II] line emission, 4.85 GHz radio, and both 60$μ$m and 100$μ$m infrared continuum emissions, suggesting some potential for excitation by shock heating. We estimated the photo-ionisation from O-type and B-type stars in the region (including those from the OB associations Ser OB1B, Ser OB2 and Sct OB3) and found that this mechanism could supply the excitation to account for the observed H$α$ luminosity of the spine and bow-shock of $\sim$1e36 - 2e36 erg/s (d/2.5 kpc)$^2$. Recent MHD simulations by Drozdov et al. (2022) demonstrate the potential for supernova events to drive outflow and bow-shock types of features of the same energetic nature and physical scale as the H$α$ emission we observe here. While this clearly requires many supernova events over time, we speculate that one contributing event could have come from the presumably energetic supernova (hypernova) birth of the magnetar tentatively identified in the X-ray binary LS 5039.

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arXiv2024

Type Ia supernova explosion models are inherently multidimensional

Theoretical and observational approaches to settling the important questions surrounding the progenitor systems and the explosion mechanism of normal Type Ia supernovae have thus far failed. With its unique capability to obtain continuous spectra through the near- and mid-infrared, JWST now offers completely new insights into Type Ia supernovae. In particular, observing them in the nebular phase allows us to directly see the central ejecta and thereby constrain the explosion mechanism. We aim to understand and quantify differences in the structure and composition of the central ejecta of various Type Ia supernova explosion models. We examined the currently most popular explosion scenarios using self-consistent multidimensional explosion simulations of delayed-detonation and pulsationally assisted, gravitationally confined delayed detonation Chandrasekhar-mass models and double-detonation sub-Chandrasekhar-mass and violent merger models. We find that the distribution of radioactive and stable nickel in the final ejecta, both observable in nebular spectra, are significantly different between different explosion scenarios. Therefore, comparing synthetic nebular spectra with JWST observations should allow us to distinguish between explosion models. We show that the explosion ejecta are inherently multidimensional for all models, and the Chandrasekhar-mass explosions simulated in spherical symmetry in particular lead to a fundamentally unphysical ejecta structure. Moreover, we show that radioactive and stable nickel cover a significant range of densities at a fixed velocity of the homologously expanding ejecta. Any radiation transfer postprocessing has to take these variations into account to obtain faithful synthetic observables; this will likely require multidimensional radiation transport simulations.

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arXiv2024

HdC and EHe stars through the prism of Gaia DR3: Evolution of RV amplitude and dust formation rate with effective temperature

The Gaia DR3 release includes heliocentric radial velocity measurements and velocity variability indices for tens of millions of stars observed over 34 months.In this study, we utilise these indices to investigate the intrinsic radial velocity variations of Hydrogen-deficient Carbon (HdC) stars and Extreme Helium (EHe) stars across their large ranges of temperature and brightness. Taking advantage of the newly defined HdC temperature classes, we examine the evolution of the total velocity amplitude with effective temperature. Additionally, we analyse the variation in the dust production rate of R Coronae Borealis (RCB) stars with temperature using two different proxies for the photometric state of RCB stars: one from Gaia and another from the 2MASS survey. Our observations revealed a trend in the evolution of the maximum radial velocity amplitude across each HdC temperature class. Similarly, we also observed a correlation between stellar temperature and the dust production rate. Interestingly, we possibly observed for the first time some variations of the intrinsic radial velocity amplitude and the dust production rate with HdC temperature class. If confirmed, these variations would indicate that the helium shell-burning giant stage starts with strong atmospheric motions that decrease in strength, up to $\sim$6000 K, before picking up again as the HdC star atmosphere shrinks further in size and reaches warmer temperatures. Moreover, the dust formation rate appears to be much higher in colder RCB stars compared to warmer ones.

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arXiv2024

HdC and EHe stars through the prism of Gaia DR3: 3D distribution and Gaia's chromatic PSF effects

Upon its release the Gaia DR3 catalogue has led to tremendous progress in multiple fields of astronomy by providing the complete astrometric solution for nearly 1.5 billion sources. We analysed the photometric and astrometric results for Hydrogen-deficient Carbon (HdC), Extreme Helium (EHe), and DYPer type stars to identify any potential biases and thus to select stars suitable for kinematic and spatial distribution studies. We investigated the impact of photometric declines in R Coronae Borealis (RCB) stars on Gaia astrometry using information from the Gaia IPD process cross-matched with light curves. We have reached the conclusion that the astrometric fits for numerous RCB stars are not valid due to the Gaia PSF chromaticity effect in both shape and centroid. The astrometric results of all stars with a significant time-dependent colour variation should be similarly affected. RCB stars might thus be promising sources to correct this effect in future Gaia releases. Furthermore, after validating the Gaia astrometric results for 92 stars, we observed that the majority of HdC and EHe stars are distributed across the three old stellar structures, the thick disk, the bulge and the halo. However, we have also uncovered evidence indicating that some of them exhibit orbits characteristic of the thin disk. This is also particularly true for all DYPer type stars studied. Finally, we have produced a list of star memberships for each Galactic substructure, and provided a list of heliocentric radial velocities and associated errors for targets not observed by Gaia DR3. We are beginning to observe a relationship between kinematics, stellar population, and metallicity in RCB and EHe stars. That relation can be explained, within the double degenerate scenario, by the large range in the delay time distribution expected from population synthesis simulations, particularly through the HybCO merger channel.

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arXiv2023

ATCA Study of Small Magellanic Cloud Supernova Remnant 1E 0102.2-7219

We present new and archival Australia Telescope Compact Array and Atacama Large Millimeter/submillimeter Array data of the Small Magellanic Cloud supernova remnant 1E 0102.2-7219 at 2100, 5500, 9000, and 108000 MHz; as well as Hi data provided by the Australian Square Kilometre Array Pathfinder. The remnant shows a ring-like morphology with a mean radius of 6.2 pc. The 5500 MHz image reveals a bridge-like structure, seen for the first time in a radio image. This structure is also visible in both optical and X-ray images. In the 9000 MHz image we detect a central feature that has a flux density of 4.3 mJy but rule out a pulsar wind nebula origin, due to the lack of significant polarisation towards the central feature with an upper limit of 4 per cent. The mean fractional polarisation for 1E 0102.2-7219 is 7 +- 1 and 12 +- 2 per cent for 5500 and 9000 MHz, respectively. The spectral index for the entire remnant is -0.61 +- 0.01. We estimate the line-of-sight magnetic field strength in the direction of 1E 0102.2-7219 of ~44 microG with an equipartition field of 65 +- 5 microG. This latter model, uses the minimum energy of the sum of the magnetic field and cosmic ray electrons only. We detect an Hi cloud towards this remnant at the velocity range of ~160-180 km s-1 and a cavity-like structure at the velocity of 163.7-167.6 km s-1. We do not detect CO emission towards 1E 0102.2-7219.

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arXiv2023

No plateau observed in late-time near-infrared observations of the underluminous Type Ia supernova 2021qvv

Near-infrared (NIR) observations of normal Type Ia supernovae (SNe Ia) obtained between 150 to 500 d past maximum light reveal the existence of an extended plateau. Here, we present observations of the underluminous, 1991bg-like SN 2021qvv. Early, ground-based optical and NIR observations show that SN 2021qvv is similar to SN 2006mr, making it one of the dimmest, fastest-evolving 1991bg-like SNe to date. Late-time (170-250 d) Hubble Space Telescope observations of SN 2021qvv reveal no sign of a plateau. An extrapolation of these observations backwards to earlier-phase NIR observations of SN 2006mr suggests the complete absence of a NIR plateau, at least out to 250 d. This absence may be due to a higher ionization state of the ejecta, as predicted by certain sub-Chandrasekhar-mass detonation models, or to the lower temperatures of the ejecta of 1991bg-like SNe, relative to normal SNe Ia, which might preclude their becoming fluorescent and shifting ultraviolet light into the NIR. This suggestion can be tested by acquiring NIR imaging of a sample of 1991bg-like SNe that covers the entire range from slowly-evolving to fast-evolving events ($0.2 \lesssim s_\mathrm{BV} \lesssim 0.6$). A detection of the NIR plateau in slower-evolving, hotter 1991bg-like SNe would provide further evidence that these SNe exist along a continuum with normal SNe Ia. Theoretical progenitor and explosion scenarios would then have to match the observed properties of both SN Ia subtypes.

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arXiv2023

Observational constraints on the origin of the elements. V. Non-LTE abundance ratios of [Ni/Fe] in Galactic stars and enrichment by sub-Chandrasekhar mass SNe

We constrain the role of different SN Ia channels in the chemical enrichment of the Galaxy by studying the abundances of nickel in Galactic stars. We investigate four different SN Ia sub-classes, including the classical single-degenerate near-Chandrasekhar mass SN Ia, the fainter SN Iax systems associated with He accretion from the companion, as well as two sub-Ch mass SN Ia channels. The latter include the double-detonation of a white dwarf accreting helium-rich matter and violent white dwarf mergers. NLTE models of Fe and Ni are used in the abundance analysis. In the GCE models, we include new delay time distributions arising from the different SN Ia channels, as well as recent yields for core-collapse supernovae and AGB stars. The data-model comparison is performed using a Markov chain Monte Carlo framework that allows us to explore the entire parameter space allowed by the diversity of explosion mechanisms and the Galactic SN Ia rate, taking into account the uncertainties of the observed data. We show that NLTE effects have a non-negligible impact on the observed [Ni/Fe] ratios in the Galactic stars. The NLTE corrections to Ni abundances are not large, but strictly positive, lifting the [Ni/Fe] ratios by ~+0.15 dex at [Fe/H] =-2. We find that that the distributions of [Ni/Fe] in LTE and in NLTE are very tight, with a scatter of < 0.1 dex at all metallicities, supporting earlier work. In LTE, most stars have scaled-solar Ni abundances, [Ni/Fe] = 0, with a slight tendency for sub-solar [Ni/Fe] ratios at lower [Fe/H]. In NLTE, however, we find a mild anti-correlation between [Ni/Fe] and metallicity, and a slightly elevated [Ni/Fe] ratios at [Fe/H] < -1.0. The NLTE data can be explained by the GCE models calculated with a substantial, ~ 75%, fraction of sub-Ch SN Ia.

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arXiv2022

On the fate of the secondary white dwarf in double-degenerate double-detonation Type Ia supernovae

The progenitor systems and explosion mechanism of Type Ia supernovae are still unknown. Currently favoured progenitors include double-degenerate systems consisting of two carbon-oxygen white dwarfs with thin helium shells. In the double-detonation scenario, violent accretion leads to a helium detonation on the more massive primary white dwarf that turns into a carbon detonation in its core and explodes it. We investigate the fate of the secondary white dwarf, focusing on changes of the ejecta and observables of the explosion if the secondary explodes as well rather than survives. We simulate a binary system of a $1.05\,\mathrm{M_\odot}$ and a $0.7\,\mathrm{M_\odot}$ carbon-oxygen white dwarf with $0.03\,\mathrm{M_\odot}$ helium shells each. We follow the system self-consistently from inspiral to ignition, through the explosion, to synthetic observables. We confirm that the primary white dwarf explodes self-consistently. The helium detonation around the secondary white dwarf, however, fails to ignite a carbon detonation. We restart the simulation igniting the carbon detonation in the secondary white dwarf by hand and compare the ejecta and observables of both explosions. We find that the outer ejecta at $v~>~15\,000$\,km\,s$^{-1}$ are indistinguishable. Light curves and spectra are very similar until $\sim~40\,\mathrm{d}$ after explosion and the ejecta are much more spherical than violent merger models. The inner ejecta differ significantly slowing down the decline rate of the bolometric light curve after maximum of the model with a secondary explosion by $\sim20$ per cent. We expect future synthetic 3D nebular spectra to confirm or rule out either model.

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arXiv2022

The dawn of a new era for dustless HdC stars with GAIA eDR3

Decades after their discovery, only four hydrogen-deficient carbon (HdC) stars were known to have no circumstellar dust shell. This is in complete contrast to the $\sim$130 known Galactic HdC stars that are notorious for being heavy dust producers, i.e. the R Coronae Borealis (RCB) stars. Together they form a rare class of supergiant stars that are thought to originate from the merger of CO/He white dwarf binary systems, otherwise known as the double-degenerate scenario. We searched for new dustless HdC (dLHdC) stars. We used primarily the 2MASS and GAIA eDR3 catalogues to select candidates that were followed-up spectroscopically. We discovered 27 new dLHdC stars, one new RCB star and two new EHe stars. Surprisingly, 20 of the new dLHdC stars share a characteristic of the known dLHdC star HD 148839, having lower atmospheric hydrogen deficiencies. The uncovered population of dLHdC stars exhibit a Bulge-like distribution, like the RCB stars, but show multiple differences from those that indicate they are a different population of HdC stars following its own evolutionary sequence with a fainter luminosity and also a narrow range of effective temperature. We found indication of a current low dust production activity for four of the new dLHdC stars which could be typical RCB stars passing through a transition time. We have evidence for the first time of a large range of absolute magnitudes in the overall population of HdC stars, spanning over 3 mag. In the favoured formation framework, this is explained by a large range in the initial total WD binary mass which leads to a series of evolutionary sequences with distinct maximum brightness and initial temperature. The cold Galactic RCB stars are also noticeably fainter than the Magellanic ones, possibly due to a difference in metallicity resulting in different WD mass ratio. In our Galaxy, there could be as many dLHdC stars as RCB stars.

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arXiv2020

LIN 358: A symbiotic binary accreting above the steady hydrogen fusion limit

Symbiotic binaries are long period interacting binaries consisting of a white dwarf (WD) accreting material from a cool evolved giant star via stellar winds. In this paper we study the symbiotic binary LIN 358 located in the SMC. We have observed LIN 358 with the integral field spectrograph WiFeS and obtained its line emission spectrum. With the help of the plasma simulation and spectral synthesis code Cloudy, we have constructed a 2D photo-ionisation model of LIN 358. From comparison with the observations, we have determined the colour temperature of the WD in LIN 358 to be 19 eV, its bolometric luminosity $L = (1.02 \pm 0.15) \times 10^{38}$ erg s$^{-1}$, and the mass-loss rate from the donor star to be $ 1.2 \times 10^{-6}$ M$_{\odot}$ yr$^{-1}$. Assuming a solar H to He ratio in the wind material, a lower limit to the accreted mass fraction in LIN 358 is 0.31. The high mass-accretion efficiency of a wind Roche lobe overflow implies that the WD is accreting above the upper boundary of stable hydrogen fusion and thus growing in mass with the maximal rate of $\approx 4 \times 10^{-7}$ M$_{\odot}$ yr$^{-1}$. This causes the WD photosphere to expand, which explains its low colour temperature. Our calculations show that the circumstellar material in LIN 358 is nearly completely ionized except for a narrow cone around the donor star, and that the WD emission is freely escaping the system. However, due to its low colour temperature, this emission can be easily attenuated by even moderate amounts of neutral ISM. We speculate that other symbiotic systems may be operating in a similar regime, thus explaining the paucity of observed systems.

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arXiv2020

A supernova remnant associated with a nascent black hole low-mass X-ray binary

Energy released when the core of a high-mass star collapses into a black hole often powers an explosion that creates a supernova remnant. Black holes have limited windows of observability, and consequently are rarely identified in association with supernova remnants. Analysing multi-messenger data, we show that MAXI J1535-571 is the black hole produced in the stellar explosion that gave rise to the supernova remnant G323.7-1.0, making it the first case of an association between a black hole low-mass X-ray binary and a supernova remnant. Given this connection, we can infer from our modelling that the progenitor system was a close binary whose primary star had an initial mass of approx. 23-35 solar masses with a companion star about 10 times less massive.

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arXiv2020

Nucleosynthesis imprints from different Type Ia Supernova explosion scenarios and implications for galactic chemical evolution

We analyze the nucleosynthesis yields of various Type Ia supernova explosion simulations including pure detonations in sub- Chandrasekhar mass white dwarfs, double detonations and pure helium detonations of sub-Chandrasekhar mass white dwarfs with an accreted helium envelope, a violent merger model of two white dwarfs and deflagrations as well as delayed detonations in Chandrasekhar mass white dwarfs. We focus on the iron peak elements Mn, Zn and Cu. To this end, we also briefly review the different burning regimes and production sites of these elements as well as the results of abundance measurements and several galactic chemical evolution studies. We find that super-solar values of [Mn/Fe] are not restricted to Chandrasekhar mass explosion models. Scenarios including a helium detonation can significantly contribute to the production of Mn, in particular the models proposed for calcium-rich transients. Although Type Ia supernovae are often not accounted for as production sites of Zn and Cu, our models involving helium shell detonations can produce these elements in super-solar ratios relative to Fe. Our results suggest a re-consideration of Type Ia supernova yields in galactic chemical evolution models. A detailed comparison with observations can provide new insight into the progenitor and explosion channels of these events.

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arXiv2020

White dwarf deflagrations for Type Iax supernovae: Polarisation signatures from the explosion and companion interaction

Growing evidence suggests that Type Iax supernovae might be the result of thermonuclear deflagrations of Chandrasekhar-mass white dwarfs in binary systems. We carry out Monte Carlo radiative transfer simulations and predict spectropolarimetric features originating from the supernova explosion and subsequent ejecta interaction with the companion star. Specifically, we calculate viewing-angle dependent flux and polarisation spectra for a 3D model simulating the deflagration of a Chandrasekhar-mass white dwarf and, for a second model, simulating the ejecta interaction with a main-sequence star. We find that the intrinsic signal is weakly polarised and only mildly viewing-angle dependent, owing to the overall spherical symmetry of the explosion and the depolarising contribution of iron-group elements dominating the ejecta composition. The interaction with the companion star carves out a cavity in the ejecta and produces a detectable, but modest signal that is significant only at relatively blue wavelengths ($\lesssim$ 5000 $\unicode{x212B}$). In particular, increasingly fainter and redder spectra are predicted for observer orientations further from the cavity, while a modest polarisation signal $P\sim0.2$ per cent is found at blue wavelengths for orientations 30$^\circ$ and 45$^\circ$ away from the cavity. We find a reasonable agreement between the interaction model viewed from these orientations and spectropolarimetric data of SN 2005hk and interpret the maximum-light polarisation signal seen at blue wavelengths for this event as a possible signature of the ejecta-companion interaction. We encourage further polarimetric observations of SNe Iax to test whether our results can be extended and generalised to the whole SN Iax class.

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arXiv2019

Monte Carlo radiative transfer for the nebular phase of Type Ia supernovae

We extend the range of validity of the ARTIS 3D radiative transfer code up to hundreds of days after explosion, when Type Ia supernovae are in their nebular phase. To achieve this, we add a non-local thermodynamic equilibrium (non-LTE) population and ionisation solver, a new multi-frequency radiation field model, and a new atomic dataset with forbidden transitions. We treat collisions with non-thermal leptons resulting from nuclear decays to account for their contribution to excitation, ionisation, and heating. We validate our method with a variety of tests including comparing our synthetic nebular spectra for the well-known one-dimensional W7 model with the results of other studies. As an illustrative application of the code, we present synthetic nebular spectra for the detonation of a sub-Chandrasekhar white dwarf in which the possible effects of gravitational settling of Ne22 prior to explosion have been explored. Specifically, we compare synthetic nebular spectra for a 1.06 M$_\odot$ white dwarf model obtained when 5.5 Gyr of very-efficient settling is assumed to a similar model without settling. We find that this degree of Ne22 settling has only a modest effect on the resulting nebular spectra due to increased Ni58 abundance. Due to the high ionisation in sub-Chandrasekhar models, the nebular [Ni II] emission remains negligible, while the [Ni III] line strengths are increased and the overall ionisation balance is slightly lowered in the model with Ne22 settling. In common with previous studies of sub-Chandrasekhar models at nebular epochs, these models overproduce [Fe III] emission relative to [Fe II] in comparison to observations of normal Type Ia supernovae.

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arXiv2019

A Supernova Remnant Counterpart for HESS J1832-085

We examine the new Galactic supernova remnant (SNR) candidate, G23.11+0.18, as seen by the Murchison Widefield Array (MWA) radio telescope. We describe the morphology of the candidate and find a spectral index of -0.63+/-0.05 in the 70-170MHz domain. A coincident TeV gamma-ray detection in High-Energy Stereoscopic System (HESS) data supports the SNR nature of G23.11+0.18 and suggests that G23.11+0.18 is accelerating particles beyond TeV energies, thus making this object a promising new cosmic ray hadron source candidate. The remnant cannot be seen in current optical, infrared and X-ray data-sets. We do find, however, a dip in CO-traced molecular gas at a line-of-sight velocity of ~85 km/s, suggesting the existence of a G23.11+0.18 progenitor wind-blown bubble. Furthermore, the discovery of molecular gas clumps at a neighbouring velocity towards HESS J1832-085 adheres to the notion that a hadronic gamma-ray production mechanism is plausible towards the north of the remnant. Based on these morphological arguments, we propose an interstellar medium association for G23.11+0.18 at a kinematic distance of 4.6+/-0.8 kpc.

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arXiv2019

Identification of the Central Compact Object in the young supernova remnant 1E0102.2-7219

Oxygen-rich young supernova remnants are valuable objects for probing the outcome of nucleosynthetic processes in massive stars, as well as the physics of supernova explosions. Observed within a few thousand years after the supernova explosion, these systems contain fast-moving oxygen-rich and hydrogen-poor filaments visible at optical wavelengths: fragments of the progenitor's interior expelled at a few 1000 km/s during the supernova explosion. Here we report the first identification of the compact object in 1E0102.2-7219 in reprocessed Chandra X-ray Observatory data, enabled via the discovery of a ring-shaped structure visible primarily in optical recombination lines of Ne I and O I. The optical ring, discovered in integral field spectroscopy observations from the Multi Unit Spectroscopic Explorer (MUSE) at the Very Large Telescope, has a radius of $(2.10\pm0.35)$ arcsec = $(0.63\pm0.11)$ pc, and is expanding at a velocity of $90.5_{-30}^{+40}$ km/s. It surrounds an X-ray point source with an intrinsic X-ray luminosity $L_{i}$ (1.2--2.0 keV)= $(1.4\pm0.2)\times10^{33}$ erg/s. The energy distribution of the source indicates that this object is an isolated neutron star: a Central Compact Object akin to those present in the Cas A and Puppis A supernova remnants, and the first of its kind to be identified outside of our Galaxy.

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