ORCID Profile
0000-0002-5044-2988
Current Organisation
UNSW Australia
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Astronomical and Space Sciences | Galactic Astronomy | Astronomical sciences | Stellar Astronomy and Planetary Systems | Astronomy And Astrophysics | High Energy Astrophysics; Cosmic Rays | Astronomical sciences not elsewhere classified | Astronomical instrumentation | Cosmology and Extragalactic Astronomy | Astronomical and Space Instrumentation |
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Physical Sciences | Physical sciences | Expanding Knowledge in Technology |
Related Links
Publications
The late-time light curve of the Type Ia supernova SN 2011fe
Publisher: Oxford University Press (OUP)
Date: 22-03-2017
DOI: 10.1093/MNRAS/STX683
Spectral modelling of the ‘super-Chandrasekhar’ Type Ia SN 2009dc – testing a 2 M⊙white dwarf explosion model and alternatives
Publisher: Oxford University Press (OUP)
Date: 20-11-2012
ASYMMETRY AND THE NUCLEOSYNTHETIC SIGNATURE OF NEARLY EDGE-LIT DETONATION IN WHITE DWARF CORES
Publisher: American Astronomical Society
Date: 09-12-2011
Extremely late photometry of the nearby SN 2011fe
Publisher: Oxford University Press (OUP)
Date: 29-08-2017
Locating the CSM Emission within the Type Ia Supernova Remnant N103B
Publisher: American Astronomical Society
Date: 02-2022
Abstract: We present results from deep Chandra observations of the young Type Ia supernova remnant (SNR) 0509–68.7, also known as N103B, located in the Large Magellanic Cloud (LMC). The remnant displays an asymmetry in brightness, with the western hemisphere appearing significantly brighter than the eastern one. Previous multiwavelength observations have attributed the difference to a density gradient and suggested origins in circumstellar material, drawing similarities to Kepler’s SNR. We apply a clustering technique combined with traditional imaging analysis to spatially locate various emission components within the remnant. We find that O and Mg emission is strongest along the blast wave, and coincides with Spitzer observations of dust emission and optical emission from the nonradiative shocks. The abundances of O and Mg in these regions are enhanced relative to the average LMC abundances and appear as a distinct spatial distribution compared to the ejecta products, supporting the interpretation based on a circumstellar medium. We also find that the spatial distribution of Cr is identical to that of Fe in the interior of the remnant, and does not coincide at all with the O and Mg emission.
Excluding supersoft X-ray sources as progenitors for four Type Ia supernovae in the Large Magellanic Cloud
Publisher: Oxford University Press (OUP)
Date: 16-01-2019
DOI: 10.1093/MNRAS/STZ065
Nucleosynthesis in surface detonation models of Type Ia supernovae
Publisher: Sissa Medialab
Date: 06-07-2011
DOI: 10.22323/1.100.0069
Multi-dimensional models of Type Ia supernovae
Publisher: Sissa Medialab
Date: 06-07-2011
DOI: 10.22323/1.100.0067
SN1991bg-like supernovae are associated with old stellar populations
Publisher: Cambridge University Press (CUP)
Date: 2019
DOI: 10.1017/PASA.2019.24
Abstract: SN1991bg-like supernovae are a distinct subclass of thermonuclear Type Ia supernovae (SNe Ia). Their spectral and photometric peculiarities indicate that their progenitors and explosion mechanisms differ from ‘normal’ SNe Ia. One method of determining information about supernova progenitors we cannot directly observe is to observe the stellar population adjacent to the apparent supernova explosion site to infer the distribution of stellar population ages and metallicities. We obtain integral field observations and analyse the spectra extracted from regions of projected radius $\\sim\\,\\text{kpc}$ about the apparent SN explosion site for 11 91bg-like SNe in both early- and late-type galaxies. We utilise full-spectrum spectral fitting to determine the ages and metallicities of the stellar population within the aperture. We find that the majority of the stellar populations that hosted 91bg-like supernovae have little recent star formation. The ages of the stellar populations suggest that that 91bg-like SN progenitors explode after delay times of Gyr, much longer than the typical delay time of normal SNe Ia, which peaks at $\\sim$ 1 Gyr.
Measuring nickel masses in Type Ia supernovae using cobalt emission in nebular phase spectra
Publisher: Oxford University Press (OUP)
Date: 23-10-2015
Three-dimensional pure deflagration models with nucleosynthesis and synthetic observables for Type Ia supernovae
Publisher: Oxford University Press (OUP)
Date: 31-12-2013
The late-time light curves of Type Ia supernovae: confronting models with observations
Publisher: Oxford University Press (OUP)
Date: 20-06-2022
Abstract: Type Ia supernovae (SNe Ia) play a crucial role as standardizable candles in measurements of the Hubble constant and dark energy. Increasing evidence points towards multiple possible explosion channels as the origin of normal SNe Ia, with possible systematic effects on the determination of cosmological parameters. We present, for the first time, a comprehensive comparison of publicly available SN Ia model nucleosynthetic data with observations of late-time light curve observations of SN Ia events. These models span a wide range of white dwarf (WD) progenitor masses, metallicities, explosion channels, and numerical methodologies. We focus on the influence of 57Ni and its isobaric decay product 57Co in powering the late-time (t & 1000 d) light curves of SNe Ia. 57Ni and 57Co are neutron-rich relative to the more abundant radioisotope 56Ni, and are consequently a sensitive probe of neutronization at the higher densities of near-Chandrashekhar (near-MCh) progenitor WDs. We demonstrate that observations of one SN Ia event, SN 2015F is only consistent with a sub-Chandrasekhar (sub-MCh) WD progenitor. Observations of four other events (SN 2011fe, SN 2012cg, SN 2014J, and SN2013aa) are consistent with both near-MCh and sub-MCh progenitors. Continued observations of late-time light curves of nearby SNe Ia will provide crucial information on the nature of the SN Ia progenitors.
Solar abundance of manganese: a case for near Chandrasekhar-mass Type Ia supernova progenitors
Publisher: EDP Sciences
Date: 11-2013
arepo white dwarf merger simulations resulting in edge-lit detonation and run-away hypervelocity companion
Publisher: Oxford University Press (OUP)
Date: 11-05-2023
Abstract: We present a series of high-resolution simulations generated with the moving-mesh code arepo to model the merger of a 1.1-M⊙ carbon-oxygen primary white dwarf (WD) with an outer helium layer and a 0.35-M⊙ secondary helium WD. Our simulations lead to detonations that are consistent with the edge-lit scenario, where a helium detonation is ignited at the base of the helium layer of the primary WD, which triggers an off-centre carbon detonation. This produces an asymmetric ejecta pattern and differences in line-of-sight observables (e.g. mean atomic weight). The ejecta that are flung into space are dominated by 56Ni, 4He, 28Si, and 32S. Our simulations result in a surviving degenerate companion of mass 0.22–0.25 M⊙ moving at & $\\mathrm{km}\\, \\mathrm{s}^{-1}$, consistent with the observational findings of hypervelocity WDs. The secondary’s surface layers are enriched by heavy metals, with 56Ni making up approximately 0.8 per cent of the remaining mass. We also analyse the sensitivity of the outcome on simulation parameters, including the ‘inspiral time’, which defines a period of accelerated angular momentum loss. We find that the choice of ‘inspiral time’ qualitatively influences the simulation result, including the survival of the secondary. We argue that the shorter inspiral cases result in qualitatively and quantitatively similar outcomes. We also investigate the sensitivity of our results on the primary’s chemical profile by comparing simulations using isothermal, constant composition models with the same mass and central composition and characterized by either a bare carbon-oxygen core (no helium) or a carbon-oxygen core enveloped by a thick helium layer.
Type Ia Supernovae from Sub-Chandrasekhar Mass White Dwarfs
Publisher: Cambridge University Press (CUP)
Date: 07-2011
DOI: 10.1017/S1743921312015189
Abstract: We argue that detonations of sub-Chandrasekhar mass white dwarfs can lead to bright explosions with light curves and spectra similar to those of observed Type Ia supernovae. Given that binary systems containing accreting sub-Chandrasekhar mass white dwarfs should be common, this suggests that a non-negligible fraction of the observed Type Ia supernova rate may arise from sub-Chandrasekhar mass explosions, if they can be ignited. We discuss aspects of how such explosions might be realized in nature and both merits and challenges associated with invoking sub-Chandrasekhar mass explosion models to account for observed Type Ia supernovae.
Author Correction: The messy death of a multiple star system and the resulting planetary nebula as observed by JWST
Publisher: Springer Science and Business Media LLC
Date: 03-01-2023
INITIATION OF THE DETONATION IN THE GRAVITATIONALLY CONFINED DETONATION MODEL OF TYPE Ia SUPERNOVAE
Publisher: American Astronomical Society
Date: 06-07-2009
First extragalactic measurement of the turbulence driving parameter: ALMA observations of the star-forming region N159E in the Large Magellanic Cloud
Publisher: Oxford University Press (OUP)
Date: 21-10-2021
Abstract: Studying the driving modes of turbulence is important for characterizing the impact of turbulence in various astrophysical environments. The driving mode of turbulence is parameterized by b, which relates the width of the gas density PDF to the turbulent Mach number b ≈ 1/3, 1, and 0.4 correspond to driving that is solenoidal, compressive, and a natural mixture of the two, respectively. In this work, we use high-resolution (sub-pc) ALMA 12CO (J = 2–1), 13CO (J = 2–1), and C18O (J = 2–1) observations of filamentary molecular clouds in the star-forming region N159E (the Papillon Nebula) in the Large Magellanic Cloud (LMC) to provide the first measurement of turbulence driving parameter in an extragalactic region. We use a non-local thermodynamic equilibrium (NLTE) analysis of the CO isotopologues to construct a gas density PDF, which we find to be largely log-normal in shape with some intermittent features indicating deviations from lognormality. We find that the width of the log-normal part of the density PDF is comparable to the supersonic turbulent Mach number, resulting in b ≈ 0.9. This implies that the driving mode of turbulence in N159E is primarily compressive. We speculate that the compressive turbulence could have been powered by gravo-turbulent fragmentation of the molecular gas, or due to compression powered by H I1.2ex flows that led to the development of the molecular filaments observed by ALMA in the region. Our analysis can be easily applied to study the nature of turbulence driving in resolved star-forming regions in the local as well as the high-redshift Universe.
Remnants and ejecta of thermonuclear electron-capture supernovae
Publisher: EDP Sciences
Date: 30-01-2019
DOI: 10.1051/0004-6361/201834381
Abstract: The explosion mechanism of electron-capture supernovae (ECSNe) remains equivocal: it is not completely clear whether these events are implosions in which neutron stars are formed, or incomplete thermonuclear explosions that leave behind bound ONeFe white dwarf remnants. Furthermore, the frequency of occurrence of ECSNe is not known, though it has been estimated to be of the order of a few per cent of all core-collapse supernovae. We attempt to constrain the explosion mechanism (neutron-star-forming implosion or thermonuclear explosion) and the frequency of occurrence of ECSNe using nucleosynthesis simulations of the latter scenario, population synthesis, the solar abundance distribution, pre-solar meteoritic oxide grain isotopic ratio measurements and the white dwarf mass–radius relation. Tracer particles from the 3d hydrodynamic simulations were post-processed with a large nuclear reaction network in order to determine the complete compositional state of the bound ONeFe remnant and the ejecta, and population synthesis simulations were performed in order to estimate the ECSN rate with respect to the CCSN rate. The 3d deflagration simulations drastically overproduce the neutron-rich isotopes 48 Ca, 50 Ti, 54 Cr , 60 Fe and several of the Zn isotopes relative to their solar abundances. Using the solar abundance distribution as our constraint, we place an upper limit on the frequency of thermonuclear ECSNe as 1−3% the frequency at which core-collapse supernovae (FeCCSNe) occur. This is on par with or 1 dex lower than the estimates for ECSNe from single stars. The upper limit from the yields is also in relatively good agreement with the predictions from our population synthesis simulations. The 54 Cr/ 52 Cr and 50 Ti/ 48 Ti isotopic ratios in the ejecta are a near-perfect match with recent measurements of extreme pre-solar meteoritc oxide grains, and 53 Cr/ 52 Cr can also be matched if the ejecta condenses before mixing with the interstellar medium. The composition of the ejecta of our simulations implies that ECSNe, including accretion-induced collapse of oxygen-neon white dwarfs, could actually be partial thermonuclear explosions and not implosions that form neutron stars. There is still much work to do to improve the hydrodynamic simulations of such phenomena, but it is encouraging that our results are consistent with the predictions from stellar evolution modelling and population synthesis simulations, and can explain several key isotopic ratios in a sub-set of pre-solar oxide meteoritic grains. Theoretical mass–radius relations for the bound ONeFe WD remnants of these explosions are apparently consistent with several observational WD candidates. The composition of the remnants in our simulations can reproduce several, but not all, of the spectroscopically-determined elemental abundances from one such candidate WD.
The ANU WiFeS SuperNovA Programme (AWSNAP)
Publisher: Cambridge University Press (CUP)
Date: 2016
DOI: 10.1017/PASA.2016.47
Abstract: This paper presents the first major data release and survey description for the ANU WiFeS SuperNovA Programme. ANU WiFeS SuperNovA Programme is an ongoing supernova spectroscopy c aign utilising the Wide Field Spectrograph on the Australian National University 2.3-m telescope. The first and primary data release of this programme (AWSNAP-DR1) releases 357 spectra of 175 unique objects collected over 82 equivalent full nights of observing from 2012 July to 2015 August. These spectra have been made publicly available via the WISEREP supernova spectroscopy repository. We analyse the ANU WiFeS SuperNovA Programme s le of Type Ia supernova spectra, including measurements of narrow sodium absorption features afforded by the high spectral resolution of the Wide Field Spectrograph instrument. In some cases, we were able to use the integral-field nature of the Wide Field Spectrograph instrument to measure the rotation velocity of the SN host galaxy near the SN location in order to obtain precision sodium absorption velocities. We also present an extensive time series of SN 2012dn, including a near-nebular spectrum which both confirms its ‘super-Chandrasekhar’ status and enables measurement of the sub-solar host metallicity at the SN site.
Neutrino and gravitational wave signal of a delayed-detonation model of type Ia supernovae
Publisher: American Physical Society (APS)
Date: 09-12-2015
LATE-TIME PHOTOMETRY OF TYPE IA SUPERNOVA SN 2012cg REVEALS THE RADIOACTIVE DECAY OF57Co
Publisher: American Astronomical Society
Date: 24-02-2016
Searching for Surviving Companion in the Young SMC Supernova Remnant 1E 0102.2–7219
Publisher: American Astronomical Society
Date: 29-06-2021
Abstract: 1E 0102.2–7219 (hereafter E0102) is a young supernova remnant (SNR) in the Small Magellanic Cloud. It contains oxygen-rich SN ejecta, a possible neutron star (NS), and a small amount of fast-moving H-rich ejecta material. These properties are also seen in Cas A it has thus been suggested that E0102 is also a Type IIb SNR, whose SN progenitor’s hydrogen envelope was stripped off possibly via interactions with a companion star. To search for a surviving companion of E0102's SN progenitor, we have used archival Hubble Space Telescope (HST) continuum images to make photometric measurements of stars projected in the SNR to construct color–magnitude diagrams and compare the stars with those expected from surviving companions of Type IIb SNe. We have also used the Multi-Unit Spectroscopic Explorer observations taken with the Very Large Telescope to perform spectroscopic analyses of stars and search for peculiar radial velocities as diagnostics of surviving companions. We further use the HST and Gaia data to inspect proper motions of stars for complementary kinetic studies. No plausible companion candidates are found if the SN explosion site was near the NS, while the B3 V star 34a may be a plausible companion candidate if the SN explosion site is near the SN ejecta’s expansion center. If the NS is real and associated with E0102, it needs a ∼1000 km s −1 runaway velocity, which has been observed in other SNRs and can be acquired from an asymmetric SN explosion or a kick by the SN explosion of a massive companion.
An X-Ray Proper-motion Study of the Large Magellanic Cloud Supernova Remnant 0509-67.5
Publisher: American Astronomical Society
Date: 02-11-2022
Abstract: We present a third epoch of Chandra observations of the Type Ia Large Magellanic Cloud Supernova remnant 0509-67.5. With these new observations from 2020, the baseline for proper-motion measurements of the expansion has grown to 20 yr (from the earliest Chandra observations in 2000). We report here the results of these new expansion measurements. The lack of nearby bright point sources renders absolute image alignment difficult. However, we are able to measure the average expansion of the diameter of the remnant along several projection directions. We find that the remnant is expanding with an average velocity of 6120 (4900–7360) km s −1 . This high shock velocity is consistent with previous works, and also consistent with the inference that 0509-67.5 is expanding into a very low density surrounding medium. At the distance of the LMC, this velocity corresponds to an undecelerated age of 600 yr, with the real age somewhat smaller.
Late-time supernova light curves: the effect of internal conversion and Auger electrons
Publisher: Oxford University Press (OUP)
Date: 21-11-2009
Companions of post-common envelope sdB binaries
Publisher: Springer Science and Business Media LLC
Date: 2004
LIN 358: a symbiotic binary accreting above the steady hydrogen fusion limit
Publisher: Oxford University Press (OUP)
Date: 10-11-2020
Abstract: 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 Small Magellanic Cloud. 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 photoionization 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 ± 0.15) × 1038 erg s−1, and the mass-loss rate from the donor star to be 1.2 × 10−6 M⊙ 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 ≈4 × 10−7 M⊙ 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 interstellar medium. We speculate that other symbiotic systems may be operating in a similar regime, thus explaining the paucity of observed systems.
Predicting polarization signatures for double-detonation and delayed-detonation models of Type Ia supernovae
Publisher: Oxford University Press (OUP)
Date: 18-07-2016
A spectral classification system for hydrogen-deficient carbon stars
Publisher: Oxford University Press (OUP)
Date: 02-02-2023
Abstract: Stellar spectral classification has been highly useful in the study of stars. While there is a currently accepted spectral classification system for carbon stars, the subset of hydrogen-deficient carbon (HdC) stars has not been well described by such a system, due predominantly to their rarity and their variability. Here we present the first system for the classification of HdCs based on their spectra, which is made wholly on their observable appearance. We use a combination of dimensionality reduction and clustering algorithms with human classification to create such a system with eight total classes corresponding to temperature, and an additional second axis corresponding to the carbon molecular band strength. We classify over half of the known s le of HdC stars using this, and roughly calibrate the temperatures of each class using their colours. Additionally, we express trends in the occurrence of certain spectral peculiarities such as the presence of hydrogen and lithium lines. We also present three previously unpublished spectra, report the discovery of two new Galactic dustless HdC stars, and additionally discuss one especially unique star that appears to border between the hottest HdCs and the coolest extreme helium stars.
Proton-rich Nuclear Statistical Equilibrium
Publisher: American Astronomical Society
Date: 05-09-2008
DOI: 10.1086/592501
VERY LATE PHOTOMETRY OF SN 2011fe
Publisher: American Astronomical Society
Date: 17-11-2014
A kilonova as the electromagnetic counterpart to a gravitational-wave source
Publisher: Springer Science and Business Media LLC
Date: 16-10-2017
DOI: 10.1038/NATURE24303
Abstract: Gravitational waves were discovered with the detection of binary black-hole mergers and they should also be detectable from lower-mass neutron-star mergers. These are predicted to eject material rich in heavy radioactive isotopes that can power an electromagnetic signal. This signal is luminous at optical and infrared wavelengths and is called a kilonova. The gravitational-wave source GW170817 arose from a binary neutron-star merger in the nearby Universe with a relatively well confined sky position and distance estimate. Here we report observations and physical modelling of a rapidly fading electromagnetic transient in the galaxy NGC 4993, which is spatially coincident with GW170817 and with a weak, short γ-ray burst. The transient has physical parameters that broadly match the theoretical predictions of blue kilonovae from neutron-star mergers. The emitted electromagnetic radiation can be explained with an ejected mass of 0.04 ± 0.01 solar masses, with an opacity of less than 0.5 square centimetres per gram, at a velocity of 0.2 ± 0.1 times light speed. The power source is constrained to have a power-law slope of -1.2 ± 0.3, consistent with radioactive powering from r-process nuclides. (The r-process is a series of neutron capture reactions that synthesise many of the elements heavier than iron.) We identify line features in the spectra that are consistent with light r-process elements (atomic masses of 90-140). As it fades, the transient rapidly becomes red, and a higher-opacity, lanthanide-rich ejecta component may contribute to the emission. This indicates that neutron-star mergers produce gravitational waves and radioactively powered kilonovae, and are a nucleosynthetic source of the r-process elements.
Modelling the ionization state of Type Ia supernovae in the nebular phase
Publisher: Oxford University Press (OUP)
Date: 05-04-2022
Abstract: The nebular spectra of Type Ia supernovae (⪆100 d after explosion) consist mainly of emission lines from singly and doubly ionized Fe-group nuclei. However, theoretical models for many scenarios predict that non-thermal ionization leads to multiply ionized species whose recombination photons ionize and deplete Fe+, resulting in negligible [Fe ii] emission. We investigate a method to determine the collisional excitation conditions from [Fe ii] line ratios independently from the ionization state and find that it cannot be applied to highly ionized models due to the influence of recombination cascades on Fe+ level populations. When the ionization state is artificially lowered, the line ratios (and excitation conditions) are too similar to distinguish between explosion scenarios. We investigate changes to the treatment of non-thermal energy deposition as a way to reconcile overionized theoretical models with observations and find that a simple work function approximation provides closer agreement with the data for sub-Mch models than a detailed Spencer–Fano treatment with widely used cross-section data. To quantify the magnitude of additional heating processes that would be required to sufficiently reduce ionization from fast leptons, we artificially boost the rate of energy loss to free electrons. We find that the equivalent of as much as an eight times increase to the plasma loss rate would be needed to reconcile the sub-Mch model with observed spectra. Future studies could distinguish between reductions in the non-thermal ionization rates and increased recombination rates, such as by clumping.
Type Ia supernovae from exploding oxygen-neon white dwarfs
Publisher: EDP Sciences
Date: 08-2015
Integral Field Spectroscopy of Balmer-dominated Shocks in the Magellanic Cloud Supernova Remnant N103B
Publisher: American Astronomical Society
Date: 29-09-2017
SPONTANEOUS INITIATION OF DETONATIONS IN WHITE DWARF ENVIRONMENTS: DETERMINATION OF CRITICAL SIZES
Publisher: American Astronomical Society
Date: 15-04-2009
Nucleosynthesis in Thermonuclear Supernovae
Publisher: Springer International Publishing
Date: 2017
Nucleosynthesis in Thermonuclear Supernovae
Publisher: Springer International Publishing
Date: 2017
Monte Carlo radiative transfer for the nebular phase of Type Ia supernovae
Publisher: Oxford University Press (OUP)
Date: 31-12-2019
Abstract: We extend the range of validity of the artis 3D radiative transfer code up to hundreds of days after explosion, when Type Ia supernovae (SNe Ia) are in their nebular phase. To achieve this, we add a non-local thermodynamic equilibrium population and ionization solver, a new multifrequency radiation field model, and a new atomic data set with forbidden transitions. We treat collisions with non-thermal leptons resulting from nuclear decays to account for their contribution to excitation, ionization, 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 (WD) in which the possible effects of gravitational settling of 22Ne prior to explosion have been explored. Specifically, we compare synthetic nebular spectra for a 1.06 M⊙ WD model obtained when 5.5 Gyr of very efficient settling is assumed to a similar model without settling. We find that this degree of 22Ne settling has only a modest effect on the resulting nebular spectra due to increased 58Ni abundance. Due to the high ionization in sub-Chandrasekhar models, the nebular [Ni ii] emission remains negligible, while the [Ni iii] line strengths are increased and the overall ionization balance is slightly lowered in the model with 22Ne 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 SNe Ia.
Sub-Chandrasekhar models for Type Ia supernovae and astrophysical transients
Publisher: Sissa Medialab
Date: 24-04-2013
DOI: 10.22323/1.146.0050
A metric space for Type Ia supernova spectra: a new method to assess explosion scenarios
Publisher: Oxford University Press (OUP)
Date: 22-12-2016
Erratum: three-dimensional delayed-detonation models with nucleosynthesis for Type Ia supernovae
Publisher: Oxford University Press (OUP)
Date: 16-08-2014
Connecting the progenitors, pre-explosion variability and giant outbursts of luminous blue variables with Gaia16cfr
Publisher: Oxford University Press (OUP)
Date: 13-10-2017
STUDY OF THE DETONATION PHASE IN THE GRAVITATIONALLY CONFINED DETONATION MODEL OF TYPE Ia SUPERNOVAE
Publisher: American Astronomical Society
Date: 05-03-2009
The messy death of a multiple star system and the resulting planetary nebula as observed by JWST
Publisher: Springer Science and Business Media LLC
Date: 08-12-2022
Late-time Observations of ASASSN-14lp Strengthen the Case for a Correlation between the Peak Luminosity of Type Ia Supernovae and the Shape of Their Late-time Light Curves
Publisher: American Astronomical Society
Date: 05-10-2018
Preliminary Results From CCD Monitoring: Light Curves Of Subdwarf B Stars
Publisher: Springer Netherlands
Date: 2003
Discovery of a new class of pulsating stars: Gravity-mode pulsators among subdwarf B stars
Publisher: Springer Science and Business Media LLC
Date: 2003
The effect of helium accretion efficiency on rates of Type Ia supernovae: double detonations in accreting binaries
Publisher: Oxford University Press (OUP)
Date: 08-03-2014
Optical Tomography of Chemical Elements Synthesized in Type Ia Supernovae
Publisher: American Physical Society (APS)
Date: 22-07-2019
THE ORIGIN OF THE IRON-RICH KNOT IN TYCHO’S SUPERNOVA REMNANT
Publisher: American Astronomical Society
Date: 09-01-2017
Calibrating Interstellar Abundances Using Supernova Remnant Radiative Shocks
Publisher: American Astronomical Society
Date: 14-01-2019
Deflagrations in hybrid CONe white dwarfs: a route to explain the faint Type Iax supernova 2008ha
Publisher: Oxford University Press (OUP)
Date: 09-05-2015
DOI: 10.1093/MNRAS/STV886
Neutrinos from type Ia supernovae: The gravitationally confined detonation scenario
Publisher: American Physical Society (APS)
Date: 21-02-2017
Type Ia supernovae: exposing models to observations
Publisher: Sissa Medialab
Date: 24-04-2013
DOI: 10.22323/1.146.0046
3D deflagration simulations leaving bound remnants: a model for 2002cx-like Type Ia supernovae★
Publisher: Oxford University Press (OUP)
Date: 21-12-2012
DOI: 10.1093/MNRAS/STS498
SN1991bg-like supernovae are a compelling source of most Galactic antimatter
Publisher: Cambridge University Press (CUP)
Date: 07-2017
DOI: 10.1017/S1743921316011911
Abstract: The Milky Way Galaxy glows with the soft gamma ray emission resulting from the annihilation of ~5 × 10 43 electron-positron pairs every second. The origin of this vast quantity of antimatter and the peculiar morphology of the 511keV gamma ray line resulting from this annihilation have been the subject of debate for almost half a century. Most obvious positron sources are associated with star forming regions and cannot explain the rate of positron annihilation in the Galactic bulge, which last saw star formation some 10 Gyr ago, or else violate stringent constraints on the positron injection energy. Radioactive decay of elements formed in core collapse supernovae (CCSNe) and normal Type Ia supernovae (SNe Ia) could supply positrons matching the injection energy constraints but the distribution of such potential sources does not replicate the required morphology. We show that a single class of peculiar thermonuclear supernova - SN1991bg-like supernovae (SNe 91bg) - can supply the number and distribution of positrons we see annihilating in the Galaxy through the decay of 44 Ti synthesised in these events. Such 44 Ti production simultaneously addresses the observed abundance of 44 Ca, the 44 Ti decay product, in solar system material.
5.9-keV Mn K-shell X-ray luminosity from the decay of 55Fe in Type Ia supernova models
Publisher: Oxford University Press (OUP)
Date: 31-12-2014
[Fe XIV] and [Fe XI] reveal the forward shock in SNR 1E 0102.2-7219
Publisher: EDP Sciences
Date: 06-2017
Identification of the central compact object in the young supernova remnant 1E 0102.2–7219
Publisher: Springer Science and Business Media LLC
Date: 02-04-2018
Neutrinos from type Ia supernovae: The deflagration-to-detonation transition scenario
Publisher: American Physical Society (APS)
Date: 19-07-2016
Proton Rich Nuclear Statistical Equilibrium
Publisher: Sissa Medialab
Date: 29-07-2009
DOI: 10.22323/1.053.0125
Linking the X3D Pathway to Integral Field Spectrographs: YSNR 1E 0102.2-7219 in the SMC as a Case Study
Publisher: IOP Publishing
Date: 17-04-2017
DOI: 10.1088/1538-3873/129/975/058012
Abstract: The concept of the x3d pathway was introduced by Vogt et al. as a new approach to sharing and publishing three-dimensional structures interactively in online scientific journals. The core characteristics of the x3d pathway are that: (1) it does not rely on specific software, but rather a file format ( x3d ), (2) it can be implemented using fully open-source tools, and (3) article readers can access the interactive models using most main stream web browsers without the need for any additional plugins. In this article, we further demonstrate the potential of the x3d pathway to visualize data sets from optical integral field spectrographs. We use recent observations of the oxygen-rich young supernova remnant 1E 0102.2-7219 in the Small Magellanic Cloud to implement additional x3dom tools & techniques and expand the range of interactions that can be offered to article readers. In particular, we present a set of javascript functions allowing the creation and interactive handling of clip planes, effectively allowing users to take measurements of distances and angles directly from the interactive model itself.
New optically identified supernova remnants in the Large Magellanic Cloud
Publisher: Oxford University Press (OUP)
Date: 02-11-2021
Abstract: We present a new optical s le of three Supernova Remnants (SNRs) and 16 Supernova Remnant (SNR) candidates in the Large Magellanic Cloud (LMC). These objects were originally selected using deep H α, [S ii], and [O iii] narrow-band imaging. Most of the newly found objects are located in less dense regions, near or around the edges of the LMC’s main body. Together with previously suggested MCSNR J0541–6659, we confirm the SNR nature for two additional new objects: MCSNR J0522–6740 and MCSNR J0542–7104. Spectroscopic follow-up observations for 12 of the LMC objects confirm high [S ii]/H α emission-line ratios ranging from 0.5 to 1.1. We consider the candidate J0509–6402 to be a special ex le of the remnant of a possible type Ia Supernova (SN) which is situated some 2° (∼1.75 kpc) north from the main body of the LMC. We also find that the SNR candidates in our s le are significantly larger in size than the currently known LMC SNRs by a factor of ∼2. This could potentially imply that we are discovering a previously unknown but predicted, older class of large LMC SNRs that are only visible optically. Finally, we suggest that most of these LMC SNRs are residing in a very rarefied environment towards the end of their evolutionary span where they become less visible to radio and X-ray telescopes.
A year-long plateau in the late-time near-infrared light curves of type Ia supernovae
Publisher: Springer Science and Business Media LLC
Date: 07-10-2019
First Results of the SkyMapper Transient Survey
Publisher: Cambridge University Press (CUP)
Date: 11-2019
DOI: 10.1017/S1743921318002077
Abstract: The SkyMapper Transient survey (SMT) is exploring variability in the southern sky by performing (a) a rolling search to discover and study supernovæ, and (b) a Target of Opportunity programme that uses the robotic SkyMapper Telescope at Siding Spring Observatory. The supernova survey is obtaining a non-targeted s le of Type Ia supernovæ (SNe Ia) at low redshifts, z 0.1, and studying other interesting transients found with the search strategy. We have a Target of Opportunity programme with an automatic response mechanism to search for optical counterparts to gravitational-wave and fast radio-burst events it benefits from SkyMapper’s large field of view of 5.7 sq. deg. and a rapid data reduction pipeline. We present first results of the SMT survey. The SMT pipeline can process and obtain potential candidates within 12 hours of observation. It disentangles real transients from processing artefacts using a machine-learning algorithm. To date, SMT has discovered over 60 spectroscopically confirmed supernovæ, several peculiar objects, and over 40 SNe Ia including one (SNIa 2016hhd) which was found within the first few days of explosion. We have also participated in searches for optical counterparts of gravitational waves, fast radio bursts and other transients, and have published observations of the optical counterpart of the gravitational-wave event GW170817. We also participate in coordinated observations with the Deeper Wider Faster programme, and the Kepler K2 cosmology project.
THE LIGHT CURVE OF SN 1987A REVISITED: CONSTRAINING PRODUCTION MASSES OF RADIOACTIVE NUCLIDES
Publisher: American Astronomical Society
Date: 08-08-2014
THE FIRST MAXIMUM-LIGHT ULTRAVIOLET THROUGH NEAR-INFRARED SPECTRUM OF A TYPE Ia SUPERNOVA ,
Publisher: American Astronomical Society
Date: 13-06-2012
On the brightness distribution of Type Ia supernovae from violent white dwarf mergers
Publisher: Oxford University Press (OUP)
Date: 17-12-2012
DOI: 10.1093/MNRAS/STS423
Discovery of A New Class of Pulsating Stars: Gravity-Mode Pulsators among Subdwarf B Stars
Publisher: American Astronomical Society
Date: 20-01-2003
DOI: 10.1086/367929
Do electron-capture supernovae make neutron stars?
Publisher: EDP Sciences
Date: 09-2016
Internal conversion electrons and supernova light curves
Publisher: Elsevier BV
Date: 04-2011
MUSE Integral Field Observations of the Oxygen-rich SNR 1E 0102.2-7219
Publisher: Cambridge University Press (CUP)
Date: 02-2017
DOI: 10.1017/S174392131700477X
Abstract: We have observed the oxygen-rich SNR 1E 0102.2-7219 with the integral field spectrograph WiFeS at Siding Spring Observatory and discovered sulfur-rich ejecta for the first time. Follow-up deep DDT observations with MUSE on the VLT (8100 s on source) reaching down to a noise level of ~5 × 10 −20 ergs −1 cm −2 Å −1 spaxel −1 have led to the additional discovery of fast-moving hydrogen as well as argon-rich and chlorine-rich material. The detection of fast-moving hydrogen knots challenges the interpretation that the progenitor of 1E 0102 was a compact core of a Wolf-Rayet star that had shed its entire envelope. In addition to the detection of hydrogen and the products of oxygen-burning, this unprecedented sharp (0.2″ spaxel size at ~0.7″ seeing) and deep MUSE view of an oxygen-rich SNR in the Magellanic Clouds reveals further exciting discoveries, including [Fe xiv ]λ5303 and [Fe xi ]λ7892 emission, which we associate with the forward shock. We present this exciting data set and discuss some of its implications for the explosion mechanism and nucleosynthesis of the associated supernova.
Modeling Type Ia supernova explosions
Publisher: Elsevier BV
Date: 04-2011
CONSTRAINING TYPE Ia SUPERNOVA MODELS: SN 2011fe AS A TEST CASE
Publisher: American Astronomical Society
Date: 13-04-2012
Discovery of Gravity‐Mode Pulsators among Subdwarf B Stars: PG 1716+426, the Class Prototype
Publisher: American Astronomical Society
Date: 20-05-2004
DOI: 10.1086/383260
SNe Ia from double detonations: Impact of core-shell mixing on the carbon ignition mechanism
Publisher: EDP Sciences
Date: 03-2020
DOI: 10.1051/0004-6361/201936494
Abstract: Sub-Chandrasekhar mass white dwarfs accreting a helium shell on a carbon-oxygen core are potential progenitors of normal Type Ia supernovae. This work focuses on the details of the onset of the carbon detonation in the double detonation sub-Chandrasekhar model. In order to simulate the influence of core-shell mixing on the carbon ignition mechanism, the helium shell and its detonation are followed with an increased resolution compared to the rest of the star treating the propagation of the detonation wave more accurately. This significantly improves the predictions of the nucleosynthetic yields from the helium burning. The simulations were carried out with the A REPO code. A carbon-oxygen core with a helium shell was set up in one dimension and mapped to three dimensions. We ensured the stability of the white dwarf with a relaxation step before the hydrodynamic detonation simulation started. Synthetic observables were calculated with the radiative transfer code A RTIS . An ignition mechanism of the carbon detonation was observed, which received little attention before. In this “scissors mechanism”, the impact the helium detonation wave has on unburnt material when converging opposite to its ignition spot is strong enough to ignite a carbon detonation. This is possible in a carbon enriched transition region between the core and shell. The detonation mechanism is found to be sensitive to details of the core-shell transition and our models illustrate the need to consider core-shell mixing taking place during the accretion process. Even though the detonation ignition mechanism differs form the converging shock mechanism, the differences in the synthetic observables are not significant. Though they do not fit observations better than previous simulations, they illustrate the need for multi-dimensional simulations.
Type Ia supernovae from violent mergers of carbon–oxygen white dwarfs: polarization signatures
Publisher: Oxford University Press (OUP)
Date: 07-11-2015
From Supernova to Supernova Remnant: Comparison of Thermonuclear Explosion Models
Publisher: American Astronomical Society
Date: 12-01-2021
The Three-dimensional Expansion of the Ejecta from Tycho's Supernova Remnant
Publisher: American Astronomical Society
Date: 08-06-2017
FORBIDDEN IRON LINES AND DUST DESTRUCTION IN SUPERNOVA REMNANT SHOCKS: THE CASE OF N49 IN THE LARGE MAGELLANIC CLOUD
Publisher: American Astronomical Society
Date: 27-07-2016
Nucleosynthesis in thermonuclear supernovae with tracers: convergence and variable mass particles
Publisher: Oxford University Press (OUP)
Date: 23-07-2010
Observations of SN 2015F Suggest a Correlation between the Intrinsic Luminosity of Type Ia Supernovae and the Shape of Their Light Curves >900 Days after Explosion
Publisher: American Astronomical Society
Date: 25-05-2018
No plateau observed in late-time near-infrared observations of the underluminous Type Ia supernova 2021qvv
Publisher: Oxford University Press (OUP)
Date: 28-09-2023
Effect of positron-alkali metal atom interactions in the diffuse interstellar medium
Publisher: American Physical Society (APS)
Date: 18-07-2018
Nucleosynthesis in Surface Detonation Type Ia Supernovae
Publisher: AIP
Date: 2008
DOI: 10.1063/1.2943630
Nucleosynthetic post-processing of Type Ia supernovae with variable tracer masses
Publisher: Sissa Medialab
Date: 06-07-2011
DOI: 10.22323/1.100.0256
Imagery and UV Spectroscopy of the LMC Supernova Remnant N103B Using HST
Publisher: American Astronomical Society
Date: 10-2020
Abstract: We present Hubble Space Telescope (HST)/Wide Field Camera 3 multiband imagery of N103B, which is the remnant of a SN Ia in the Large Magellanic Cloud, as well as HST/Cosmic Origins Spectrograph (COS) ultraviolet spectroscopy of the brightest radiatively shocked region. The images show a wide range of morphology and relative emission-line intensities, from smooth Balmer-line dominated collisionless shocks that are due to the primary blast wave to clumpy radiative shock filaments that are due to secondary shocks in density enhancements. The COS data show strong FUV line emissions, despite a moderately high extinction along this line of sight. We use the COS data with previous optical spectra to constrain the shock conditions, we refine the abundance analysis, and we find abundances that are typical of the local interstellar medium within the uncertainties. Under an assumption that the material being shocked was shed from the pre-supernova system, this finding places constraints on any significant enrichment in that material, and thus on the non-degenerate star in what was presumably a single-degenerate SN Ia.
Helium as a signature of the double detonation in Type Ia supernovae
Publisher: Oxford University Press (OUP)
Date: 19-07-2023
Abstract: The double detonation is a widely discussed mechanism to explain Type Ia supernovae from explosions of sub-Chandrasekhar mass white dwarfs. In this scenario, a helium detonation is ignited in a surface helium shell on a carbon/oxygen white dwarf, which leads to a secondary carbon detonation. Explosion simulations predict high abundances of unburnt helium in the ejecta, however, radiative transfer simulations have not been able to fully address whether helium spectral features would form. This is because helium can not be sufficiently excited to form spectral features by thermal processes, but can be excited by collisions with non-thermal electrons, which most studies have neglected. We carry out a full non-local thermodynamic equilibrium radiative transfer simulation for an instance of a double detonation explosion model, and include a non-thermal treatment of fast electrons. We find a clear He i λ10830 feature which is strongest in the first few days after explosion and becomes weaker with time. Initially this feature is blended with the Mg ii λ10927 feature but over time separates to form a secondary feature to the blue wing of the Mg ii λ10927 feature. We compare our simulation to observations of iPTF13ebh, which showed a similar feature to the blue wing of the Mg ii λ10927 feature, previously identified as C i. Our simulation shows a good match to the evolution of this feature and we identify it as high velocity He i λ10830. This suggests that He i λ10830 could be a signature of the double detonation scenario.
The white dwarf’s carbon fraction as a secondary parameter of Type Ia supernovae
Publisher: EDP Sciences
Date: 27-11-2014
Type Ia Supernovae (invited talk)
Publisher: Sissa Medialab
Date: 06-06-2011
DOI: 10.22323/1.123.0074
A Supernova Remnant Counterpart for HESS J1832−085
Publisher: American Astronomical Society
Date: 07-11-2019
DETONATIONS IN SUB-CHANDRASEKHAR-MASS C+O WHITE DWARFS
Publisher: American Astronomical Society
Date: 04-2010
ATCA study of Small Magellanic Cloud supernova remnant 1E 0102.2–7219
Publisher: Oxford University Press (OUP)
Date: 27-10-2023
Prospects of direct detection of 48V gamma-rays from thermonuclear supernovae
Publisher: Oxford University Press (OUP)
Date: 23-09-2021
Abstract: Detection of gamma-rays emitted by radioactive isotopes synthesized in stellar explosions can give important insights into the processes that power transients such as supernovae, as well as providing a detailed census of the abundance of different isotope species relevant to the chemical evolution of the Universe. Observations of nearby supernovae have yielded observational proof that 57Co powered the late-time evolution of SN1987A’s light curve, and conclusive evidence that 56Ni and its daughter nuclei power the light curves of Type Ia supernovae. In this paper, we describe the prospects for detecting nuclear decay lines associated with the decay of 48V, the daughter nucleus of 48Cr, which is expected to be synthesized in large quantities – $M_{\\mathrm{Cr}}\\sim 1.9\\times 10^{-2}\\, \\mathrm{M_\\odot }$ – in transients initiated by explosive helium burning (α-capture) of a thick helium shell. We calculate emergent gamma-ray line fluxes for a simulated explosion model of a thermonuclear explosion of carbon–oxygen white dwarf core of mass $0.45\\, \\mathrm{ M}_{\\odot }$ surrounded by a thick helium layer of mass $0.21\\, \\mathrm{ M}_{\\odot }$. We present observational limits on the presence of 48V in nearby SNe Ia 2014J using the INTEGRAL space telescope, excluding a 48Cr production on the surface of more than $0.1\\, \\mathrm{M_{\\odot }}$. We find that the future gamma-ray mission the All-Sky Medium Energy Gamma-Ray Observatory (AMEGO) will have an approximately 5 per cent chance of observing 48V gamma-rays from such events during the currently planned operational lifetime, based on our birthrate predictions of faint thermonuclear transients. We describe the conditions for a 3σ detection by the gamma-ray telescopes INTEGRAL/SPI, Compton Spectrometer and Imager (COSI) , and AMEGO.
Spectroscopy of the Type Ia supernova 2011fe past 1000 d
Publisher: Oxford University Press (OUP)
Date: 10-01-2015
Rapid Expansion of the Young Type Ia Supernova Remnant 0519–69.0: More Evidence for a Circumstellar Shell
Publisher: American Astronomical Society
Date: 03-2023
Abstract: The nature of Type Ia supernovae remains controversial. The youngest remnants of Ia supernovae hold clues to the explosion and to the immediate surroundings. We present a third epoch of Chandra observations of the ∼600 yr old Type Ia remnant 0519–69.0 in the Large Magellanic Cloud, extending the time baseline to 21 yr from the initial 2000 observations. We find rapid expansion of X-ray emitting material, with an average velocity of 4760 km s −1 . At the distance of the LMC, this corresponds to an undecelerated age of 750 yr, with the true age somewhat lower. We also find that the bright ring of emission has expanded by 1.3%, corresponding to a velocity of 1900 km s −1 and an undecelerated age of 1600 yr. The high velocity of the peripheral X-rays, contrasted with the modest expansion of the main X-ray shell, provides further evidence for a massive shell of circumstellar material.
The type Iax supernova, SN 2015H
Publisher: EDP Sciences
Date: 19-04-2016
Three-dimensional delayed-detonation models with nucleosynthesis for Type Ia supernovae
Publisher: Oxford University Press (OUP)
Date: 05-12-2012
DOI: 10.1093/MNRAS/STS402
Flame Evolution During Type Ia Supernovae and the Deflagration Phase in the Gravitationally Confined Detonation Scenario
Publisher: American Astronomical Society
Date: 20-10-2007
DOI: 10.1086/521013
Integral Field Spectroscopy of Supernova Remnant 1E0102–7219 Reveals Fast-moving Hydrogen and Sulfur-rich Ejecta
Publisher: American Astronomical Society
Date: 02-02-2018
On the formation of neutron stars via accretion-induced collapse in binaries
Publisher: Oxford University Press (OUP)
Date: 05-01-2019
DOI: 10.1093/MNRAS/STZ001
Extensive HST ultraviolet spectra and multiwavelength observations of SN 2014J in M82 indicate reddening and circumstellar scattering by typical dust
Publisher: Oxford University Press (OUP)
Date: 06-08-2014
The key role of SNIa at different metallicities for galactic chemical evolution of p-nuclei
Publisher: Sissa Medialab
Date: 09-10-2015
DOI: 10.22323/1.204.0032
Double-detonation sub-Chandrasekhar supernovae: can minimum helium shell masses detonate the core?
Publisher: EDP Sciences
Date: 05-2010
On the fate of the secondary white dwarf in double-degenerate double-detonation Type Ia supernovae
Publisher: Oxford University Press (OUP)
Date: 09-11-2022
Abstract: 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 $v~\\gt ~15\\, 000$ 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 ∼20 per cent. We expect future synthetic 3D nebular spectra to confirm or rule out either model.
Positron annihilation in the nuclear outflows of the Milky Way
Publisher: Oxford University Press (OUP)
Date: 21-11-2018
Discovery of a New Class of Pulsating Stars: Gravity-Mode Pulsators among Subdwarf B Stars
Publisher: Springer Netherlands
Date: 2003
Thermonuclear explosions of rapidly differentially rotating white dwarfs: Candidates for superluminous Type Ia supernovae?
Publisher: EDP Sciences
Date: 10-2018
DOI: 10.1051/0004-6361/201833475
Abstract: The observed sub-class of “superluminous” Type Ia supernovae lacks a convincing theoretical explanation. If the emission of such objects were powered exclusively by radioactive decay of 56 Ni formed in the explosion, a progenitor mass close to or even above the Chandrasekhar limit for a non-rotating white dwarf star would be required. Masses significantly exceeding this limit can be supported by differential rotation. We, therefore, explore explosions and predict observables for various scenarios resulting from differentially rotating carbon–oxygen white dwarfs close to their respective limit of stability. Specifically, we have investigated a prompt detonation model, detonations following an initial deflagration phase (“delayed detonation” models), and a pure deflagration model. In postprocessing steps, we performed nucleosynthesis and three-dimensional radiative transfer calculations, that allow us, for the first time, to consistently derive synthetic observables from our models. We find that all explosion scenarios involving detonations produce very bright events. The observables predicted for them, however, are inconsistent with any known subclass of Type Ia supernovae. Pure deflagrations resemble 2002cx-like supernovae and may contribute to this class. We discuss implications of our findings for the explosion mechanism and for the existence of differentially rotating white dwarfs as supernova progenitors.
SN 2017ens: The Metamorphosis of a Luminous Broadlined Type Ic Supernova into an SN IIn
Publisher: American Astronomical Society
Date: 09-11-2018
White dwarf deflagrations for Type Iax supernovae: polarisation signatures from the explosion and companion interaction
Publisher: EDP Sciences
Date: 03-2020
DOI: 10.1051/0004-6361/201937245
Abstract: 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 (≲5000 Å). In particular, increasingly fainter and redder spectra are predicted for observer orientations further from the cavity, while a modest polarisation signal P ~ 0.2 per cent is found at blue wavelengths for orientations 30° and 45° 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.
Three-dimensional simulations of gravitationally confined detonations compared to observations of SN 1991T
Publisher: EDP Sciences
Date: 25-07-2016
SN 2010LP—A TYPE IA SUPERNOVA FROM A VIOLENT MERGER OF TWO CARBON-OXYGEN WHITE DWARFS
Publisher: American Astronomical Society
Date: 06-11-2013
Type Ia Supernovae: Energetics, Neutronization and Nucleosynthesis
Publisher: American Institute of Physics
Date: 2007
DOI: 10.1063/1.2774860
THE IMPACT OF TYPE Ia SUPERNOVA EXPLOSIONS ON HELIUM COMPANIONS IN THE CHANDRASEKHAR-MASS EXPLOSION SCENARIO
Publisher: American Astronomical Society
Date: 13-08-2013
Type Ia Supernova Models: Asymmetric Remnants and Supernova Remnant G1.9+0.3
Publisher: American Astronomical Society
Date: 12-2021
Abstract: The youngest Galactic supernova remnant, G1.9+0.3, probably the result of a Type Ia supernova, shows surprising anomalies in the distribution of its ejecta in space and velocity. In particular, high-velocity shocked iron is seen in several locations far from the remnant center, in some cases beyond prominent silicon and sulfur emission. These asymmetries strongly suggest a highly asymmetric explosion. We present high-resolution hydrodynamic simulations in two and three dimensions of the evolution from ages of 100 s to hundreds of years of two asymmetric Type Ia models, expanding into a uniform medium. At the age of G1.9+0.3 (about 100 yr), our 2D model shows almost no iron shocked to become visible in X-rays. Only in a much higher-density environment could significant iron be shocked, at which time the model's expansion speed is completely inconsistent with the observations of G1.9+0.3. Our 3D model, evolving the most asymmetric of a suite of Type Ia supernova models from Seitenzahl et al. (2013), shows some features resembling G1.9+0.3. We characterize its evolution with images of composition in three classes: C and O, intermediate-mass elements (IMEs), and iron-group elements (IGEs). From ages of 13 to 1800 yr, we follow the evolution of the highly asymmetric initial remnant as the explosion asymmetries decrease in relative strength, to be replaced by asymmetries due to evolutionary hydrodynamic instabilities. At an age of about 100 yr, our 3D model has comparable shocked masses of C+O, IMEs, and IGEs, with about 0.03 M ⊙ each. Evolutionary changes appear to be rapid enough that continued monitoring with the Chandra X-ray Observatory may show significant variations.
Flow and flood: mobilities, life in roads and abiotic actors of the (m)ôtô ‐cene
Publisher: Berghahn Books
Date: 23-04-2021
SN 2018bsz: significant dust formation in a nearby superluminous supernova
Publisher: Research Square Platform LLC
Date: 15-09-2021
DOI: 10.21203/RS.3.RS-872252/V1
Abstract: We investigate the thermal emission and extinction from dust associated with the nearby superluminous supernova (SLSN) 2018bsz. Our dataset has daily cadence and simultaneous optical and near-infrared coverage up to ~ 100 days, together with late time (+1.7 yr) MIR observations. At 230 days after light curve peak the SN is not detected in the optical, but shows a surprisingly strong near-infrared excess, with r - J 3 mag and r - K s 5 mag. The time evolution of the infrared light curve enables us to investigate if the mid-infrared emission is from newly formed dust inside the SN ejecta, from a pre-existing circumstellar envelope, or interstellar material heated by the radiation from the SN. We find the latter two scenarios can be ruled out, and a scenario where new dust is forming in the SN ejecta at epochs 200 days can self-consistently reproduce the evolution of the SN flux. We can fit the spectral energy distribution well at +230d with 5x10 -4 solar mass of carbon dust, increasing over the following several hundred days to 10 -2 solar mass by +535d. SN 2018bsz is the first SLSN showing evidence for dust formation within the SN ejecta, and appears to form ten times more dust than normal core-collapse SNe at similar epochs. Together with their preference for low mass, low metallicity host galaxies, we suggest that SLSNe may be a significant contributor to dust formation in the early Universe.
PROSPECT OF STUDYING HARD X- AND GAMMA-RAYS FROM TYPE Ia SUPERNOVAE
Publisher: American Astronomical Society
Date: 02-11-2012
The Expansion of the Young Supernova Remnant 0509-68.7 (N103B)
Publisher: American Astronomical Society
Date: 24-09-2018
Nuclear statistical equilibrium for Type Ia supernova simulations
Publisher: Elsevier BV
Date: 2009
Diffuse Galactic antimatter from faint thermonuclear supernovae in old stellar populations
Publisher: Springer Science and Business Media LLC
Date: 22-05-2017
Shocked Interstellar Clouds and Dust Grain Destruction in the LMC Supernova Remnant N132D
Publisher: American Astronomical Society
Date: 10-07-2018
A subgrid-scale model for deflagration-to-detonation transitions in Type Ia supernova explosion simulations
Publisher: EDP Sciences
Date: 11-2013
Type Ia supernova diversity: white dwarf central density as a secondary parameter in three-dimensional delayed detonation models
Publisher: Oxford University Press (OUP)
Date: 19-04-2011
DOUBLE-DETONATION SUB-CHANDRASEKHAR SUPERNOVAE: SYNTHETIC OBSERVABLES FOR MINIMUM HELIUM SHELL MASS MODELS
Publisher: American Astronomical Society
Date: 26-07-2010
Nucleosynthesis imprints from different Type Ia supernova explosion scenarios and implications for galactic chemical evolution
Publisher: EDP Sciences
Date: 12-2020
DOI: 10.1051/0004-6361/202038721
Abstract: 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 and 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.
Evidence for a Dense, Inhomogeneous Circumstellar Medium in the Type Ia SNR 0519-69.0
Publisher: American Astronomical Society
Date: 08-2022
Abstract: We perform an expansion study of the Balmer-dominated outer shock of the SNR 0519−69.0 in the LMC by using a combination of new Hubble Space Telescope (HST) WFC3 imagery obtained in 2020 and archival ACS images from 2010 and 2011. Thanks to the very long time baseline, our proper motion measurements are of unprecedented accuracy. We find a wide range of shock velocities, with the fastest shocks averaging 5280 km s −1 and the slowest grouping of shocks averaging just 1670 km s −1 . We compare the H α images from HST with X-ray images from Chandra and mid-IR images from Spitzer, finding a clear anticorrelation between the brightness of the remnant in a particular location and the velocity of the blast wave at that location, supporting the idea that the bright knots of X-ray and IR emission result from an interaction with a dense inhomogeneous circumstellar medium. We find no evidence for X-ray emission, thermal or nonthermal, associated with the fastest shocks, as expected if the fastest velocities are the result of the blast wave encountering the lower density ambient medium of the LMC. We derive an age of the remnant of ≤670 ± 70 yr, consistent with results derived from previous investigations.
Manganese Indicates a Transition from Sub- to Near-Chandrasekhar Type Ia Supernovae in Dwarf Galaxies
Publisher: American Astronomical Society
Date: 06-03-2020
Synthetic light curves and spectra for three-dimensional delayed-detonation models of Type Ia supernovae
Publisher: Oxford University Press (OUP)
Date: 16-09-2013
Thermonuclear Supernova Explosions from White Dwarfs in Different Progenitor Systems
Publisher: Cambridge University Press (CUP)
Date: 07-2011
DOI: 10.1017/S1743921312015177
Abstract: Several progenitor scenarios have been suggested for Type Ia supernovae. Here we discuss the consequences for the explosion mechanism and for observables of some of them, which are explored by means of multi-dimensional hydrodynamic and radiation transfer simulations. While the observables predicted from delayed detonations of Chandrasekhar-mass white dwarfs agree reasonably well with the data, the corresponding progenitor systems may be too rare to account for the observed rate of Type Ia supernovae. Several alternatives are investigated of which violent mergers of two white dwarfs and, perhaps, double detonations of sub-Chandrasekhar mass white dwarfs hold promise for reproducing the observables of normal Type Ia supernovae.
Gamma-ray diagnostics of Type Ia supernovae
Publisher: EDP Sciences
Date: 06-2013
From Supernova to Supernova Remnant: The Three-dimensional Imprint of a Thermonuclear Explosion
Publisher: American Astronomical Society
Date: 04-06-2019
Capturing the Fire: Flame Energetics and Neutronization for Type Ia Supernova Simulations
Publisher: American Astronomical Society
Date: 10-02-2007
DOI: 10.1086/510709
The dawn of a new era for dustless HdC stars withGaiaeDR3
Publisher: EDP Sciences
Date: 11-2022
DOI: 10.1051/0004-6361/202142916
Abstract: Context. 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 ∼130 known Galactic HdC stars that are notorious for being heavy dust producers, that is 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 (WD) binary systems, otherwise known as the double-degenerate scenario. Aims. We searched for new dustless HdC (dLHdC) stars to understand their Galactic distribution, to estimate their total number in the Milky Way, and to study their evolutionary link with RCB stars and extreme helium (EHe) stars, the final phase of HdC stars. Methods. We primarily used the 2MASS and Gaia eDR3 all-sky catalogues to select candidates that were then followed-up spectroscopically. We studied the distribution of known and newly discovered stars in the Hertzsprung-Russell diagram. Results. 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 exhibits a bulge-like distribution, like the RCB stars, but show multiple differences from RCB stars that indicate that they are a different population of HdC stars. This population follows its own evolutionary sequence with a fainter luminosity and also a narrow range of effective temperatures, between 5000 and 8000 K. Not all the new dLHdC stars belong to this new population, as we found an indication of a current low dust production activity around 4 of them: the warm F75, F152, and C526, and the cold A166. They might be typical RCB stars passing through a transition time, entering or leaving the RCB phase. Conclusions. For the first time, we have evidence of a wide range of absolute magnitudes in the overall population of HdC stars, spanning more than 3 mag. In the favoured formation framework, this is explained by a wide 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 RCB stars, possibly due to a difference in metallicity between the original population of stars, resulting in a different WD mass ratio. The unveiled population of dLHdC stars indicates that the ability to create dust might be linked to the initial total mass. In our Galaxy, there could be as many dLHdC stars as RCB stars.
The effects of variations in nuclear interactions on nucleosynthesis in thermonuclear supernovae
Publisher: EDP Sciences
Date: 12-08-2013
500 days of SN 2013dy: spectra and photometry from the ultraviolet to the infrared
Publisher: Oxford University Press (OUP)
Date: 12-08-2015
An X-ray expansion and proper motion study of the Magellanic Cloud Supernova Remnant J0509–6731 with the Chandra X-ray observatory
Publisher: Oxford University Press (OUP)
Date: 08-05-2018
Forbidden Line Emission from Type Ia Supernova Remnants Containing Balmer-dominated Shells
Publisher: American Astronomical Society
Date: 12-2021
Abstract: Balmer-dominated shells in supernova remnants (SNRs) are produced by collisionless shocks advancing into a partially neutral medium and are most frequently associated with Type Ia supernovae. We have analyzed Hubble Space Telescope (HST) images and Very Large Telescope (VLT)/Multi-Unit Spectroscopic Explorer (MUSE) or AAT/Wide Field Integral Spectrograph observations of five Type Ia SNRs containing Balmer-dominated shells in the LMC: 0509–67.5, 0519–69.0, N103B, DEM L71, and 0548–70.4. Contrary to expectations, we find bright forbidden-line emission from small dense knots embedded in four of these SNRs. The electron densities in some knots are higher than 10 4 cm −3 . The size and density of these knots are not characteristic for interstellar medium—they most likely originate from a circumstellar medium ejected by the SN progenitor. Physical property variations of dense knots in the SNRs appear to reflect an evolutionary effect. The recombination timescales for high densities are short, and HST images of N103B taken 3.5 yr apart already show brightness changes in some knots. VLT/MUSE observations detect [Fe xiv ] line emission from reverse shocks into SN ejecta as well as forward shocks into the dense knots. Faint [O iii ] line emission is also detected from the Balmer shell in 0519–69.0, N103B, and DEM L71. We exclude the postshock origin because the [O iii ] line is narrow. For the preshock origin, we considered three possibilities: photoionization precursor, cosmic-ray precursor, and neutral precursor. We conclude that the [O iii ] emission arises from oxygen that has been photoionized by [He ii ] λ 304 photons and is then collisionally excited in a shock precursor heated mainly by cosmic rays.
Observational constraints on the origin of the elements
Publisher: EDP Sciences
Date: 03-2020
DOI: 10.1051/0004-6361/201936603
Abstract: The abundance ratios of manganese to iron in late-type stars across a wide metallicity range place tight constraints on the astrophysical production sites of Fe-group elements. In this work, we investigate the chemical evolution of Mn in the Milky Way galaxy using high-resolution spectroscopic observations of stars in the Galactic disc and halo stars, as well as a s le of globular clusters. Our analysis shows that local thermodynamic equilibrium (LTE) leads to a strong imbalance in the ionisation equilibrium of Mn I and Mn II lines. Mn I produces systematically (up to 0.6 dex) lower abundances compared to the Mn II lines. Non-LTE (NLTE) radiative transfer satisfies the ionisation equilibrium across the entire metallicity range, of −3 ≲ [Fe/H] ≲ −1, leading to consistent abundances from both ionisation stages of the element. We compare the NLTE abundances with Galactic Chemical Evolution models computed using different sources of type Ia and type II supernova (SN Ia and SN II) yields. We find that a good fit to our observations can be obtained by assuming that a significant (∼75%) fraction of SNe Ia stem from a sub-Chandrasekhar (sub- M ch ) channel. While this fraction is larger than that found in earlier studies (∼50%), we note that we still require ∼25% near- M ch SNe Ia to obtain solar [Mn/Fe] at [Fe/H] = 0. Our new data also suggest higher SN II Mn yields at low metallicity than typically assumed in the literature.
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