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| 2. |
- Bobrick, Alexey, et al.
(författare)
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Transients from ONe white dwarf - neutron star/black hole mergers
- 2022
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 510:3, s. 3758-3777
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Tidskriftsartikel (refereegranskat)abstract
- We conduct the first 3D hydrodynamic simulations of oxygen-neon white dwarf-neutron star/black hole mergers (ONe WD-NS/BH mergers). Such mergers constitute a significant fraction, and may even dominate, the inspiral rates of all WD-NS binaries. We post-process our simulations to obtain the nuclear evolution of these systems and couple the results to a supernova spectral synthesis code to obtain the first light curves and spectra for these transients. We find that the amount of 56Ni synthesized in these mergers grows as a strong function of the WD mass, reaching typically 0.05 and up to 0.1M⊙ per merger. Photodisintegration leads to similar amounts of 4He and about a ten times smaller amount of 1H. The nuclear yields from these mergers, in particular those of 55Mn, may contribute significantly to Galactic chemical evolution. The transients expected from ONe WD-NS mergers are dominantly red/infrared, evolve on month-long time-scales and reach bolometric magnitudes of up to -16.5. The current surveys must have already detected these transients or are, alternatively, putting strong constraints on merger scenarios. The properties of the expected transients from WD-NS mergers best agree with faint type Iax supernovae. The Vera Rubin Observatory (LSST) will be detecting up to thousands of merging ONe WD-NS systems per year. We simulate a subset of our models with 2D axisymmetric FLASH code to investigate why they have been challenging for previous studies. We find that the likely main challenge has been effectively modelling the nuclear statistical equilibrium regime in such mergers.
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| 3. |
- Jacobson-Galán, Wynn V., et al.
(författare)
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Late-time Observations of Calcium-rich Transient SN 2019ehk Reveal a Pure Radioactive Decay Power Source
- 2021
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 908:2
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Tidskriftsartikel (refereegranskat)abstract
- We present multiband Hubble Space Telescope imaging of the calcium-rich supernova (SN) SN 2019ehk at 276-389 days after explosion. These observations represent the latest B-band to near-IR photometric measurements of a calcium-rich transient to date and allow for the first opportunity to analyze the late-time bolometric evolution of an object in this observational SN class. We find that the late-time bolometric light curve of SN 2019ehk can be described predominantly through the radioactive decay of 56Co for which we derive a mass of M(56Co) = (2.8 ± 0.1) × 10-2 M o. Furthermore, the rate of decline in bolometric luminosity requires the leakage of γ-rays on timescale t γ = 53.9 ± 1.30 days, but we find no statistical evidence for incomplete positron trapping in the SN ejecta. While our observations cannot constrain the exact masses of other radioactive isotopes synthesized in SN 2019ehk, we estimate a mass ratio limit of M(57Co)/M(56Co) ≤ 0.030. This limit is consistent with the explosive nucleosynthesis produced in the merger of low-mass white dwarfs, which is one of the favored progenitor scenarios in early-time studies of SN 2019ehk.
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| 4. |
- Wang, Qinan, et al.
(författare)
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Revealing the Progenitor of SN 2021zby through Analysis of the TESS Shock-cooling Light Curve
- 2023
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8205 .- 2041-8213. ; 943:2
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Tidskriftsartikel (refereegranskat)abstract
- We present early observations and analysis of the double-peaked Type IIb supernova (SN IIb) SN 2021zby. TESS captured the prominent early shock-cooling peak of SN 2021zby within the first ∼10 days after explosion with a 30 minute cadence. We present optical and near-infrared spectral series of SN 2021zby, including three spectra during the shock-cooling phase. Using a multiband model fit, we find that the inferred properties of its progenitor are consistent with a red supergiant or yellow supergiant, with an envelope mass of ∼0.30–0.65 M⊙ and an envelope radius of ∼120–300 R⊙. These inferred progenitor properties are similar to those of other SNe IIb with a double-peaked feature, such as SNe 1993J, 2011dh, 2016gkg, and 2017jgh. This study further validates the importance of the high cadence and early coverage in resolving the shape of the shock-cooling light curve, while the multiband observations, particularly UV, are also necessary to fully constrain the progenitor properties.
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| 5. |
- Zenati, Yossef, et al.
(författare)
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Faint Rapid Red Transients from Neutron Star - CO White Dwarf Mergers
- 2020
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 493:3, s. 3956-3965
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Tidskriftsartikel (refereegranskat)abstract
- Mergers of neutron stars (NS) and white dwarfs (WD) may give rise to observable explosive transientevents. We use 3D hydrodynamical (SPH) simulations, as well as 2D hydrodynamical-thermonuclearsimulations (using the FLASH AMR code) to model the disruption of CO-WDs by NSs, whichproduce faint transient events. We post-process the simulations using a large nuclear network andmake use of the SuperNu radiation-transfer code to predict the observational signatures and detailedproperties of these transients. We calculate the light-curves (LC) and spectra for five models of NS -CO-WD mergers. The small yields of56Ni (few×10−3M) result in faint, rapidly-evolving reddenedtransients (RRTs) with B (R) - peak magnitudes of at most∼−12 (−13) to∼−13 (−15), muchshorter and fainter than both regular and faint/peculiar type-Ia SNe. These transients are likely to beaccompanied by several months-long, 1–2 mag dimmer red/IR afterglows. We show that the spectraof RRTs share some similarities with rapidly-evolving transients such as SN2010x, although RRTsare significantly fainter, especially in the I/R bands, and show far stronger Si lines. We estimate thatthe upcoming Large Synoptic Survey Telescope could detect RRTs at a rate of up to∼10−70 yr−1,through observations in the R/I bands. The qualitative agreement between the SPH and FLASHapproaches supports the earlier hydrodynamical studies of these systems.
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