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Jones, O. C., Kavanagh, P. J., Barlow, M. J., Temim, T., Fransson, C., Larsson, J., . . . Vandenbussche, B. (2023). Ejecta, Rings, and Dust in SN 1987A with JWST MIRI/MRS. Astrophysical Journal, 958(1), Article ID 95.
Open this publication in new window or tab >>Ejecta, Rings, and Dust in SN 1987A with JWST MIRI/MRS
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2023 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 958, no 1, article id 95Article in journal (Refereed) Published
Abstract [en]

Supernova (SN) 1987A is the nearest supernova in ∼400 yr. Using the JWST MIRI Medium Resolution Spectrograph, we spatially resolved the ejecta, equatorial ring (ER), and outer rings in the mid-infrared 12,927 days (35.4 yr) after the explosion. The spectra are rich in line and dust continuum emission, both in the ejecta and the ring. The broad emission lines (280–380 km s−1 FWHM) that are seen from all singly-ionized species originate from the expanding ER, with properties consistent with dense post-shock cooling gas. Narrower emission lines (100–170 km s−1 FWHM) are seen from species originating from a more extended lower-density component whose high ionization may have been produced by shocks progressing through the ER or by the UV radiation pulse associated with the original supernova event. The asymmetric east–west dust emission in the ER has continued to fade, with constant temperature, signifying a reduction in dust mass. Small grains in the ER are preferentially destroyed, with larger grains from the progenitor surviving the transition from SN into SNR. The ER dust is fit with a single set of optical constants, eliminating the need for a secondary featureless hot dust component. We find several broad ejecta emission lines from [Ne ii], [Ar ii], [Fe ii], and [Ni ii]. With the exception of [Fe ii] 25.99 μm, these all originate from the ejecta close to the ring and are likely to be excited by X-rays from the interaction. The [Fe ii] 5.34 to 25.99 μm line ratio indicates a temperature of only a few hundred K in the inner core, which is consistent with being powered by 44 Ti decay.

National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-224277 (URN)10.3847/1538-4357/ad0036 (DOI)001102209200001 ()2-s2.0-85178039569 (Scopus ID)
Available from: 2023-12-18 Created: 2023-12-18 Last updated: 2023-12-18Bibliographically approved
Arendt, R. G., Boyer, M. L., Dwek, E., Matsuura, M., Ravi, A. P., Rest, A., . . . Woodward, C. E. (2023). JWST NIRCam Observations of SN 1987A: Spitzer Comparison and Spectral Decomposition. Astrophysical Journal, 959(2), Article ID 95.
Open this publication in new window or tab >>JWST NIRCam Observations of SN 1987A: Spitzer Comparison and Spectral Decomposition
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2023 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 959, no 2, article id 95Article in journal (Refereed) Published
Abstract [en]

JWST Near Infrared Camera (NIRCam) observations at 1.5–4.5 μm have provided broadband and narrowband imaging of the evolving remnant of SN 1987A with unparalleled sensitivity and spatial resolution. Comparing with previous marginally spatially resolved Spitzer Infrared Array Camera (IRAC) observations from 2004 to 2019 confirms that the emission arises from the circumstellar equatorial ring (ER), and the current brightness at 3.6 and 4.5 μm was accurately predicted by extrapolation of the declining brightness tracked by IRAC. Despite the regular light curve, the NIRCam observations clearly reveal that much of this emission is from a newly developing outer portion of the ER. Spots in the outer ER tend to lie at position angles in between the well-known ER hotspots. We show that the bulk of the emission in the field can be represented by five standard spectral energy distributions, each with a distinct origin and spatial distribution. This spectral decomposition provides a powerful technique for distinguishing overlapping emission from the circumstellar medium and the supernova ejecta, excited by the forward and reverse shocks, respectively.

Keywords
Circumstellar dust, Core-collapse supernovae, Infrared astronomy, Large Magellanic Cloud, Ring nebulae, Supernova remnants
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-225384 (URN)10.3847/1538-4357/acfd95 (DOI)001121381500001 ()2-s2.0-85181891573 (Scopus ID)
Available from: 2024-01-19 Created: 2024-01-19 Last updated: 2024-01-19Bibliographically approved
Kangas, T., Ahola, A., Fransson, C., Larsson, J., Lundqvist, P., Mattila, S. & Leibundgut, B. (2023). Near-infrared evolution of the equatorial ring of SN 1987A. Astronomy and Astrophysics, 675, Article ID A166.
Open this publication in new window or tab >>Near-infrared evolution of the equatorial ring of SN 1987A
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2023 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 675, article id A166Article in journal (Refereed) Published
Abstract [en]

We used adaptive optics imaging and integral field spectroscopy from the Very Large Telescope, together with images from the Hubble Space Telescope, to study the near-infrared (NIR) evolution of the equatorial ring (ER) of SN 1987A. We studied the NIR flux and morphology over time in order to lay the groundwork for James Webb Space Telescope observations of the system. We also studied the differences in the interacting ring structure and flux between optical, NIR, and other wavelengths, and between line and continuum emission, to constrain the underlying physical processes. For the most part, the evolution is similar in the NIR and optical. The morphology of the ER has been skewed toward the west side (with roughly two-thirds of the NIR emission originating there) since around 2010. A steady decline in the ER flux, broadly similar to the mid-infrared and the optical, has been ongoing since roughly this time as well. The expansion velocity of the ER hotspots in the NIR is fully consistent with the optical. However, continuum emission forms roughly 70% of the NIR luminosity, and has been stronger outside the hotspot-defined extent of the ER (relative to the hotspots themselves) than the optical emission or the NIR line emission since 2012–2013, suggesting a faster-expanding continuum component. We find that this outer NIR emission can have a significant synchrotron contribution. Even if emission from hot dust (~2000 K) is dominant within the ER, the mass of this dust must be vanishingly small (a few times 10−12 M) compared to the total dust mass in the ER (≳10−5 M) to account for the observed HKs flux. The NIR continuum emission, however, expands more slowly than the more diffuse 180-K dust emission that dominates in the MIR, indicating a different source, and the same hot dust component cannot account for the J-band emission.

Keywords
supernovae, individual, SN 1987A, ISM, supernova remnants, stars, mass-loss
National Category
Physical Sciences Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-221062 (URN)10.1051/0004-6361/202245829 (DOI)001032953600009 ()2-s2.0-85166246062 (Scopus ID)
Available from: 2023-09-25 Created: 2023-09-25 Last updated: 2023-09-25Bibliographically approved
West, S. L., Lunnan, R., Omand, C. M. B., Kangas, T., Schulze, S., Strotjohann, N. L., . . . Shupe, D. (2023). SN 2020qlb: A hydrogen-poor superluminous supernova with well-characterized light curve undulations. Astronomy and Astrophysics, 670, Article ID A7.
Open this publication in new window or tab >>SN 2020qlb: A hydrogen-poor superluminous supernova with well-characterized light curve undulations
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2023 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 670, article id A7Article in journal (Refereed) Published
Abstract [en]

Context. SN 2020qlb (ZTF20abobpcb) is a hydrogen-poor superluminous supernova (SLSN-I) that is among the most luminous (maximum Mg = −22.25 mag) and that has one of the longest rise times (77 days from explosion to maximum). We estimate the total radiated energy to be > 2.1 × 1051 erg. SN 2020qlb has a well-sampled light curve that exhibits clear near and post peak undulations, a phenomenon seen in other SLSNe, whose physical origin is still unknown.

Aims. We discuss the potential power source of this immense explosion as well as the mechanisms behind its observed light curve undulations.

Methods. We analyze photospheric spectra and compare them to other SLSNe-I. We constructed the bolometric light curve using photometry from a large data set of observations from the Zwicky Transient Facility (ZTF), Liverpool Telescope (LT), and Neil Gehrels Swift Observatory and compare it with radioactive, circumstellar interaction and magnetar models. Model residuals and light curve polynomial fit residuals are analyzed to estimate the undulation timescale and amplitude. We also determine host galaxy properties based on imaging and spectroscopy data, including a detection of the [O III]λ4363, auroral line, allowing for a direct metallicity measurement.

Results. We rule out the Arnett 56Ni decay model for SN 2020qlb’s light curve due to unphysical parameter results. Our most favored power source is the magnetic dipole spin-down energy deposition of a magnetar. Two to three near peak oscillations, intriguingly similar to those of SN 2015bn, were found in the magnetar model residuals with a timescale of 32 ± 6 days and an amplitude of 6% of peak luminosity. We rule out centrally located undulation sources due to timescale considerations; and we favor the result of ejecta interactions with circumstellar material (CSM) density fluctuations as the source of the undulations.

Keywords
supernovae: general, supernovae: individual: SN 2020qlb
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-216284 (URN)10.1051/0004-6361/202244086 (DOI)000940346000010 ()2-s2.0-85147138889 (Scopus ID)
Available from: 2023-04-13 Created: 2023-04-13 Last updated: 2023-04-13Bibliographically approved
Gal-Yam, A., Bruch, R., Schulze, S., Yang, Y., Perley, D. A., Irani, I., . . . Knezevic, N. (2022). A WC/WO star exploding within an expanding carbon-oxygen-neon nebula. Nature, 601(7892), 201-204
Open this publication in new window or tab >>A WC/WO star exploding within an expanding carbon-oxygen-neon nebula
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2022 (English)In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 601, no 7892, p. 201-204Article in journal (Refereed) Published
Abstract [en]

The final fate of massive stars, and the nature of the compact remnants they leave behind (black holes and neutron stars), are open questions in astrophysics. Many massive stars are stripped of their outer hydrogen envelopes as they evolve. Such Wolf-Rayet stars(1) emit strong and rapidly expanding winds with speeds greater than 1,000 kilometres per second. A fraction of this population is also helium-depleted, with spectra dominated by highly ionized emission lines of carbon and oxygen (types WC/WO). Evidence indicates that the most commonly observed supernova explosions that lack hydrogen and helium (types Ib/Ic) cannot result from massive WC/WO stars(2,3), leading some to suggest that most such stars collapse directly into black holes without a visible supernova explosion(4). Here we report observations of SN 2019hgp, beginning about a day after the explosion. Its short rise time and rapid decline place it among an emerging population of rapidly evolving transients(5-8). Spectroscopy reveals a rich set of emission lines indicating that the explosion occurred within a nebula composed of carbon, oxygen and neon. Narrow absorption features show that this material is expanding at high velocities (greater than 1,500 kilometres per second), requiring a compact progenitor. Our observations are consistent with an explosion of a massive WC/WO star, and suggest that massive Wolf-Rayet stars may be the progenitors of some rapidly evolving transients.

National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-201938 (URN)10.1038/s41586-021-04155-1 (DOI)000742123100009 ()35022591 (PubMedID)2-s2.0-85122889405 (Scopus ID)
Available from: 2022-02-10 Created: 2022-02-10 Last updated: 2022-11-14Bibliographically approved
Fransson, C., Sollerman, J., Strotjohann, N. L., Yang, S., Schulze, S., Barbarino, C., . . . Kasliwal, M. M. (2022). SN 2019zrk, a bright SN 2009ip analog with a precursor. Astronomy and Astrophysics, 666, Article ID A79.
Open this publication in new window or tab >>SN 2019zrk, a bright SN 2009ip analog with a precursor
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2022 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 666, article id A79Article in journal (Refereed) Published
Abstract [en]

We present photometric and spectroscopic observations of the Type IIn supernova SN 2019zrk (also known as ZTF 20aacbyec). The SN shows a > 100 day precursor, with a slow rise, followed by a rapid rise to M ≈ −19.2 in the r and g bands. The post-peak light-curve decline is well fit with an exponential decay with a timescale of ∼39 days, but it shows prominent undulations, with an amplitude of ∼1 mag. Both the light curve and spectra are dominated by an interaction with a dense circumstellar medium (CSM), probably from previous mass ejections. The spectra evolve from a scattering-dominated Type IIn spectrum to a spectrum with strong P-Cygni absorptions. The expansion velocity is high, ∼16 000 km s−1, even in the last spectra. The last spectrum ∼110 days after the main eruption reveals no evidence for advanced nucleosynthesis. From analysis of the spectra and light curves, we estimate the mass-loss rate to be ∼4 × 10−2M yr−1 for a CSM velocity of 100 km s−1, and a CSM mass of 1 M. We find strong similarities for both the precursor, general light curve, and spectral evolution with SN 2009ip and similar SNe, although SN 2019zrk displays a brighter peak magnitude. Different scenarios for the nature of the 09ip-class of SNe, based on pulsational pair instability eruptions, wave heating, and mergers, are discussed.

Keywords
supernovae: general, supernovae: individual: ZTF20aacbyec, SN 2019zrk, SN 2009ip, circumstellar matter
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-210731 (URN)10.1051/0004-6361/202243452 (DOI)000864854000004 ()
Available from: 2022-10-27 Created: 2022-10-27 Last updated: 2022-10-27Bibliographically approved
Ergon, M. & Fransson, C. (2022). Spectral modelling of Type IIb supernovae Comparison with SN 2011dh and the effect of macroscopic mixing. Astronomy and Astrophysics, 666, Article ID A104.
Open this publication in new window or tab >>Spectral modelling of Type IIb supernovae Comparison with SN 2011dh and the effect of macroscopic mixing
2022 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 666, article id A104Article in journal (Refereed) Published
Abstract [en]

We use the new non-local-thermodynamical-equilibrium (NLTE) light curve and spectral synthesis code JEKYLL to evolve a macro-scopically mixed ejecta model of a Type IIb supernova (SN) originating from a star with an initial mass of 12 M through the photospheric and nebular phase. The ejecta model is adopted from earlier work and has a mass of 1.7 M, has a kinetic energy of 0.7 foe, and contains 0.075 M of 56Ni. The macroscopic mixing is simulated through a statistical representation of ejecta fragmented into small clumps but spherically symmetric on average. We compare our model with SN 2011dh and find that both the spectra and the light curves are well reproduced in both the photospheric and nebular phase, although there are also some differences. Our work further strengthens the evidence that this SN originated from a star with an initial mass of ~12 M that had lost all but a tiny (<0.1 M) fraction of its hydrogen envelope, strongly suggesting a binary origin. We also investigate the effects of the macroscopic mixing by comparing macroscopically and microscopically mixed models and by varying the clumping geometry. In the photospheric phase, we find strong effects on the effective opacity in the macroscopically mixed regions, which affects the model light curves. The diffusion peak is considerably narrower (rise time decreased by 11%) in the macroscopically mixed case and differs strongly (rise time decreased by 29%) if the radioactive material in the helium envelope is allowed to expand more than in our standard model. The effect is mainly geometrical and is driven by the expansion of the clumps that contain radioactive material, which tend to decrease the effective opacity. In the limit of optically thick clumps, the decrease is roughly given by the product of the (volume) expansion and filling factors for the radioactive material, and in our models values up to ~8 are explored. These findings have implications for light curve modelling of stripped-envelope SNe in general, and the effect would increase the estimated ejecta masses. In the nebular phase, we find strong effects on the collisional cooling rates in the macroscopically mixed regions, which affects lines driven by collisional cooling, in particular the [Ca II] 7291, 7323 Å and [O I] 6300, 6364 Å lines. The effect is mainly related to differences in composition between macroscopically and microscopically mixed ejecta. As these lines are often used for mass determinations, this highlights the importance of how and to what extent the calcium- and oxygen-rich material is mixed. As shown in this and earlier work, both NLTE and macroscopic mixing are essential ingredients for accurately modelling the light curves and spectra of Type IIb SNe throughout their evolution.

Keywords
supernovae: general, supernovae: individual: SN 2011dh, radiative transfer
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-211065 (URN)10.1051/0004-6361/202243448 (DOI)000868825900013 ()
Available from: 2022-11-10 Created: 2022-11-10 Last updated: 2022-11-10Bibliographically approved
Kangas, T., Fransson, C., Larsson, J., France, K., Chevalier, R. A., Kirshner, R. P., . . . Utrobin, V. P. (2022). The morphology of the ejecta of SN 1987A at 31 yr from 1150 to 10 000 Å. Monthly notices of the Royal Astronomical Society, 511(2), 2977-2993
Open this publication in new window or tab >>The morphology of the ejecta of SN 1987A at 31 yr from 1150 to 10 000 Å
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2022 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 511, no 2, p. 2977-2993Article in journal (Refereed) Published
Abstract [en]

We present spectroscopy of the ejecta of SN 1987A in 2017 and 2018 from the Hubble Space Telescope and the Very Large Telescope, covering the wavelength range between 1150 and 10 000 Å. At 31 yr, this is the first epoch with coverage over the ultraviolet-to-near-infrared range since 1995. We create velocity maps of the ejecta in the H α, Mg II λλ2796, 2804 and [O I] λλ6302, 6366 (vacuum) emission lines and study their morphology. All three lines have a similar morphology, but Mg II is blueshifted by ∼1000 km s−1 relative to the others and stronger in the north-west. We also study the evolution of the line fluxes, finding a brightening by a factor of ∼9 since 1999 in Mg II, while the other line fluxes are similar in 1999 and 2018. We discuss implications for the power sources of emission lines at late times: thermal excitation due to heating by the X-rays from the ejecta–ring interaction is found to dominate the ultraviolet Mg II lines, while the infrared Mg II doublet is powered mainly by Ly α fluorescence. The X-ray deposition is calculated based on merger models of SN 1987A. Far-ultraviolet emission lines of H2 are not detected. Finally, we examine the combined spectrum of recently discovered hotspots outside the equatorial ring. Their unresolved Balmer emission lines close to zero velocity are consistent with the interaction of fast ejecta and a clumpy, slowly moving outflow. A clump of emission in this spectrum, south of the equatorial ring at ∼1500 km s−1, is likely associated with the reverse shock.

Keywords
supernovae: individual: SN 1987A, ISM: supernova remnants
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-203534 (URN)10.1093/mnras/stab3683 (DOI)000767859900005 ()2-s2.0-85125506644 (Scopus ID)
Available from: 2022-04-06 Created: 2022-04-06 Last updated: 2022-04-06Bibliographically approved
Kangas, T., Yan, L., Schulze, S., Fransson, C., Sollerman, J., Lunnan, R., . . . Yao, Y. (2022). The Zwicky Transient Facility phase I sample of hydrogen-rich superluminous supernovae without strong narrow emission lines. Monthly notices of the Royal Astronomical Society, 516(1), 1193-1218
Open this publication in new window or tab >>The Zwicky Transient Facility phase I sample of hydrogen-rich superluminous supernovae without strong narrow emission lines
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2022 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 516, no 1, p. 1193-1218Article in journal (Refereed) Published
Abstract [en]

We present a sample of 14 hydrogen-rich superluminous supernovae (SLSNe II) from the Zwicky Transient Facility (ZTF) between 2018 and 2020. We include all classified SLSNe with peaks Mg < −20 mag with observed broad but not narrow Balmer emission, corresponding to roughly 20 per cent of all hydrogen-rich SLSNe in ZTF phase I. We examine the light curves and spectra of SLSNe II and attempt to constrain their power source using light-curve models. The brightest events are photometrically and spectroscopically similar to the prototypical SN 2008es, while others are found spectroscopically more reminiscent of non-superluminous SNe II, especially SNe II-L. 56Ni decay as the primary power source is ruled out. Light-curve models generally cannot distinguish between circumstellar interaction (CSI) and a magnetar central engine, but an excess of ultraviolet (UV) emission signifying CSI is seen in most of the SNe with UV data, at a wide range of photometric properties. Simultaneously, the broad H α profiles of the brightest SLSNe II can be explained through electron scattering in a symmetric circumstellar medium (CSM). In other SLSNe II without narrow lines, the CSM may be confined and wholly overrun by the ejecta. CSI, possibly involving mass lost in recent eruptions, is implied to be the dominant power source in most SLSNe II, and the diversity in properties is likely the result of different mass loss histories. Based on their radiated energy, an additional power source may be required for the brightest SLSNe II, however – possibly a central engine combined with CSI.

Keywords
transients: supernovae, stars: magnetars, stars: mass-loss, galaxies: statistics
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-209274 (URN)10.1093/mnras/stac2218 (DOI)000849496600005 ()
Available from: 2022-09-14 Created: 2022-09-14 Last updated: 2022-09-14Bibliographically approved
Larsson, J., Sollerman, J., Lyman, J. D., Spyromilio, J., Tenhu, L., Fransson, C. & Lundqvist, P. (2021). Clumps and Rings of Ejecta in SNR 0540-69.3 as Seen in 3D. Astrophysical Journal, 922(2), Article ID 265.
Open this publication in new window or tab >>Clumps and Rings of Ejecta in SNR 0540-69.3 as Seen in 3D
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2021 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 922, no 2, article id 265Article in journal (Refereed) Published
Abstract [en]

The distribution of ejecta in young supernova remnants offers a powerful observational probe of their explosions and progenitors. Here we present a 3D reconstruction of the ejecta in SNR 0540-69.3, which is an O-rich remnant with a pulsar wind nebula located in the LMC. We use observations from the Very Large Telescope (VLT)/MUSE to study Hβ, [O iii] λλ4959, 5007, Hα, [S ii] λλ6717, 6731, [Ar iii] λ7136, and [S iii] λ9069. This is complemented by 2D spectra from VLT/X-shooter, which also cover [O ii] λλ3726, 3729, and [Fe ii] λ12567. We identify three main emission components: (i) clumpy rings in the inner nebula (≲1000 km s−1) with similar morphologies in all lines; (ii) faint extended [O iii] emission dominated by an irregular ring-like structure with radius ∼1600 km s−1 and inclination ∼40°, but with maximal velocities reaching ∼3000 km s−1; and (iii) a blob of Hα and Hβ located southeast of the pulsar at velocities ∼1500–3500 km s−1. We analyze the geometry using a clump-finding algorithm and use the clumps in the [O iii] ring to estimate an age of 1146 ± 116 yr. The observations favor an interpretation of the [O iii] ring as ejecta, while the origin of the H-blob is more uncertain. An alternative explanation is that it is the blown-off envelope of a binary companion. From the detection of Balmer lines in the innermost ejecta we confirm that SNR 0540 was a Type II supernova and that hydrogen was mixed down to low velocities in the explosion.

Keywords
Supernova remnants, Core-collapse supernovae, Supernova dynamics
National Category
Physical Sciences
Identifiers
urn:nbn:se:su:diva-200903 (URN)10.3847/1538-4357/ac2a41 (DOI)000727017000001 ()
Available from: 2022-01-14 Created: 2022-01-14 Last updated: 2022-01-14Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-8532-3594

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