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- Lin, Weili, et al.
(författare)
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A superluminous supernova lightened by collisions with pulsational pair-instability shells
- 2023
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Ingår i: Nature Astronomy. - 2397-3366. ; 7:7, s. 779-789
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Tidskriftsartikel (refereegranskat)abstract
- Superluminous supernovae are among the most energetic stellar explosions in the Universe, but their energy sources remain an open question. Here we present long-term observations of one of the closest examples of the hydrogen-poor superluminous supernovae subclass SLSNe-I, supernova SN 2017egm, revealing the most complicated known luminosity evolution of SLSNe-I. Three distinct post-peak bumps were recorded in its light curve collected at about 100–350 days after maximum brightness, challenging current popular power models such as magnetar, fallback accretion, and interaction between ejecta and a circumstellar shell. However, the complex light curve can be well modelled by successive interactions with multiple circumstellar shells with a total mass of about 6.8–7.7 M⊙. In this scenario, large energy deposition from interaction-induced reverse shocks results in ionization of neutral oxygen in the supernova ejecta and hence a much lower nebular-phase line ratio of [O I] λ6,300/([Ca II] + [O II]) λ7,300 (~0.2) compared with that derived for other superluminous and normal stripped-envelope supernovae. The pre-existing multiple shells indicate that the progenitor of SN 2017egm experienced pulsational mass ejections triggered by pair instability within 2 years before explosion, in robust agreement with theoretical predictions for a pre-pulsation helium-core mass of 48–51 M⊙.
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- Zhang, Kaicheng, et al.
(författare)
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SN 2014J in M82 : new insights on the spectral diversity of Type Ia supernovae
- 2018
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 481:1, s. 878-893
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Tidskriftsartikel (refereegranskat)abstract
- We present extensive spectroscopic observations for one of the closest Type Ia supernovae (SNe Ia), SN 2014J discovered in M82, ranging from 10.4 d before to 473.2 d after B-band maximum light. The diffuse interstellar band features detected in a high-resolution spectrum allow an estimate of line-of-sight extinction as A(v) similar to 1.9 +/- 0.6 mag. Spectroscopically, SN 2014J can be put into the high-velocity (HV) subgroup in Wang's classification with a velocity of Si II lambda 6355 at maximum light of upsilon(0) = 1.22 +/- 0.01 x 10(4) km s(-1) but has a low velocity gradient (LVG, following Benetti's classification) of (v) over bar = 41 +/- 2 km s(-1) d(-1), which is inconsistent with the trend that HV SNe Ia generally have larger velocity gradients. We find that the HV SNe Ia with LVGs tend to have relatively stronger Si III (at similar to 4400 angstrom) absorptions in early spectra, larger ratios of S II lambda 5468 to S II lambda 5640, and weaker Si II 5972 absorptions compared to their counterparts with similar velocities but high velocity gradients. This shows that the HV+ LVG subgroup of SNe Ia may have intrinsically higher photospheric temperature, which indicates that their progenitors may experience more complete burning in the explosions relative to the typical HV SNe Ia.
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- Zhang, Tianmeng, et al.
(författare)
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Observations of a Fast-expanding and UV-bright Type Ia Supernova SN 2013gs
- 2019
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 872:1
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present extensive optical and ultraviolet (UV) observations of the type Ia supernova (SN Ia) 2013gs discovered during the Tsinghua-NAOC Transient Survey. The photometric observations in the optical show that the light curves of SN 2013gs are similar to those of normal SNe Ia, with an absolute peak magnitude of M-B = -19.25 +/- 0.15 mag and a post-maximum decline rate Delta m(15)(B) = 1.00 +/- 0.05 mag. Gehrels Swift Ultr-Violet/Optical Telescope observations indicate that SN 2013gs shows unusually strong UV emission (especially in the uvw1 band) at around the maximum light (M-uvw1 similar to -18.9 mag). The SN is characterized by relatively weak Fe II III absorptions at similar to 5000 angstrom in the early spectra and a larger expansion velocity (v(Si) similar to 13,000 km s(-1) around the maximum light) than the normal-velocity SNe Ia. We discuss the relation between the uvw1 - v color and some observables, including Si II velocity, line strength of Si II lambda 6355 and Fe II/III lines, and Delta m(15)(B). Compared to other fast-expanding SNe Ia, SN 2013gs exhibits Si and Fe absorption lines with similar strength and bluer uvw1 - v color. We briefly discussed the origin of the observed UV dispersion of SNe Ia.
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