1. Eruptive mass loss less than a year before the explosion of superluminous supernovae : I. The cases of SN 2020xga and SN 2022xgcA. Gkini, C. Fransson, Ragnhild Lunnan, S. Schulze, F. Poidevin, N. Sarin, R. Könyves-Tóth, Jesper Sollerman, Mateusz Bronikowski, Tanja Petrushevska, 2025, izvirni znanstveni članek Opis: We present photometric and spectroscopic observations of SN 2020xga and SN 2022xgc, two hydrogen-poor superluminous supernovae (SLSNe-I) at z = 0.4296 and z = 0.3103, respectively, which show an additional set of broad Mg II absorption lines, blueshifted by a few thousands kilometer second−1 with respect to the host galaxy absorption system. Previous work interpreted this as due to resonance line scattering of the SLSN continuum by rapidly expanding circumstellar material (CSM) expelled shortly before the explosion. The peak rest-frame g-band magnitude of SN 2020xga is −22.30 ± 0.04 mag and of SN 2022xgc is −21.97 ± 0.05 mag, placing them among the brightest SLSNe-I. We used high-quality spectra from ultraviolet to near-infrared wavelengths to model the Mg II line profiles and infer the properties of the CSM shells. We find that the CSM shell of SN 2020xga resides at ∼1.3 × 1016 cm, moving with a maximum velocity of 4275 km s−1, and the shell of SN 2022xgc is located at ∼0.8 × 1016 cm, reaching up to 4400 km s−1. These shells were expelled ∼11 and ∼5 months before the explosions of SN 2020xga and SN 2022xgc, respectively, possibly as a result of luminous-blue-variable-like eruptions or pulsational pair instability (PPI) mass loss. We also analyzed optical photometric data and modeled the light curves, considering powering from the magnetar spin-down mechanism. The results support very energetic magnetars, approaching the mass-shedding limit, powering these SNe with ejecta masses of ∼7 − 9 M⊙. The ejecta masses inferred from the magnetar modeling are not consistent with the PPI scenario pointing toward stars > 50 M⊙ He-core; hence, alternative scenarios such as fallback accretion and CSM interaction are discussed. Modeling the spectral energy distribution of the host galaxy of SN 2020xga reveals a host mass of 107.8 M⊙, a star formation rate of 0.96−0.26+0.47 M⊙ yr−1, and a metallicity of ∼0.2 Z⊙.
Ključne besede: eruptive mass, loss, supernovae
Objavljeno v RUNG: 04.03.2025; Ogledov: 565; Prenosov: 7
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2. A population of Type Ibc supernovae with massive progenitors : broad lightcurves not uncommon in (i)PTFE. Karamehmetoglu, Jesper Sollerman, F. Taddia, C. Barbarino, U. Feindt, U. C. Fremling, Avishay Gal-Yam, M. M. Kasliwal, Tanja Petrushevska, S. Schulze, 2023, izvirni znanstveni članek Ključne besede: astronomy, supernova progenitors
Objavljeno v RUNG: 10.10.2023; Ogledov: 1807; Prenosov: 8
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3. The Palomar Transient Factory core-collapse supernova host-galaxy sample : Host- galaxy distribution functions and environment dependence of core-collapse supernovaeSteve Schulze, Ofer Yaron, Jesper Sollerman, Giorgos Leloudas, Amit Gal, Angus H. Wright, Ragnhild Lunnan, Avishay Gal-Yam, Eran O. Ofek, Tanja Petrushevska, 2021, izvirni znanstveni članek Ključne besede: supernovae, galaxies, core-collapse supernovae, astronomy
Objavljeno v RUNG: 23.08.2021; Ogledov: 3167; Prenosov: 123
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4. Supernova spectra below strong circumstellar interactionGiorgos Leloudas, E.Y. Hsiao, Joel Johansson, Keichi Maeda, T.J. Moriya, Jakob Nordin, Tanja Petrushevska, J. M. Silverman, Jesper Sollerman, M.D. Stritzinger, Francesco Taddia, D. Xu, 2015, izvirni znanstveni članek Opis: We construct spectra of supernovae (SNe) interacting strongly with a circumstellar medium (CSM) by adding SN templates, a blackbody
continuum, and an emission-line spectrum. In a Monte Carlo simulation we vary a large number of parameters, such as the SN
type, brightness and phase, the strength of the CSM interaction, the extinction, and the signal to noise ratio (S/N) of the observed
spectrum. We generate more than 800 spectra, distribute them to ten different human classifiers, and study how the different simulation
parameters affect the appearance of the spectra and their classification. The SNe IIn showing some structure over the continuum were
characterized as “SNe IInS” to allow for a better quantification. We demonstrate that the flux ratio of the underlying SN to the
continuum fV is the single most important parameter determining whether a spectrum can be classified correctly. Other parameters,
such as extinction, S/N, and the width and strength of the emission lines, do not play a significant role. Thermonuclear SNe get
progressively classified as Ia-CSM, IInS, and IIn as fV decreases. The transition between Ia-CSM and IInS occurs at fV ∼ 0.2−0.3. It
is therefore possible to determine that SNe Ia-CSM are found at the (un-extincted) magnitude range −19.5 > M > −21.6, in very good
agreement with observations, and that the faintest SN IIn that can hide a SN Ia has M = −20.1. The literature sample of SNe Ia-CSM
shows an association with 91T-like SNe Ia. Our experiment does not support that this association can be attributed to a luminosity bias
(91T-like being brighter than normal events). We therefore conclude that this association has real physical origins and we propose that
91T-like explosions result from single degenerate progenitors that are responsible for the CSM. Despite the spectroscopic similarities
between SNe Ibc and SNe Ia, the number of misclassifications between these types was very small in our simulation and mostly at low
S/N. Combined with the SN luminosity function needed to reproduce the observed SN Ia-CSM luminosities, it is unlikely that SNe Ibc
constitute an important contaminant within this sample. We show how Type II spectra transition to IIn and how the Hα profiles vary
with fV . SNe IIn fainter than M = −17.2 are unable to mask SNe IIP brighter than M = −15. A more advanced simulation, including
radiative transfer, shows that our simplified model is a good first order approximation. The spectra obtained are in good agreement
with real data.
Ključne besede: supernovae
Objavljeno v RUNG: 22.01.2018; Ogledov: 4926; Prenosov: 0
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