| 1. |
- Brennan, Seán J., 1995-, et al.
(författare)
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Spectroscopic observations of progenitor activity 100 days before a Type Ibn supernova
- 2024
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 684
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Tidskriftsartikel (refereegranskat)abstract
- Obtaining spectroscopic observations of the progenitors of core-collapse supernovae is often unfeasible, due to an inherent lack of knowledge as to what stars experience supernovae and when they will explode. In this Letter we present photometric and spectroscopic observations of the progenitor activity of SN 2023fyq before the He-rich progenitor explodes as a Type Ibn supernova. The progenitor of SN 2023fyq shows an exponential rise in flux prior to core collapse. Complex He I emission line features are observed in the progenitor spectra, with a P Cygni-like profile, as well as an evolving broad base with velocities of the order of 10 000 km s−1. The luminosity and evolution of SN 2023fyq is consistent with a Type Ibn, reaching a peak r-band magnitude of −18.8 mag, although there is some uncertainty regarding the distance to the host, NGC 4388, which is located in the Virgo cluster. We present additional evidence of asymmetric He-rich material being present both prior to and after the explosion of SN 2023fyq, which suggests that this material survived the ejecta interaction. Broad [O I], C I, and the Ca II triplet lines are observed at late phases, confirming that SN 2023fyq was a genuine supernova, rather than a non-terminal interacting transient. SN 2023fyq provides insight into the final moments of a massive star’s life, demonstrating that the progenitor is likely highly unstable before core collapse.
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| 2. |
- Aarø, L. E., et al.
(författare)
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Nordic adolescents responding to demanding survey scales in boring contexts: Examining straightlining
- 2022
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Ingår i: Journal of Adolescence. - : Wiley. - 0140-1971 .- 1095-9254. ; 94:6, s. 829-843
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Straightlining, or identical responses across all items within a multi-item scale, is often taken as an indication that responses to all items in a questionnaire are of poor quality. The purpose of this study was to examine straightlining on two scales: The Sense of Unity Scale (SUS) and the short version of the Warwick-Edinburgh Mental Well-being Scale (SWEMWBS). Methods: Data stem from the 2017–2018 data collections in four Nordic countries of the Health Behaviour in School-children study (HBSC) (15-year-old students only; 50.9% girls; n = 5928). Data were weighted to adjust for oversampling of Swedish-speaking Finnish students and to equalize sample size across countries. The main analyses were done with general linear modeling with adjustments for cluster effects (school classes). Results: The proportion with straightlining on SUS was 22.8%, varying from 5.8% among Swedish girls to 46.4% among Finnish boys. The proportion with straightlining on SWEMWBS was 18.4%, varying from 5.2% among Norwegian girls to 46.0% among Finnish boys. Straightlining on one of the scales correlated with straightlining on the other one. Straightlining tended to inflate Cronbach's αvalues and reduce number of factors in factor analyses. Associations between the two scales and external variables tended to be lower among straightlining students. Associations between external variables (other than SUS/SWEMWBS) are on average slightly weaker among straightliners. Straightlining students obtained more favorable scores on several resource-related variables. Conclusion: Although some problems have been identified, straightlining does not serve well as a general indicator of poor data quality.
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| 3. |
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| 4. |
- Chen, Ping, et al.
(författare)
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A 12.4-day periodicity in a close binary system after a supernova
- 2024
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Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 625:7994, s. 253-258
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Tidskriftsartikel (refereegranskat)abstract
- Neutron stars and stellar-mass black holes are the remnants of massive star explosions1. Most massive stars reside in close binary systems2, and the interplay between the companion star and the newly formed compact object has been theoretically explored3, but signatures for binarity or evidence for the formation of a compact object during a supernova explosion are still lacking. Here we report a stripped-envelope supernova, SN 2022jli, which shows 12.4-day periodic undulations during the declining light curve. Narrow Hα emission is detected in late-time spectra with concordant periodic velocity shifts, probably arising from hydrogen gas stripped from a companion and accreted onto the compact remnant. A new Fermi-LAT γ-ray source is temporally and positionally consistent with SN 2022jli. The observed properties of SN 2022jli, including periodic undulations in the optical light curve, coherent Hα emission shifting and evidence for association with a γ-ray source, point to the explosion of a massive star in a binary system leaving behind a bound compact remnant. Mass accretion from the companion star onto the compact object powers the light curve of the supernova and generates the γ-ray emission.
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| 5. |
- Harvey, L., et al.
(författare)
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Early-time spectroscopic modelling of the transitional Type Ia Supernova 2021rhu with tardis
- 2023
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Ingår i: Monthly notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 522:3, s. 4444-4467
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Tidskriftsartikel (refereegranskat)abstract
- An open question in SN Ia research is where the boundary lies between 'normal' Type Ia supernovae (SNe Ia) that are used in cosmological measurements and those that sit off the Phillips relation. We present the spectroscopic modelling of one such '86G-like' transitional SN Ia, SN 2021rhu, that has recently been employed as a local Hubble Constant calibrator using a tip of the red-giant branch measurement. We detail its modelling from -12 d until maximum brightness using the radiative-transfer spectral-synthesis code tardis. Please check and correct this paper accordingly. We base our modelling on literature delayed-detonation and deflagration models of Chandrasekhar mass white dwarfs, as well as the double-detonation models of sub-Chandrasekhar mass white dwarfs. We present a new method for 'projecting' abundance profiles to different density profiles for ease of computation. Due to the small velocity extent and low outer densities of the W7 profile, we find it inadequate to reproduce the evolution of SN 2021rhu as it fails to match the high-velocity calcium components. The host extinction of SN 2021rhu is uncertain but we use modelling with and without an extinction correction to set lower and upper limits on the abundances of individual species. Comparing these limits to literature models we conclude that the spectral evolution of SN 2021rhu is also incompatible with double-detonation scenarios, lying more in line with those resulting from the delayed-detonation mechanism (although there are some discrepancies, in particular a larger titanium abundance in SN 2021rhu compared to the literature). This suggests that SN 2021rhu is likely a lower luminosity, and hence lower temperature, version of a normal SN Ia.
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| 6. |
- Irani, Ido, et al.
(författare)
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SN 2022oqm-A Ca-rich Explosion of a Compact Progenitor Embedded in C/O Circumstellar Material
- 2024
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 962:2
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Tidskriftsartikel (refereegranskat)abstract
- We present the discovery and analysis of SN 2022oqm, a Type Ic supernova (SN) detected <1 day after the explosion. The SN rises to a blue and short-lived (2 days) initial peak. Early-time spectral observations of SN 2022oqm show a hot (40,000 K) continuum with high ionization C and O absorption features at velocities of 4000 km s−1, while its photospheric radius expands at 20,000 km s−1, indicating a pre-existing distribution of expanding C/O material. After ∼2.5 days, both the spectrum and light curves evolve into those of a typical SN Ic, with line velocities of ∼10,000 km s−1, in agreement with the evolution of the photospheric radius. The optical light curves reach a second peak at t ≈ 15 days. By t = 60 days, the spectrum of SN 2022oqm becomes nearly nebular, displaying strong Ca ii and [Ca ii] emission with no detectable [O i], marking this event as Ca-rich. The early behavior can be explained by 10−3M⊙ of optically thin circumstellar material (CSM) surrounding either (1) a massive compact progenitor such as a Wolf–Rayet star, (2) a massive stripped progenitor with an extended envelope, or (3) a binary system with a white dwarf. We propose that the early-time light curve is powered by both the interaction of the ejecta with the optically thin CSM and shock cooling (in the massive star scenario). The observations can be explained by CSM that is optically thick to X-ray photons, is optically thick in the lines as seen in the spectra, and is optically thin to visible-light continuum photons that come either from downscattered X-rays or from the shock-heated ejecta. Calculations show that this scenario is self-consistent.
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| 7. |
- Sharma, Yashvi, et al.
(författare)
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Dramatic Rebrightening of the Type-changing Stripped-envelope Supernova SN 2023aew
- 2024
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 966:2
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Tidskriftsartikel (refereegranskat)abstract
- Multipeaked supernovae with precursors, dramatic light-curve rebrightenings, and spectral transformation are rare, but are being discovered in increasing numbers by modern night-sky transient surveys like the Zwicky Transient Facility. Here, we present the observations and analysis of SN 2023aew, which showed a dramatic increase in brightness following an initial luminous (−17.4 mag) and long (∼100 days) unusual first peak (possibly precursor). SN 2023aew was classified as a Type IIb supernova during the first peak but changed its type to resemble a stripped-envelope supernova (SESN) after the marked rebrightening. We present comparisons of SN 2023aew's spectral evolution with SESN subtypes and argue that it is similar to SNe Ibc during its main peak. P-Cygni Balmer lines are present during the first peak, but vanish during the second peak's photospheric phase, before Hα resurfaces again during the nebular phase. The nebular lines ([O i], [Ca ii], Mg i], Hα) exhibit a double-peaked structure that hints toward a clumpy or nonspherical ejecta. We analyze the second peak in the light curve of SN 2023aew and find it to be broader than that of normal SESNe as well as requiring a very high 56Ni mass to power the peak luminosity. We discuss the possible origins of SN 2023aew including an eruption scenario where a part of the envelope is ejected during the first peak and also powers the second peak of the light curve through interaction of the SN with the circumstellar medium.
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| 8. |
- Goobar, Ariel, 1962-, et al.
(författare)
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Uncovering a population of gravitational lens galaxies with magnified standard candle SN Zwicky
- 2023
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Ingår i: Nature Astronomy. - 2397-3366. ; 7:9, s. 1098-1107
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Tidskriftsartikel (refereegranskat)abstract
- Detecting gravitationally lensed supernovae is among the biggest challenges in astronomy. It involves a combination of two very rare phenomena: catching the transient signal of a stellar explosion in a distant galaxy and observing it through a nearly perfectly aligned foreground galaxy that deflects light towards the observer. Here we describe how high-cadence optical observations with the Zwicky Transient Facility, with its unparalleled large field of view, led to the detection of a multiply imaged type Ia supernova, SN Zwicky, also known as SN 2022qmx. Magnified nearly 25-fold, the system was found thanks to the standard candle nature of type Ia supernovae. High-spatial-resolution imaging with the Keck telescope resolved four images of the supernova with very small angular separation, corresponding to an Einstein radius of only θE = 0.167″ and almost identical arrival times. The small θE and faintness of the lensing galaxy are very unusual, highlighting the importance of supernovae to fully characterize the properties of galaxy-scale gravitational lenses, including the impact of galaxy substructures.
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| 9. |
- Liu, Chang, et al.
(författare)
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SN 2022joj : A Peculiar Type Ia Supernova Possibly Driven by an Asymmetric Helium-shell Double Detonation
- 2023
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 958:2
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Tidskriftsartikel (refereegranskat)abstract
- We present observations of SN 2022joj, a peculiar Type Ia supernova discovered by the Zwicky Transient Facility. SN 2022joj exhibits an unusually red g ZTF - r ZTF color at early times and a rapid blueward evolution afterward. Around maximum brightness, SN 2022joj shows a high luminosity ( MgZTF,max similar or equal to-19.7 mag), a blue broadband color (g ZTF - r ZTF similar or equal to -0.2 mag), and shallow Si ii absorption lines, consistent with those of overluminous, SN 1991T-like events. The maximum-light spectrum also shows prominent absorption around 4200 angstrom, which resembles the Ti ii features in subluminous, SN 1991bg-like events. Despite the blue optical-band colors, SN 2022joj exhibits extremely red ultraviolet minus optical colors at maximum luminosity (u - v similar or equal to 0.6 mag and uvw1 - v similar or equal to 2.5 mag), suggesting a suppression of flux at similar to 2500-4000 angstrom. Strong C ii lines are also detected at peak. We show that these unusual spectroscopic properties are broadly consistent with the helium-shell double detonation of a sub-Chandrasekhar mass (M similar or equal to 1 M circle dot) carbon/oxygen white dwarf from a relatively massive helium shell (M s similar or equal to 0.04-0.1 M circle dot), if observed along a line of sight roughly opposite to where the shell initially detonates. None of the existing models could quantitatively explain all the peculiarities observed in SN 2022joj. The low flux ratio of [Ni ii] lambda 7378 to [Fe ii] lambda 7155 emission in the late-time nebular spectra indicates a low yield of stable Ni isotopes, favoring a sub-Chandrasekhar mass progenitor. The significant blueshift measured in the [Fe ii] lambda 7155 line is also consistent with an asymmetric chemical distribution in the ejecta, as is predicted in double-detonation models.
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| 10. |
- Solstad, B. E., et al.
(författare)
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Initial psychometric testing of the coach-adapted version of the empowering and disempowering motivational climate questionnaire: A Bayesian approach
- 2020
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Ingår i: Journal of Sports Sciences. - : Informa UK Limited. - 0264-0414 .- 1466-447X. ; 38:6, s. 626-643
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Tidskriftsartikel (refereegranskat)abstract
- The present study examined the psychometric properties of the coach-adapted version of the Empowering and Disempowering Motivational Climate Questionnaire (EDMCQ) using Bayesian structural equation modelling (BSEM). The sample included 780 (M-age = 36.4; SD = 10.8; males n = 698; females n = 54; 28 participants did not report sex) youth sport coaches representing five European countries (i.e., England, France, Greece, Norway, and Spain). The results did not support a 34-item five-factor, hierarchical, a two-factor BSEM, or a bifactor BSEM model across the participating countries. However, the results supported a reduced 19-item first-order, two-factor BSEM model that largely showed approximate metric invariance, but not approximate scalar invariance across the five countries. The pool of items constituting empowering and disempowering motivational climates should be refined to further enhance the empirical operationalisation of the coach-adapted version of the EDMCQ. Advancing the quality of translation-back-translation procedures across cultures and conducting multi-national pilot testing seems warranted as well. These recommendations may help to identify the distinctive aspects of each underlying sub-dimension of the EDMCQ, where coaches are the respondents, and pave the way for further examination of the proposed hierarchical multidimensional factor structure and the cross-cultural equivalence of the EDMCQ for this population.
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