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Publications (10 of 61) Show all publications
Chen, P., Gal-Yam, A., Sollerman, J., Schulze, S., Post, R. S., Liu, C., . . . Yan, L. (2024). A 12.4-day periodicity in a close binary system after a supernova. Nature, 625(7994), 253-258
Open this publication in new window or tab >>A 12.4-day periodicity in a close binary system after a supernova
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2024 (English)In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 625, no 7994, p. 253-258Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-226987 (URN)10.1038/s41586-023-06787-x (DOI)001143579000018 ()38200292 (PubMedID)2-s2.0-85181900770 (Scopus ID)
Available from: 2024-03-04 Created: 2024-03-04 Last updated: 2024-03-04Bibliographically approved
Schady, P., Yates, R. M., Christensen, L., De Cia, A., Rossi, A., D'Elia, V., . . . Wiseman, P. (2024). Comparing emission- and absorption-based gas-phase metallicities in GRB host galaxies at z =2-4 using JWST. Monthly notices of the Royal Astronomical Society, 529(3), 2807-2831
Open this publication in new window or tab >>Comparing emission- and absorption-based gas-phase metallicities in GRB host galaxies at z =2-4 using JWST
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2024 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 529, no 3, p. 2807-2831Article in journal (Refereed) Published
Abstract [en]

Much of what is known of the chemical composition of the universe is based on emission line spectra from star-forming galaxies. Emission-based inferences are, nevertheless, model-dependent and they are dominated by light from luminous star-forming regions. An alternative and sensitive probe of the metallicity of galaxies is through absorption lines imprinted on the luminous afterglow spectra of long gamma ray bursts (GRBs) from neutral material within their host galaxy. We present results from a JWST/NIRSpec programme to investigate for the first time the relation between the metallicity of neutral gas probed in absorption by GRB afterglows and the metallicity of the star-forming regions for the same host galaxy sample. Using an initial sample of eight GRB host galaxies at z = 2.1–4.7, we find a tight relation between absorption and emission line metallicities when using the recently proposed 𝑅^ metallicity diagnostic (±0.2 dex). This agreement implies a relatively chemically homogeneous multiphase interstellar medium and indicates that absorption and emission line probes can be directly compared. However, the relation is less clear when using other diagnostics, such as R23 and R3. We also find possible evidence of an elevated N/O ratio in the host galaxy of GRB 090323 at z = 4.7, consistent with what has been seen in other z > 4 galaxies. Ultimate confirmation of an enhanced N/O ratio and of the relation between absorption and emission line metallicities will require a more direct determination of the emission line metallicity via the detection of temperature-sensitive auroral lines in our GRB host galaxy sample.

Keywords
gamma-ray burst: general, ISM: abundances, galaxies: abundances, galaxies: high-redshift, galaxies: ISM, quasars: absorption lines
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-228652 (URN)10.1093/mnras/stae677 (DOI)001188770300012 ()2-s2.0-85188705507 (Scopus ID)
Available from: 2024-04-26 Created: 2024-04-26 Last updated: 2024-04-26Bibliographically approved
Sarin, N. & Schulze, S. (2024). Heavy-element production in a compact object merger observed by JWST. Nature, 626, 737-741
Open this publication in new window or tab >>Heavy-element production in a compact object merger observed by JWST
2024 (English)In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 626, p. 737-741Article in journal (Refereed) Published
Abstract [en]

The mergers of binary compact objects such as neutron stars and black holes are of central interest to several areas of astrophysics, including as the progenitors of gamma-ray bursts (GRBs)1, sources of high-frequency gravitational waves (GWs)2 and likely production sites for heavy-element nucleosynthesis by means of rapid neutron capture (the r-process)3. Here we present observations of the exceptionally bright GRB 230307A. We show that GRB 230307A belongs to the class of long-duration GRBs associated with compact object mergers4,5,6 and contains a kilonova similar to AT2017gfo, associated with the GW merger GW170817 (refs. 7,8,9,10,11,12). We obtained James Webb Space Telescope (JWST) mid-infrared imaging and spectroscopy 29 and 61 days after the burst. The spectroscopy shows an emission line at 2.15 microns, which we interpret as tellurium (atomic mass A = 130) and a very red source, emitting most of its light in the mid-infrared owing to the production of lanthanides. These observations demonstrate that nucleosynthesis in GRBs can create r-process elements across a broad atomic mass range and play a central role in heavy-element nucleosynthesis across the Universe.

National Category
Atom and Molecular Physics and Optics Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-227416 (URN)10.1038/s41586-023-06759-1 (DOI)001169196100001 ()37879361 (PubMedID)2-s2.0-85182219102 (Scopus ID)
Available from: 2024-03-14 Created: 2024-03-14 Last updated: 2024-04-29Bibliographically approved
Irani, I., Chen, P., Morag, J., Schulze, S., Gal-Yam, A., Strotjohann, N. L., . . . Medford, M. S. (2024). SN 2022oqm-A Ca-rich Explosion of a Compact Progenitor Embedded in C/O Circumstellar Material. Astrophysical Journal, 962(2), Article ID 109.
Open this publication in new window or tab >>SN 2022oqm-A Ca-rich Explosion of a Compact Progenitor Embedded in C/O Circumstellar Material
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2024 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 962, no 2, article id 109Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-226985 (URN)10.3847/1538-4357/ad04d7 (DOI)001159919400001 ()2-s2.0-85184936369 (Scopus ID)
Available from: 2024-03-05 Created: 2024-03-05 Last updated: 2024-03-05Bibliographically approved
Pessi, T., Prieto, J. L., Anderson, J. P., Galbany, L., Lyman, J. D., Kochanek, C., . . . Shappee, B. (2023). A characterization of ASAS-SN core-collapse supernova environments with VLT+MUSE I. Sample selection, analysis of local environments, and correlations with light curve properties. Astronomy and Astrophysics, 677, Article ID A28.
Open this publication in new window or tab >>A characterization of ASAS-SN core-collapse supernova environments with VLT+MUSE I. Sample selection, analysis of local environments, and correlations with light curve properties
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2023 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 677, article id A28Article in journal (Refereed) Published
Abstract [en]

Context. The analysis of core-collapse supernova (CCSN) environments can provide important information on the life cycle of massive stars and constrain the progenitor properties of these powerful explosions. The MUSE instrument at the Very Large Telescope (VLT) enables detailed local environment constraints of the progenitors of large samples of CCSNe. Using a homogeneous SN sample from the All-Sky Automated Survey for Supernovae (ASAS-SN) survey, an untargeted and spectroscopically complete transient survey, has enabled us to perform a minimally biased statistical analysis of CCSN environments.

Aims. We analyze 111 galaxies observed by MUSE that hosted 112 CCSNe – 78 II, nine IIn, seven IIb, four Ic, seven Ib, three Ibn, two Ic-BL, one ambiguous Ibc, and one superluminous SN – detected or discovered by the ASAS-SN survey between 2014 and 2018. The majority of the galaxies were observed by the All-weather MUse Supernova Integral field Nearby Galaxies (AMUSING) survey. Here we analyze the immediate environment around the SN locations and compare the properties between the different CCSN types and their light curves.

Methods. We used stellar population synthesis and spectral fitting techniques to derive physical parameters for all H II regions detected within each galaxy, including the star formation rate (SFR), Hα equivalent width (EW), oxygen abundance, and extinction.

Results. We found that stripped-envelope supernovae (SESNe) occur in environments with a higher median SFR, Hα EW, and oxygen abundances than SNe II and SNe IIn/Ibn. Most of the distributions have no statistically significant differences, except between oxygen abundance distributions of SESNe and SNe II, and between Hα EW distributions of SESNe and SNe II. The distributions of SNe II and IIn are very similar, indicating that these events explode in similar environments. For the SESNe, SNe Ic have higher median SFRs, Hα EWs, and oxygen abundances than SNe Ib. SNe IIb have environments with similar SFRs and Hα EWs to SNe Ib, and similar oxygen abundances to SNe Ic. We also show that the postmaximum decline rate, s, of SNe II correlates with the Hα EW, and that the luminosity and the Δm15 parameter of SESNe correlate with the oxygen abundance, Hα EW, and SFR at their environments. This suggests a connection between the explosion mechanisms of these events to their environment properties.

Keywords
supernovae: general, galaxies: abundances
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-223857 (URN)10.1051/0004-6361/202346512 (DOI)001073813400002 ()2-s2.0-85169929131 (Scopus ID)
Available from: 2023-11-22 Created: 2023-11-22 Last updated: 2023-11-22Bibliographically approved
Levan, A. J., Malesani, D. B., Gompertz, B. P., Nugent, A. E., Nicholl, M., Oates, S. R., . . . Tanvir, N. R. (2023). A long-duration gamma-ray burst of dynamical origin from the nucleus of an ancient galaxy. Nature Astronomy, 7(8), 976-985
Open this publication in new window or tab >>A long-duration gamma-ray burst of dynamical origin from the nucleus of an ancient galaxy
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2023 (English)In: Nature Astronomy, E-ISSN 2397-3366, Vol. 7, no 8, p. 976-985Article in journal (Refereed) Published
Abstract [en]

The majority of long-duration (>2 s) gamma-ray bursts (GRBs) arise from the collapse of massive stars, with a small proportion created from the merger of compact objects. Most of these systems form via standard stellar evolution pathways. However, a fraction of GRBs may result from dynamical interactions in dense environments. These channels could also contribute substantially to the samples of compact object mergers detected as gravitational wave sources. Here we report the case of GRB 191019A, a long GRB (a duration of T90 = 64.4 ± 4.5 s), which we pinpoint close (⪅100 pc projected) to the nucleus of an ancient (>1 Gyr old) host galaxy at z = 0.248. The lack of evidence for star formation and deep limits on any supernova emission disfavour a massive star origin. The most likely route for progenitor formation is via dynamical interactions in the dense nucleus of the host. The progenitor, in this case, could be a compact object merger. These may form in dense nuclear clusters or originate in a gaseous disc around the supermassive black hole. Identifying, to the best of our knowledge, a first example of a dynamically produced GRB demonstrates the role that such bursts may have in probing dense environments and constraining dynamical fractions in gravitational wave populations.

National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-221078 (URN)10.1038/s41550-023-01998-8 (DOI)001019740000004 ()2-s2.0-85162673864 (Scopus ID)
Available from: 2023-09-25 Created: 2023-09-25 Last updated: 2023-09-25Bibliographically approved
Karamehmetoglu, E., Sollerman, J., Taddia, F., Barbarino, C., Feindt, U., Fremling, C., . . . Zapartas, E. (2023). A population of Type Ibc supernovae with massive progenitors Broad lightcurves not uncommon in (i)PTF. Astronomy and Astrophysics, 678, Article ID A87.
Open this publication in new window or tab >>A population of Type Ibc supernovae with massive progenitors Broad lightcurves not uncommon in (i)PTF
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2023 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 678, article id A87Article in journal (Refereed) Published
Abstract [en]

If high-mass stars (≳20 − 25 M) are the progenitors of stripped-envelope (SE) supernovae (SNe), their massive ejecta should lead to broad, long-duration lightcurves. Instead, literature samples of SE SNe have reported relatively narrow lightcurves corresponding to ejecta masses between 1 − 4 M that favor intermediate-mass progenitors (≲20 − 25 M). Working with an untargeted sample from a single telescope to better constrain their rates, we searched the Palomar Transient Factory (PTF) and intermediate-PTF (iPTF) sample of SNe for SE SNe with broad lightcurves. Using a simple observational marker of g- or r-band lightcurve stretch compared to a template to measure broadness, we identified eight significantly broader Type Ibc SNe after applying quantitative sample selection criteria. The lightcurves, broad-band colors, and spectra of these SNe are found to evolve more slowly relative to typical Type Ibc SNe, proportional with the stretch parameter. Bolometric lightcurve modeling and their nebular spectra indicate high ejecta masses and nickel masses, assuming radioactive decay powering. Additionally, these objects are preferentially located in low-metallicity host galaxies with high star formation rates, which may account for their massive progenitors, as well as their relative absence from the literature. Our study thus supports the link between broad lightcurves (as measured by stretch) and high-mass progenitor stars in SE SNe with independent evidence from bolometric lightcurve modeling, nebular spectra, host environment properties, and photometric evolution. In the first systematic search of its kind using an untargeted sample, we used the stretch distribution to identify a higher than previously appreciated fraction of SE SNe with broad lightcurves (∼13%). Correcting for Malmquist and lightcurve duration observational biases, we conservatively estimate that a minimum of ∼6% of SE SNe are consistent with high-mass progenitors. This result has implications for the progenitor channels of SE SNe, including late stages of massive stellar evolution, the origin of the observed oxygen fraction in the universe, and formation channels for stellar-mass black holes.

Keywords
supernovae: general, methods: statistical, surveys, methods: data analysis, techniques: photometric
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-223850 (URN)10.1051/0004-6361/202245231 (DOI)001084587200004 ()2-s2.0-85175010454 (Scopus ID)
Available from: 2023-11-20 Created: 2023-11-20 Last updated: 2023-11-20Bibliographically approved
Aamer, A., Nicholl, M., Jerkstrand, A., Gomez, S., Oates, S. R., Smartt, S. J., . . . Young, D. R. (2023). A precursor plateau and pre-maximum [O ii] emission in the superluminous SN2019szu: a pulsational pair-instability candidate. Monthly notices of the Royal Astronomical Society, 527(4), 11970-11995
Open this publication in new window or tab >>A precursor plateau and pre-maximum [O ii] emission in the superluminous SN2019szu: a pulsational pair-instability candidate
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2023 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 527, no 4, p. 11970-11995Article in journal (Refereed) Published
Abstract [en]

We present a detailed study on SN2019szu, a Type I superluminous supernova at z = 0.213 that displayed unique photometric and spectroscopic properties. Pan-STARRS and ZTF forced photometry show a pre-explosion plateau lasting ∼40 d. Unlike other SLSNe that show decreasing photospheric temperatures with time, the optical colours show an apparent temperature increase from ∼15 000 to ∼20 000 K over the first 70 d, likely caused by an additional pseudo-continuum in the spectrum. Remarkably, the spectrum displays a forbidden emission line (likely attributed to λλ7320,7330) visible 16 d before maximum light, inconsistent with an apparently compact photosphere. This identification is further strengthened by the appearances of [O III] λλ4959, 5007, and [O III] λ4363 seen in the spectrum. Comparing with nebular spectral models, we find that the oxygen line fluxes and ratios can be reproduced with ∼0.25 M of oxygen-rich material with a density of ∼10−15 g cm−3⁠. The low density suggests a circumstellar origin, but the early onset of the emission lines requires that this material was ejected within the final months before the terminal explosion, consistent with the timing of the precursor plateau. Interaction with denser material closer to the explosion likely produced the pseudo-continuum bluewards of ∼5500 Å. We suggest that this event is one of the best candidates to date for a pulsational pair-instability ejection, with early pulses providing the low density material needed for the formation of the forbidden emission line, and collisions between the final shells of ejected material producing the pre-explosion plateau.

Keywords
stars: massive, supernovae: general, supernovae: individual: SN2019szu, transients: supernovae
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-226499 (URN)10.1093/mnras/stad3776 (DOI)001157351800001 ()2-s2.0-85182401745 (Scopus ID)
Available from: 2024-02-19 Created: 2024-02-19 Last updated: 2024-03-12Bibliographically approved
Kool, E. C., Pearson Johansson, J., Sollerman, J., Moldón, J., Moriya, T. J., Mattila, S., . . . Stern, D. (2023). A radio-detected type Ia supernova with helium-rich circumstellar material. Nature, 617(7961), 477-482
Open this publication in new window or tab >>A radio-detected type Ia supernova with helium-rich circumstellar material
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2023 (English)In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 617, no 7961, p. 477-482Article in journal (Refereed) Published
Abstract [en]

Type Ia supernovae (SNe Ia) are thermonuclear explosions of degenerate white dwarf stars destabilized by mass accretion from a companion star1, but the nature of their progenitors remains poorly understood. A way to discriminate between progenitor systems is through radio observations; a non-degenerate companion star is expected to lose material through winds2 or binary interaction3 before explosion, and the supernova ejecta crashing into this nearby circumstellar material should result in radio synchrotron emission. However, despite extensive efforts, no type Ia supernova (SN Ia) has ever been detected at radio wavelengths, which suggests a clean environment and a companion star that is itself a degenerate white dwarf star4,5. Here we report on the study of SN 2020eyj, a SN Ia showing helium-rich circumstellar material, as demonstrated by its spectral features, infrared emission and, for the first time in a SN Ia to our knowledge, a radio counterpart. On the basis of our modelling, we conclude that the circumstellar material probably originates from a single-degenerate binary system in which a white dwarf accretes material from a helium donor star, an often proposed formation channel for SNe Ia (refs. 6,7). We describe how comprehensive radio follow-up of SN 2020eyj-like SNe Ia can improve the constraints on their progenitor systems.

National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-223960 (URN)10.1038/s41586-023-05916-w (DOI)001078324200011 ()37198310 (PubMedID)2-s2.0-85159611552 (Scopus ID)
Available from: 2023-11-24 Created: 2023-11-24 Last updated: 2023-11-24Bibliographically approved
Ho, A. Y. Q., Perley, D. A., Gal-Yam, A., Lunnan, R., Sollerman, J., Schulze, S., . . . Winters, J. M. (2023). A Search for Extragalactic Fast Blue Optical Transients in ZTF and the Rate of AT2018cow-like Transients. Astrophysical Journal, 949(2), Article ID 120.
Open this publication in new window or tab >>A Search for Extragalactic Fast Blue Optical Transients in ZTF and the Rate of AT2018cow-like Transients
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2023 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 949, no 2, article id 120Article in journal (Refereed) Published
Abstract [en]

We present a search for extragalactic fast blue optical transients (FBOTs) during Phase I of the Zwicky Transient Facility (ZTF). We identify 38 candidates with durations above half-maximum light 1 day < t (1/2) < 12 days, of which 28 have blue (g - r less than or similar to -0.2 mag) colors at peak light. Of the 38 transients (28 FBOTs), 19 (13) can be spectroscopically classified as core-collapse supernovae (SNe): 11 (8) H- or He-rich (Type II/IIb/Ib) SNe, 6 (4) interacting (Type IIn/Ibn) SNe, and 2 (1) H&He-poor (Type Ic/Ic-BL) SNe. Two FBOTs (published previously) had predominantly featureless spectra and luminous radio emission: AT2018lug (The Koala) and AT2020xnd (The Camel). Seven (five) did not have a definitive classification: AT 2020bdh showed tentative broad H alpha in emission, and AT 2020bot showed unidentified broad features and was 10 kpc offset from the center of an early-type galaxy. Ten (eight) have no spectroscopic observations or redshift measurements. We present multiwavelength (radio, millimeter, and/or X-ray) observations for five FBOTs (three Type Ibn, one Type IIn/Ibn, one Type IIb). Additionally, we search radio-survey (VLA and ASKAP) data to set limits on the presence of radio emission for 24 of the transients. All X-ray and radio observations resulted in nondetections; we rule out AT2018cow-like X-ray and radio behavior for five FBOTs and more luminous emission (such as that seen in the Camel) for four additional FBOTs. We conclude that exotic transients similar to AT2018cow, the Koala, and the Camel represent a rare subset of FBOTs and use ZTF's SN classification experiments to measure the rate to be at most 0.1% of the local core-collapse SN rate.

National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:su:diva-218369 (URN)10.3847/1538-4357/acc533 (DOI)001001445700001 ()2-s2.0-85161632715 (Scopus ID)
Available from: 2023-06-27 Created: 2023-06-27 Last updated: 2023-06-27Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-6797-1889

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